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Of Hosts and Microbes: Mutualism, Pathogenesis and Evolution

Date:
26
Tuesday
March
2024
-
28
Thursday
March
2024
Lecture / Seminar
Time: 08:00 - 20:00
Lecturer: TBA
Organizer: Department of Immunology and Regenerative Biology
Contact: s.jung@weizmann.ac.il

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    Ultra-Repellent Aerophilic Surfaces Underwater”

    Date:
    30
    Wednesday
    August
    2023
    Lecture / Seminar
    Time: 11:00-12:00
    Location: Gerhard M.J. Schmidt Lecture Hall
    Lecturer: Dr. Alexander B. Tesler
    Organizer: Department of Molecular Chemistry and Materials Science
    Contact: ana.naamat@weizmann.ac.il
    Abstract: Wetting describes the ability of liquids to maintain contact with a solid surfac ... Read more Wetting describes the ability of liquids to maintain contact with a solid surface, a phenomenon that is ubiquitous in nature.1 However, in engineering and medical applications, contact of solid surfaces with aqueous media leads to undesirable phenomena such as corrosion, chemo- and biofouling, which have extremely negative economic, health, and environmental impacts. Therefore, control of wetting on solid surfaces is key to mitigating its detrimental effects. The latter can be achieved by minimizing the contact of the solid substrate with aqueous media, so-called superhydrophobic surfaces (SHS). Although SHS have been studied for decades to overcome wetting challenges,2 they are still rarely used in engineering applications. When immersed underwater, a special type of SHS can trap air on its surface, so-called air plastron, also known as an aerophilic surface. To date, plastrons have been reported to be impractical for underwater engineering due to their short lifetime. Here, I will describe aerophilic surfaces made of titanium alloy (Ti) with an extended lifetime of plastron conserved for months underwater.3 The extended methodology was developed to unambiguously describe the wetting regime on such aerophilic surfaces since conventional goniometric measurements are simply impractical. My aerophilic surfaces drastically reduce the adhesion of blood, and when immersed in aqueous media, prevent the adhesion of bacteria, and marine organisms such as barnacles, and mussels. Applying thermodynamic stability theories, we describe a generic strategy to achieve long-term stability of plastron on aerophilic surfaces for demanding and hitherto unattainable applications. (1) Quéré, D. Wetting and Roughness. Annual Review of Materials Research 2008, 38 (1), 71-99. (2) Cassie, A. B. D.; Baxter, S. Wettability of porous surfaces. Transactions of the Faraday Society 1944, 40, 546-551. (3) Tesler, A.B.;* Kolle, S.; Prado, L.H.; Thievessen, I.; Böhringer, D.; Backholm, M.; Karunakaran, B.; Nurmi, H.A.; Latikka, M.; Fischer, L.; Stafslien, S.; Cenev, Z.M.; Timonen, J.V.I.; Bruns, M.; Mazare, A.; Lohbauer, U.; Virtanen, S.; Fabry, B.; Schmuki, P.; Ras, R.H.A.; Aizenberg, J.; Goldmann, W.H. Long-Lasting Aerophilic Metallic Surfaces Underwater. Nature Materials 2023, accepted. *Corresponding author
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    Microbes in Cancer

    Date:
    17
    Monday
    July
    2023
    Lecture / Seminar
    Time: 11:15-13:00
    Location: Wolfson Building for Biological Research
    Lecturer: Dr. Ilana Livyatan
    Organizer: Life Sciences
    Contact: levana.ayvazo@weizmann.ac.il
    Details: Lab of Ravid Straussman, Dept. of Molecular Cell Biology Within the FGS cours ... Read more Lab of Ravid Straussman, Dept. of Molecular Cell Biology Within the FGS course on Translational Cancer Research Host: Zvi Livneh
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    Solar Panels for Light-to-Chemical Conversion

    Date:
    29
    Monday
    May
    2023
    Colloquium
    Time: 11:00-12:15
    Title: 2023 G.M.J. SCHMIDT MEMORIAL LECTURE
    Location: Gerhard M.J. Schmidt Lecture Hall
    Lecturer: Prof. Erwin Reisner
    Organizer: Faculty of Chemistry
    Contact: sarah.amzallag@weizmann.ac.il
    Abstract: Solar panels are well known to produce electricity, but they are also in early-s ... Read more Solar panels are well known to produce electricity, but they are also in early-stage development for the production of sustainable fuels and chemicals. These panels mimic plant leaves in shape and function as demonstrated for overall solar water splitting to produce green H2 by the laboratories of Nocera and Domen.1,2 This presentation will give an overview of our recent progress to construct prototype solar panel devices for the conversion of carbon dioxide and solid waste streams into fuels and higher-value chemicals through molecular surface-engineering of solar panels with suitable catalysts. Specifically, a standalone ‘photoelectrochemical leaf’ based on an integrated lead halide perovskite-BiVO4 tandem light absorber architecture has been built for the solar CO2 reduction to produce syngas.3 Syngas is an energy-rich gas mixture containing CO and H2 and currently produced from fossil fuels. The renewable production of syngas may allow for the synthesis of renewable liquid oxygenates and hydrocarbon fuels. Recent advances in the manufacturing have enabled the reduction of material requirements to fabricate such devices and make the leaves sufficiently light weight to even float on water, thereby enabling application on open water sources.4 The tandem design also allows for the integration of biocatalysts and the selective and bias-free conversion of CO2-to-formate has been demonstrated using enzymes.5 The versatility of the integrated leaf architecture has been demonstrated by replacing the perovskite light absorber by BiOI for solar water and CO2 splitting to demonstrate week-long stability.6 An alternative solar carbon capture and utilisation technology is based on co-deposited semiconductor powders on a conducting substrate.2 Modification of these immobilized powders with a molecular catalyst provides us with a photocatalyst sheet that can cleanly produce formic acid from aqueous CO2.7 CO2-fixing bacteria grown on such a ‘photocatalyst sheet’ enable the production of multicarbon products through clean CO2-to-acetate conversion.8 The deposition of a single semiconductor material on glass gives panels for the sunlight-powered conversion plastic and biomass waste into H2 and organic products, thereby allowing for simultaneous waste remediation and fuel production.9 The concept and prospect behind these integrated systems for solar energy conversion,10 related approaches,11 and their relevance to secure and harness sustainable energy supplies in a fossil-fuel free economy will be discussed.
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    Solar Panels for Light-to-Chemical Conversion Colloquium website

