Distribution of Mannan-degrading Bacteria in Aquatic Environments

Abstract

Mannan-degrading bacteria were isolated by the surface inoculation method from various natural habitats. The Mannan employed was prepared from a green seaweed Codium fragile, and the colonies surrounded with a clear zone on mannan-containing agar media were judged to be mannan-degrading bacteria. In total, 117 isolates were obtained from 433 samples collected from sea, freshwater, and land environments. Identification according to Bergey's Manual of Determinative Bacteriology permitted assignment of most isolates to eight genera: Pseudomonas, Alcaligenes, Klebsiella, Enterobacter, Vibrio, Aeromonas, Moraxella, and Bacillus.
Simultaneously, an enumeration of mannan-degrading bacteria was carried out by the pour plate method. The population density of the bacteria ranged from 0-1.0×lO³cells/ml in coastal sea water, 0-4.0×10⁵cells/g in sea bottom mud, 0-5.5×10⁵cells/g in seaweed, 0-1.8×10⁵cells/ml in river and pond waters, 1.0×10⁵-8.7×10⁷cells/g in the intestinal contents of marine and freshwater fish, and 3.0×10⁴-7.7×1O⁵cells/g in land soil.