Reduction of hydrogen peroxide accumulation and toxicity by a catalase from Mycoplasma iowae.

Rachel E Pritchard,John D Osborne,Mitchell F Balish,Alexandre J Prassinos,Ziv Raviv,Glenn Francis Browning

doi:10.1371/journal.pone.0105188

Rachel E Pritchard, John D Osborne + Show 4 more

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https://doi.org/10.1371/journal.pone.0105188

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Abstract

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 H2O2 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 H2O2 production through glycerol catabolism but also the first documented mycoplasma gene for catalase, which degrades H2O2. To test the activity of M. iowae catalase in degrading H2O2, we studied catalase activity and H2O2 accumulation by both M. iowae serovar K strain DK-CPA, whose genome we sequenced, and strains of the H2O2-producing species Mycoplasma gallisepticum engineered to produce M. iowae catalase by transformation with the M. iowae putative catalase gene, katE. H2O2-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 H2O2 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 H2O2 as a virulence factor by mycoplasmas might not be absolute.

Highlights

Mycoplasma iowae is an economically important avian mycoplasma primarily associated with turkeys and occasionally found in chickens [1]
We speculated that the absence of H2O2 accumulation was due to the presence and activity of a catalase, likely intracellular, which provides M. iowae with the ability to break down exogenous H2O2 and might remove H2O2 generated through the glycerol catabolism pathway before it accumulates to detectable levels
Catalase activity resulted in reduced or even undetectable H2O2 production by M. gallisepticum transformants, and a C. elegans toxicity assay revealed a correlation between reduced H2O2 production and decreased toxicity

Summary

Introduction

Mycoplasma iowae is an economically important avian mycoplasma primarily associated with turkeys and occasionally found in chickens [1]. Occurring infections in turkeys commonly result in late embryo mortality, leading to a 2–5% decrease in hatchability, and leg abnormalities in offspring [2,3,4]. M. iowae can be recovered from the respiratory tract, gastrointestinal tract, spleen, and kidneys of orally infected day-old poults, suggesting invasiveness [5]. Among cultured mycoplasmas, M. iowae exhibits a predilection for the intestinal tract. Yolk sac inoculation of eight-day old turkey embryos results in intestinal binding and colonization [6]. Oral inoculation of day-old poults results in intestinal colonization with no signs of disease, with mycoplasmas isolated more frequently from the intestinal walls than its contents, for at least 21 d after inoculation [5]

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