Bulletin of the American Physical Society
APS March Meeting 2023
Volume 68, Number 3
Las Vegas, Nevada (March 5-10)
Virtual (March 20-22); Time Zone: Pacific Time
Session W06: Bacterial Communities IIFocus
|
Hide Abstracts |
Sponsoring Units: DBIO Chair: Jay Tang, Brown University Room: Room 129 |
Thursday, March 9, 2023 3:00PM - 3:36PM |
W06.00001: Electron Flow in Biofilm Matrix: Impact of Chemical Composition and Context Invited Speaker: Jinyang Li Bacterial biofilms are a serious global health concern because they are notoriously difficult to eradicate. In biofilms, cells are subjected to resource limitations (e.g., O2). To promote anaerobic survival, certain microbes, such as Pseudomonas aeruginosa (P.a.), can use diffusible extracellular electron shuttles to transport electrons to O2 at a distance, a process known as extracellular electron transfer (EET). How do these small molecule electron shuttles catalyze EET in a complex and dynamically changing extracellular matrix without being lost to the environment? In other words, how do electrons move efficiently within the biofilm? Our recent work demonstrated that the extracellular P.a. biofilm matrix supports efficient electron transfer by retaining phenazines, a well-studied electron shuttle class, through binding extracellular DNA (eDNA). This discovery raises questions about the electron transfer mechanisms underpinning EET (e.g., molecular diffusion vs. electron hopping), and how they can be tuned as a function of matrix composition and environmental context. Here we show exopolysaccharides, another key component of the matrix, can compete with the binding between phenazines and eDNA by interacting with eDNA, and these interactions depend on the chemical environment within biofilms (e.g., redox and pH). To provide a mechanistic understanding of EET in biofilms, we fabricated well-defined synthetic hydrogels mimicking P.a. biofilm matrices, and characterized the mechanisms underpinning EET efficiency of both hydrogels and P.a. biofilms with distinct compositions under different conditions. This work begins to shed light on how microbes adapt to changing environmental conditions by producing matrices of different electronic properties, and raises the possibility that the extracellular matrix composition is a strategy whereby diverse microbes optimize EET. |
Thursday, March 9, 2023 3:36PM - 3:48PM |
W06.00002: Spontaneous phase separation in Vibrio cholerae bacterial biofilms Alexis P Moreau Bacterial biofilms are ubiquitous surface-associated bacterial communities embedded in a matrix. However, how the matrix components interact with each other and with cells to scaffold the biofilm structure remains poorly understood. The biofilm matrix in Vibrio cholerae (Vc), the causative agent of pandemic cholera and our model biofilm former is primarily composed of Vibrio polysaccharide (VPS), accessary matrix proteins, and in some cases extracellular DNA. Here, we couple bacterial genetics, high-resolution imaging, and biochemistry to study the self-organization of extracellular matrix in biofilms formed by Vc. We found, surprisingly, that Vc culture undergoes spontaneous phase separation (PS), both in vitro and in vivo, since Vc cells do not possess a specific attraction to their own secreted polymers. Furthermore, by coupling single-cell imaging techniques with immunostaining, we followed the evolution of VPS structures during PS. Our approach addresses the critical need to understand the formation of bacterial biofilms to posteriori use new strategies to disrupt and/or eliminate biofilms by interfering with the PS process. |
Thursday, March 9, 2023 3:48PM - 4:00PM |
W06.00003: How bacteria use electrochemical potentials to solve complex problems Gurol Suel |
Thursday, March 9, 2023 4:00PM - 4:12PM |
W06.00004: Experimental macroecology in microbial systems William R Shoemaker, Alvaro Sanchez, Jacopo Grilli Historically the field of ecology has benefitted by characterizing statistical patterns of biodiversity within and across communities, i.e., macroecology. This approach has achieved considerable success in microbial ecology in recent years, having identified universal patterns of diversity and abundance that can be captured by a single effective model: the stochastic logistic model of growth (SLM). Experimentation has simultaneously played a crucial role in the field’s development, as the manipulation of high-replication time-series has revealed novel forces that govern community dynamics. However, there remains a gap between the experiments we perform in the laboratory and the patterns we observe in nature. Here, we bridge the gap between the experimental manipulation of communities and their resulting macroecological effects. Using high-replication time-series of experimental microbial communities, we demonstrate that macroecological laws observed in nature can be readily recapitulated in a laboratory setting and unified under the SLM. We find that demographic manipulations and their effect on variation can alter specific empirical patterns in a manner that diverges from our predictions, though the predictive capacity of the SLM can be restored by explicitly incorporating experimental details. Finally, we demonstrate the extent that experimental manipulations are capable of altering macroecological patterns under the SLM, establishing a demarcation between patterns we can and cannot observe in a laboratory setting. |
