A pigment-producing pseudomonad which discolors culture containers of embryos of a bivalve mollusk

A recurring pink discoloration found at the bottom of polyethylene buckets containing embryos of hard clams (Mercenaria mercenaria) is produced by a red-pigmented pseudomonad. The pink discoloration itself is not a problem, but the number of bacterial cells present is cause for concern. This study showed that at concentrations below 103 cells per milliliter of culture of clam embryos the bacterium could produce the discoloration without being detrimental to the clams. Above this concentration, however, either embryonic development decreased or mortality occurred. Chloramphenicol and neomycin were used effectively in preventing the growth of the pigment-producing bacterium and the concomitant adverse effects on clam embryos.