The role of quorum sensing mediated developmental traits in the resistance of Serratia marcescens biofilms against protozoan grazing

Abstract

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.

Effect of chitosan solution on the bacterial septicemia disease of Bombyx mori (Lepidoptera: Bombycidae) caused by Serratia marcescens

“…Further, Chung and Chen (2008) found that the inactivation of Escherichia coli by chitosan occurs via a two-step sequential mechanism: initial separation of the cell wall from its cell membrane, followed by destruction of the cell membrane. Hejazi and Falkiner (1997) demonstrated that S. marcescens mannose-dependent fimbriae can adhere to biological surfaces and form biofilms, which are aggregations of bacteria and extracellular secretions (Queck et al, 2006). Fimbriae are among the virulent cell-surface structures of S. marcescens which contain the adhesins mediating adherence to eukaryotic cell surfaces, via recognition of specific carbohydrate moieties on the host cell surface glycoconjugates.…”

Evidence for the dynamics of Acyl homoserine lactone and AHL-producing bacteria during subtidal biofilm formation

“…For examples, the cross-domain communication by AHLs between bacteria in biofilms and spores of green alga Ulva indicated a direct function of AHLs in biofouling development (Joint et al, 2002). Furthermore, it was reported that QS mediated developmental traits in the resistance of Serratia marcescens biofilms against protozoan grazing (Queck et al, 2006). The potential roles of AHLs in marine environments remain to be explored.…”

“…As a global regulation signals for bacterial activities, AHLs may affect not only the biofilm composition, but also the consequence of biofilm activities in environment such as biofouling development, nitrogen fixation, sulfate reduction, the degradation of organic matter and, moreover, provide shelter for certain bacteria (Costerton et al, 1995;Qian, 1999;Decho, 2000;Valle et al, 2004;Queck et al, 2006;Huang et al, 2007b;Case et al, 2008). For examples, the cross-domain communication by AHLs between bacteria in biofilms and spores of green alga Ulva indicated a direct function of AHLs in biofouling development (Joint et al, 2002).…”

Effects of protozoan grazing within river biofilms under semi-natural conditions

“…This finding in the natural biofilm setting is in accordance with earlier studies in which the formation of grazing-resistant bacterial microcolonies in the presence of HF in the plankton was reported (Hahn & Höfle 1999, 2imek et al 2001. Subsequent laboratory studies on singlespecies bacterial biofilms have further shown that the formation of surface-attached microcolonies and consequently of bacterial biofilms was stimulated by the presence of HF (Matz et al 2004, Weitere et al 2005, Queck et al 2006.…”

“…Hall-Stoodley et al 2004). Recent experiments with single-species biofilms have shown that surface-associated microcolony formation is stimulated in the presence of potential protozoan grazers, and that they can resist high grazer densities (Matz et al 2004, Queck et al 2006. Nevertheless, this grazing resistance of bacterial microcolonies and biofilms is not a priori applicable to all protozoan types.…”