    An Innate Immunity Pathway Against Invading Microbes Targets the Paternal Mitochondria for Destruction after Fertilization

    Date:
    10
    Wednesday
    May
    2023
    Lecture / Seminar
    Time: 10:00-11:15
    Location: Arthur and Rochelle Belfer Building for Biomedical Research
    Lecturer: Prof. Eli Arama
    Organizer: Department of Brain Sciences
    Contact: naomi.moses@weizmann.ac.il

    Animal and Microbial Rhodopsins

    Date:
    08
    Monday
    May
    2023
    Colloquium
    Time: 11:00-12:15
    Location: Gerhard M.J. Schmidt Lecture Hall
    Lecturer: Prof. Hideki Kandori
    Organizer: Faculty of Chemistry
    Contact: sarah.amzallag@weizmann.ac.il
    Details: Schmidt Auditorium
    Abstract: Rhodopsins are photoreceptive membrane proteins containing a retinal chromophore ... Read more Rhodopsins are photoreceptive membrane proteins containing a retinal chromophore in animals and microbes. Animal and microbial rhodopsins possess 11-cis and all-trans retinal, respectively, and undergo isomerization into all-trans and 13-cis retinal by light. While animal rhodopsins are G protein coupled receptors, the function of microbial rhodopsins is highly divergent, including light-driven ion pumps, light-gated ion channels, photosensors, and light-activated enzymes. Microbial rhodopsins have been the main tools in optogenetics. Function of rhodopsins starts in 10-15 sec, and activation of rhodopsins occurs in the protein environment that has been optimized during evolution (1015 sec). We thus need various methods to understand these events of 30 orders of magnitude in time. We have studied molecular mechanism of rhodopsins by use of spectroscopic methods. Using ultrafast spectroscopy, we showed the primary event in our vision being retinal photoisomerization. In rhodopsins, photoisomerization of retinal, the shape-changing reaction, occurs even at 77 K. Using low-temperature infrared spectroscopy, we detected protein-bound water molecules of rhodopsins before X-ray crystallography. Detailed vibrational analysis provided structural information such as our color discrimination mechanism. I will talk about our spectroscopic study of animal and microbial rhodopsins. Recent unexpected findings such as unusual isomerization pathways and temperature effects are also presented.
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    Animal and Microbial Rhodopsins Colloquium website

    Shigella flexneri vacuolar rupture : Near-native in cellulo structure-function analysis

    Date:
    12
    Sunday
    March
    2023
    Lecture / Seminar
    Time: 13:30-14:30
    Location: Nella and Leon Benoziyo Building for Biological Sciences
    Lecturer: Léa SWISTAK
    Organizer: Department of Biomolecular Sciences
    Contact: levana.ayvazo@weizmann.ac.il
    Abstract: Shigella flexneri is a bacterial entero-invasive pathogen transmitted through th ... Read more Shigella flexneri is a bacterial entero-invasive pathogen transmitted through the fecal/oral route causing bacillary dysentery in humans. Shigella pathogenicity solely relies on a needle-like molecular syringe, the Type 3 Secretion System (T3SS) that injects more than 20 bacterial effectors to infect colonic epithelial cells. The T3SS is composed of a basal body that controls and initiates effector secretion and a needle complex that acts as a conduit for effector delivery. The needle is capped by a tip complex that regulates whether the needle is closed or whether it secretes. Sensing of host cells by the needle tip complex induces a conformational switch that remodels the tip and activates the T3SS to form a channel, the translocon pore at the distal end. Effectors are then actively secreted, promoting cell invasion and endocytosis of the bacteria in a tight vacuole derived from the host plasma membrane called Bacteria Containing Vacuole (BCV). Quickly after entry, the pathogen ruptures its BCV and establish a replicative cytosolic niche. Vacuolar rupture consists of a first step of BCV breakage followed by BCV remnants unpeeling. The team has identified bacterial effectors promoting efficient vacuole unpeeling but the direct role of the T3SS in membrane destabilization is not clear. I have overcome these limitations by investigating the T3SS/vacuole interactions at the onset of vacuolar rupture using a novel cryo-Correlative Light Electron Microscopy (CLEM) workflow applied in situ, during the host-pathogen crosstalk. Cryo-CLEM allows the combination of high-resolution information in 3D, accessed via cryo-Electron Tomography (cryo-ET) to functional information brought by light microscopy. This pipeline benefits from in-house custom-built genetically encoded reporter cell lines which are used to identify precise steps of the infection at high spatiotemporal resolution. Using this workflow, I collected cryo-ET data on Shigella-infected epithelial cells. I have been able to visualize the Shigella T3SS at molecular resolution providing unprecedented information. Particularly, I am looking at (i) the contact sites between T3SS and BCV membrane; (ii) T3SS morphologies depending on its activation state. Together this work will allow to precisely describe the interplay between host and bacteria processes.
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    High resolution in vivo NMR spectroscopy: A tale about cells, a fish and a worm

