Zhang Mengru, Chen Jian, Zhang Juan, Du Guocheng
Key Laboratory of Industrial Biotechnology, Ministry of Education, Jiangnan University, Wuxi, 214122, People's Republic of China; School of Biotechnology, Jiangnan University, Wuxi, 214122, People's Republic of China.
J Sci Food Agric. 2014 Dec;94(15):3125-33. doi: 10.1002/jsfa.6662. Epub 2014 May 6.
Multiple stresses could cause damage to DNA and other macromolecules. RecO, belonging to the family of DNA repair proteins, plays an important part in homologous recombination and replication repair. In order to explore the role of RecO in overcoming multiple stresses, a mutant of recO deletion is constructed in Lactococcus lactis ssp. cremoris NZ9000.
Compared with the mutant strain, the original strain L. lactis NZ9000 shows better performance in growth under multiple stresses. The survival rates of the original strain under acid, osmotic and chill stresses are 13.49-, 2.78- and 60.89-fold higher. In our deeper research on fermentation capability under osmotic stress, lactate dehydrogenase activity after 8 h fermentation, maximum lactate acid production, lactate yield and maximum lactate productivity of L. lactis NZ9000 are 1.63-, 1.28-, 1.28- and 1.5-fold higher, respectively.
Results indicate that RecO has positively improved the survival of L. lactis NZ9000, protected its key enzymes and enhanced its fermentation efficiencies. Our research confirms the role of RecO in enhancing tolerances to multiple stresses of L. lactis NZ9000, and puts forward the suggestion that RecO could be used in other industrial microorganisms as a new anti-stress component to improve their resistance to various stresses.
多种应激因素可导致DNA及其他大分子受损。RecO属于DNA修复蛋白家族，在同源重组和复制修复中发挥重要作用。为探究RecO在克服多种应激中的作用，在乳酸乳球菌乳脂亚种NZ9000中构建了recO缺失突变体。
与突变株相比，原始菌株乳酸乳球菌NZ9000在多种应激下的生长表现更佳。原始菌株在酸、渗透和冷应激下的存活率分别高出13.49倍、2.78倍和60.89倍。在我们对渗透应激下发酵能力的深入研究中，乳酸乳球菌NZ9000发酵8小时后的乳酸脱氢酶活性、最大乳酸产量、乳酸产率和最大乳酸生产率分别高出1.63倍、1.28倍、1.28倍和1.5倍。
结果表明，RecO对乳酸乳球菌NZ9000的存活具有正向促进作用，保护了其关键酶，并提高了其发酵效率。我们的研究证实了RecO在增强乳酸乳球菌NZ9000对多种应激的耐受性方面的作用，并提出RecO可作为一种新的抗应激成分应用于其他工业微生物，以提高它们对各种应激的抗性。
