一株转化琼胶为新琼寡糖菌株的筛选及鉴定

Screening and identification of a bacterium capable of converting agar to neoagaro oligosaccharides

【目的】筛选一株可以将琼胶转化为新琼寡糖的菌株,并对该菌株进行鉴定。【方法】从紫菜生长区域采集紫菜和该区域海水,用含1‰琼胶的培养基富集培养,逐级稀释涂布、平板划线进行初筛,液体培养进行复筛,DNS法测定琼胶降解产物中还原糖的含量。通过16S r DNA序列分析,结合菌体形态、菌落特征及生理生化特性,确立该菌的系统发育学地位。【结果】从紫菜振荡液中筛选出一株可以产琼胶酶的菌株HJPHYXJ-1,该菌属于革兰氏阴性菌,16S r DNA序列同源性与需钠弧菌(Vibrio natriegens)的达到了99%,结合形态特征和生理生化实验结果鉴定该菌为需钠弧菌。HPLC法测定酶解产物为新琼寡糖。【结论】HJPHYXJ-1被筛选用于转化琼胶,酶解产物的聚合度在2-12之间,是以二糖为单位的新琼寡糖,该菌产生的酶为β-琼胶酶。

[ Objective ] To screen and identify a bacterium capable of converting agar to neoagaro oligosaccharides. [ Methods] We took samples of porphyra haitanensis and nearby seawater, and then used the medium containing 1% agar to enrich the target bacteria. The target isolates were obtained by dilution-plate method, of which crude enzymes were further obtained by liquid culture. We adopted DNS method to determine the target bacteria which can convert agar to neoagaro oligosaccharides. The phylogenetics was identified by analyzing 16S rDNA sequence and combining the strain＇ s morphological and bacterial colonial physiological biochemical characteristics. [ Results] We isolated a gram-negative bacterial strain HJPHYXJ-1 capable of transforming agar to neoagaro oligosaccharides. Basic Local Alignment Search Tool （BLAST） search of HJPHYXJ-I＇s 16S rDNA sequence on GenBank suggested that the similarity between this strain and Vibrio natriegens reached 99%. In addition, the morphological and physiological biochemical characteristics of HJPHYXJ-1 also showed highly similarity to Vibrio natriegens. So we identified HJPHYXJ-1 as Vibrio natriegens. The results of HPLC suggested that the metabolite of enzymatic degradation was neoagaro oligosaccharides. [ Conclusions] HJPHYXJ-1 or the new isolate of Vibrio natriegens was capable of converting agar to neoagaro oligosaccharides.