    Date:
    23
    Thursday
    February
    2023
    Lecture / Seminar
    Time: 09:30-10:30
    Location: Gerhard M.J. Schmidt Lecture Hall
    Lecturer: Prof. Andrés Binolfi
    Organizer: The Helen and Martin Kimmel Institute for Magnetic Resonance Research
    Contact: ana.naamat@weizmann.ac.il
    Abstract: To understand the functional properties of biomolecules, such a small metabolite ... Read more To understand the functional properties of biomolecules, such a small metabolites, protein or nucleic acids, we ought to study them with high resolution in their native context. NMR spectroscopy allows the direct observation of NMR-active nuclei in complex, undefined environments and can thus be employed to investigate isotopically enriched molecules inside live cells. This methodology is known as In-cell NMR and has been used to evaluate the structural properties of proteins, nucleic acids and other biomolecules in physiological environments and to resolve their functional characteristics in a cellular context. These methods have been applied to bacteria, yeasts or cultured mammalian cells. However these cells are clonally grown at high densities in artificial media, lacking the complex tissue context present in higher organisms and its associated biological activities. We funnel our efforts to extend In-cell NMR applications to in vivo conditions using zebrafish embryos and the nematode C. elegans as model organisms. We deliver 15N-isotopically enriched biomolecules, such as small compounds and proteins into fish embryos to delineate their conformational properties and enzymatic conversions. We also enrich live C. elegans with 13C atoms to directly interrogate about their metabolic compositions and enzymatic activities. Combined, these studies provide methodological advancements with regard to high resolution in vivo NMR applications.
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    Between Southern Caucasus and Near East: The Kura-Araxes culture in a wider context

    Date:
    26
    Thursday
    January
    2023
    Lecture / Seminar
    Time: 13:30
    Location: Room 590, Benoziyo Building for Biological Science, Weizmann Institute of Science
    Lecturer: Dr. Elena Rova
    Contact: harsh.raj@weizmann.ac.il
    Details: Please follow the link or Zoom ID to join remotely. Join Zoom Meeting: https:/ ... Read more Please follow the link or Zoom ID to join remotely. Join Zoom Meeting: https://weizmann.zoom.us/j/4845901524?pwd=dkYybWIvTXVSaW40YmF2TEVxVFg0UT09 Meeting ID: 484 590 1524 Meeting password: 045940
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    The Kura-Araxes culture between Caucasus and Near East: An Introduction Part 1

    Date:
    19
    Thursday
    January
    2023
    Lecture / Seminar
    Time: 13:30
    Location: Room 590, Benoziyo Building for Biological Science, Weizmann Institute of Science
    Lecturer: Dr. Elena Rova
    Contact: harsh.raj@weizmann.ac.il
    Details: Join Zoom Meeting: https://weizmann.zoom.us/j/4845901524?pwd=dkYybWIvTXVSaW40Ym ... Read more Join Zoom Meeting: https://weizmann.zoom.us/j/4845901524?pwd=dkYybWIvTXVSaW40YmF2TEVxVFg0UT09 Meeting ID: 484 590 1524 Meeting password: 045940
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    Biosynthesis of Plant Natural Products: from the Colours of Beet to Defences in Wheat

    Date:
    27
    Tuesday
    December
    2022
    Lecture / Seminar
    Time: 11:30-12:30
    Location: Nella and Leon Benoziyo Building for Biological Sciences
    Lecturer: Dr. Guy Polturak
    Organizer: Department of Plant and Environmental Sciences
    Contact: david.zeevi@weizmann.ac.il
    Abstract: Plants produce a vast range of specialized metabolites that serve various roles, ... Read more Plants produce a vast range of specialized metabolites that serve various roles, including mediating interactions with their immediate environments and providing defence against (a)biotic stresses. The ‘omics era’ has brought a new golden age for plant specialized metabolism research, vastly accelerating the discovery of novel metabolites and our understanding of their biosynthesis, roles and regulation. Two studies exemplifying omics-driven discovery of metabolic pathways, in beet and in wheat, will be presented: 1. Betalains are red-violet and yellow pigments restricted to order Caryophyllales, which have attracted interest due to their health-promoting properties and use as food colorants. Transcriptomics-led discovery of enzymes catalyzing the last unknown step in betalain biosynthesis in red beet enabled us to heterologously produce these pigments in plants and microbes, providing a valuable platform for studying their in-planta roles and enabling their subsequent utilization as reporter genes and plant transformation markers. 2. Wheat is one of the most widely grown crops in the world but is susceptible to numerous pests and pathogens, leading to major annual losses. Despite its agricultural importance, current knowledge of wheat chemical defenses remains very limited. Using a genome mining approach we uncovered six previously unknown pathogen-induced metabolic pathways in hexaploid bread wheat, which produce a diverse set of molecules and are encoded by biosynthetic gene clusters. Discovery and characterization of these cluster-encoded metabolic pathways provides key insights into the molecular basis of biotic stress responses in wheat, thus opening new potential avenues for improvement of this major food crop.
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    Beneficial microbe-plant interactions in milpa traditional agroecosystems and the effect of human intervention

    Date:
    15
    Tuesday
    November
    2022
    Lecture / Seminar
    Time: 11:30-12:30
    Location: Nella and Leon Benoziyo Building for Biological Sciences
    Lecturer: Dr. Jorge Rocha
    Organizer: Department of Plant and Environmental Sciences
    Contact: einat.segev@weizmann.ac.il
    Details: Host: Dr. Einat Segev
    Abstract: The health of plants depends largely on their interactions with microbes. Howeve ... Read more The health of plants depends largely on their interactions with microbes. However, crop modernization affects these interactions, resulting in plants that rely on excessive inputs such as fertilizers, pesticides, irrigation, etc. Milpas are rain-fed polyculture agroecosystems found in Mesoamerica, where native maize landraces are grown in association with other species. Plant health in milpas is achieved with traditional practices and, therefore, plant-microbe beneficial interactions play an essential role in productivity. Milpas are central to the lives people in rural populations, as local or even familiar traditions, festivities and food preferences influence agricultural practices, resulting in unique characteristics of each parcel that potentially generates a wide diversity of beneficial plant-microbe interactions. In this seminar, we will review our recent progress in the study of beneficial microbe-plant interactions in milpas, including: 1) abundance, functions and structure of maize seed-endophytic communities comparing native vs. modern hybrid varieties, where the effect of modernization can be analyzed; and 2) the contribution of microbes for drought tolerance of native maize landraces adapted to arid regions, to explore the selection of microbes with specific beneficial functions as a result of the farmers’ preferences.
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    “The immune system of bacteria: Beyond CRISPR”

