OBJECTIVETo investigate the biological function of mscL gene in S. epidermidis.

METHODSA plasmid pMAD-δmscL including the upstream and downstream homologous regions of mscL and spectinomycin resistance gene (spc) was constructed and transformed into S. epidermidis 1457 by electroporation with continuous subculture at 42 degrees celsius with shaking. The mscL knockout mutant (SE1457-δmscL) was selected by blue-white colony screening and antibiotic resistance. The D600 and numbers of viable cells were measured in the mutant and parent strains before and after an osmotic downshift of 0.9 M. The effect of the mscL knockout on biofilm formation was assessed using a semi-quantitative microtiter plate assay.

RESULTSThe plasmid pMAD-δmscL was constructed and mscL was deleted from the genome of S. epidermidis 1457. The mscL mutant was verified by PCR of the genomic DNA, direct sequencing and RT-PCR. During the exponential growth phase, the mutant showed significantly reduced ability to survive osmotic downshock in comparison with the wild-type strain but their capacity to form biofilm remained similar.

CONCLUSIONThe mscL gene may be involved in osmoregulation during the logarithmic growth of S. epidermidis, but it dose not affect biofilm formation of the bacterium.