网箱养殖海区底泥产芽孢细菌多样性

DIVERSITY OF SPORE-FORMING BACTERIA IN MARINE SEDIMENTS BELOW FISH-CAGE

采用培养与16S rRNA基因序列比对的方法,对海水网箱养殖区底泥中的可培养细菌进行研究。结果表明,网箱正下方的产芽孢细菌比例高达50%,随着离网箱距离的增加,产芽孢细菌的比例明显降低,200m远时,其比例降至17%。从3个采样点分离纯化出91株产芽孢细菌,对其菌落形态、菌体形态的研究和部分菌株16S rRNA基因的DGGE带型和序列分析表明,91株产芽孢细菌中,有85株属于芽孢杆菌属(Bacillus)的10个种,25个发育型;6株属于盐芽孢杆菌属(Halobacillus)的1个种,3个发育型。芽孢杆菌属的B.marisflavi、B.baekryungensis、B.aquaemaris、B.pumilu等4个种为优势类群。此外,接近半数的产芽孢细菌能代谢含硫化合物,部分菌株能够还原硝酸盐或分解无机磷化合物,仅有3株菌具有亚硝酸盐还原作用。

Spore-forming bacteria have been widely studied for their capability to secrete various extracellular enzymes such as proteaes, amylase etc., but less for their distribution and ecological roles in natural environment. The diversity of spore-forming bacteria in marine sediments of cage culture area were investigated in this paper. Results indicate that the proportion of spore-forming bacteria in sediment just below cage is as much as 50% of culturable heterotrophic bacteria. Distant from cage, the proportion of spore-forming bacteria reduces significantly. At a place 200m distant, the proportion dropped to 17%. Ninety one strains of spore-forming bacteria in three localities were isolated. Based on the sequences of 16S rRNA gene, these bacteria can be grouped into 2 genera. Of the 91 strains, 85 belong to Bacillus, including 10 species, 25 phylotypes; six strains are from 1 species of Halobacillus, containing 3 phylotypes. B. marisflavi, B. baekryungensis, B. aquaemaris and B. pumilu are dominant groups. As ecological function, about half of the spore-forming bacteria can metabolize sulfide, some can reduce nitrate or break down phosphate compound, and only 3 strains can reduce nitrite.