The Mycobacterium marinum mel2 locus displays similarity to bacterial bioluminescence systems and plays a role in defense against reactive oxygen and nitrogen species.
BACKGROUND
Mycobacteria have developed a number of pathways that provide partial protection against both reactive oxygen species (ROS) and reactive nitrogen species (RNS). We recently identified a locus in Mycobacterium marinum, mel2, that plays a role during infection of macrophages. The molecular mechanism of mel2 action is not well understood.


RESULTS
To better understand the role of the M. marinum mel2 locus, we examined these genes for conserved motifs in silico. Striking similarities were observed between the mel2 locus and loci that encode bioluminescence in other bacterial species. Since bioluminescence systems can play a role in resistance to oxidative stress, we postulated that the mel2 locus might be important for mycobacterial resistance to ROS and RNS. We found that an M. marinum mutant in the first gene in this putative operon, melF, confers increased susceptibility to both ROS and RNS. This mutant is more susceptible to ROS and RNS together than either reactive species alone.


CONCLUSIONS
These observations support a role for the M. marinum mel2 locus in resistance to oxidative stress and provide additional evidence that bioluminescence systems may have evolved from oxidative defense mechanisms.
Subbian
Selvakumar
S
Dept, Microbial and Molecular Pathogenesis, Texas A&M University Health Sciences Center-College of Medicine, College Station, TX 77843-1114, USA. SSubbian@medicine.tamhsc.edu <SSubbian@medicine.tamhsc.edu>
Mehta
Parmod K
PK
Cirillo
Suat L G
SL
Cirillo
Jeffrey D
JD
D020816:Amino Acid Motifs; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001426:Bacterial Proteins / Q000235:genetics / Q000502:physiology*; D019295:Computational Biology; D017124:Conserved Sequence; D017353:Gene Deletion; D005816:Genetic Complementation Test; D006360:Heat-Shock Proteins / Q000235:genetics / Q000502:physiology*; D008164:Luminescent Proteins / Q000235:genetics / Q000502:physiology*; D016254:Mutagenesis, Insertional; D009154:Mutation; D019910:Mycobacterium marinum / Q000187:drug effects* / Q000235:genetics / Q000502:physiology*; D009876:Operon / Q000235:genetics; D026361:Reactive Nitrogen Species / Q000494:pharmacology*; D017382:Reactive Oxygen Species / Q000494:pharmacology*
D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D006360:Heat-Shock Proteins; D008164:Luminescent Proteins; D026361:Reactive Nitrogen Species; D017382:Reactive Oxygen Species