Ref ID : 6970
James L. Sinclair and Martin Alexander; Effect of protozoan predation on relative abundance of fast- and slow-growing bacteria. Can.J.Microbiol. 35:578-582, 1989
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The survival of six bacterial species that had different growth rates was tested in raw sewage and sewage that was rendered free of protozoa. When test baceria were added to protozoa-free sewage at densities of approximately 10E5 to 10E6 cells/mL, five of the six species did not decline below 10E5 cells/mL. If protozoa were present, the population sizes of all test species were markedly reduced, but bacterial species able to grow faster in artificial media had the larger number of survivors. Wen the same bacteria were inoculated into protozoa-free sewage at densities of less than 10E3 cells/mL, only the three species able to grow quickly in artificial media increased in abundance. When the six species were inoculated at the same densities into sewage containing protozoa, the three slow-growing species were rapidly eliminated, and two of the three fast-growing species survived in detectable numbers. We suggest that in environments with intense protozoan predation, protozoa may alter the composition of the bacterial community by eliminating slow-growing bacteria.