Incidence of bacteriophage lysogeny in temperate and extreme soil environments
A previous study indicated that approximately 30% of cultivable soil bacteria may contain inducible prophage; however, the degree to which this cultivation-based estimate applies to indigenous soil bacteria is unknown. To estimate the prevalence of lysogeny within soil bacterial communities, induction assays were carried out by extracting bacteria from soil and subsequently exposing extracts to mitomycin C, or by exposing bacteria to mitomycin C through direct addition to soil slurries. Induction was assessed as an increase in viral direct counts relative to those obtained in controls, as detected by epifluorescence microscopy. Extracting bacteria from soils followed by 18 hours mitomycin C exposure generated significantly higher prophage induction than all other treatments. For three Antarctic soil samples, estimates of inducible fraction were statistically indistinguishable across two independent assays, indicating that this approach is highly reproducible. Although the inducible fraction was lower in Antarctic soils and higher in temperate Delaware soils (22-68%), no clear correlations were found between lysogeny and soil physical properties. For Delaware soils, inducible fraction estimates were similar between whole soil assays (44%) and cultivation-based approaches (30%). While these data suggest that lysogeny is common among soil bacteria, the specific factors which promote temperate interactions remain unclear.
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Tags: Antibiotics, Bacteria, Biology, Environment, Microbiology, Science, Virology
