Cellulase-producing bacteria of Aeromonas are dominant and indigenous in the gut of Ctenopharyngodon idellus (Valenciennes)

Abstract

Herbivorous grass carp (Ctenopharyngodon idella) has a powerful capability to digest aquatic weed. Cellulase activity or cellulase-producing bacteria were found in the gut of grass carp. However, it remains uncertain whether the cellulase-producing bacteria were a part of indigenous intestinal microbiota that the fish harboured or were introduced with food. In the present study, the bacterial diversities and population abundance in the gut of starved grass carps have been investigated by sequencing 16S rRNA gene libraries. The 16S rRNA gene libraries revealed that 28 parasitic bacteria from gut were affiliated to seven genera of Vibrio, Acinetobacter, Providencia, Yersinia, Pseudominas, Morganella or Aeromonas, respectively, and Aeromonas was identified as the most dominant genus in the gut of C. idella. All of cellulase-producing bacteria isolated from the gut of C. idella in this research belonged to Aeromonas. On the whole, the results in this research showed that cellulase activity within C. idella should be at least partially resulting from bacteria of Aeromonas with cellulase-producing capabilities, which were indigenous and dominant intestinal species.