Thursday, March 9, 2023 4:12PM - 4:24PM |
W06.00005: Host heterogeneity in C. elegans drives variation in gut microbial composition Satya Spandana Boddu, K. Michael Martini, Ilya M Nemenman, Nic M Vega Microbiomes are coexisting communities of microbes that are important for the functioning and health of the host. Microbiome composition and structure vary across individual hosts, but the sources of variation observed in microbiomes are not understood. Differences in interactions among microbes and between microbes and the host can contribute to this variation. We use a bottom-up experimental approach to understand microbiome assembly rules from in vivo monocolonization of the C. elegans gut by members of the native worm microbiome. We measure variation in bacterial abundance across the population of clonal hosts at different times in the colonization process. By fitting the resulting data to a simple stochastic model, we extract parameters of host-microbe association and identify sources of inter-host variation. To the extent that large inter-host variation is present even when bacterial interactions are eliminated, host heterogeneity drives the colonization variability. These results provide an initial step in understanding the role of host heterogeneity in general assembly rules for C. elegans gut microbiome. |
Thursday, March 9, 2023 4:24PM - 4:36PM |
W06.00006: Mechanics and microstructure in biofilms and their interactions with the immune system: Why you should care, and why I think this intersection is understudied. Vernita Gordon, Gordon Christopher, Kendra P Rumbaugh Biofilms are aggregates of bacteria and other microbes that are bound together in a matrix of polymer and protein. When a person develops a biofilm infection, neutrophils, a type of white blood cell, try to clear the infection. Neutrophils' initial clearance attempts are based on phagocytosis, or engulfing microbes, but they are ~10x smaller than typical aggregates in biofilm infections, so they cannot engulf the aggregate whole - if they are to clear biofilm microbes by phagocytosis, they must do so one to a few cells at a time, by extracting pathogens from the biofilm matrix and engulfing them. This is a slow, mechanically-localized process about which almost nothing is known. |
Thursday, March 9, 2023 4:36PM - 4:48PM |
W06.00007: Pseudomonas aeruginosa contracts mucus to rapidly form biofilms in tissue-engineered human airways Tamara Rossy, Tania Distler, Joern Pezoldt, Jaemin Kim, Lorenzo Talà, Nikolaos Bouklas, Bart Deplancke, Alexandre Persat Bacteria predominantly live as biofilms, a lifestyle conferring protection against threats such as antibiotics and a common cause of chronic infections. Studies of biofilms are mostly performed on stiff abiotic substrates, thereby lacking physical aspects of soft human tissues. To understand how mechanical tissue properties influence biofilm biogenesis, we developed a tissue-engineered airway called AirGel, composed of a tube-shaped epithelium in an optically-clear matrix. Cells in AirGels secrete a viscoelastic mucus gel, which is the first line of defense against inhaled pathogens. By infecting AirGels with Pseudomonas aeruginosa we could visualize biofilm formation in real time. We found that biofilms form unexpectedly rapidly, within hours. A contraction of the mucus gel substrate speeds up biofilm formation. We found that P. aeruginosa caused this contraction using retractile filaments called type IV pili. As mucus contracts, bacteria are brought closer to each other, nucleating aggregation and fusion of existing clusters. Overall, we uncovered a novel mechanism of mucus-pathogen interaction. |
Thursday, March 9, 2023 4:48PM - 5:00PM |
W06.00008: Active bulging promotes biofilm formation in a bacterial swarm Siyu Liu, Ye Li, Yilin Wu, Daniel Kearns Microbial communities such as biofilms are commonly found at interfaces. However, it is unclear how the physical environment of interfaces may contribute to the development and behavior of surface-associated microbial communities. Combining multi-mode imaging, single-cell tracking and numerical simulations, here we discovered that an interfacial process denoted as "active bulging" promotes biofilm formation. During this process, an initially two-dimensional layer of swarming bacteria spontaneously develops scattered liquid bulges; the bulges have a higher propensity to transit from motile to sessile biofilm state, presumably due to the enrichment of pre-existing immotile cells in the colony. We further demonstrate that the formation of liquid bulges can be controlled reversibly by manipulating the speed and local density of cells with light. Our findings reveal a unique physical mechanism of biofilm formation and provide a new strategy for biofilm patterning in engineered living materials as well as for directed self-assembly in active fluids. |
