Handke L D, Conlon K M, Slater S R, Elbaruni S, Fitzpatrick F, Humphreys H, Giles W P, Rupp M E, Fey P D, O'Gara J P
Departments of Pathology and Microbiology1 and Internal Medicine3, University of Nebraska Medical Center, Omaha, NE, USA 2Department of Microbiology, Royal College of Surgeons in Ireland, Dublin, Ireland 4Department of Biology, University of Nebraska-Lincoln, Lincoln, NE, USA.
J Med Microbiol. 2004 May;53(Pt 5):367-374. doi: 10.1099/jmm.0.05372-0.
Production of biofilm in Staphylococcus epidermidis is mediated through enzymes produced by the four-gene operon ica and is subject to phenotypic variation. The purpose of these experiments was to investigate the regulation of ica and icaR transcription in phenotypic variants produced by multiple unrelated isolates of S. epidermidis. Ten isolates were chosen for the study, four of which contained IS256. IS256 mediates a reversible inactivation of ica in approximately 30 % of phenotypic variants. All ten strains produced at least two types of phenotypic variant (intermediate and smooth) in which biofilm formation was significantly impaired. Reversion studies indicated that all phenotypic variants were stable after overnight growth, but began to revert to other phenotypic forms after 5 days of incubation at 37 degrees C. ica transcriptional analysis was performed on phenotypic variants from three IS256-negative isolates; 1457, SE5 and 14765. This analysis demonstrated that ica transcription was significantly reduced in the majority of phenotypic variants, although two variants from SE5 and 1457 produced wild-type quantities of ica transcript. Analysis of seven additional phenotypic variants from SE5 revealed that ica expression was only reduced in three. Expression of icaR transcript was unaffected in all smooth phenotypic variants. Mutations within ica were identified in two SE5 variants with wild-type levels of ica transcription. It is concluded that mutation and transcriptional regulation of ica are the primary mechanisms that govern phenotypic variation of biofilm formation within IS256-negative S. epidermidis.
表皮葡萄球菌生物膜的产生是由四基因操纵子ica产生的酶介导的，并且存在表型变异。这些实验的目的是研究ica和icaR转录在由多种不相关的表皮葡萄球菌分离株产生的表型变异体中的调控。选择了10个分离株进行研究，其中4个含有IS256。IS256在大约30%的表型变异体中介导ica的可逆失活。所有10个菌株都产生了至少两种类型的表型变异体（中间型和光滑型），其中生物膜形成显著受损。回复研究表明，所有表型变异体在过夜生长后是稳定的，但在37℃孵育5天后开始回复到其他表型形式。对来自三个IS256阴性分离株1457、SE5和14765的表型变异体进行了ica转录分析。该分析表明，在大多数表型变异体中ica转录显著降低，尽管来自SE5和1457的两个变异体产生野生型数量的ica转录本。对来自SE5的另外七个表型变异体的分析表明，只有三个变异体中的ica表达降低。icaR转录本的表达在所有光滑表型变异体中均未受影响。在两个ica转录水平为野生型的SE5变异体中鉴定出ica内的突变。得出的结论是，ica的突变和转录调控是控制IS256阴性表皮葡萄球菌生物膜形成表型变异的主要机制。
