Minimalistic mycoplasmas harbor different functional toxin-antitoxin systems

PLoS Genet. 2021 Oct 21;17(10):e1009365. doi: 10.1371/journal.pgen.1009365. eCollection 2021 Oct.

Abstract

Mycoplasmas are minute bacteria controlled by very small genomes ranging from 0.6 to 1.4 Mbp. They encompass several important medical and veterinary pathogens that are often associated with a wide range of chronic diseases. The long persistence of mycoplasma cells in their hosts can exacerbate the spread of antimicrobial resistance observed for many species. However, the nature of the virulence factors driving this phenomenon in mycoplasmas is still unclear. Toxin-antitoxin systems (TA systems) are genetic elements widespread in many bacteria that were historically associated with bacterial persistence. Their presence on mycoplasma genomes has never been carefully assessed, especially for pathogenic species. Here we investigated three candidate TA systems in M. mycoides subsp. capri encoding a (i) novel AAA-ATPase/subtilisin-like serine protease module, (ii) a putative AbiEii/AbiEi pair and (iii) a putative Fic/RelB pair. We sequence analyzed fourteen genomes of M. mycoides subsp. capri and confirmed the presence of at least one TA module in each of them. Interestingly, horizontal gene transfer signatures were also found in several genomic loci containing TA systems for several mycoplasma species. Transcriptomic and proteomic data confirmed differential expression profiles of these TA systems during mycoplasma growth in vitro. While the use of heterologous expression systems based on E. coli and B. subtilis showed clear limitations, the functionality and neutralization capacities of all three candidate TA systems were successfully confirmed using M. capricolum subsp. capricolum as a host. Additionally, M. capricolum subsp. capricolum was used to confirm the presence of functional TA system homologs in mycoplasmas of the Hominis and Pneumoniae phylogenetic groups. Finally, we showed that several of these M. mycoides subsp. capri toxins tested in this study, and particularly the subtilisin-like serine protease, could be used to establish a kill switch in mycoplasmas for industrial applications.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Animals
  • Bacteria / genetics
  • Bacteria / metabolism
  • Bacterial Proteins / genetics
  • Bacterial Proteins / metabolism
  • Goats / microbiology
  • Mycoplasma / genetics*
  • Mycoplasma / metabolism*
  • Phylogeny
  • Proteomics / methods
  • Toxin-Antitoxin Systems / genetics*
  • Transcriptome / genetics

Substances

  • Bacterial Proteins

Grants and funding

This study was supported by the National Science Foundation, USA [to JJ (grant number IOS-1110151, www.nsf.gov)] The study was also supported by the Swiss National Science Foundation [to JJ (grant number 310030_201152, www.snf.ch/en)]. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.