Cheng Jun-Hui, Wang Yan, Zhang Xiao-Yu, Sun Mei-Ling, Zhang Xia, Song Xiao-Yan, Zhang Yu-Zhong, Zhang Yi, Chen Xiu-Lan
State Key Laboratory of Microbial Technology, Marine Biotechnology Research Center, Shandong University, Qingdao, China.
College of Marine Life Sciences, and Frontiers Science Center for Deep Ocean Multispheres and Earth System, Ocean University of China, Qingdao, China.
Front Microbiol. 2021 Mar 16;12:643508. doi: 10.3389/fmicb.2021.643508. eCollection 2021.
Protease-producing bacteria play key roles in the degradation of marine organic nitrogen. Although some deep-sea bacteria are found to produce proteases, there has been no report on protease-secreting from marine hydrothermal vent regions. Here, we analyzed the diversity and functions of the proteases, especially the extracellular proteases, of 1A02591, a protease-secreting strain isolated from a deep-sea hydrothermal vent sediment of the East Pacific Ocean. Strain 1A02591 is a thermophilic bacterium with a strong protease-secreting ability, which displayed the maximum growth rate (0.139 h) and extracellular protease production (307.99 U/mL) at 55°C. Strain 1A02591 contains 75 putative proteases, including 65 intracellular proteases and 10 extracellular proteases according to signal peptide prediction. When strain 1A02591 was cultured with casein, 12 proteases were identified in the secretome, in which metalloproteases (6/12) and serine proteases (4/12) accounted for the majority, and a thermolysin-like protease of the M4 family was the most abundant, suggesting that strain 1A02591 mainly secreted a thermophilic metalloprotease. Correspondingly, the secreted proteases of strain 1A02591 showed the highest activity at the temperature as high as 70°C, and was inhibited 70% by metalloprotease inhibitor -phenanthroline and 50% by serine protease inhibitor phenylmethylsulfonyl fluoride. The secreted proteases could degrade different proteins, suggesting the role of strain 1A02591 in organic nitrogen degradation in deep-sea hydrothermal ecosystem. These results provide the first insight into the proteases of an strain from deep-sea hydrothermal ecosystem, which is helpful in understanding the function of in the marine biogeochemical cycle.
产蛋白酶细菌在海洋有机氮的降解中起着关键作用。尽管发现一些深海细菌能产生蛋白酶，但尚无关于海洋热液喷口区分泌蛋白酶的报道。在此，我们分析了从东太平洋深海热液喷口沉积物中分离出的一株分泌蛋白酶的菌株1A02591的蛋白酶，尤其是胞外蛋白酶的多样性和功能。菌株1A02591是一种具有强大蛋白酶分泌能力的嗜热细菌，在55℃时显示出最高生长速率（0.139 h⁻¹）和胞外蛋白酶产量（307.99 U/mL）。根据信号肽预测，菌株1A02591含有75种假定的蛋白酶，包括65种胞内蛋白酶和10种胞外蛋白酶。当菌株1A02591用酪蛋白培养时，在分泌组中鉴定出12种蛋白酶，其中金属蛋白酶（6/12）和丝氨酸蛋白酶（4/12）占多数，且M4家族的一种嗜热菌蛋白酶样蛋白酶最为丰富，这表明菌株1A02591主要分泌嗜热金属蛋白酶。相应地，菌株1A02591分泌的蛋白酶在高达70℃的温度下显示出最高活性，并且被金属蛋白酶抑制剂邻菲啰啉抑制70%，被丝氨酸蛋白酶抑制剂苯甲基磺酰氟抑制50%。分泌的蛋白酶能够降解不同的蛋白质，表明菌株1A02591在深海热液生态系统中有机氮降解中的作用。这些结果首次揭示了来自深海热液生态系统的一株菌株的蛋白酶情况，有助于理解其在海洋生物地球化学循环中的功能。
