CARBON-DIOXIDE AS A REGULATOR OF GENE-EXPRESSION IN MICROORGANISMS

CO2 regulates gene expression across a diverse group of microorganisms including fungi, and both photosynthetic and non photosynthetic bacte ria. The processes that CO2 regulates are diverse. Several CO2-respons ive random promoter lacZ fusions of unknown function have been isolate d from a marine Synechococcus and a Pseudoalteromonas sp., highlightin g the wide effect of CO2 control in these organisms. Regulatory protei ns have been described that mediate the CO2 response at transcription level in Bacillus anthracis, the group A streptococci and two Rhodobac ter spp.. These regulatory proteins include: AcpA and AtxA that are in volved in CO2 control of B. anthracis capsule and toxin production; Mg a that regulates surface associated virulence factors in the group A s treptococci; and RegB/A, a two component signal transduction system th at responds to environmental stimuli including CO2, to regulate photos ynthetic apparatus and CO2 fixation enzyme synthesis in Rhodobacter sp p..