Dobinsky Sabine, Bartscht Katrin, Mack Dietrich
Institut für Medizinische Mikrobiologie und Immunologie, Universitätsklinikum Hamburg-Eppendorf, Martinistrasse 52, Hamburg, D-20246, Germany.
Plasmid. 2002 Jan;47(1):10-7. doi: 10.1006/plas.2001.1554.
Insertion of Tn917 into the icaADBC operon determines a biofilm-negative phenotype in biofilm-producing Staphylococcus epidermidis due to the inactivation of the genes responsible for the synthesis of the polysaccharide intercellular adhesin. We previously characterized six isogenic biofilm-negative transposon mutants of S. epidermidis 1457 with Tn917 insertions in either icaA or icaC. Northern blot analysis using ica- and Tn917-specific probes revealed that ica sequences located upstream and downstream of the transposon insertion site were still transcribed in five mutants in which Tn917 was inserted in the same transcriptional orientation. Outward-directed transcription initiating from within the transposon resulted in the complete expression of individual ica genes. Our results indicate that not only the inactivation of the entire operon but the isolated interruption of individual icaA and icaC genes led to a biofilm-negative phenotype in S. epidermidis. Tn917 mutagenesis may also result in the activation of genes located downstream of the insertion site.
由于负责合成多糖细胞间黏附素的基因失活，Tn917插入icaADBC操纵子会导致产生物膜的表皮葡萄球菌出现生物膜阴性表型。我们之前鉴定了表皮葡萄球菌1457的六个同基因生物膜阴性转座子突变体，其Tn917插入icaA或icaC中。使用ica和Tn917特异性探针进行的Northern印迹分析表明，在五个转座子以相同转录方向插入的突变体中，位于转座子插入位点上游和下游的ica序列仍被转录。从转座子内部起始的外向转录导致各个ica基因的完整表达。我们的结果表明，不仅整个操纵子的失活，而且单个icaA和icaC基因的单独中断都会导致表皮葡萄球菌出现生物膜阴性表型。Tn917诱变也可能导致插入位点下游基因的激活。