    Date:
    08
    Tuesday
    November
    2022
    Lecture / Seminar
    Time: 10:00-11:00
    Location: Nella and Leon Benoziyo Building for Biological Sciences
    Lecturer: Prof. Rotem Sorek
    Organizer: Department of Biomolecular Sciences
    Contact: levana.ayvazo@weizmann.ac.il
    Abstract: The arms race between bacteria and phages led to the development of sophisticate ... Read more The arms race between bacteria and phages led to the development of sophisticated anti-phage defense systems, including CRISPR-Cas and restriction systems. We have recently reported that the microbial pan-genome contains many new defense systems whose function was so far unexplored. The talk will describe the functions of recently discovered new anti-phage systems. These include systems that utilize secondary metabolites for intracellular or as chemical defense against phages. Surprisingly, our studies show that bacterial defense from phage gave rise to key components in the eukaryotic immune system.
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    Mapping internal representations with adaptive sampling, massive online experiments and cross-cultural research

    Date:
    24
    Monday
    October
    2022
    Lecture / Seminar
    Time: 11:00-12:00
    Location: Nella and Leon Benoziyo Building for Biological Sciences
    Lecturer: Dr. Nori Jacoby
    Organizer: Department of Brain Sciences
    Contact: naomi.moses@weizmann.ac.il
    Details: ROOM 191 C-NEW
    Abstract: Our brain relies on internal representations to support perception, action, and ... Read more Our brain relies on internal representations to support perception, action, and decision-making. Internal representations are usually rich, multidimensional, and cannot be directly observed. How can these internal representations be characterized? How are they affected by experience? My work develops adaptive behavioral paradigms that integrate human decisions into computer algorithms via human-in-the-loop experiments. I combine these paradigms with a data-intensive expansion of the scale and scope of behavioral research by means of massive online experiments and cross-cultural comparative research. This talk presents “adaptive sampling,” a type of experimental paradigm inspired by Monte Carlo Markov Chain techniques. Each successive stimulus depends on a subject's response to the previous stimulus. This process allows us to sample from the complex and high-dimensional joint distribution associated with internal representations and obtain high-resolution maps of perceptual spaces. After introducing these methods and describing their implementation via large-scale online experiments and field experiments around the world, I demonstrate how they can be applied to fundamental questions in the understanding of the human mind. Specifically, I examine how biology and culture influence internal representations and how semantics influence perception.
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    How microbial interactions shape the exo-metabolic landscape of the ocean

    Date:
    12
    Tuesday
    July
    2022
    Lecture / Seminar
    Time: 11:30-12:30
    Location: Nella and Leon Benoziyo Building for Biological Sciences
    Lecturer: Dr. Constanze Kuhlisch
    Organizer: Department of Plant and Environmental Sciences
    Contact: david.zeevi@weizmann.ac.il
    Details: Host: Prof. Assaf Vardi
    Abstract: Algal blooms are events of high primary productivity and rapid population growth ... Read more Algal blooms are events of high primary productivity and rapid population growth that can cover vast oceanic regions. They thus play an important role for the marine food web and for the global carbon and sulfur cycling. Furthermore, algal blooms are hotspots of microbial interactions with e.g. grazers, heterotrophic bacteria, fungi and viruses. These interactions are mediated by metabolite signals, they can modulate metabolic pathways and can induce biosynthetic gene clusters – the diversity of microbial communities in natural blooms is thus crucial in understanding the chemical ecology of algal blooms. In my talk, I will show how lipid remodeling during the infection of E. huxleyi blooms by its giant virus imprints the marine dissolved organic matter pool. Further, I will present how a tripartite interaction between alga, virus and associated microbes leads to a unique halogenation activity during bloom demise. Lastly, I will discuss the potential ecological role of indole derivatives that accumulate in the blooms of E. huxleyi.
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    Self-assembling structure and function using equilibrium and non-equilibrium statistical mechanics

    Date:
    26
    Tuesday
    April
    2022
    Lecture / Seminar
    Time: 11:00-12:00
    Location: Gerhard M.J. Schmidt Lecture Hall
    Lecturer: Dr, Matan Ya Ben Zion
    Organizer: Department of Molecular Chemistry and Materials Science
    Contact: ana.naamat@weizmann.ac.il
    Abstract: Self-assembly and self-organization are two big challenges in the natural scienc ... Read more Self-assembly and self-organization are two big challenges in the natural sciences. What are the rules governing the emergence of greater structures from unassuming elements? Does statistical-mechanics restrict their complexity? Biochemical processes can shape highly specific structures and function on the macro-scale using only molecular information. Although stereochemistry has been a central focus of molecular sciences since Pasteur, its synthetic province has been restricted to the nanometric scale. In my talk, I will describe how to propagate molecular information to self-assemble free-form architectures on the micron-scale and beyond. These architectures are a thousand times greater than their constituent molecules yet have a preprogrammed geometry and chirality. I will then show how to animate such synthetic microstructures into bacteria-like micro-swimmers. Previous artificial microswimmers relied on an external chemical fuel to drive their propulsion which restricted their operational concentration as they competed locally over fuel. I will demonstrate how to use material science and physical chemistry to self-assemble fuel-free micro-swimmers that are driven solely by light. The fuel independence allows the swimmers to stay active even at high densities, where they form turbulent flow structures (previously seen in living fluids), and cooperate to perform a greater task.
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    Host innate immunity and bacterial commensals prevent fungal dysbiosis in Arabidopsis roots

