Study on ecology of chitin-decomposing microorganisms in donghu lake (in wuhan, china)

Abstract

对武汉东湖水柱和沉积物中几丁质分解菌的种类组成、数量分布及动态的研究结果表明:几丁质分解菌中.放线菌居于优势,在水柱中约为总数的50-72.3%;在沉积物中约为63-88.5%。经鉴定的102株放线菌中,链霉菌属(Steptomyces)占总数的70.6%;链孢囊菌属(Streptosporangium)、小单孢菌属(Micromonospora)、小多孢菌属(Micropolyspora)分别为8.8%、9.8%和10.8%。细菌中主要是芽孢杆菌属(Bacillus),占鉴定菌株数的42%,其次为沙雷氏菌属(Serratia)、气单胞菌属(Aeromonas)、微球菌属(Micrococcus)和短杆菌属(Brevibacterium)的-些菌株。在数量分布上,沉积物中高于水柱2-3个数量级;东湖Ⅰ站高于Ⅱ站。随着季节更迭,水温上升,其数量亦有相应变化。对菌株分解几丁质的能力和其它生物活性作了比较,并就所得结果进行了讨论。;Chitin is the second most abundant polysaccharide in nature. It has been estimated that 10u tons of chitin are produced annually in the aquatic biosphere in such forms as the exoskeletons of crustanceans, mollusca, coelenterates, in protozoa and in the cell walls of fungi and algae. Therefore the decomposition of chitin is an important component in the recycling of carbon and nitrogen in aquatic ecosystems. In the nature, conversion of chitin to β-1,4 N-acetylglucosamine(NAG) depends on microorganisms. In the present work, the dynamics and distribution of population, the species composition and the decomposing activity of chitin-decomposing microorganism in Donghu Lake (a eutrophic shallow lake in Wuhan, China) were studied. 1. Dynamics and distribution:During March-May, 1991, the numbers of chitin-decomposing microorganisms are higher in the Station I than in the Station I;and much higher in the sediment than in the water column (about 10²-10³). As the temperature increased from 9℃ to 25℃, the chitin-decomposing microorganisms increased with a higher ratio of actinomycetes. (Tab. l, Fig. 1). 2. Spesies composition Actinomycetes and bacteria are included in chitin-decomposing microorganisms. In 155 identified strains of microorganisms there are Streptomyces (72 strains), Streptosporangium (9 strains), Micromonospora (10 strains). Micropolyspora (11 strains), Bacillus (20 strains), (Serreatia (10 strains), Micrococcus (11 strains Aeromonas (11 strains), Brevibacterium (1 strain) and 2 strains unidentified. The Streptomyces and Bacillus are the dominant groups (45.9% and 12.7% respectively). 3. Comparison of decomposing activity of strains; Acording to the value of decomposing clear zone to colony size, the results are shown in Table 2. Worth mentioning is that there are about 55% strains which belong to actinomycetes with higher decomposing activity for chitin, the CZ/CS value over 2.