Patterns of differential digestion of bacteria in deposit feeders: A test of resource partitioning

Abstract

Diverse strains of bacteria vary in their susceptibilities to lysis by the digestive fluids of deposit-feeding invertebrates. Thus, sedimentary bacterial communities are influenced both qualitatively and quantitatively with gut passage. We tested the hypothesis that the rank order of lytic susceptibility of bacterial strains is consistent for an array of deposit feeders. A turbidimetric assay was used to test the lytic susceptibility of logarithmic phase cultures of 10 environmental isolates to the digestive fluids of 6 deposit feeders from diverse taxa. Lysis varied significantly among bacterial strains (p = 0.0002) and among deposit feeders from which digestive fluids were taken (p = 0.0258). Using rank correlation, we rejected the null hypothesis of independence among susceptibility trends. Particular bacterial strains showed fairly consistent patterns in their relative susceptibilities. At least qualitatively, models constructed to predict microbial community responses to gut passage, based on experiments with model organisms, should be applicable to diverse deposit-feeding taxa.