The lactic acid bacterium Tetragenococcus halophilus, which is used as a starter to brew soy sauce, comprises both cluster-forming strains and dispersed strains. The cluster-forming strains are industrially useful for obtaining clear soy sauce, because the cell clusters are trapped by filter cloth when the soy sauce mash is pressed. However, the molecular mechanism underlying cell cluster formation is unknown. Whole genome sequence analysis and subsequent target sequence analysis revealed that the cluster-forming strains commonly have functional defects in N-acetylglucosaminidase CseA, a peptidoglycan hydrolase. CseA is a multimodular protein that harbors a GH73 domain and six peptidoglycan-binding LysM domains. Recombinant CseA hydrolyzed peptidoglycan and promoted cell separation. Functional analysis of truncated CseA derivatives revealed that the LysM domains play an important role in efficient peptidoglycan degradation and cell separation. Taken together, the results of this study identify CseA as a factor that greatly affects the cluster formation in T. halophilus.

用作酿造酱油的起子的乳酸细菌嗜盐球菌（Tetragenococcus halophilus）既包括成簇菌株，也包括分散菌株。成簇的菌株在工业上可用于获得澄清的酱油，因为当压制酱油时，细胞团被滤布捕获。但是，细胞簇形成的分子机制尚不清楚。全基因组序列分析和随后的靶序列分析表明，成簇菌株通常在N-乙酰氨基葡萄糖苷酶CseA，一种肽聚糖水解酶。CseA是具有GH73结构域和六个肽聚糖结合LysM结构域的多模块蛋白。重组CseA水解肽聚糖并促进细胞分离。截短的CseA衍生物的功能分析表明，LysM结构域在有效的肽聚糖降解和细胞分离中起重要作用。两者合计，这项研究的结果确定CseA是极大地影响嗜盐丁酸杆菌簇形成的一个因素。