Molecular characterization of regulatory genes associated with biofilm variation in a Staphylococcus aureus strain.
Biofilm formation in association with the intercellular adhesion (icaADBC) gene cluster is a serious problem in nosocomial infections of Staphylococcus aureus. In all 112 S. aureus strains tested, the ica genes were present, and none of these strains formed biofilms. The biofilm formation is known to be changeable by environmental factors. We have found about 30% of phase variation in these strains with treatment of tetracycline, pristinamycin, and natrium chloride. However, this phenotype disappeared without these substances. Therefore, we have constructed stable biofilm-producing variants through a passage culture method. To explain the mechanism of this variation, nucleotide changes of ica genes were tested in strain S. aureus 483 and the biofilm-producing variants. No differences of DNA sequence in ica genes were found between the strains. Additionally, molecular analysis of three regulatory genes, the accessory gene regulator (agr) and the staphylococcal accessory regulator (sarA), and in addition, alternative transcription factor sigma B (sigB), was performed. The data of Northern blot and complementation showed that SigB plays an important role for this biofilm variation in S. aureus 483 and the biofilm-producing variants. Sequence analysis of the sigB operon indicated three point mutations in the rsbU gene, especially in the stop codon, and two point mutations in the rsbW gene. This study shows that this variation of biofilm formation in S. aureus is deduced by the role of sigB, not agr and sarA.
Kim
Jong-Hyun
JH
Division of Enteric Bacterial Infections, Center for Infectious Diseases, National Institute of Health, Seoul 122-701, Korea.
Kim
Cheorl-Ho
CH
Hacker
Jörg
J
Ziebuhr
Wilma
W
Lee
Bok Kwon
BK
Cho
Seung-hak
SH
D000595:Amino Acid Sequence; D001422:Bacterial Adhesion; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D001483:Base Sequence; D018441:Biofilms / Q000254:growth & development*; D003470:Culture Media; D015964:Gene Expression Regulation, Bacterial; D005809:Genes, Regulator; D014644:Genetic Variation; D006801:Humans; D008969:Molecular Sequence Data; D009876:Operon; D012808:Sigma Factor / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D013211:Staphylococcus aureus / Q000145:classification / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism; D014158:Transcription, Genetic
D001426:Bacterial Proteins; D003470:Culture Media; C079011:SigB protein, Bacteria; D012808:Sigma Factor