Open AccessThe Transcriptional Repressor FarR Is Not Involved in Meningococcal Fatty Acid Resistance Mediated by the FarAB Efflux Pump and Dependent on Lipopolysaccharide Structure
Author(s) -
Stephanie Schielke,
Corinna Schmitt,
Carolin Spatz,
Matthias Frosch,
Alexandra SchubertUnkmeir,
Oliver Kurzai
Publication year - 2010
Publication title -
applied and environmental microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.552
H-Index - 324
eISSN - 1070-6291
pISSN - 0099-2240
DOI - 10.1128/aem.02833-09
Subject(s) - efflux , repressor , lipopolysaccharide , chemistry , microbiology and biotechnology , fatty acid , bacteria , neisseria meningitidis , biochemistry , gene , biology , genetics , gene expression , immunology
Free fatty acids are important antimicrobial substances regulating the homeostasis of colonizing bacteria on epithelial surfaces. Here, we show that meningococci express a functionalfarAB efflux pump, which is indispensable for fatty acid resistance. However, other than inNeisseria gonorrhoeae , the transcriptional regulator FarR is not involved in regulation of this operon inNeisseria meningitidis . We tested the susceptibility of 23 meningococcal isolates against saturated and unsaturated long-chain fatty acids, proving that meningococci are generally highly resistant, with the exception of serogroup Y strains belonging to sequence type 23. Using genetically determined lipopolysaccharide (LPS)-truncated mutant strains, we show that addition of the LPS core oligosaccharide and hexa-acylation of its membrane anchor lipid A are imperative for fatty acid resistance of meningococci. The sensitivity of the serogroup Y strains is due to naturally occurring mutations within thelpxL1 gene, which is responsible for addition of the sixth acyl chain on the LPS membrane anchor lipid A. Therefore, fatty acid resistance in meningococci is provided by both the active efflux pump FarAB and by the natural permeability barrier of the Gram-negative outer membrane. The transcriptional regulator FarR is not implicated in fatty acid resistance in meningococci, possibly giving rise to a constitutively active FarAB efflux pump system and thus revealing diverse mechanisms of niche adaptation in the two closely relatedNeisseria species.