ABSTRACT
Microbial viruses can control host abundances via density-dependent lytic predator-prey dynamics. Less clear is how temperate viruses, which coexist and replicate with their host, influence microbial communities. Here we show that virus-like particles are relatively less abundant at high host densities. This suggests suppressed lysis where established models predict lytic dynamics are favoured. Meta-analysis of published viral and microbial densities showed that this trend was widespread in diverse ecosystems ranging from soil to freshwater to human lungs. Experimental manipulations showed viral densities more consistent with temperate than lytic life cycles at increasing microbial abundance. An analysis of 24 coral reef viromes showed a relative increase in the abundance of hallmark genes encoded by temperate viruses with increased microbial abundance. Based on these four lines of evidence, we propose the Piggyback-the-Winner model wherein temperate dynamics become increasingly important in ecosystems with high microbial densities; thus 'more microbes, fewer viruses'.
Subject(s)
Anthozoa/virology , Ecosystem , Host-Pathogen Interactions , Viruses/pathogenicity , Animals , Anthozoa/physiology , Bacteriophages/pathogenicity , Bacteriophages/physiology , Coral Reefs , Genes, Viral/genetics , Lysogeny , Models, Biological , Virulence/genetics , Viruses/genetics , Viruses/isolation & purificationABSTRACT
A fluid genome is a great advantage to prokaryotes, enabling quick adaptation to various types of ecological niches and to diverse environmental selective pressures. A substantial portion of these sudden changes is mediated by lateral gene transfer (LGT), through genetic recombination mechanisms, such as transformation, conjugation and transduction. The recent sequencing of several organisms has offered a new approach to the study of LGT, using comparison and analysis of nucleotide sequences dispersed throughout the genome of these species. This analysis in Choromobacterium violaceum has revealed four prophage and 12 insertion sequences, suggesting genetic exchange with several other bacterial species, including Salmonella enterica, Ralstonia and Xanthomonas. An Rhs (recombination hot spot) element (containing a vgr-like gene) was also observed, the function of which remains unknown, but it has a sequence related to species of Acinetobacter and Sphingomonas. These results support the role of LGT in the acquisition of new traits by C. violaceum