    Date:
    12
    Tuesday
    April
    2022
    Lecture / Seminar
    Time: 11:30-12:30
    Location: VIA ZOOM: https://weizmann.zoom.us/j/98989152393?pwd=a050Mm4rSlEwb2hLN1FiKy9oT24xdz09 Meeting ID: 989 8915 2393 Password: 002663
    Lecturer: Prof. Stéphane Hacquard
    Organizer: Department of Plant and Environmental Sciences
    Contact: david.zeevi@weizmann.ac.il
    Details: Host: Dr. Daniel Dar
    Abstract: Understanding how host–microbe homeostasis is controlled and maintained in pla ... Read more Understanding how host–microbe homeostasis is controlled and maintained in plant roots is key to enhance plant productivity. However, the factors that contribute to the maintenance of this equilibrium between plant roots and their multikingdom microbial communities remain largely unknown. Using a microbiota deconstruction-reconstruction approach in gnotobiotic plant systems with synthetic, yet representative communities of bacteria, fungi, and oomycetes, we observe a link between fungal assemblages/load in roots and plant health. We show that modulation of fungal abundance in roots is tightly controlled by a two-layer regulatory circuit involving the host innate immune system on one hand and bacterial root commensals on another hand. We also report that fungi with the most detrimental activities in mono-association experiments with the host are part of the core root mycobiome in nature. Our results shed a light into how host–microbe and microbe–microbe interactions act in concert to prevent fungal dysbiosis in roots, thereby promoting plant health and maintaining growth-promoting activities of multikingdom microbial consortia.
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    Role of forces in membrane dynamics and tissue morphogenesis

    Date:
    05
    Tuesday
    April
    2022
    Lecture / Seminar
    Time: 10:00-11:00
    Location: Nella and Leon Benoziyo Building for Biological Sciences
    Lecturer: Prof. Marino Zerial
    Organizer: Department of Biomolecular Sciences
    Contact: levana.ayvazo@weizmann.ac.il
    Abstract: Our work has highlighted the function of Rab GTPases as key components for the b ... Read more Our work has highlighted the function of Rab GTPases as key components for the biogenesis, transport and function of cellular membrane organelles. The specificity and directionality of membrane fusion is mediated by Rab GTPases and tethering effectors, such as EEA1, which is recruited on the early endosome membrane and binds to Rab5. EEA1 is a long dimeric coiled-coil tether molecule. Upon binding to its N-terminus, Rab5 induces conformational changes on EEA1, from extended to a more flexible “collapsed” state, giving rise to an effective force. Our recent studies suggest that Rab5 and EEA1 effectively constitute a two-component molecular motor, cyclically converting the free energy of GTP binding and hydrolysis into mechanical work. We are now combining biochemical, quantitative image analysis and 3D primary cell culture approaches to explore the role of Rab GTPases and endocytic mechanisms in liver tissue organization and regeneration. Hepatocytes are polarized cells at the interface of both sinusoidal endothelial and bile canaliculi (BC) networks that transport blood and bile between portal and central vein, respectively. In contrast to simple epithelia, where the cells have a single apical surface facing the lumen of organs, hepatocytes exhibit a multipolar (biaxial) organization, i.e. have multiple apical and basal domains. We studied the mechanism of hepatocyte polarization by using a hepatoblasts culture system. We discovered that, during lumen formation, hepatoblasts create apical protrusions along the tight junction belt that connects them, suggesting that these are responsible for the anisotropic growth of apical lumina. These protrusions form a pattern reminiscent of the bulkheads of boats ships and planes. Similarly, the apical bulkheads of hepatocytes are structural elements which can provide such anisotropy and mechanical stability to the elongating cylindrical lumen under inner pressure.
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    Microbial and Antimicrobial Amyloids in the Fight Against Infections

    Date:
    29
    Tuesday
    March
    2022
    Lecture / Seminar
    Time: 10:00-11:00
    Location: Nella and Leon Benoziyo Building for Biological Sciences
    Lecturer: Prof. Meytal Landau
    Organizer: Department of Biomolecular Sciences
    Contact: levana.ayvazo@weizmann.ac.il
    Abstract: Amyloids are protein fibers with unique and strong structures, known mainly in t ... Read more Amyloids are protein fibers with unique and strong structures, known mainly in the context of neurodegenerative diseases. Surprisingly, amyloid fibers are secreted by species across kingdoms of life, including by microorganisms, and helps their survival and activity. Our laboratory published the first molecular structures of functional bacterial amyloid fibrils, which serve as key “weapons” making infections more aggressive. This exposed new routes for the development of novel antivirulence drugs. In addition, we identified peptides produced across species that provide antimicrobial protection that form amyloid fibrils, and determined their first high resolution structures. This amyloid-antimicrobial link signifies a physiological role in neuroimmunity for human amyloids.
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    New metabolic functions can rapidly evolve in microbes by multiple convergent mechanisms

    Date:
    01
    Tuesday
    February
    2022
    Lecture / Seminar
    Time: 11:30-12:30
    Title: Special Guest Seminar with Dr. Avihu Yona via zoom
    Location: https://weizmann.zoom.us/j/95436548996?pwd=Uk9yOVFrK0ZuTnRsdm5TY1JiM1NzQT09 Meeting ID: 954 3654 8996 Password: 356165
    Lecturer: Dr. Avihu Yona
    Organizer: Department of Plant and Environmental Sciences
    Contact: david.zeevi@weizmann.ac.il
    Details: Host: Dr. David Zeevi
    Abstract: Many plant foods contain oxalate C2O4(-2) that reaches the colon when we eat pla ... Read more Many plant foods contain oxalate C2O4(-2) that reaches the colon when we eat plant foods. When oxalate reaches high concentrations it can crystalize together with Ca+2 to form kidney stones. Humans don’t have enzymes to degrade oxalate, but microbes do. Therefore oxalate-degrading probiotics are a potential treatment for hyperoxaluria. Since clinical trials with oxalate-degrading microbes, like Oxalobacter Formigenes, could not show oxalate reduction, additional microbes that can degrade oxalate are of high interest, especially those that can perform in the human gut. In my talk I will describe how we harnessed lab evolution to develop novel gut microbes that can degrade oxalate. We obtained E. coli isolates from the stool of human volunteers and evolved them to metabolize oxalate in an anaerobic chamber. While no E. coli is known to utilize oxalate, our isolates evolved robust growth on oxalate as a sole source of carbon and energy. In my talk I will present findings on the genetic and molecular mechanism underlying this evolution.
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    Membraneless Organelles and Wisdom of the Crowds: Novel Mechanisms Underlying Regulation in Bacteria

