本研究旨在对能和不能有氧呼吸代谢的乳酸乳球菌呼吸链基因同源性和细胞色素氧化酶活力进行分析，为确定乳酸乳球菌的有氧呼吸必要条件奠定基础。首先，分别测定已筛选到的菌株KLDS4.0325和KLDS4.1102在发酵和有氧呼吸代谢时的生长曲线；其次，提取KLDS4.1102的基因组DNA，随后利用PCR扩增其呼吸链编码基因并进行DNA测序；最后，从GenBank数据库下载KLDS4.0325的呼吸链编码基因序列，利用DNAMAN软件比较这两株菌呼吸链编码基因的同源性，并测定这两株菌的细胞色素氧化酶活性。结果表明在有氧呼吸条件下KLDS4.0325的生物量和pH都显著增大，而KLDS4.1102在两种条件下呈现一致的生长趋势，呼吸链编码基因的同源性分析显示KLDS4.1102具备完整的呼吸链，而酶活测定结果却显示KLDS4.1102无细胞色素氧化酶活性，这表明KLDS4.1102不能进行有氧呼吸代谢不是由于编码基因缺陷造成的，可能是某些编码基因不能正常表达，导致其细胞色素氧化酶不能正常发挥作用。

The homology of genes coding for respiratory chain and cytochrome oxidase activity of Lactococcus lactis strains that can or cannot undergo aerobic respiration were compared to provide a foundation for determining the necessary conditions for aerobic respiration in Lactococcus lactis. Firstly, growth curves of the two selected strains, KLDS4.0325 and KLDS4.1102, were determined under fermentation and aerobic respiration conditions. Secondly, the genomic DNA of strain KLDS4.1102 was extracted, and its respiratory chain-encoding genes were amplified by polymerase chain reaction (PCR), followed by DNA sequencing. Finally, the sequences of genes coding for the respiratory chain of KLDS4.0325 were downloaded from the GenBank database, the homology of genes coding for the respiratory chain in the two Lactococcus lactis strains was compared by DNAMAN software, and the cytochrome oxidase activities of these two strains were determined. The biomass and pH of KLDS4.0325 undergoing aerobic respiration increased significantly, but KLDS4.1102 presented a consistent growth trend between the two physiological conditions. The homology analysis of the genes coding for respiratory chain of two strains showed that KLDS4.1102 possessed a complete respiratory chain, while cytochrome oxidase activity could not be detected in KLDS4.1102. This finding suggests that KLDS4.1102 cannot undergo respiratory metabolism normally, possibly because some gene cannot be expressed normally, leading to abnormal cytochrome oxidase function.

国家自然科学基金项目（31401512）；国家863项目（2012AA022108，2011AA100902）