High frequency of phage-infected bacterial cells in a rice field soil in Japan

Abstract

Phages cause significant mortality of bacteria in aquatic environments and thus play an important role in biogeochemical nutrient cycles through biomass turnover. This study evaluated the frequency of phage infection to bacterial cells and resultant potential for mortality and lysis of bacteria in three soil layers in a Japanese rice field. The frequency of visibly infected bacterial cells (FVIC) was from 8.9% to 12.1% on average in these soil layers. This was significantly greater than the reported FVIC values in aquatic environments, and the estimated fraction of bacterial mortality from phage lysis reached far over 100% in every soil layer. The phage infection to bacterial cells tended to be more frequent for short-rod cells than for long-rod cells. The medians of phage-like particles in a bacterial cell (burst size) ranged from 12.5 to 16 particles cell−1 with the low and high quartiles of 7 and 27, respectively.