Department of Biochemical Engineering, School of Chemical Engineering and Technology, Tianjin University, Tianjin, People's Republic of China.
J Bacteriol. 2024 Aug 22;206(8):e0013324. doi: 10.1128/jb.00133-24. Epub 2024 Jul 16.
The peptidoglycan hydrolases responsible for the cell separation of cells are collectively referred to as autolysins. However, the role of each autolysin in the cell separation of is not fully understood. In this study, we constructed a series of cell separation-associated autolysin deficient strains and strains overexpressing the transcription factors SlrR and SinR, and the morphological changes of these strains in liquid culture were observed. The results showed that the absence of D,L-endopeptidases CwlS and LytF only increased the cell chain length in the early exponential phase. The absence of D,L-endopeptidase LytE or N-acetylmuramyl-L-alanine amidase LytC can cause cells to form chains throughout the growth of , although the cell chain length was significantly shortened during the stationary phase. However, the absence of peptidoglycan N-acetylglucosaminidase LytD only caused minor defect in cell separation. Therefore, we concluded that LytE and LytC were the major autolysins that ensure the timely separation of daughter cells, whereas CwlS, LytF, and LytD were the minor autolysins. In addition, overexpression of the transcription factors SinR and SlrR in the mutant enabled cells to form ultra-long chains in the vegetative phase, and its biomass level was basically the same as that of the wild type. This led to the conclusion that besides inhibiting the expression of and , the SinR-SlrR complex also has other potential mechanisms to inhibit cell separation.In this study, the effects of CwlS, LytC, LytD, LytF, LytE, and SinR-SlrR complex on the cell separation of at different growth phases were studied, and an ultra-long-chained strain was constructed. In microbial fermentation, due to its large cell size, this ultra-long-chained strain may be more likely to be precipitated or intercepted during the removal of bacterial process with centrifugation and membrane filtration as the main methods, which is crucial to improve the purity of the product.
负责细胞分离的肽聚糖水解酶统称为自溶素。然而，每种自溶素在 细胞分离中的作用尚未完全了解。在这项研究中，我们构建了一系列与细胞分离相关的自溶素缺陷菌株和转录因子 SlrR 和 SinR 过表达菌株，并观察了这些菌株在液体培养中的形态变化。结果表明，D,L-内肽酶 CwlS 和 LytF 的缺失仅在指数早期增加细胞链长度。D,L-内肽酶 LytE 或 N-乙酰胞壁酰-L-丙氨酸酰胺酶 LytC 的缺失可导致细胞在整个生长过程中形成链，尽管在静止期细胞链长度明显缩短。然而，肽聚糖 N-乙酰氨基葡萄糖苷酶 LytD 的缺失仅导致细胞分离的轻微缺陷。因此，我们得出结论，LytE 和 LytC 是确保 子细胞及时分离的主要自溶素，而 CwlS、LytF 和 LytD 是次要自溶素。此外，转录因子 SinR 和 SlrR 在 突变体中的过表达使 细胞在营养期形成超长链，其生物量水平基本与野生型相同。这得出结论，除了抑制 和 的表达外，SinR-SlrR 复合物还具有其他潜在机制来抑制细胞分离。在这项研究中，研究了 CwlS、LytC、LytD、LytF、LytE 和 SinR-SlrR 复合物对不同生长阶段 细胞分离的影响，并构建了超长链 菌株。在微生物发酵中，由于其细胞体积较大，这种超长链 菌株在以离心和膜过滤为主要方法的细菌去除过程中，更有可能在沉淀或截留过程中被去除，这对提高产品的纯度至关重要。
