Unité Flore Lactique et Environnement Carné, UR309, INRA, Domaine de Vilvert, Jouy en Josas, France.
Appl Environ Microbiol. 2010 May;76(9):2932-9. doi: 10.1128/AEM.02451-09. Epub 2010 Mar 5.
We recently showed that Lactobacillus sakei, a natural meat-borne lactic acid bacterium, can colonize the gastrointestinal tracts (GIT) of axenic mice but that this colonization in the intestinal environment selects L. sakei mutants showing modified colony morphology (small and rough) and cell shape, most probably resulting from the accumulation of various mutations that confer a selective advantage for persistence in the GIT. In the present study, we analyzed such clones, issued from three different L. sakei strains, in order to determine which functions were modified in the mutants. In the elongated filamentous cells of the rough clones, transmission electron microscopy (TEM) analysis showed a septation defect and dotted and slanted black bands, suggesting the presence of a helical structure around the cells. Comparison of the cytoplasmic and cell wall/membrane proteomes of the meat isolate L. sakei 23K and of one of its rough derivatives revealed a modified expression for 38 spots. The expression of six oxidoreductases, several stress proteins, and four ABC transporters was strongly reduced in the GIT-adapted strain, while the actin-like MreB protein responsible for cell shaping was upregulated. In addition, the expression of several enzymes involved in carbohydrate metabolism was modified, which may correlate with the observation of modified growth of mutants on various carbon sources. These results suggest that the modifications leading to a better adaptation to the GIT are pleiotropic and are characterized in a rough mutant by a different stress status, a cell wall modification, and modified use of energy sources, leading to an improved fitness for the colonization of the GIT.
我们最近表明，天然存在于肉类中的乳酸菌片球菌可以在无菌小鼠的胃肠道（GIT）中定植，但这种在肠道环境中的定植会选择出具有改良菌落形态（小而粗糙）和细胞形状的片球菌突变体，这很可能是由于积累了各种赋予在 GIT 中持续存在选择性优势的突变所致。在本研究中，我们分析了来自三个不同片球菌菌株的此类克隆，以确定突变体中哪些功能发生了改变。在粗糙克隆的伸长丝状细胞中，透射电子显微镜（TEM）分析显示出隔膜缺陷和点状和倾斜的黑色带，表明细胞周围存在螺旋结构。比较肉源分离株片球菌 23K 和其粗糙衍生物之一的细胞质和细胞壁/膜蛋白质组，发现 38 个斑点的表达发生了改变。在适应 GIT 的菌株中，六种氧化还原酶、几种应激蛋白和四个 ABC 转运蛋白的表达强烈降低，而负责细胞成形的肌动蛋白样 MreB 蛋白上调。此外，参与碳水化合物代谢的几种酶的表达也发生了改变，这可能与观察到突变体在各种碳源上生长的改变有关。这些结果表明，导致更好地适应 GIT 的修饰是多效的，在粗糙突变体中表现为不同的应激状态、细胞壁修饰和能量来源的改变利用，从而提高了对 GIT 定植的适应性。
