Biology subjects

Borin, J. M.

Publications and source records attributed to Borin, J. M..

7 recordsLinked to original sources

bioRxiv2024

Bacteriophage {Phi}21s receptor-binding protein evolves new functions through destabilizing mutations that generate non-genetic phenotypic heterogeneity

How viruses evolve to expand their host range is a major question with implications for predicting the next pandemic. Gain-of-function experiments have revealed that host-range expansions can occur through relatively few mutations in viral receptor-binding proteins, and the search for molecular mechanisms that explain such expansions are underway. Previous research on expansions of receptor use in bacteriophage {lambda} has shown that mutations that destabilize {lambda}s receptor-binding protein cause the receptor-binding protein to fold into new conformations that can utilize novel receptors but have weakened thermostability. These observations led us to hypothesize that other viruses may take similar paths to expand their host range. Here, we find support for our hypothesis by studying another virus, bacteriophage 21 ({Phi}21), which evolves to use two new host receptors within two weeks of laboratory evolution. By measuring the thermodynamic stability of {Phi}21 and its descendants, we show that, as {Phi}21 evolves to use new receptors and expands its host range, it becomes less stable and produces viral particles that are genetically identical but vary in their thermostabilities. Next, we show that this non-genetic heterogeneity between particles is directly associated with receptor use innovation, as phage particles with more derived receptor use capabilities are more unstable and decay faster. Lastly, by manipulating the expression of protein chaperones during {Phi}21 infection, we demonstrate that heterogeneity in thermostability and receptor use breadth of phage particles is directly related to the folding of phage proteins into different conformers. Altogether, our results provide support for the hypothesis that viruses can evolve new receptor-use tropisms through mutations that destabilize the receptor-binding protein and produce multiple protein conformers.

evolutionary biology↗

bioRxiv2023

Rapid bacteria-phage coevolution drives the emergence of multi-scale networks

Interactions between species have catalyzed the evolution of multiscale ecological networks-including both nested and modular elements that regulate the function of diverse communities. One common assumption is that such complex pattern formation requires long evolutionary timescales, spatial isolation, or other exogenous processes. Here we show that multiscale network structure can evolve rapidly under simple ecological conditions without spatial structure. In just 21 days of laboratory coevolution, Escherichia coli and bacteriophage {Phi}21 coevolve and diversify to form elaborate cross-infection networks. By measuring [~]10,000 phage-bacteria infections and testing the genetic basis of interactions, we identify the mechanisms that create each component of the multiscale pattern. Initially, nested patterns form through an arms race where hosts successively lose the original receptor (LamB) and phages evolve to use a second (OmpC) and then a third (OmpF) receptor. Next, modules form when the cost of losing the third receptor, OmpF, increases and bacteria evolve resistance mutations that modify the OmpF receptors extramembrane loops. In turn, phages evolve adaptations that facilitate specialized interactions with different OmpF variants. Nestedness reemerges within modules as bacteria evolve increased resistance and phages enhance infectivity against module-specific receptor variants. Our results demonstrate how multiscale networks evolve in parasite-host systems, illustrating Darwins idea that simple adaptive processes can generate entangled banks of ecological interactions.

evolutionary biology↗

bioRxiv2023

Fecal virome transplantation is sufficient to alter fecal microbiota and drive lean and obese body phenotypes in mice

BackgroundThe gastrointestinal microbiome plays a significant role in numerous host processes and has an especially large impact on modulating the host metabolism. Prior studies have shown that when mice receive fecal transplants from obese donors that were fed high-fat diets (HFD) (even when recipient mice are fed normal diets after transplantation), they develop obese phenotypes. These studies demonstrate the prominent role that the gut microbiota play in determining lean and obese phenotypes. While much of the credit has been given to gut bacteria, studies have not measured the impact of gut viruses on these phenotypes. To address this shortcoming, we gavaged mice with viromes isolated from donors fed HFD or normal chow. By characterizing the mices gut bacterial biota and weight-gain phenotypes over time, we demonstrate that viruses can shape the gut bacterial community and affect weight gain or loss. ResultsWe gavaged mice longitudinally over 4 weeks while measuring their body weights and collecting fecal samples for 16S rRNA amplicon sequencing. We evaluated mice that were fed normal chow or high-fat diets, and gavaged each group with either chow-derived fecal viromes, HFD-derived fecal viromes, or phosphate buffered saline controls. We found a significant effect of gavage type, where mice fed chow but gavaged with HFD-derived viromes gained significantly more weight than their counterparts receiving chow-derived viromes. The converse was also true: mice fed HFD but gavaged with chow-derived viromes gained significantly less weight than their counterparts receiving HFD-derived viromes. These results were replicated in two separate experiments and the phenotypic changes were accompanied by significant and identifiable differences in the fecal bacterial biota. Notably, there were differences in Lachnospirales and Clostridia in mice fed chow but gavaged with HFD-derived fecal viromes, and in Peptostreptococcales, Oscillospirales, and Lachnospirales in mice fed HFD but gavaged with chow-derived fecal viromes. Due to methodological limitations, we were unable to identify specific bacterial species or strains that were responsible for respective phenotypic changes. ConclusionsThis study confirms that virome-mediated perturbations can alter the fecal microbiome in an in vivo model and indicates that such perturbations are sufficient to drive lean and obese phenotypes in mice.

microbiology↗

bioRxiv2022

Comparison of bacterial suppression by phage cocktails, dual-receptor generalists, and coevolutionarily trained phages

