Abstract
Bacteriophages, the viruses of bacteria, are proposed to drive bacterial population dynamics, yet direct evidence of their impact on natural populations is limited. Here we identified viral sequences in a metapopulation of wild plant-associated Pseudomonas spp. genomes. We discovered that the most abundant viral cluster does not encode an intact phage but instead encodes a tailocin - a phage-derived element that bacteria use to kill competitors for interbacterial warfare. Each pathogenic Pseudomonas sp. strain carries one of a few distinct tailocin variants, which target variable polysaccharides in the outer membrane of co-occurring pathogenic strains. Analysis of historic herbarium samples from the last 170 years revealed that the same tailocin and receptor variants have persisted in the Pseudomonas populations for at least two centuries, suggesting the continued use of a defined set of tailocin haplotypes and receptors. These results indicate that tailocin genetic diversity can be mined to develop targeted “tailocin cocktails” for microbial control.
One-Sentence Summary Bacterial pathogens in a host-associated metapopulation use a repurposed prophage to kill their competitors.
Competing Interest Statement
The authors have declared no competing interest.
Footnotes
TB, talia.backman{at}utah.edu, SML, s.latorre{at}ucl.ac.uk, ES, u6030864{at}umail.utah.edu, AM, muszynski{at}ccrc.uga.edu, EB, u1346590{at}utah.edu, LE, lauren.eads{at}utah.edu, PM, paulina.martinez{at}utah.edu, SS, u1263424{at}utah.edu, AH, aubrey.hawks{at}utah.edu, ADG, ag8612{at}nyu.edu, DMB, david.belnap{at}utah.edu, AM, allison.manuel{at}cores.utah.edu, AD, amdeutschbauer{at}lbl.gov, JB, jb7684{at}nyu.edu, PA, azadi{at}ccrc.uga.edu
We have substantially expanded the experiments and analyses of the manuscript to identify the tailocin receptor and determine the coevolution of the receptor in natural populations of Pseudomonas. To this aim, we bring to our team experts in glycobiology from the Georgia Carbohydrate Research Center. The set of experiments includes: 1. TnSeq Mutagenesis screen to identify important LPS receptors(Figure4A) 2. Mass-spectrometry of LPScomposition (Figure 4C,Table S2) and further carbohydrate analysis (Figure 4B). 3.Plant infection assays to test the in vivo effect of tailocins. With these new experiments we have determined: 1. That components of the lipopolysaccharide(LPS)O-chain are the receptor for the tailocin in the target cell. 2.The LPS residues,in concert with the tailocin tail fibers, are co-evolving in the Pseudomonas populations. 3. The Pseudomonas population that colonizes A. thaliana is polymorphic in the production of rhamnose residues in the LPS and mutation of these residues confers resistance. 4.The tailocin is naturally induced in plant infections and shows killing activity of neighboring bacteria in plant infections. Our co-infection results reveal that a wild type tailocin-encoding strain can completely suppress a competing strain in a plant infection.