    Date:
    14
    Tuesday
    December
    2021
    Lecture / Seminar
    Time: 11:30-12:30
    Location: Nella and Leon Benoziyo Building for Biological Sciences
    Lecturer: Prof. Orna Amster-Choder
    Organizer: Department of Plant and Environmental Sciences
    Contact: david.zeevi@weizmann.ac.il
    Details: Host: Dr. David Zeevi
    Abstract: The poles of rod-shaped bacteria are emerging as a “microBrain”, serving as ... Read more The poles of rod-shaped bacteria are emerging as a “microBrain”, serving as hubs for sensing and regulation. Not only do they contain specific proteins, but we have shown that they contain a unique RNA population, which includes most small regulatory RNAs (sRNA). Upon stress, most sRNAs massively accumulate at the poles with the RNA chaperone Hfq. We have recently provided a proof-of-concept for the existence of a polygenic plan for sRNA-mediated regulation, with the poles providing an arena for its implementation. In my talk, I will show that the mechanism underlying this plan is assembly of Hfq with polar condensates, which a new pole-localizer, TmaR, forms by liquid-liquid phase separation (LLPS). I will further show that this LLPS-driven membraneless polar organelle serves as a hub for regulating various bacterial survival strategies.
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    Physics Colloquium

    Date:
    09
    Thursday
    December
    2021
    Colloquium
    Time: 11:15-12:30
    Title: Cell cycle regulation in microbes
    Location: Edna and K.B. Weissman Building of Physical Sciences
    Lecturer: Prof. Ariel Amir
    Organizer: Faculty of Physics
    Contact: tamar.fuchs@weizmann.ac.il
    Details: 10:50 - Coffee, tea and more in Benozyio physics lobby
    Abstract: Microbial cells are remarkable in their abilities to adapt to different environm ... Read more Microbial cells are remarkable in their abilities to adapt to different environments while maintaining cellular homeostasis. How cells coordinate the various events within the cell cycle, notably cell division and DNA replication, remains an outstanding problem for cells of all domains of life. I will discuss our current understanding of cell cycle regulation in microbes, including recent results demonstrating a tight coupling between DNA replication and cell division in E. coli.
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    MicroEco2 Microbial Ecology Symposium for Young Researchers

    Date:
    09
    Thursday
    December
    2021
    Conference
    Time: 08:00
    Location: David Lopatie Conference Centre
    Organizer: Knell Family Center for Microbiology
    Contact: noa.barak@weizmann.ac.il
    MicroEco2 Microbial Ecology Symposium for Young Researchers Conference website

    Biogeochemical consequences of host-virus interactions in marine diatoms

    Date:
    23
    Tuesday
    November
    2021
    Lecture / Seminar
    Time: 11:30-12:30
    Title: Guest seminar
    Location: Benoziyo Bldg. for Biological Sciences Auditorium - Floor 1
    Lecturer: Dr. Chana Kranzler
    Organizer: Department of Plant and Environmental Sciences
    Contact: david.zeevi@weizmann.ac.il
    Details: Host: Prof. David Zeevi
    Abstract: Diatoms are among the most globally distributed and ecologically successful orga ... Read more Diatoms are among the most globally distributed and ecologically successful organisms in the modern ocean, contributing upwards of 40% of total marine primary productivity. Diatom production is tightly coupled with carbon export through the ballasted nature of the silica-based cell wall, linking the oceanic silicon and carbon cycles. While viruses are considered key players in ocean biogeochemical cycles, little is known about how viral infection specifically impacts diatom populations. Using a suite of molecular, physiological and geochemical approaches, we explored diatoms and associated viruses across diverse nutrient regimes in the northeast Pacific. We found that silicon (Si) limitation facilitated virus infection and mortality in diatoms while the onset of iron (Fe) limitation, in sharp contrast, substantially reduced viral replication. These findings, recapitulated in model systems, suggest that virus-mediated mortality in Si-limited regimes would facilitate diatom remineralization in the surface ocean, while diatoms in Fe-limited regimes may escape viral lysis, ultimately contributing to carbon export. We also explored how viral infection of diatoms might impact the microbial processing of organic matter in the ocean. Using bacterial isolates and model diatom host-virus systems, we tested how bacteria respond to dissolved organic matter generated during viral infection in diatoms. We found that this material can significantly stimulate ectoproteolytic activity, implicating viral infection of diatoms in bacteria-mediated recycling of organic matter and silica in the surface ocean. Together, these findings highlight the dynamic role that diatom host–virus interactions play in shaping the biogeochemical landscape the global ocean.
    Close abstract

