Phenotypes of a naturally defective recB allele in Neisseria meningitidis clinical isolates.
Neisseria meningitidis strains belonging to the hypervirulent lineage ET-37 and several unrelated strains are extremely UV sensitive. The phenotype is consequent to the presence of a nonfunctional recB(ET-37) allele carrying multiple missense mutations. Phenotypic analysis has been performed with congenic meningococcal strains harboring either the wild-type recB allele or the recB(ET-37) allele. Congenic recB(ET-37) meningococci, in addition to being sensitive to UV, were defective both in repair of DNA lesions induced by UV treatment and, partially, in recombination-mediated transformation. Consistently, the wild-type, but not the recB(ET-37), allele was able to complement the Escherichia coli recB21 mutation to UV resistance and proficiency in recombination. recB(ET-37) meningococci did not exhibit higher frequencies of spontaneous mutation to rifampin resistance than recB-proficient strains. However, mutation rates were enhanced following UV treatment, a phenomenon not observed in the recB-proficient counterpart. Interestingly, the results of PCR-based assays demonstrated that the presence of the recB(ET-37) allele considerably increased the frequency of recombination at the pilin loci. The main conclusion that can be drawn is that the presence of the defective recB(ET-37) allele in N. meningitidis isolates causes an increase in genetic diversity, due to an ineffective RecBCD-dependent DNA repair and recombination pathway, and an increase in pilin antigenic variation.
Dipartimento di Biologia e Patologia Cellulare e Molecolare L. Califano, Università di Napoli Federico II, and Centro di Endocrinologia ed Oncologia Sperimentale G. Salvatore, Consiglio Nazionale delle Ricerche, 80131 Naples, Italy.
Paola
P
Salvatore
Cecilia
C
Bucci
Caterina
C
Pagliarulo
Maurizio
M
Tredici
Roberta
R
Colicchio
Giuseppina
G
Cantalupo
Marcellino
M
Bardaro
Luigi
L
Del Giudice
Domenica R
DR
Massardo
Alfredo
A
Lavitola
Carmelo B
CB
Bruni
Pietro
P
Alifano
D000483:Alleles; D000595:Amino Acid Sequence; D001483:Base Sequence; D004269:DNA, Bacterial; D029968:Escherichia coli Proteins; D043211:Exodeoxyribonuclease V; D005090:Exodeoxyribonucleases / Q000235:genetics*; D005798:Genes, Bacterial; D006801:Humans; D007558:Italy / Q000453:epidemiology; D008589:Meningococcal Infections / Q000453:epidemiology / Q000382:microbiology*; D008969:Molecular Sequence Data; D009345:Neisseria meningitidis / Q000235:genetics* / Q000302:isolation & purification / Q000528:radiation effects; D010641:Phenotype; D017386:Sequence Homology, Amino Acid; D012689:Sequence Homology, Nucleic Acid; D014466:Ultraviolet Rays
D004269:DNA, Bacterial; D029968:Escherichia coli Proteins; D005090:Exodeoxyribonucleases; D043211:Exodeoxyribonuclease V; C468322:exodeoxyribonuclease V, E coli