Mutations affecting gyrase in Haemophilus influenzae
Mutants separately resistant to novobiocin, coumermycin, nalidixic acid, and oxolinic acid contained gyrase activity as measured in vitro that was resistant to the antibiotics, indicating that the mutations represented structural alterations of the enzyme. One Novr mutant contained an altered B subunit of the enzyme, as judged by the ability of a plasmid, pNov1, containing the mutation to complement a temperature-sensitive gyrase B mutation in Escherichia coli and to cause novobiocin resistance in that strain. Three other Novr mutations did not confer antibiotic resistance to the gyrase but appeared to increase the amount of active enzyme in the cell. One of these, novB1, could only act in cis, whereas a new mutation, novC, could act in trans. An RNA polymerase mutation partially substituted for the novB1 mutation, suggesting that novB1 may be a mutation in a promoter region for the B subunit gene. Growth responses of strains containing various combinations of mutations on plasmids or on the chromosome indicated that low-level resistance to novobiocin or coumermycin may have resulted from multiple copies of wild-type genes coding for the gyrase B subunit, whereas high-level resistance required a structural change in the gyrase B gene and was also dependent on alteration in a regulatory region. When there was mismatch at the novB locus, with the novB1 mutation either on a plasmid or the chromosome, and the corresponding wild-type gene present in trans, chromosome to plasmid recombination during transformation was much higher than when the genes matched, probably because plasmid to chromosome recombination, eliminating the plasmid, was inhibited by the mismatch.
- Research Organization:
- Brookhaven National Lab., Upton, NY
- OSTI ID:
- 6290725
- Journal Information:
- J. Bacteriol.; (United States), Journal Name: J. Bacteriol.; (United States) Vol. 2; ISSN JOBAA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
59 BASIC BIOLOGICAL SCIENCES
ANTI-INFECTIVE AGENTS
ANTIBIOTICS
BACTERIA
BIOLOGICAL RECOVERY
BIOLOGICAL REPAIR
CHROMOSOMES
DNA HELICASES
DNA REPAIR
DRUGS
ENZYME ACTIVITY
ENZYMES
ESCHERICHIA COLI
GENE REGULATION
GENES
HAEMOPHILUS
MICROORGANISMS
MUTANTS
NUCLEIC ACIDS
NUCLEOTIDYLTRANSFERASES
ORGANIC COMPOUNDS
PHENOTYPE
PHOSPHORUS-GROUP TRANSFERASES
POLYMERASES
R FACTORS
RECOVERY
REPAIR
RNA
TRANSFERASES