Standardized analysis of nuclease activities in Mycoplasma species colonizing swine, poultry, and small ruminants.

Secreted nucleases, either cell-attached or released in the environment, play varied roles in bacteria-host interactions during an infection. They help to provide nucleotides essential for bacterial growth by degrading host nucleic acids, are involved in the degradation of extracellular traps and hence in immune evasion, and can have direct cytotoxic activity in host cells. Nuclease expression in bacteria of the Mycoplasma genus has been poorly studied so far. In this study, a standardized set of methods was used to detect the in vitro nuclease activities of major animal mycoplasmas. Nucleases were detected in swine (Mycoplasma (M.) hyopneumoniae, M. hyorhinis, and M. flocculare) as well as avian (M. gallisepticum, M. iowae, and M. synoviae) species, but not in the small ruminant subspecies M. mycoides subsp. capri and M. capricolum subsp. capricolum. In swine species, nuclease activity was detected in both the cell pellet and the supernatant, whereas in poultry species, the results were more variable. We showed that detection of nuclease activity-in terms of presence/absence in our experimental conditions-was strain dependent in M. iowae and M. synoviae. The DNA from macrophage extracellular traps was further demonstrated to be a substrate for mycoplasma-expressed nucleases, suggesting that several Mycoplasma species and/or strains infecting animals could feed on resulting nucleotides and hence escape the traps, two features contributing to persistence of the infection.