Influence of Hot Spring Phages on Community Carbon Metabolism: Win, Lose or Draw?

Abstract

Abundant virus-like particles were concentrated from large-volume samples from two hot springs. Both addition of viral concentrates and addition of samples induced by addition of mitomycin-C changed patterns of carbon source utilization by hot spring microbial communities. Specific effects of the two treatments depended upon both temperature and incubation period. Increased metabolic capability with greater exposure to free phages, consistent with the view that phages are major lateral transporters of metabolic genes, was observed most clearly in microbes incubated at a temperature lower than that encountered in situ . On the other hand, decreases in the diversity of utilizable C sources upon exposure to phages may have been due to lytic activity in which susceptible bacterial populations were differentially reduced by infective viruses, consistent with the “ killing the winner ” hypothesis. Treatment of cultures with MC-treated culture extracts, assumed to increase exposure to excised prophages, resulted in higher average metabolic rates after 18 h, but lower rates after 48 h of incubation. With incubation at in situ temperature, this same treatment led to an initial increase in the number of readily utilized C sources, followed by a decrease in community metabolic diversity relative to controls in samples from both hot springs. Thus, treatments designed to increase the interaction between hot spring microbes and either free or newly-excised phages had observable time- and temperature-dependent effects on community metabolism, demonstrating an important, yet complex, ecological role for phages in hot spring waters.