Chagneau Claudia, Saier Milton H
Division of Biological Sciences, University of California at San Diego, La Jolla, CA 92093-0116, USA.
J Mol Microbiol Biotechnol. 2004;8(3):177-88. doi: 10.1159/000085790.
Many bacteria can adopt organized, sessile, communal lifestyles. The gram-positive bacterium, Bacillus subtilis,forms biofilms on solid surfaces and at air-liquid interfaces, and biofilm development is dependent on environmental conditions. We demonstrate that biofilm formation by B. subtilis strain JH642 can be either activated or repressed by glucose, depending on the growth medium used, and that these glucose effects are at least in part mediated by the catabolite control protein, CcpA. Starting with a chromosomal Tn917-LTV3 insertional library, we isolated mutants that are defective for biofilm formation. The biofilm defects of these mutants were observable in both rich and minimal media, and both on polyvinylchloride abiotic surfaces and in borosilicate tubes. Two mutants were defective in flagellar synthesis. Chemotaxis was shown to be less important for biofilm formation than was flagellar-driven motility. Although motility is known to be required for biofilm formation in other bacteria, this had not previously been demonstrated for B. subtilis. In addition, our study suggests roles for glutamate synthase, GltAB, and an aminopeptidase, AmpS. The loss of these enzymes did not decrease growth or cellular motility but had dramatic effects on biofilm formation under all conditions assayed. The effect of the gltAB defect on biofilm formation could not be due to a decrease in poly-gamma-glutamate synthesis since this polymer proved to be nonessential for robust biofilm formation. High exogenous concentrations of glutamate, aspartate, glutamine or proline did not override the glutamate synthase requirement. This is the first report showing that glutamate synthase and a cytoplasmic aminopeptidase play roles in bacterial biofilm formation. Possible mechanistic implications and potential roles of biofilm formation in other developmental processes are discussed.
许多细菌能够呈现有组织的、固着的群体生活方式。革兰氏阳性菌枯草芽孢杆菌在固体表面和气液界面形成生物膜，生物膜的形成依赖于环境条件。我们证明，枯草芽孢杆菌JH642菌株形成生物膜的过程可被葡萄糖激活或抑制，这取决于所使用的生长培养基，并且这些葡萄糖效应至少部分是由分解代谢物控制蛋白CcpA介导的。从一个染色体Tn917-LTV3插入文库开始，我们分离出了生物膜形成有缺陷的突变体。这些突变体的生物膜缺陷在丰富培养基和基本培养基中均能观察到，在聚氯乙烯非生物表面和硼硅酸盐管中也能观察到。有两个突变体在鞭毛合成方面存在缺陷。结果表明，趋化作用对生物膜形成的重要性低于鞭毛驱动的运动。虽然已知在其他细菌中生物膜形成需要运动性，但此前尚未在枯草芽孢杆菌中得到证实。此外，我们的研究表明谷氨酸合酶GltAB和一种氨肽酶AmpS发挥了作用。这些酶的缺失并没有降低生长或细胞运动性，但在所有检测条件下对生物膜形成都有显著影响。gltAB缺陷对生物膜形成的影响不可能是由于聚γ-谷氨酸合成减少，因为这种聚合物被证明对强大的生物膜形成并非必需。高浓度的外源谷氨酸、天冬氨酸、谷氨酰胺或脯氨酸并不能取代对谷氨酸合酶的需求。这是首次报道表明谷氨酸合酶和一种细胞质氨肽酶在细菌生物膜形成中发挥作用。文中还讨论了可能的作用机制以及生物膜形成在其他发育过程中的潜在作用。
