Marine viruses (principally bacteriophages) are the most abundant biological entities on the planet. Lytic phages can divert carbon flow in grazing food chains towards the dissolved organic matter (DOM) pool, thus fueling heterotrophic activity and potentially augmenting atmospheric CO2 levels. In contrast, marine temperate phages can replicate lytically (also potentially increasing DOM levels during prophage induction events) but are also capable of altering host phenotype. Both types of phages can participate in gene transfer and alter microbial genotypes. Yet despite their biogeochemical and genetic importance, only a limited number of marine phage genomes appear in GenBank.
With the support of an NSF Biocomplexity award, we are investigating the interaction of viral genomes with their environments by sequencing several temperate/pseudotemperate marine phage genomes. The occurrence of lysogeny in the marine environment is complex, as indicated by the seasonal distribution of lysogens we have observed in estuarine environments. We hypothesize that the lytic-lysogenic shift is the result of viral genes responding to environmental cues, neither of which are known at this time. Our research objectives are:
- To determine what physiological and environmental cues catalyze the shift from lysogenic to lytic lifestyles in cultures and natural microbial populations.
- To sequence the genomes of several temperate phages, including those infecting marine Synechococcus.
- To determine how phage genes work together to confer lytic or lysogenic existence in marine bacteria.
- To incorporate the effects of temperate phage into models of the marine microbial food web.