Deletion of the rpoZ gene, encoding the omega subunit of RNA polymerase, results in pleiotropic surface-related phenotypes in Mycobacterium smegmatis.
The omega subunit, the smallest subunit of bacterial RNA polymerase, is known to be involved in maintaining the conformation of the beta' subunit and aiding its recruitment to the rest of the core enzyme assembly in Escherichia coli. It has recently been shown in Mycobacterium smegmatis, by creating a deletion mutation of the rpoZ gene encoding omega, that the physiological role of the omega subunit also includes providing physical protection to beta'. Interestingly, the mutant had altered colony morphology. This paper demonstrates that the mutant mycobacterium has pleiotropic phenotypes including reduced sliding motility and defective biofilm formation. Analysis of the spatial arrangement of biofilms by electron microscopy suggests that the altered phenotype of the mutant arises from a deficiency in generation of extracellular matrix. Complementation of the mutant strain with a copy of the wild-type rpoZ gene integrated in the bacterial chromosome restored both sliding motility and biofilm formation to the wild-type state, unequivocally proving the role of omega in the characteristics observed for the mutant bacterium. Analysis of the cell wall composition demonstrated that the mutant bacterium had an identical glycopeptidolipid profile to the wild-type, but failed to synthesize the short-chain mycolic acids characteristic of biofilm growth in M. smegmatis.
Mathew
Renjith
R
Molecular Biophysics Unit, Indian Institute of Science, Bangalore 560012, India.
Mukherjee
Raju
R
Molecular Biophysics Unit, Indian Institute of Science, Bangalore 560012, India.
Balachandar
Radhakrishnan
R
Molecular Biophysics Unit, Indian Institute of Science, Bangalore 560012, India.
Chatterji
Dipankar
D
Molecular Biophysics Unit, Indian Institute of Science, Bangalore 560012, India.
D001426:Bacterial Proteins; D018441:Biofilms / Q000254:growth & development*; D004268:DNA-Binding Proteins; D012321:DNA-Directed RNA Polymerases / Q000235:genetics*; D005109:Extracellular Matrix / Q000378:metabolism; D017353:Gene Deletion; D008855:Microscopy, Electron, Scanning; D020102:Mycobacterium smegmatis / Q000235:genetics* / Q000254:growth & development / Q000502:physiology*; D010641:Phenotype; D012808:Sigma Factor
D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; C087501:RpoZ protein, Streptomyces aureofaciens; D012808:Sigma Factor; C111232:RNA polymerase omega subunit; D012321:DNA-Directed RNA Polymerases