Multiple controls affect arsenite oxidase gene expression in Herminiimonas arsenicoxydans

Area of Science:

• Microbiology
• Environmental Science
• Biochemistry

Background:

• Bacterial transformations significantly influence arsenic speciation, toxicity, and environmental contamination, particularly in drinking water.
• Herminiimonas arsenicoxydans, isolated from arsenic-rich environments, possesses mechanisms to cope with arsenic, including oxidizing toxic As(III) to less harmful As(V).

Purpose of the Study:

• To identify genes and regulatory mechanisms involved in the response of H. arsenicoxydans to As(III).
• To elucidate the molecular mechanisms underlying arsenite oxidase activity and its regulation.

Main Methods:

• Differential transcriptome analysis to identify responsive genes.
• Tn5 transposon mutagenesis to uncover genes essential for arsenite oxidase activity.
• Western blotting and quantitative RT-PCR to validate gene product involvement.
• Rapid amplification of cDNA ends (RACE) to determine transcriptional start sites.

Main Results:

• The AoxRS two-component system regulates the transcription of the aox operon.
• The alternative sigma factor RpoN (sigma54) and co-chaperone DnaJ are involved in controlling arsenite oxidase gene expression.
• A sigma54-dependent promoter motif (-12/-24) was identified upstream of the aoxAB operon.

Conclusions:

• Novel molecular regulatory processes govern arsenite oxidase expression in H. arsenicoxydans.
• A model integrating arsenite oxidation into the adaptive response to As(III) was established for this microorganism.