Premium
Deciphering the genetic basis of M oraxella catarrhalis complement resistance: a critical role for the disulphide bond formation system
Author(s) -
Vries Stefan P. W.,
Rademakers Rob J. A.,
Gaastde Jongh Christa E.,
Eleveld Marc J.,
Hermans Peter W. M.,
Bootsma Hester J.
Publication year - 2014
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/mmi.12475
Subject(s) - biology , complement system , virulence , bacterial outer membrane , gene , mutant , microbiology and biotechnology , factor h , virulence factor , innate immune system , cd46 , transposon mutagenesis , alternative complement pathway , genetics , phenotype , transposable element , immune system , escherichia coli
Summary The complement system is an important innate defence mechanism, and the ability to resist complement‐mediated killing is considered a key virulence trait of the respiratory tract pathogen M . catarrhalis . We studied the molecular basis of complement resistance by transcriptional profiling and Tn ‐seq, a genome‐wide negative‐selection screenings technology. Exposure of M . catarrhalis to human serum resulted in increased expression of 84 genes and reduced expression of 134 genes, among which genes encoding ABC transporter systems and surface proteins UspA 1 and McaP . By subjecting a ∼ 15 800 transposon mutant library to serum, mutants of 53 genes were negatively selected, including the key complement‐resistance factor uspA2H . Validation with directed mutants confirmed Tn ‐seq phenotypes of uspA2H and 11 newly identified genes, with mutants of MCR _0424, olpA , MCR _1483, and dsbB most severely attenuated. Detailed analysis showed that both components of the disulphide bond formation ( DSB ) system, DsbB and DsbA , were required for complement‐resistance in multiple isolates, and fulfil a critical role in evasion of IgG ‐dependent classical pathway‐mediated killing. Lipooligosaccharide ( LOS ) structure and membrane stability were severely affected in Δ dsbA strains, suggesting a pivotal role for the DSB system in LOS structure safeguarding and membrane stability maintenance.