The evolution and spread of antibiotic resistant bacteria have renewed interest in phage therapy, the use of bacterial viruses (phages) to combat bacterial infections. The delivery of phages in cocktails where constituent phages target different modalities (e.g., receptors) may improve treatment outcomes by making it more difficult for bacteria to evolve resistance. However, the multipartite nature of cocktails may lead to unintended evolutionary and ecological outcomes. Here, we compare a 2-phage cocktail with a largely unconsidered group of phages: generalists that can infect through multiple, independent receptors. We find that both generalists and cocktails that target the same receptors suppress bacteria similarly for ~2 d. Yet a "trained" generalist phage, which previously adapted to its host via 28 d of coevolution, demonstrated superior suppression. To understand why the trained generalist was more effective, we measured the resistance of bacteria against each of our phages. We find that, when bacteria were assailed by 2 phages in the cocktail, they evolved mutations in manXYZ, a host inner-membrane transporter that {lambda} uses to move its DNA across the periplasmic space and into the cell for infection. This provided crossresistance against the cocktail and untrained generalist. However, these mutations were ineffective at blocking the trained generalist because, through coevolutionary training, it evolved to bypass manXYZ resistance. The trained generalists past experiences in training make it exceedingly difficult for bacteria to evolve resistance, further demonstrating the utility of coevolutionary phage training for improving the therapeutic properties of phages.

evolutionary biology↗

bioRxiv2020

Coevolutionary phage training leads to greater bacterial suppression and delays the evolution of phage resistance

The evolution of antibiotic resistant bacteria threatens to become the leading cause of worldwide mortality. This crisis has renewed interest in the practice of phage therapy. Yet, bacterias capacity to evolve resistance is likely to debilitate this therapy as well. To combat the evolution of phage resistance and improve treatment outcomes, many have suggested leveraging phages ability to counter resistance by evolving phages on target hosts before using them in therapy (phage training). We found that during in vitro experiments, a phage trained for 28 days suppressed bacteria [~]1000-fold for 3-8 times longer than its untrained ancestor. This extension was due to a delay in the evolution of resistance. Several factors contributed to this prolonged suppression. Mutations that confer resistance to trained phages are [~]100x less common and, while the target bacterium can evolve complete resistance to the untrained phage in a single step, multiple mutations are required to evolve complete resistance to trained phages. Mutations that confer resistance to trained phages are more costly than mutations for untrained phage resistance. And when resistance does evolve, trained phages are better able to suppress these forms of resistance. One way the trained phage improved was through recombination with a gene in a defunct prophage in the host genome, which doubled phage fitness. This direct transfer of information encoded by the host but originating from a relict phage provides a previously unconsidered mode of training phage. Overall, we provide a case study for successful phage training and uncover mechanisms underlying its efficacy. Significance StatementThe evolution of antibiotic resistant bacteria threatens to claim over 10 million lives annually by 2050. This crisis has renewed interest in phage therapy, the use of bacterial viruses to treat infections. A major barrier to successful phage therapy is that bacteria readily evolve phage resistance. One idea proposed to combat resistance is "training" phages by using their natural capacity to evolve to counter resistance. Here, we show that training phages by coevolving them with their host for one month enhanced their capacity for suppressing bacterial growth and delayed the emergence of resistance. Enhanced suppression was caused by several mechanisms, suggesting that the coevolutionary training protocol produces a robust therapeutic that employs complementary modes of action.

evolutionary biology↗

bioRxiv2020

Leapfrog dynamics in phage-bacteria coevolution revealed by joint analysis of cross-infection phenotypes and whole genome sequencing

Viruses and their hosts can undergo coevolutionary arms races where hosts evolve increased resistance and viruses evolve counter-resistance. Given these arms race dynamics (ARD), viruses and hosts are each predicted to evolve along a single trajectory as more recently evolved genotypes replace their predecessors. Here, by coupling phenotypic and genomic analyses of coevolving populations of bacteriophage {lambda} and Escherichia coli, we find conflicting evidence for ARD. Virus-host infection phenotypes fit the ARD model, yet whole genome analyses did not. Rather than coevolution unfolding along a single trajectory, cryptic genetic variation emerges during initial virus-host coevolution. This variation is maintained across generations and eventually supplants dominant lineages. These observations constitute what we term leapfrog coevolutionary dynamics, revealing weaknesses in the predictive power of standard coevolutionary models. The findings shed light on the mechanisms that structure coevolving ecological networks and reveal the limits of using phenotypic assays alone in characterizing coevolutionary dynamics.

evolutionary biology↗

bioRxiv2018

De novo origin of multicellularity in response to predation

The transition from unicellular to multicellular life was one of a few major events in the history of life that created new opportunities for more complex biological systems to evolve. Predation is hypothesized as one selective pressure that may have driven the evolution of multicellularity. Here we show that de novo origins of simple multicellularity can evolve in response to predation. We subjected outcrossed populations of the unicellular green alga Chlamydomonas reinhardtii to selection by the filter-feeding predator Paramecium tetraurelia. Two of five experimental populations evolved multicellular structures not observed in unselected control populations within ~750 asexual generations. Considerable variation exists in the evolved multicellular life cycles, with both cell number and propagule size varying among isolates. Survival assays show that evolved multicellular traits provide effective protection against predation. These results support the hypothesis that selection imposed by predators may have played a role in some origins of multicellularity.

evolutionary biology↗