Changes in gut-associated flora and bacterial digestive enzymes during the
development stages of abalone (Haliotis diversicolor)
The gut of abalone contains a diverse population of bacteria which contribute to food digestion and nutrient
absorption. To investigate the development of gutmicroflora in the small abalone Haliotis diversicolor and the effect
of various diets on the bacterial communities, we analyzed the composition of gut microbial flora and the bacterial
digestive enzymes in connection with four important development stages, i.e., larva, early-juvenile, late-juvenile
and grow-out. Among these cultivated bacteria, the Firmicutes group was isolated from both the larval and
early-juvenile stages; the CFB (Cytophaga/Flexibacteria/Bacterioides) group was detected in early juveniles, late
juveniles and grow-out; the γ-proteobacteria existed throughout the four development stages. The isolated Bacillus
sp. and Pseudoalteromonas sp. dominated in the larvae and were rarely detected in other stages. Subsequently, the
genus Vibrio predominated in the latter three phases after the first feeding. Cluster analysis of theDGGE (Denaturing
Gradient Gel Electrophoresis) patterns was basically congruent with the result of culture-dependent method in
which the gut bacterial community indicated the successional change in the development stages. And the artificial
diets contribute to the change of gut bacterial composition to some extent. The enzyme assay showed that the gut
bacteria isolated from the early juveniles produced the greatest diverse digestive enzymes compared with those
isolated from other development stages. Most cultivated bacteria in each development stage showed protease,
lipase or alginate-degrading activities which could help the farmed abalone H. diversicolor to digest diets. All results
showed that a unique but interrelated bacterial flora was developed in the abalone gut which was coincident with
the change of diets.