Aspects of the Characterization, Identification, and Ecology of the Bacterial Flora Associated with the Surface of Stream-Incubating Pacific Salmon (Oncorhynchus) Eggs

Abstract

Stream-incubating eggs of chum (Oncorhynchus keta) and pink (O. gorbuscha) salmon usually appeared to have a characteristic bacterial flora associated with the radiate membrane or "capsule," Cytophaga spp. predominating over pseudomonads and other species. In comparison, populations on simulated egg surfaces (polyethylene spheres) consisted mostly of Pseudomonas spp. and Chromobacterium lividum, suggesting that the surface of the incubating egg is bacteriologically selective. The bacterial flora of dead eggs consisted mostly of Pseudomonas spp., whereas the ambient stream waters contained members of Acinetobacter, Aeromonas, Enterobacter, and two actinomycetes in addition to members of the genera found on eggs and "simulated eggs."Some characteristics of the bacteria found associated with the surface of the embryonated egg are examined in relation to egg survival. The embryonated egg is regarded as part of a dynamic ecosystem, coined the "oosphere," and it is suggested that egg mortality probably depends more upon the results of complex interactions between the egg, its microflora, and its ambient waters than upon the presence of an obligate pathogen.