Reduction of Hydrogen Peroxide Accumulation and Toxicity by a Catalase from Mycoplasma iowae

Mycoplasma iowae is a well-established avian pathogen that can infect and damage many sites throughout the body. One potential mediator of cellular damage by mycoplasmas is the production of H(2)O(2) via a glycerol catabolic pathway whose genes are widespread amongst many mycoplasma species. Previous sequencing of M. iowae serovar I strain 695 revealed the presence of not only genes for H(2)O(2) production through glycerol catabolism but also the first documented mycoplasma gene for catalase, which degrades H(2)O(2). To test the activity of M. iowae catalase in degrading H(2)O(2), we studied catalase activity and H(2)O(2) accumulation by both M. iowae serovar K strain DK-CPA, whose genome we sequenced, and strains of the H(2)O(2)-producing species Mycoplasma gallisepticum engineered to produce M. iowae catalase by transformation with the M. iowae putative catalase gene, katE. H(2)O(2)-mediated virulence by M. iowae serovar K and catalase-producing M. gallisepticum transformants were also analyzed using a Caenorhabditis elegans toxicity assay, which has never previously been used in conjunction with mycoplasmas. We found that M. iowae katE encodes an active catalase that, when expressed in M. gallisepticum, reduces both the amount of H(2)O(2) produced and the amount of damage to C. elegans in the presence of glycerol. Therefore, the correlation between the presence of glycerol catabolism genes and the use of H(2)O(2) as a virulence factor by mycoplasmas might not be absolute.