A Serratia marcescens OxyR homolog mediates surface attachment and biofilm formation.
OxyR is a conserved bacterial transcription factor with a regulatory role in oxidative stress response. From a genetic screen for genes that modulate biofilm formation in the opportunistic pathogen Serratia marcescens, mutations in an oxyR homolog and predicted fimbria structural genes were identified. S. marcescens oxyR mutants were severely impaired in biofilm formation, in contrast to the hyperbiofilm phenotype exhibited by oxyR mutants of Escherichia coli and Burkholderia pseudomallei. Further analysis revealed that OxyR plays a role in the primary attachment of cells to a surface. Similar to what is observed in other bacterial species, S. marcescens OxyR is required for oxidative stress resistance. Mutations in oxyR and type I fimbrial genes resulted in severe defects in fimbria-associated phenotypes, revealing roles in cell-cell and cell-biotic surface interactions. Transmission electron microscopy revealed the absence of fimbria-like surface structures on an OxyR-deficient strain and an enhanced fimbrial phenotype in strains bearing oxyR on a multicopy plasmid. The hyperfimbriated phenotype conferred by the multicopy oxyR plasmid was absent in a type I fimbrial mutant background. Real-time reverse transcriptase PCR indicated an absence of transcripts from a fimbrial operon in an oxyR mutant that were present in the wild type and a complemented oxyR mutant strain. Lastly, chromosomal P(lac)-mediated expression of fimABCD was sufficient to restore wild-type levels of yeast agglutination and biofilm formation to an oxyR mutant. Together, these data support a model in which OxyR contributes to early stages of S. marcescens biofilm formation by influencing fimbrial gene expression.
Charles T Campbell Laboratory of Ophthalmic Microbiology, Department of Ophthalmology, UPMC Eye Center, Pittsburgh, PA 15213, USA. shanksrm@upmc.edu
Robert M Q
RM
Shanks
Nicholas A
NA
Stella
Eric J
EJ
Kalivoda
Megan R
MR
Doe
Dawn M
DM
O'Dee
Kira L
KL
Lathrop
Feng Li
FL
Guo
Gerard J
GJ
Nau
D001422:Bacterial Adhesion / Q000235:genetics / Q000502:physiology*; D001426:Bacterial Proteins / Q000235:genetics / Q000502:physiology; D018441:Biofilms / Q000254:growth & development*; D016957:Burkholderia pseudomallei / Q000235:genetics; D004251:DNA Transposable Elements; D004926:Escherichia coli / Q000235:genetics; D010861:Fimbriae, Bacterial / Q000235:genetics / Q000648:ultrastructure; D017353:Gene Deletion; D018628:Gene Dosage; D015964:Gene Expression Regulation, Bacterial; D005816:Genetic Complementation Test; D046529:Microscopy, Electron, Transmission; D016254:Mutagenesis, Insertional; D018384:Oxidative Stress / Q000235:genetics; D012329:RNA, Bacterial / Q000096:biosynthesis; D012333:RNA, Messenger / Q000096:biosynthesis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012706:Serratia marcescens / Q000235:genetics / Q000502:physiology*; D014157:Transcription Factors / Q000235:genetics / Q000502:physiology*
D001426:Bacterial Proteins; D004251:DNA Transposable Elements; D012329:RNA, Bacterial; D012333:RNA, Messenger; D014157:Transcription Factors