Departamento de Biología Molecular, Universidad Nacional de Río Cuarto, Córdoba, Argentina.
FEMS Microbiol Lett. 2010 Jan;302(1):15-21. doi: 10.1111/j.1574-6968.2009.01826.x. Epub 2009 Oct 22.
Bacterial surface polysaccharides are crucial for establishment of successful rhizobia-legume symbiosis, and in most bacteria, are also critical for biofilm formation and surface colonization. In Sinorhizobium meliloti, the regulatory protein MucR controls exopolysaccharide production. To clarify the relationship between exopolysaccharide synthesis and biofilm formation, we studied mucR expression under growth conditions that influence attachment to polyvinylchloride, developed a microtiter plate assay to quantify biofilm formation in S. meliloti strain Rm1021 and mutants defective in succinoglycan (EPS I) and/or galactoglucan (EPS II) production, and analyzed expression of EPS I and EPS II genes by quantitative reverse transcriptase-PCR. Consistent with previous studies of planktonic bacteria, we found that disruption of the mucR gene in Rm1021 biofilms increased EPS II, but reduced EPS I gene expression. mucR expression was not affected by environmental conditions that influence biofilm formation on polyvinylchloride, and biofilm formation by Rm1021 was independent of exopolysaccharide synthesis. Other factors on the Rm1021 cell surface, and growth conditions, presumably regulate attachment and/or growth as a biofilm on polyvinylchloride.
细菌表面多糖对于成功建立根瘤菌-豆科植物共生关系至关重要，在大多数细菌中，对于生物膜形成和表面定植也至关重要。在苜蓿中华根瘤菌中，调节蛋白 MucR 控制胞外多糖的产生。为了阐明胞外多糖合成与生物膜形成之间的关系，我们研究了影响与聚氯乙烯附着的生长条件下的 mucR 表达，开发了一种微量滴定板测定法来定量测定 S. meliloti 菌株 Rm1021 和缺乏琥珀酸聚糖（EPS I）和/或半乳葡聚糖（EPS II）产生突变体的生物膜形成，并用定量逆转录酶-PCR 分析 EPS I 和 EPS II 基因的表达。与先前对浮游细菌的研究一致，我们发现 Rm1021 生物膜中 mucR 基因的破坏增加了 EPS II，但降低了 EPS I 基因的表达。mucR 表达不受影响生物膜在聚氯乙烯上形成的环境条件的影响，并且 Rm1021 的生物膜形成不依赖于胞外多糖的合成。Rm1021 细胞表面上的其他因素和生长条件，可能调节附着和/或在聚氯乙烯上的生长作为生物膜。
