Selection of bacteria enhancing the growth rate of axenically hatched rotifers (Brachionus plicatilis)

The effect of bacterial strains on the growth rate of rotifers, Brachionus plicatilis, was determined under monoxenic conditions. The first objective was to obtain sterile rotifer cultures starting from rotifer resting eggs u sing merthiolate or glutaraldehyde as disinfectant. Sterile rotifer culture s were obtained, without affecting the hatching ability of the resting eggs , when 0.05 mu l/l glutaraldehyde was used. This disinfection procedure was used to examine the effect of 20 bacterial strains, isolated from well-per forming live-feed production systems, on the population growth rate of roti fers cultured under monoxenic conditions. Five out of the 20 bacterial stra ins tested were able to improve significantly the asexual reproduction of r otifers. The population growth rate (mu(pop)) of rotifer cultures treated w ith GR 12 and GR11 (respectively 0.664 +/- 0.043 and 0.622 +/- 0.062) was s ignificantly higher than the mu(pop) of the control treatment (0.512 +/- 0. 101). Overall, the egg ratio after 48 h was significantly higher in the cul tures inoculated with the bacterial strains than in the axenic control trea tment. The results show that it is possible to control the microbial commun ity in rotifer cultures started from disinfected resting eggs by adding bac terial strains which have a positive effect on the population growth rate. (C) 1999 Elsevier Science B.V. All rights reserved.