PATTERNS OF DIFFERENTIAL DIGESTION OF BACTERIA IN DEPOSIT FEEDERS - ATEST OF RESOURCE PARTITIONING

Diverse strains of bacteria vary in their susceptibilities to lysis by the digestive fluids of deposit-feeding invertebrates. Thus, sediment ary bacterial communities are influenced both qualitatively and quanti tatively with gut passage. We tested the hypothesis that the rank orde r of lytic susceptibility of bacterial strains is consistent for an ar ray of deposit feeders. A turbidimetric assay was used to test the lyt ic susceptibility of logarithmic phase cultures of 10 environmental is olates to the digestive fluids of 6 deposit feeders from diverse taxa. Lysis varied significantly among bacterial strains (p = 0.0002) and a mong deposit feeders from which digestive fluids were taken (p = 0.025 8). Using rank correlation, we rejected the null hypothesis of indepen dence among susceptibility trends. Particular bacterial strains were r esistant to digestion, regardless of the deposit-feeding consumer, whi le the remaining strains showed fairly consistent patterns in their re lative susceptibilities. At least qualitatively, models constructed to predict microbial community responses to gut passage, based on experi ments with model organisms, should be applicable to diverse deposit-fe eding taxa.