Biology subjects

Lynch, J. B.

Publications and source records attributed to Lynch, J. B..

3 recordsLinked to original sources

bioRxiv2022

Turicibacter modifies host bile acids and lipids in a strain-specific manner

Bacteria from the Turicibacter genus are prominent members of the mammalian gut microbiota and are associated with alterations in dietary fat and body weight, but the specific connections between these symbionts and host physiology are poorly understood. We genomically and phenotypically characterized a diverse set of mouse-and human-derived Turicibacter strains, and found they group into three clades that differ in their transformations of bile acids. We identified Turicibacter bile salt hydrolases that confer strain-specific differences in bile deconjugation. Colonization with individual Turicibacter strains led to changes in host bile acid profiles, generally aligning with those produced in vitro. Further, colonizing mice with another bacterium expressing bile-modifying genes from these strains decreased serum cholesterol and triglycerides, as well as adipose tissue mass. This work identifies genes that enable diverse Turicibacter strains to differentially modify host bile acids and lipid metabolism, and positions multiple Turicibacter strains as candidates for altering host fat biology. MAIN TEXT

microbiology↗

bioRxiv2021

Transitioning to confined spaces impacts bacterial swimming and escape response

Symbiotic bacteria often navigate complex environments before colonizing privileged sites in their host organism. Chemical gradients are known to facilitate directional taxis of these bacteria, guiding them towards their eventual destination. However, less is known about the role of physical features in shaping the path the bacteria take and defining how they traverse a given space. The flagellated marine bacterium Vibrio fischeri,which forms a binary symbiosis with the Hawaiian bobtail squid, Euprymna scolopes, must navigate tight physical confinement, squeezing through a bottleneck constricting to ~2 m in width on the way to its eventual home. Using microfluidic in vitro experiments, we discovered that V. fischeri cells alter their behavior upon entry into confined space, straightening their swimming paths and promoting escape from confinement. Using a computational model, we attributed this escape response to two factors: reduced directional fluctuation and a refractory period between reversals. Additional experiments in asymmetric capillary tubes confirmed that V. fischeri quickly escape from tapered ends, even when drawn into the ends by chemoattraction. This avoidance was apparent down to a limit of confinement approaching the diameter of the cell itself, resulting in a balance between chemoattraction and evasion of physical confinement. Our findings demonstrate that non-trivial distributions of swimming bacteria can emerge from simple physical gradients in the level of confinement. Tight spaces may serve as an additional, crucial cue for bacteria while they navigate complex environments to enter specific habitats. Significance StatementSymbiotic bacteria that navigate to and through specific host tissues often face tight physical confinement. This work reveals that confinement-associated changes in swimming can dramatically alter taxis, shaping bacterial localization in conjuncture with other motility-directing cues. This work helps explain how bacteria can avoid getting stuck in confined areas while transiting to privileged spaces, adding confinement as an environmental cue that symbiotic bacteria use to shape their motility behavior.

biophysics↗

bioRxiv2021

Independent host- and bacterium-based determinants protect a model symbiosis from phage predation

Summary/AbstractBacteriophages (phages) are diverse and abundant constituents of microbial communities worldwide, and are capable of modulating bacterial populations in diverse ways. Here we describe a novel phage, {phi}HNL01, which infects the marine bacterium Vibrio fischeri. We use culture-based approaches to demonstrate that mutations in the exopolysaccharide locus of V. fischeri render this bacterium resistant to infection by {phi}HNL01, highlighting the extracellular matrix as a key determinant of phage tropism in this interaction. Additionally, using the natural symbiosis between V. fischeri and the squid Euprymna scolopes, we show that during colonization, V. fischeri is protected from phage present in the ambient seawater. Taken together, these findings shed light on independent yet synergistic host- and bacterium-based strategies for resisting symbiosis-disrupting phage predation, and present important implications for understanding these strategies in the context of host-associated microbial ecosystems.

microbiology↗