An Jieran, Zhang Yuchen, Zhao Zhaoer, Huan Ran, Yi Huaxi, Wang Hui, Luan Chunguang, Feng Shengbao, Huang Heqiang, Li Shanwen, Wang Deliang, Zhai Zhengyuan, Hao Yanling
Key Laboratory of Functional Dairy, Co-constructed by the Ministry of Education and Beijing Municipality, College of Food Science and Nutritional Engineering, China Agricultural University, Beijing, China.
College of Food Science and Engineering, Ocean University of China, Qingdao, China.
Microbiol Spectr. 2023 Mar 6;11(2):e0415022. doi: 10.1128/spectrum.04150-22.
Capsular polysaccharide (CPS) can tightly attach to bacterial surfaces and plays a critical role in protecting microorganisms from environmental stresses. However, the molecular and functional properties of some plasmid-borne gene clusters are poorly understood. In this study, comparative genomics of the draft genomes of 21 Lactiplantibacillus plantarum strains revealed that the specific gene cluster for CPS biosynthesis was observed only in the 8 strains with a ropy phenotype. Furthermore, the complete genomes showed that the specific gene cluster was located on the novel plasmid pYC41 in L. plantarum YC41. analysis confirmed that the gene cluster contained the dTDP-rhamnose precursor biosynthesis operon, the repeating-unit biosynthesis operon, and the gene. The insertional inactivation of the and genes abolished the ropy phenotype and reduced the CPS yields by 93.79% and 96.62%, respectively, in YC41 mutants. These results revealed that the gene cluster was responsible for CPS biosynthesis. Moreover, the survival rates of the YC41-rmlA and YC41- mutants under acid, NaCl, and HO stresses were decreased by 56.47 to 93.67% compared to that of the control strain. Furthermore, the specific gene cluster was also confirmed to play a vital role in CPS biosynthesis in MC2, PG1, and YD2. These findings enhance our understanding of the genetic organization and gene functions of plasmid-borne gene clusters in . Capsular polysaccharide is well known to protect bacteria against various environmental stresses. The gene cluster for CPS biosynthesis is typically organized in the chromosome in bacteria. It is worth noting that complete genome sequencing showed that a novel plasmid pYC41-borne gene cluster was identified in YC41. The gene cluster included the dTDP-rhamnose precursor biosynthesis operon, the repeating-unit biosynthesis operon, and the gene, which was verified by the significantly decreased CPS yield and the absent ropy phenotype in the corresponding mutants. The gene cluster plays an important role in bacterial survival under environmental stress, and the mutants had decreased fitness under stress conditions. The vital role of this specific gene cluster in CPS biosynthesis was also confirmed in other CPS-producing strains. These results advanced a better understanding of the molecular mechanisms of plasmid-borne gene clusters and the protective functionality of CPS.
荚膜多糖（CPS）可紧密附着于细菌表面，在保护微生物免受环境压力方面发挥关键作用。然而，一些质粒携带的基因簇的分子和功能特性却知之甚少。在本研究中，对21株植物乳杆菌菌株的草图基因组进行比较基因组学分析发现，仅在8株具有黏性表型的菌株中观察到了用于CPS生物合成的特定基因簇。此外，完整基因组显示该特定基因簇位于植物乳杆菌YC41中的新型质粒pYC41上。分析证实该基因簇包含dTDP - 鼠李糖前体生物合成操纵子、重复单元生物合成操纵子以及相关基因。在YC41突变体中，相关基因的插入失活消除了黏性表型，并使CPS产量分别降低了93.79%和96.62%。这些结果表明该基因簇负责CPS的生物合成。此外，与对照菌株相比，YC41 - rmlA和YC41 - 突变体在酸、NaCl和H₂O₂胁迫下的存活率降低了56.47%至93.67%。此外，在MC2、PG1和YD2中也证实了该特定基因簇在CPS生物合成中起着至关重要的作用。这些发现增进了我们对质粒携带的基因簇在植物乳杆菌中的遗传组织和基因功能的理解。众所周知，荚膜多糖可保护细菌免受各种环境压力。在细菌中，用于CPS生物合成的基因簇通常位于染色体上。值得注意的是，完整基因组测序表明在植物乳杆菌YC41中鉴定出了一个新型质粒pYC41携带的基因簇。该基因簇包括dTDP - 鼠李糖前体生物合成操纵子、重复单元生物合成操纵子以及相关基因，这在相应突变体中CPS产量显著降低和黏性表型缺失得到了验证。该基因簇在细菌在环境胁迫下的存活中起重要作用，并且突变体在胁迫条件下适应性降低。在其他产生CPS的植物乳杆菌菌株中也证实了这个特定基因簇在CPS生物合成中的重要作用。这些结果促进了对质粒携带的基因簇的分子机制以及CPS的保护功能的更好理解。
