Abstract: Objective To investigate the biological function of mscL gene in S. epidermidis. Methods A 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 ℃ 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. Results The 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. Conclusion The mscL gene may be involved in osmoregulation during the logarithmic growth of S.
epidermidis, but it dose not affect biofilm formation of the bacterium.