Restriction-modification systems in Mycoplasma spp

Abstract

Restriction and Modification (R-M) systems are present in all Mycoplasma species sequenced so far. The presence of these genes poses barriers to gene transfer and could protect the cell against phage infections. The number and types of R-M genes between different Mycoplasma species are variable, which is characteristic of a polymorphism. The majority of the CDSs code for Type III R-M systems and particularly for methyltransferase enzymes, which suggests that functions other than the protection against the invasion of heterologous DNA may exist. A possible function of these enzymes could be the protection against the invasion of other but similar R-M systems. In Mycoplasma hyopneumoniae strain J, three of the putative methyltransferase genes were clustered in a region forming a genomic island. Many R-M CDSs were mapped in the vicinity of transposable elements suggesting an association between these genes and reinforcing the idea of R-M systems as mobile selfish DNA. Also, many R-M genes present repeats within their coding sequences, indicating that their expression is under the control of phase variation mechanisms. Altogether, these data suggest that R-M systems are a remarkable characteristic of Mycoplasma species and are probably involved in the adaptation of these bacteria to different environmental conditions.

Insight into the specific virulence related genes and toxin-antitoxin virulent pathogenicity islands in swine streptococcosis pathogen Streptococcus equi ssp. zooepidemicus strain ATCC35246

“…The major feature of this island is three strain specific genes (SeseC_02360, SeseC_02361 and SeseC_02362) that were annotated as RM system proteins, which protect bacteria from foreign DNA, such as bacteriophages. The RM system is strategy that permits bacteria to live in difference environments [39], allowing bacteria erect a barrier to gene transfer and making them resistant to phage infection [40]. Taken together, these data suggest that the RM systems is a remarkable characteristic of Sz35246 and is probably involved in the adaptation of these bacteria to different environmental conditions.…”

A survey of Type III restriction-modification systems reveals numerous, novel epigenetic regulators controlling phase-variable regulons; phasevarions

“…The mod genes containing a dinucleotide GA [n] repeat tract have been identified in Mycoplasmas previously ( 13 , 38 ). They have never been shown to be phase-variably expressed, but have been discussed as potential phase-variable regulators ( 39 ). Our analysis of phase-variable mod genes from the Mycoplasmataceae shows the presence of 12 new genes, with many of the genes containing multiple allelic variants ( Supplementary Figure 4 ).…”

DNA sequence repeats identify numerous Type I restriction‐modification systems that are potential epigenetic regulators controlling phase‐variable regulons; phasevarions

“…Where the annotation contains an "S1 + S2" suffix, the AAGAC [n] repeat tract length means that the TRD at the 3′ end of the gene (annotated as TRD 2b here) is out of frame with the 5′ end of the gene encoding TRD 1 and TRD 2a, and annotated as two separate truncated hsdS genes (S1 made up of TRD 1 + TRD 2a, and S2 made up of TRD 2b) in REBASE; B, alignments of the entire hsdS region present in REBASE showing this variation is due to the presence of multiple allelic variants of each of the three TRDs. 50 Many environmental organisms contain hsdR genes with short SSR tracts; for example, our analysis describes hsdR genes containing SSRs in diverse environmental bacterial species such as NinC115ORF23709 from Nitratireductor indicus, a deep sea bacterium isolated from the Indian Ocean 51 and MosTT16ORF11850 from Moraxella osloensis, a symbiont of nematode worm Phasmarhabditis hermaphrodita. Many Helicobacter spp.…”

“…(poly C tracts) and Mycoplasmataceae (dinucleotide tracts) are represented, which is not surprising given the prevalence of these types of repeats in these organisms, 49 with many R-M systems in Mycoplasmas previously identified as containing SSRs. 50 Many environmental organisms contain hsdR genes with short SSR tracts; for example, our analysis describes hsdR genes containing SSRs in diverse environmental bacterial species such as NinC115ORF23709 from Nitratireductor indicus, a deep sea bacterium isolated from the Indian Ocean 51 and MosTT16ORF11850 from Moraxella osloensis, a symbiont of nematode worm Phasmarhabditis hermaphrodita. 52 We also identify a number of phase-variable hsdR genes in unusual or emerging pathogens such as EleORF768 from Eggerthella lenta, an anaerobic Gram-positive bacilli associated with abdominal sepsis, and Slu143ORF9045 from Staphylococcus lugdunensis, a member of the Staphylococci that has been known to cause septic arthritis.…”