Biology subjects

Guessous, G.

Publications and source records attributed to Guessous, G..

4 recordsLinked to original sources

bioRxiv2026

Counting to two: how phages decide between lysis and lysogeny

Upon infecting a bacterium, temperate phages must decide between killing the cell to reproduce (lysis) and entering a symbiotic lifestyle (lysogeny). This choice is often informed by the cells state and by the number of infecting phage particles, or multiplicity of infection (MOI). Because the copy numbers of all phage genes scale identically with MOI, an MOI-dependent decision requires a rapidly established asymmetry between the lytic and lysogenic pathways. We introduce a minimal model showing how a simple coupling to host machinery (e.g. a protease) can generate such an asymmetry. Our analytical model yields scaling laws that predict how the lysislysogeny decision responds to perturbations of the host. It also quantitatively predicts stochastic features of infection outcomes, such as lysogeny probabilities, consistent with experimental data. By reducing complex regulatory networks to their essential components, our framework reveals the organizing principles of lysislysogeny decisions across phage species.

biophysics↗

bioRxiv2024

Competition strategies driving resource partitioning in chitin degrading communities

Resource competition strongly shapes microbial community dynamics and function. In polysaccharide-degrading communities, primary degraders secrete monomer-releasing enzymes and exploiters consume released products without investing in enzymes. By investigating competitive strategies between chitin degraders and N-acetylglucosamine (GlcNAc) exploiters, we uncover several interacting factors, including GlcNAc liberation rates, diffusive loss, and resource partitioning between competitors, which determine community viability and growth dynamics at early stages of degradation. Aside from cases involving antibiotic secretion or aggregation on particles to privatize degrading enzymes, exploiters also inhibit degraders by siphoning away limiting GlcNAc flux during early stages of particle degradation, when degraders must overcome diffusive GlcNAc loss to sustain chitinase production. Analogous to the Allee effect in population biology, these effects lead to sensitive dependences on initial species densities for a community to thrive. This study elucidates how metabolic competition at early stages of particle degradation shapes species interactions, resource partitioning, and ultimately community viability.

microbiology↗

bioRxiv2023

Sustained growth and rapid dispersal of chitin-associated marine bacteria

Many biogeochemical functions involve bacteria utilizing solid substrates. However, little is known about the coordination of bacterial growth with the kinetics of attachment to and detachment from such substrates. In this quantitative study of Vibrio sp. 1A01 growing on chitin particles, we reveal the heterogeneous nature of the exponentially growing culture, comprised of two co-existing subpopulations: a minority replicating on chitin particles and a non-replicating majority which was planktonic. This partition resulted from a high rate of cell detachment from particles. Despite high detachment, sustained exponential growth of cells on particles was enabled by the enrichment of extra-cellular chitinases excreted and left behind by detached cells. The "inheritance" of these chitinases sustains the colonizing subpopulation despite its reduced density. This simple mechanism helps to circumvent a tradeoff between growth and dispersal, allowing particle-associated marine heterotrophs to explore new habitats without compromising their fitness on the habitat they have already colonized.

microbiology↗

bioRxiv2022

A Genome-Scale Metabolic Model of Marine Heterotroph Vibrio splendidus sp. 1A01

While the Vibrio splendidus species is best known as an opportunistic pathogen in oysters, the Vibrio splendidus sp. 1A01 strain was first identified as an early colonizer of synthetic chitin particles incubated in seawater. To gain a better understanding of its metabolism, a genome-scale metabolic model (GSMM) of V. splendidus sp. 1A01 was reconstructed. GSMMs enable us to simulate all metabolic reactions in a bacterial cell using Flux Balance Analysis. A draft model was built using an automated pipeline from BioCyc. Manual curation was then performed based on experimental data, in part by gap-filling metabolic pathways and tailoring the models biomass reaction to V. splendidus sp. 1A01. The challenges of building a metabolic model for a marine microorganism like V. splendidus sp. 1A01 are described.

microbiology↗