MICROFLORA IN THE ALIMENTARY TRACT OF TILAPIA: CHARACTERIZATION AND DISTRIBUTION OF ANAEROBIC BACTERIA

Abstract

Obligate anaerobic bacteria isolated from the intestinal tracts of the freshwater fish Tilapia and identified as the genus Bacteroides were separated into two groups at the species level (Bacteroides ATS and BTS) according to morphological and physiological properties. The two groups are significantly different in NaCl requirement, optimal growth temperature, pH, metabolic products, and antibiotic susceptibility. They have little ability to degrade macromolecular compounds, except for some strains which hydrolyzed the starch or chitin. Bacteroides ATS was predominant in the intestines of all species of Tilapia throughout their lives, but Bacteroides BTS tended to increase in accordance with fish growth to a level similar to that of Bacteroides ATS.