Microbiological Studies on the Decomposition of Chitin in Marine Environment-VIII

Abstract

Microbiological investigations at the Sagami Bay were carried out to understand the role played by chitinoclastic bacteria in the mineralization of chitin in the sea. In the surface waters of the Sagami Bay, Type IN (analogous to Beneckea indolthetica), Type CH (analogous to Beneckea chitinovora), Type HY (analogous to Beneckea hyperoptica) and Type LI (analogous to Beneckea lipophaga) appeared and their appearance were the same as those observed in Aburatsubo Inlet. Type IN was dominantly isolated from sea water and plankton of the Kuroshio current throughout the year. Type IN and Type HY appeared in the Oyashio under-current throughout the year and these are considered to be largely responsible for the decomposition of chitin in the water mass. In the deep water of the Pacific Ocean Type HY was detected to be dominant. Other species of chitinoclastic bacteria, isolated at the Sagami Bay only in the presence of peptone in the medium, were analogous to Vibrio algosus (ZOBELL and UPHAM, 1944) and Pseudomonas cryothasia (CAMPBELL and WILLIAMS, 1951), which appeared in the coastal waters of the Sagami Bay and the Oyashio under-current throughout the year. The rate of chitin decomposition by them was estimated to be less than 37.5 per cent of that by Type IN strains. Chitinoclastic bacteria formed the major population in each of the water masses of the surface water, intermediate water and deep water of the Pacific Ocean, though there was a significant difference in their abundance. In each water mass the chitinoclastic bacterial population increased in summer and was as much as tenfold greater than that in winter. As the migration of chitinoclastic bacteria was not observed, the vertical migration of plankton was considered to be very important for the transport of the bacteria.