Vergara-Irigaray Marta, Maira-Litrán Tomas, Merino Nekane, Pier Gerald B, Penadés José R, Lasa Iñigo
Laboratory of Microbial Biofilms, Instituto de Agrobiotecnología, Universidad Pública de Navarra-CSIC-Gobierno de Navarra, 31006 Pamplona, Spain.
Channing Laboratory, Department of Medicine, Brigham Women's Hospital, Harvard Medical School, Boston, MA 02115, USA.
Microbiology (Reading). 2008 Mar;154(Pt 3):865-877. doi: 10.1099/mic.0.2007/013292-0.
Biofilm formation in Staphylococcus aureus is usually associated with the production of the poly-N-acetylglucosamine (PNAG) exopolysaccharide, synthesized by proteins encoded by the icaADBC operon. PNAG is a linear beta-(1-6)-linked N-acetylglucosaminoglycan that has to be partially deacetylated and consequently positively charged in order to be associated with bacterial cell surfaces. Here, we investigated whether attachment of PNAG to bacterial surfaces is mediated by ionic interactions with the negative charge of wall teichoic acids (WTAs), which represent the most abundant polyanions of the Gram-positive bacterial envelope. We generated WTA-deficient mutants by in-frame deletion of the tagO gene in two genetically unrelated S. aureus strains. The DeltatagO mutants were more sensitive to high temperatures, showed a higher degree of cell aggregation, had reduced initial adherence to abiotic surfaces and had a reduced capacity to form biofilms under both steady-state and flow conditions. However, the levels as well as the strength of the PNAG interaction with the bacterial cell surface were similar between DeltatagO mutants and their corresponding wild-type strains. Furthermore, double DeltatagO DeltaicaADBC mutants displayed a similar aggregative phenotype to that of single DeltatagO mutants, indicating that PNAG is not responsible for the aggregative behaviour observed in DeltatagO mutants. Overall, the absence of WTAs in S. aureus had little effect on PNAG production or anchoring to the cell surface, but did affect the biofilm-forming capacity, cell aggregative behaviour and the temperature sensitivity/stability of S. aureus.
金黄色葡萄球菌中的生物膜形成通常与聚 - N - 乙酰葡糖胺（PNAG）胞外多糖的产生有关，该多糖由icaADBC操纵子编码的蛋白质合成。PNAG是一种线性的β - (1 - 6)连接的N - 乙酰葡糖胺聚糖，必须部分脱乙酰化并因此带正电荷才能与细菌细胞表面结合。在此，我们研究了PNAG与细菌表面的附着是否由与壁磷壁酸（WTA）负电荷的离子相互作用介导，壁磷壁酸是革兰氏阳性细菌包膜中最丰富的聚阴离子。我们通过在两个遗传不相关的金黄色葡萄球菌菌株中对tagO基因进行框内缺失来产生WTA缺陷型突变体。Delta tagO突变体对高温更敏感，表现出更高程度的细胞聚集，对非生物表面的初始粘附减少，并且在稳态和流动条件下形成生物膜的能力降低。然而，Delta tagO突变体与其相应的野生型菌株之间PNAG与细菌细胞表面相互作用的水平和强度相似。此外，双Delta tagO Delta icaADBC突变体表现出与单Delta tagO突变体相似的聚集表型，表明PNAG不是Delta tagO突变体中观察到的聚集行为的原因。总体而言，金黄色葡萄球菌中WTA的缺失对PNAG的产生或锚定到细胞表面影响很小，但确实影响了金黄色葡萄球菌的生物膜形成能力、细胞聚集行为以及温度敏感性/稳定性。
