Biology subjects

Romeyer Dherbey, J.

Publications and source records attributed to Romeyer Dherbey, J..

2 recordsLinked to original sources

bioRxiv2023

Chloramphenicol reduces phage resistance evolution by suppressing bacterial cell surface mutants

Bacteriophages infect Gram-negative bacteria by attaching to molecules present on the bacterial outer membrane, often lipopolysaccharides (LPS). Modification of LPS can lead to resistance to phage infection. In addition, LPS modifications can impact antibiotic susceptibility, allowing for phage-antibiotic synergism. The evolutionary mechanism(s) behind such synergistic interactions remain largely unclear. Here, we show that the presence of antibiotics can affect the evolution of resistance to phage infection, using phage {Phi}X174 and Escherichia coli C. We use a collection of 34 E. coli C LPS strains, each of which is resistant to {Phi}X174, and has either a "rough" or "deep rough" LPS phenotype. Growth of the bacterial strains with the deep rough phenotype is inhibited at low concentrations of chloramphenicol (and, to a much lesser degree, gentamicin). Treating E. coli C wildtype with {Phi}X174 and chloramphenicol eliminates the emergence of mutants with the deep rough phenotype, and thereby slows the evolution of resistance to phage infection. At slightly lower chloramphenicol concentrations, phage resistance rates are similar to those observed at high concentrations; yet, we show that the diversity of possible mutants is much larger than at higher chloramphenicol concentrations. These data suggest that specific antibiotic concentrations can lead to synergistic phage-antibiotic interactions that disappear at higher antibiotic concentrations. Overall, we show that the change in survival of various {Phi}X174-resistant E. coli C mutants in the presence of antibiotics can explain the observed phage-antibiotic synergism. Classification: Biological Sciences, Evolution

evolutionary biology↗

bioRxiv2022

E. coli-{varphi}X174 genotype to phenotype map reveals flexibility and diversity in LPS structures

Phage therapy is a promising method for the treatment of multi-drug-resistant bacterial infections. However, its long-term efficacy depends on understanding the evolutionary effects of the treatment. Current knowledge of such evolutionary effects is lacking, even in well-studied systems. We used the bacterium Escherichia coli C and its bacteriophage {Phi}X174, which infects cells using host lipopolysaccharide (LPS) molecules. We first generated 31 bacterial mutants resistant to {Phi}X174 infection. Based on the genes disrupted by these mutations, we predicted that these E. coli C mutants collectively produce eight unique LPS structures. We then developed a series of evolution experiments to select for {Phi}X174 mutants capable of infecting the resistant strains. During phage adaptation, we distinguished two types of phage resistance: one that was easily overcome by {Phi}X174 with few mutational steps ("easy" resistance), and one that was more difficult to overcome ("hard" resistance). We found that increasing the diversity of the host and phage populations could accelerate the adaptation of phage {Phi}X174 to overcome the hard resistance phenotype. From these experiments, we isolated 16 {Phi}X174 mutants that, together, can infect all 31 initially resistant E. coli C mutants. Upon determining the infectivity profiles of these 16 evolved phages, we uncovered 14 distinct profiles. Given that only eight profiles are anticipated if the LPS predictions are correct, our findings highlight that the current understanding of LPS biology is insufficient to accurately forecast the evolutionary outcomes of bacterial populations infected by phage.

evolutionary biology↗