Balzer Grant J, McLean Robert J C
Department of Civil Engineering, Northwestern University, Evanston, IL 60208-3109, USA.
Can J Microbiol. 2002 Jul;48(7):675-80. doi: 10.1139/w02-060.
In order to see whether the stringent response was involved in biofilm formation, Escherichia coli DS291 (MG1655), and its isogenic relA spoT derivative were grown for 48 h in a chemostat at dilution rates of 0.025 and 0.25 h(-1) under serine limitation. The absence of the stringent response genes relA and spoT had little effect on the planktonic cell concentrations. However, a significant (P < 0.001) reduction in biofilm cell density of the relA spoT mutants was seen at a doubling time of 40 h. At a doubling time of 4 h, differences in biofilm cell density were not significant. Scanning confocal laser microscopy demonstrated the cell densities of microcolonies in the relA spoT mutant to be lower than those in the wild type. Using a microtiter plate assay, we found biofilm formation in relA spoT mutants to be similarly reduced in minimal media but to be enhanced in rich media (Luria-Bertani broth). No significant differences in biofilm formation were observed between wild type and isogenic relA mutants under any growth conditions. Overall, these results suggest that both stringent response genes relA and spoT are important in nutrient-limited biofilms.
为了探究严谨反应是否参与生物膜形成，将大肠杆菌DS291（MG1655）及其同源relA spoT衍生物在恒化器中于丝氨酸限制条件下以0.025和0.25 h⁻¹的稀释率培养48小时。缺失严谨反应基因relA和spoT对浮游细胞浓度影响不大。然而，在40小时的倍增时间时，relA spoT突变体的生物膜细胞密度显著（P < 0.001）降低。在4小时的倍增时间时，生物膜细胞密度差异不显著。扫描共聚焦激光显微镜显示relA spoT突变体中微菌落的细胞密度低于野生型。使用微量滴定板试验，我们发现relA spoT突变体在基本培养基中的生物膜形成同样减少，但在丰富培养基（Luria-Bertani肉汤）中增强。在任何生长条件下，野生型和同源relA突变体之间的生物膜形成均未观察到显著差异。总体而言，这些结果表明严谨反应基因relA和spoT在营养受限的生物膜中都很重要。
