Isolation, identification and characterization of rabbit caecal mucinolytic bacteria

The aim of our study was to isolate, identify and characterize mucinolytic bacteria from the rabbit caecum. Two hundred and thirty mucin-grown colonies from the caecal contents of 7 rabbits were examined microscopically after the Gram staining. Gram-negative irregular rods were the most numerous mucinolytic isolates (34.1%), followed by gram-negative cocci and short rods (22.5%), gram-positive rods (17.3%), gram-positive cocci (16.6%) and gram-positive sporeforming rods (9.5%). An attempt was done to identify 31 typical isolates on basis of their morphologgy, biochemical characteristics and production of metabolites. In addition, bacterial cells were hybridized with fluorescently labelled probes for Bacteroides/Prevotella and Clostridium genus. Four isolates were identified at the species level as Mitsuokella multiacidus, three isolates as Bacteroides capillosus and one isolate as Actinomyces izraeli. All isolates except the last one belong to the Bacteroidaceae family. One strain could be assigned to the Bacteroides/Prevotella genus on basis of the hybridization test. Other mucinolytic isolates were not identified as their characteristics did not correspond to any previously described bacterial species. No Clostridium sp. strain was detected. In two M. multiacidus strains high activities of extracellular mucin lyases were found. ne pH-optimum of lyases was 6.2. Calcium cations were necessary for their optimal function. This work extends general knowledge about fermentation of carbohydrate and nitrogen substrates in rabbit caecum.