Bacterial additives that consistently enhance rotifer growth under synxenic culture conditions 1. Evaluation of commercial products and pure isolates

Ž . Axenic rotifers Brachionus plicatilis Muller were cultured under aseptic conditions; they ̈ Ž . were fed either a bacteria-free artificial diet AD , or axenic Isochrysis galbana, or a combination of axenic Chlorella minutissima and the bacteria-free AD. The medium was inoculated with commercial bacterial additives or cultured strains of marine bacteria. The highest improvements in Ž . growth rate GR of rotifer populations were obtained with laboratory grown bacteria. Addition of Ž . an Alteromonas strain and an unidentified Gram negative strain B3 consistently enhanced rotifer GR in all experiments, and under all feeding regimes in comparison with control cultures inoculated with microbial communities present in seawater, or maintained bacteria-free. None of the other isolates or commercial products were consistent in their enhancement of rotifer production. q 2000 Elsevier Science B.V. All rights reserved.