Thursday, March 9, 2023 5:00PM - 5:12PM |
W06.00009: Probing Intercellular Interactions in Dynamic Clusters of Swarming Bacteria Jay X Tang Expansion of dense bacterial populations over surfaces with collective dynamics driven by flagella, known as bacterial swarming, is often considered as a precursor to the growth of biofilms. However, it is an open question whether these two major types of microbial communities are governed by similar mechanisms at the molecular and microscopic levels. Underlying questions can include: what types of cell-cell interactions exist between neighboring cells, what types of polymeric materials are present at the cell surface or in the extracellular space, what signaling or surface active molecules are involved, and what osmolytes are required, if any. To probe for intercellular interactions, we performed experiments on Pseudomonas aeruginosa and Enterobacter sp. SM3, which are two distinct species that are both strong swarmers. By observing the collective motion exhibited in the swarms of both species of bacteria, in particular the dynamic packs of motile SM3 cells upon dilution as compared with their motility in the planktonic state, our study demonstrates to what extent cell-cell interactions exist and affect collective behaviors. The experimental results of these studies will help elucidate the physical mechanisms that dictate the growth and behavior of bacterial communities. |
Thursday, March 9, 2023 5:12PM - 5:24PM |
W06.00010: Substrate stiffness impacts early biofilm formation by modulating twitching motility sigolene Lecuyer, Delphine Débarre, Sofia Gomez Ho, Karin John, Lionel Bureau Biofilms stem from the surface colonization of a wide variety of substrates, from living tissues to inert materials. The influence of mechanical interactions during this process is still unclear. Here, we explore the role of substrate rigidity on early biofilm development, using Pseudomonas aeruginosa as a model organism. |
Thursday, March 9, 2023 5:24PM - 5:36PM |
W06.00011: Run-and-Tumble Analysis of Enterobacter Sp. SM3 Silverio G Johnson, Brian Freedman, Sridhar Mani, Jay X Tang We present first findings of the run-and-tumble behavior of the newly-discovered, swarm-competent bacterium enterobacter sp. SM3. SM3 has been shown to reduce stomach lining inflammation in mice afflicted with irritable bowel disease (De et al., Gastroenterology, 2021) and it offers a new opportunity to elucidate the physical mechanism of swarming motility. To better understand the swarming motility of SM3, and thereby gain insight into the connection between swarming and inflammation, it is a useful initial step to measure SM3 in its state as individual swimmers. Here we demonstrate how relevant run-and-tumble behavior, characterized by physical parameters such as the tumble time, run time, and tumble angle, vary with factors including exposure to various chemicals and whether SM3 is taken from a swarm prior to its release in an aqueous environment. These results are compared to those of E. coli to determine the extent to which they share run-and-tumble type swimming behavior. Our data also serve as a benchmark for understanding the connection between swimming and swarming motility. |
Thursday, March 9, 2023 5:36PM - 5:48PM Author not Attending |
W06.00012: From run-and-tumble to hopping-and-trapping: Bacterial foraging in porous landscapes Miles Wetherington Recent studies using porous environments have elucidated an alternative bacterial foraging strategy to the prototypical run-and-tumble dynamics previously believed to be the sole method of foraging in Escherichia coli. Using this ‘hopping-and trapping’ foraging strategy, E. coli traverses patchy landscapes more efficiently by rapidly exploring various cell-body orientations when trapped, allowing it to exploit narrow corridors and escape confined locations. While believed to be a response to a change in porosity, exactly how the cell recognizes when to transition between these two strategies is still unknown. Additionally, it is unclear whether heightened cell density is perceived as a dynamic porous landscape leading to a foraging switch. In this work we investigate these open-ended questions using porous and patchy microfluidic landscapes. Extensions are made of this framework to Pseudomonas aeruginosa, previously characterized swimming in a ‘run-reverse-pause’ strategy using its single flagellum. |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700