    Systematic Discovery and Characterization of Microbial Toxins

    Date:
    16
    Tuesday
    November
    2021
    Lecture / Seminar
    Time: 11:30-12:30
    Title: Guest seminar
    Location: Nella and Leon Benoziyo Building for Biological Sciences
    Lecturer: Dr. Asaf Levy
    Organizer: Department of Plant and Environmental Sciences
    Contact: david.zeevi@weizmann.ac.il
    Details: Host: David Zeevi
    Abstract: Microbes use protein toxins to kill competitors and to infect host cells. Discov ... Read more Microbes use protein toxins to kill competitors and to infect host cells. Discovering new toxins and describing their function is important to understand processes in microbial ecology and host-microbe interactions. Moreover, the toxins can be used in various applications, including drugs, pesticides, vaccines, potent enzymes, etc. We study toxins in the lab by combining large-scale computational genomics and molecular microbiology. In the talk, I will tell two recent stories from the lab on microbial toxins and their secretion systems. The first study is about the mysterious extracellular contractile injection system. This toxin delivery system evolved from a phage into a molecular weapon employed by bacteria against eukaryotic cells. In the second study, I will tell about the exciting group of polymorphic toxins. These are large toxin proteins that undergo recombination to create large diversity of antimicrobial toxins. We developed methods to discover toxins from both groups, study the ecological role of the toxins, and their molecular function. These approaches led to discovery of over 30 novel microbial toxins that we study in the lab.
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    Unraveling the microscale mechanisms driving particle degradation in the ocean

    Date:
    26
    Tuesday
    October
    2021
    Lecture / Seminar
    Time: 11:30-12:30
    Location: https://weizmann.zoom.us/j/96896290817?pwd=WmoxNzZSRFArL3VzNUY3bHRpZFZoQT09 Password: 230371
    Lecturer: Dr. Uria Alcolombri
    Organizer: Department of Plant and Environmental Sciences
    Contact: merav.hagag@weizmann.ac.il
    Details: Host: Prof. Asaph Aharoni
    Abstract: The sinking of organic particles in the ocean and their degradation by marine mi ... Read more The sinking of organic particles in the ocean and their degradation by marine microorganisms drive one of the most conspicuous carbon fluxes on Earth, the biological pump. Yet, the mechanisms determining the magnitude of the pump remain poorly understood, limiting our ability to predict this carbon flux in future ocean scenarios. Current ocean models assume that the biological pump is governed by the competition between sinking speed and degradation rate, with the two processes independent from one another. In this talk, I will demonstrate that contrary to this paradigm, sinking itself is a primary determinant of the rate at which bacteria enzymatically degrade particles in the ocean. By combining video microscopy and microfluidic experiments to directly observe and quantify bacterial degradation of individual organic particles in flow, I will show that even modest sinking speeds of 8 meters per day enhance degradation rates more than 10-fold. I will further discuss the molecular mechanism behind the sinking-enhanced degradation, as well as possible ways by which bacteria can slow the sinking of particles. Finally, using the results obtained from a mathematical model, I will show that the coupling of sinking and degradation may contribute to determining the magnitude of the vertical carbon flux in the ocean, and will outline major open questions in the field.
    Close abstract

    Unraveling the microscale mechanisms driving particle degradation in the ocean

    Date:
    26
    Tuesday
    October
    2021
    Lecture / Seminar
    Time: 11:30-12:30
    Title: Guest Seminar via zoom
    Location: https://weizmann.zoom.us/j/96896290817?pwd=WmoxNzZSRFArL3VzNUY3bHRpZFZoQT09 Password: 230371
    Lecturer: Dr. Uria Alcolombri
    Organizer: Department of Plant and Environmental Sciences
    Contact: merav.hagag@weizmann.ac.il
    Details: Host: Prof. Asaph Aharoni
    Abstract: The sinking of organic particles in the ocean and their degradation by marine mi ... Read more The sinking of organic particles in the ocean and their degradation by marine microorganisms drive one of the most conspicuous carbon fluxes on Earth, the biological pump. Yet, the mechanisms determining the magnitude of the pump remain poorly understood, limiting our ability to predict this carbon flux in future ocean scenarios. Current ocean models assume that the biological pump is governed by the competition between sinking speed and degradation rate, with the two processes independent from one another. In this talk, I will demonstrate that contrary to this paradigm, sinking itself is a primary determinant of the rate at which bacteria enzymatically degrade particles in the ocean. By combining video microscopy and microfluidic experiments to directly observe and quantify bacterial degradation of individual organic particles in flow, I will show that even modest sinking speeds of 8 meters per day enhance degradation rates more than 10-fold. I will further discuss the molecular mechanism behind the sinking-enhanced degradation, as well as possible ways by which bacteria can slow the sinking of particles. Finally, using the results obtained from a mathematical model, I will show that the coupling of sinking and degradation may contribute to determining the magnitude of the vertical carbon flux in the ocean, and will outline major open questions in the field.
    Close abstract

    Plant immune system activation is necessary for efficient interaction with auxin secreting beneficial bacteria

    Date:
    12
    Tuesday
    October
    2021
    Lecture / Seminar
    Time: 15:00-16:00
    Title: Guest Seminar via Zoom
    Location: https://weizmann.zoom.us/j/97684910013?pwd=ai9wWUZQNWdVRVU2Y3laaUlWRmdwUT09 Password 973838
    Lecturer: Dr. Elhanan Tzipilevich
    Organizer: Department of Plant and Environmental Sciences
    Contact: david.zeevi@weizmann.ac.il
    Details: Host: Prof. Asaph Aharoni
    Abstract: Plants continuously monitor the presence of microorganisms through their immune ... Read more Plants continuously monitor the presence of microorganisms through their immune system to establish an adaptive response. Unlike immune recognition of pathogenic bacteria, mechanisms by which beneficial bacteria interact with the plant immune system are not well understood. Analysis of colonization of Arabidopsis thaliana by auxin producing beneficial bacteria revealed that activating the plant immune system is necessary for efficient bacterial colonization and auxin secretion. A feedback loop is established in which bacterial colonization triggers an immune reaction and production of reactive oxygen species, which, in turn, stimulate auxin production by the bacteria. Auxin promotes bacterial survival and efficient root colonization, allowing the bacteria to compete with other members of the root microbial community and inhibit fungal infection, promoting plant health.
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    Plant immune system activation is necessary for efficient interaction with auxin secreting beneficial bacteria Lecture / Seminar website

