Distribution and function of mgc - a multiple gene regulator of group G Streptococcus dysgalactiae subsp. equisimilis
Date Issued
2009
Date
2009
Author(s)
Lin, Yu-Yin
Abstract
Group G Streptococcus dysgalactiae subsp. equisimilis is an increasing recognized human pathogen. It is commensal in skin, throat, intestine, and vagina. But it may cause severe disease such as bacteremia, purulent pharyngitis, endocarditis, and streptococcal toxic shock syndrome. Many studies indicated that it resembles Group A Streptococcus pyogenes in many respects. They both are β-hemolysis on blood agar, and carry several virulence factors, for example; M protein、SpeG (streptococcal pyrogenic exotoxin G), and ScpG (C5a peptidase) etc. The mgc (multigene regulator-like) , which is 61％ identical to mga of S. pyogenes has been identified in Group C Streptococcus dysgalactiae subsp. equisimilis. But the genetic organization of mga and mgc are different. Since there is no report about mgc in group G streptococcus, thus, we investigate the distribution and characterization of mgc in Group G S. dysgalactiae subsp. equisimilis clinical isolates. First, using PCR, we found mgc locus is present in all strains tested with different emm types, and ~66％ (183/274) were the small type locus. While the size of mgc locus is associated with some emm types, we cannot link small or large type to niche specificities. Furthermore, we sequenced the mgc from two clinical isolates, with emm type stG840.0 and stG6.1, respectively. The mgc sequence from these two isolates were nearly identical (99.61％), but the sequence of cpdB gene in large type is different from the published before. And from 4 strains of large type and 4 strains of small types sequence, we found that there is truncated cpdB in small type mgc locus. The Southern blot results indicated that there is no other genes similar to cpdB in small type strains. We also confirm mgc is single copy in genome by Southern blot. By EMSA analysis, we confirm that His-tagged Mgc can bind emm promoter, suggesting that Mgc in group G Streptococcus is functional. Then we use “in vitro DNA-protein pull-down assay” to identify genes possibly regulated by Mgc.
Subjects
group G streptococcus
mgc
SDGs
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