Using experimental evolution to explore natural patterns between bacterial motility and resistance to bacteriophages

Abstract

Resistance of bacteria to phages may be gained by alteration of surface proteins to which phages bind, a mechanism that is likely to be costly as these molecules typically have critical functions such as movement or nutrient uptake. To address this potential trade-off, we combine a systematic study of natural bacteria and phage populations with an experimental evolution approach. We compare motility, growth rate and susceptibility to local phages for 80 bacteria isolated from horse chestnut leaves and, contrary to expectation, find no negative association between resistance to phages and bacterial motility or growth rate. However, because correlational patterns (and their absence) are open to numerous interpretations, we test for any causal association between resistance to phages and bacterial motility using experimental evolution of a subset of bacteria in both the presence and absence of naturally associated phages. Again, we find no clear link between the acquisition of resistance and bacterial motility, suggesting that for these natural bacterial populations, phagemediated selection is unlikely to shape bacterial motility, a key fitness trait for many bacteria in the phyllosphere. The agreement between the observed natural pattern and the experimental evolution results presented here demonstrates the power of this combined approach for testing evolutionary trade-offs.

Genomes of surface isolates of Alteromonas macleodii: the life of a widespread marine opportunistic copiotroph

“…This is probably related to this polysaccharide being the recognition target for many phages70. Interestingly a similar level of variation was found in the giant protein and the flagellum glycosylation Island what might be also related to their potential recognition by phages484950515253545556575859606162636465666768697071. A very peculiar genomic island that was found to be different in all the isolates is the one apparently involved in metal resistance.…”

Polyclonality of Concurrent Natural Populations of Alteromonas macleodii

“…Flagellatropic phages are known to reversibly bind to helical grooves on the bacterial flagellum and use the rotation of the flagellum to spiral toward the cell surface (Samuel et al 1999). Any change in flagellin structure or glycosylation would alter phage susceptibility (Koskella et al 2011). Interestingly, we found an intermediate level of variation in genes involved in the regulation of flagellum synthesis.…”

Genetics of dispersal

“…Based on genetic analyses of domestication traits, Fuller & Allaby () inferred that domestication first imposed selection on seed size and germination even before agriculture was widely practiced, and as crops became cultivated, selection for lack of dispersal followed. Similarly in bacteria, experimental evolution and selection experiments show that bacterial motility, as well as sporulation, are evolvable traits (Girgis et al, ; Brown et al, ; Koskella et al, ; Taylor & Buckling, ). Mobility was also successfully selected for in the nematode Caenorhabditis elegans (Friedenberg, ), in a protist (Fronhofer & Altermatt, ), and in different mite species (Gu & Danthanarayana, ; Knülle, ; Nachappa et al, ; Bal, Michel & Grewal, ).…”