Although protease-producing bacteria are key players in the degradation of organic nitrogen and essential for the nitrogen recycling in marine sediments, diversity of both these bacteria and their extracellular proteases is still largely unknown. This study investigated the diversity of the cultivable protease-producing bacteria and their extracellular proteases in the sediments of the eutrophied Jiaozhou Bay, China through phylogenetic analysis and protease inhibitor tests. The abundance of the cultivable protease-producing bacteria was up to 10(4) cells/g in all six sediment samples. The cultivated protease-producing bacteria mostly belonged to the phyla Proteobacteria and Firmicutes with the predominant genera being Photobacterium (39.4%), Bacillus (25.8%), and Vibrio (19.7%). Protease inhibitor tests revealed that extracellular proteases secreted by the bacteria were mainly serine proteases and/or metalloproteases with relatively low proportions of cysteine proteases. This study represents the first comprehensive analysis on the diversity of protease-producing bacteria and their extracellular proteases in sediments of a eutrophic bay.

中文翻译：

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胶州湾沉积物中可培养蛋白酶的细菌多样性

尽管产生蛋白酶的细菌是有机氮降解的关键因素，并且是海洋沉积物中氮再循环的关键，但这些细菌及其细胞外蛋白酶的多样性仍是未知之数。本研究通过系统发育分析和蛋白酶抑制剂试验研究了富营养化胶州湾沉积物中可培养的蛋白酶产生细菌及其细胞外蛋白酶的多样性。在所有六个沉积物样品中，可培养的蛋白酶生产细菌的丰度最高为10（4）个细胞/ g。培养的产生蛋白酶的细菌主要属于门菌属的Proteobacteria和Fimicutes，主要属为光细菌（39.4％），芽孢杆菌（25.8％）和弧菌（19.7％）。蛋白酶抑制剂测试表明，细菌分泌的细胞外蛋白酶主要是丝氨酸蛋白酶和/或金属蛋白酶，半胱氨酸蛋白酶的比例相对较低。这项研究代表了对富营养化海湾沉积物中产生蛋白酶的细菌及其细胞外蛋白酶多样性的首次全面分析。