Name: Jennifer DeBruyn

Email: jdebruyn@utk.edu

Author: Krishnakali Roy, Dhritiman Ghosh, Katherine Sides, Jennifer DeBruyn* and Mark Radosevich

Author affiliation: Department of Biosystems Engineering and Soil Science, The University of Tennessee, Knoxville, TN, USA

Abstract title: Terrestrial phage ecology: Lysogeny in agricultural, native and groundwater ecosystems

Absstract:

Abstract: Our current understanding of environmental bacteriophage ecology is largely basedon aquatic viral research, revealing the importance of phage to host community structure, abundance, and evolution, and impacts on global biogeochemical cycles. The extent to which phage infection influences these processes in terrestrial systems in unknown. In the soil microbiology lab (Radosevich) at the University of Tennessee, we currently have several projects which aim to answer questions about the distributions and dynamics of phage in soils and groundwater. In particular, our work seeks to answer questions about the prevalence of temperate bacteriophage, and determination of environmental and edaphic dynamics that select for lysogenic lifecycles. Seasonal dynamics of lysogenic and lytic phage across soil treatments at a Long Term Ecological Research site: Temporal viral and bacterial dynamics across types of soil treatments (agricultural, successional, and native forest) were examined at Kellogg Biological Station LTER (Hickory corners, MI). Viral and bacterial abundances varied seasonally and between land treatments, paralleled by differences in bacterial community structure (determined using T-RFLPs). The estimated fraction of the bacterial community containing mitomycin C-inducible prophage varied from 25-75%, and was positively associated with soil moisture, however no temporal trend was apparent. Evaluation of lysogenic phage during biostimulation at a uranium-contaminated groundwater aquifer: Viral abundance was consistently two orders of magnitude lower in a uranium-contaminated aquifer undergoing acetate biostimulation (Rifle, CO, USA) compared to various surface soils. However, the bacterial community from the sampling well closest to the acetate injection site contained inducible prophage, evidenced by a 5-10 fold increase in viral abundance upon exposure to mitC or antibiotic norfloxicin. Induction of lysogenic phage by quorum sensing compounds (AHL): Induction of prophage under stressful conditions is well documented. However, SOS-independent spontaneous prophage induction has also been observed though the mechanisms have not been elucidated. In a variety of soils, groundwater and bacterial isolates we have observed prophage induction upon exposure to quorum sensing compounds (N-butyl-homoserine lactones). In a series of model co-culture experiments we have directly determined that this recA-independent induction response involves sdiA (quorum sensing receptor) and rcsA (transcriptional regulator of exopolysaccharide production) in the lambda lysogen of E. coli. This finding is the first to relate prophage induction to chemical signals associated with high host cell abundance providing an alternative paradigm for SOS-independent spontaneous prophage induction.