Queck Shu-Yeong, Weitere Markus, Moreno Ana María, Rice Scott A, Kjelleberg Staffan
School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, NSW 2052, Australia.
Environ Microbiol. 2006 Jun;8(6):1017-25. doi: 10.1111/j.1462-2920.2006.00993.x.
Resistance against protozoan grazers is a crucial factor that is important for the survival of many bacteria in their natural environment. However, the basis of resistance to protozoans and how resistance factors are regulated is poorly understood. In part, resistance may be due to biofilm formation, which is known to protect bacteria from environmental stress conditions. The ubiquitous organism Serratia marcescens uses quorum sensing (QS) control to regulate virulence factor expression and biofilm formation. We hypothesized that the QS system of S. marcescens also regulates mechanisms that protect biofilms against protozoan grazing. To investigate this hypothesis, we compared the interactions of wild-type and QS mutant strains of S. marcescens biofilms with two protozoans having different feeding types under batch and flow conditions. Under batch conditions, S. marcescens forms microcolony biofilms, and filamentous biofilms are formed under flow conditions. The microcolony-type biofilms were protected from grazing by the suspension feeder, flagellate Bodo saltans, but were not protected from the surface feeder, Acanthamoeba polyphaga. In contrast, the filamentous biofilm provided protection against A. polyphaga. The main findings presented in this study suggest that (i) the QS system is not involved in grazing resistance of S. marcescens microcolony-type biofilms; (ii) QS in S. marcescens regulates antiprotozoan factor(s) that do not interfere with the grazing efficiency of the protozoans; and (iii) QS-controlled, biofilm-specific differentiation of filaments and cell chains in biofilms of S. marcescens provides an efficient mechanism against protozoan grazing.
对原生动物食草动物的抗性是许多细菌在其自然环境中生存的关键因素。然而，对原生动物的抗性基础以及抗性因子如何被调控却知之甚少。部分抗性可能归因于生物膜的形成，已知生物膜可保护细菌免受环境压力条件的影响。无处不在的粘质沙雷氏菌利用群体感应（QS）控制来调节毒力因子表达和生物膜形成。我们假设粘质沙雷氏菌的QS系统也调节保护生物膜免受原生动物捕食的机制。为了研究这一假设，我们比较了粘质沙雷氏菌野生型和QS突变株生物膜在分批培养和流动条件下与两种具有不同摄食类型的原生动物的相互作用。在分批培养条件下，粘质沙雷氏菌形成微菌落生物膜，在流动条件下形成丝状生物膜。微菌落型生物膜受到悬浮摄食者鞭毛虫盐生波豆的捕食保护，但不受表面摄食者多噬棘阿米巴的保护。相反，丝状生物膜对多噬棘阿米巴提供了保护。本研究提出的主要发现表明：（i）QS系统不参与粘质沙雷氏菌微菌落型生物膜的抗捕食作用；（ii）粘质沙雷氏菌中的QS调节不干扰原生动物捕食效率的抗原生动物因子；（iii）粘质沙雷氏菌生物膜中QS控制的丝状和细胞链的生物膜特异性分化提供了一种有效的抗原生动物捕食机制。