    Conservation of TIR immune signaling in bacteria and plants

    Date:
    06
    Tuesday
    July
    2021
    Lecture / Seminar
    Time: 11:30-12:30
    Title: Guest Seminar via Zoom
    Location: https://weizmann.zoom.us/j/94920680518?pwd=MDhOVUZsQWRaMGZSYndIME5lZGtRdz09 Password 151190
    Lecturer: Gal Ofir
    Organizer: Department of Plant and Environmental Sciences
    Contact: nicole.friesem@weizmann.ac.il
    Details: Host: Prof. Avraham Levy

    Synchronization and spatial coherence of noisy circadian clocks in a multicellular1-d organism

    Date:
    24
    Thursday
    June
    2021
    Colloquium
    Time: 11:15-12:30
    Location: https://weizmann.zoom.us/j/94477142638?pwd=aWNlZGVzNmdJdnJVZVNZUi9sZ0VBZz09
    Lecturer: Joel Stavans
    Organizer: Faculty of Physics
    Contact: tamar.fuchs@weizmann.ac.il
    Details: 11:00: coffee, tea and more. The colloquium will be Hybrid - you can attend i ... Read more 11:00: coffee, tea and more. The colloquium will be Hybrid - you can attend in person in Weissman Auditorium and it will be also broadcast in zoom.
    Close details
    Abstract: The collective behavior of oscillators is a venerable subject in Physics since H ... Read more The collective behavior of oscillators is a venerable subject in Physics since Huygens’ seminal contributions. Living systems, from simple unicellular bacteria to multicellular plants and mammals also display oscillatory dynamics, the most conspicuous of which are circadian rhythms, coupling the biology of these organisms to day/night cycles on Earth. While considerable headway has been made in understanding the behavior of individual circadian clocks and their molecular components, the behavior of a large collection of clocks is still poorly understood, constituting a fertile ground of inquiry. We studied at the single-cell level the collective behavior of one-dimensional arrays of clocks in Anabaena, a cyanobacterial organism of ancient origin, as a model system. Anabaena filaments display remarkable synchrony and spatial coherence at the organismal scale, despite considerable and yet inevitable fluctuations in each cell –demographic noise-, stemming from the stochastic nature of biochemical reactions. Furthermore, we provide experimental evidence supporting the notion that spatio-temporal coherence is largely due to the coupling of clocks by cell-cell communication, and that the clock controls other cellular processes such as cell division. A stochastic, one-dimensional toy model of coupled clocks shows that demographic noise can seed stochastic oscillations outside the region where deterministic limit cycles with circadian periods occur. The model reproduces the observed spatio-temporal coherence along filaments and provides a robust description of coupled circadian clocks in a multicellular organism.
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    The human body from a quantitative perspective: cells, bacteria and SARS-CoV-2

    Date:
    01
    Tuesday
    June
    2021
    Lecture / Seminar
    Time: 11:30-12:30
    Title: Hybrid Dept. Seminar
    Location: Nella and Leon Benoziyo Building for Biological Sciences
    Lecturer: Ron Sender
    Organizer: Department of Plant and Environmental Sciences
    Contact: nicole.friesem@weizmann.ac.il
    Details: Host: Prof. Ron Milo

    Aerobic Bacteria Produce Nitric Oxide Through Denitrification During Microbial Interactions

    Date:
    06
    Tuesday
    April
    2021
    Lecture / Seminar
    Time: 11:30-12:30
    Title: Dept. Seminar via Zoom
    Location: https://weizmann.zoom.us/j/93820152550?pwd=c0QzK3VTcjZpditUSGNwQzBKb0gvUT09 Password 419056
    Lecturer: Dr. Adi Abada
    Organizer: Department of Plant and Environmental Sciences
    Contact: nicole.friesem@weizmann.ac.il
    Details: Host: Dr. Einat Segev

    Diatom modulation of associated bacteria

    Date:
    09
    Tuesday
    March
    2021
    Lecture / Seminar
    Time: 11:30-12:30
    Title: Guest Seminar via Zoom
    Location: https://weizmann.zoom.us/j/91943922657?pwd=QnF1eThwV0lWTk45ZWFBWnlHeGx2Zz09Password620591
    Lecturer: Dr. Ahmed Shibl
    Organizer: Department of Plant and Environmental Sciences
    Contact: nicole.friesem@weizmann.ac.il
    Details: Host: Dr. Einat Segev

    Live imaging of chromatin distribution reveals novel principles of nuclear architecture and chromatin compartmentalization”.

    Date:
    31
    Sunday
    January
    2021
    Lecture / Seminar
    Time: 11:00-12:00
    Lecturer: Prof. Talila Volk
    Organizer: Department of Molecular Chemistry and Materials Science
    Contact: ana.naamat@weizmann.ac.il
    Abstract: Zoom Link: https://weizmann.zoom.us/j/91657907719?pwd=M2F2WlRKWGRuUHlxN0tNWF ... Read more Zoom Link: https://weizmann.zoom.us/j/91657907719?pwd=M2F2WlRKWGRuUHlxN0tNWFhZVUVzZz09 The genetic material of live organisms is packed and stored within the nucleus. It contains DNA wrapped around the nucleosomes, which then organized into chromatin fibers that partition into distinct compartments, which eventually fill the entire nucleus. Chromatin three dimensional topology is essential for proper accessibility of transcription factors, which control tissue-specific gene expression programs. Whereas chromatin partition into specific domains has been described in cells in culture conditions, information regarding chromatin 3 dimensional distribution in tissues within live organisms is still missing. We have imaged the chromatin in muscle fibers of live, intact Drosophila larvae, and revealed its 3 dimensional structure. Our results demonstrate novel 3 dimensional architecture of the chromatin which is evolutionary conserved, and has important implications on the regulation of gene expression.
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    MicroEco 2020

    Date:
    06
    Wednesday
    January
    2021
    -
    07
    Thursday
    January
    2021
    Conference
    Time: 08:00
    Location: David Lopatie Conference Centre
    Contact: microeco2020@gmail.com
    MicroEco 2020 Conference website