ABSTRACT
Several genetic systems that allow the use of iron-protoporphyrin IX (heme) have been described for the pathogenic bacterium Neisseria meningitidis. However, many questions about the process of heme acquisition and utilization remain to be answered. To isolate and analyze unidentified genes that play a role in heme iron uptake and utilization, a Himar1 transposon mutant library was screened in N. meningitidis serogroup A strain IR4162. One locus identified by transposon mutagenesis conferred protection against heme toxicity. A mutant with a deletion in a gene termed ght (gene of hydrophobic agent tolerance) within this locus was susceptible to heme and other hydrophobic agents compared to the parental strain. Transcriptional analysis indicated that ght is cotranscribed with an upstream open reading frame NMA2149. Uncharacterized orthologues of ght were identified in many other gram-negative bacteria. We present genetic evidence for the importance of ght in resistance to hydrophobic agents and its potential role in interaction with other hydrophobic agent resistance mechanisms within N. meningitidis.
Subject(s)
Genes, Bacterial , Heme/metabolism , Iron/metabolism , Neisseria meningitidis/genetics , Neisseria meningitidis/metabolism , Amino Acid Sequence , Genetic Complementation Test , Heme/toxicity , Metalloporphyrins/toxicity , Molecular Sequence Data , Neisseria meningitidis/drug effects , Open Reading Frames , Sequence Alignment , Sequence Homology, Amino AcidABSTRACT
It has been proposed that increased phase variation frequencies in Neisseria meningitidis augment transmissibility and invasiveness. A Himar1 mariner transposon mutant library was constructed in serogroup A N. meningitidis and screened for clones with increased phase variation frequencies. Insertions increasing the frequency of slippage events within mononucleotide repeat tracts were identified in three known phase variation-modulating genes (mutS, mutL, and uvrD), as well as six additional loci (pilP, fbpA, fbpB, NMA1233, and two intergenic regions). The implications of these insertion mutations are discussed.
Subject(s)
Bacterial Proteins/genetics , Gene Expression Regulation, Bacterial , Mutagenesis, Insertional , Neisseria meningitidis, Serogroup A/genetics , Repetitive Sequences, Nucleic Acid/genetics , Bacterial Proteins/metabolism , Chromosome Mapping , Chromosomes, Bacterial , Gene Library , Humans , Neisseria meningitidis, Serogroup A/classification , Species Specificity , TransposasesABSTRACT
Biofilm formation by the human pathogen Neisseria meningitidis was analyzed. Biofilm-forming meningococcal strains were identified and quantitated by crystal violet staining. Laser scanning confocal microscopy of the meningococcal biofilm revealed variable layers up to 90 microm in thickness. A total of 39 meningococcal isolates were studied; 23 were nasopharyngeal-carriage isolates, and 16 were invasive-disease isolates. Thirty percent of carriage isolates and 12.5% of invasive-disease isolates formed biofilms proficiently on a polystyrene surface. Generally, the strains that formed biofilms showed high-level cell surface hydrophobicity, characteristic of strains lacking a capsule. The inhibitory role of capsule in biofilm formation was further confirmed by comparing the biofilm-forming capabilities of a serogroup B wild-type strain of a disease-associated isolate to those of its capsule-deficient mutant (ctrA). Some strains of meningococci form biofilms, and this process is likely important in menigococcal colonization.
