Spontaneous deletion of an "ORFanage" region facilitates host adaptation in a "photosynthetic" cyanophage
MetadataShow full item record
Viruses have been suggested to be the largest source of genetic diversity on Earth. Genome sequencing and metagenomic surveys reveal that novel genes with unknown functions are abundant in viral genomes. Yet few observations exist for the processes and frequency by which these genes are gained and lost. The surface waters of marine environments are dominated by marine picocyanobacteria and their co-existing viruses (cyanophages). Recent genome sequencing of cyanophages has revealed a vast array of genes that have been acquired from their cyanobacterial hosts. Here, we re-sequenced the cyanophage S-PM2 genome after 10 years of near continuous passage through its marine Synechococcus host. During this time a spontaneous mutant (S-PM2d) lacking 13% of the S-PM2 ORFs became dominant in the cyanophage population. These ORFs are found at one loci and are not homologous to any proteins in any other sequenced organism (ORFans). We demonstrate a fitness cost to S-PM2(WT) associated with possession of these ORFs under standard laboratory growth. Metagenomic surveys reveal these ORFs are present in various aquatic environments, are likely of cyanophage origin and appear to be enriched in environments from the extremes of salinity (freshwater and hypersaline). We posit that these ORFs contribute to the flexible gene content of cyanophages and offer a distinct fitness advantage in freshwater and hypersaline environments.
Puxty , R J , Perez-Sepulveda , B , Rihtman , B , Evans , D J , Millard , A D & Scanlan , D J 2015 , ' Spontaneous deletion of an "ORFanage" region facilitates host adaptation in a "photosynthetic" cyanophage ' PLoS One , vol 10 , no. 7 , e0132642 . DOI: 10.1371/journal.pone.0132642
Copyright 2015 Puxty et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Items in the St Andrews Research Repository are protected by copyright, with all rights reserved, unless otherwise indicated.