Tn5-induced mutants of Azotobacter vinelandii affected in nitrogen fixation under Mo-deficient and Mo-sufficient conditions

Journal Article · Sat Nov 01 00:00:00 EST 1986 · J. Bacteriol.; (United States)

OSTI ID:6897056

Joerger, R D; Premakumar, R; Bishop, P E

Mutants of Azotobacter vinelandii affected in N/sub 2/ fixation in the presence of 1 ..mu..M Na/sub 2/MoO/sub 4/ (conventional system), 50 nM V/sub 2/O/sub 5/, or under Mo deficiency (alternative system) have been isolated after Tn5 mutagenesis with the suicide plasmid pSUP1011. These mutants are grouped into four broad phenotypic classes. Mutants in the first class are Nif/sup -/ under Mo sufficiency but Nif/sup +/ under Mo deficiency or in the presence of V/sub 2/O/sub 5/. Mutants in the second class are Nif/sup -/ under all conditions. An FeMo-cofactor-negative mutant (NifB/sup -/) belongs to this class. The third mutant class consists of mutants incapable of N/sub 2/-dependent growth under Mo deficiency. Most of the mutants of this class are also affected in N/sub 2/ fixation in the presence of 1 ..mu..M Na/sub 2/MoO/sub 4/, with acetylene reduction rates ranging from 28 to 51% of the rates of the wild type. Strains constructed by genetic transfer of the Kan/sup r/ marker of mutants from this class into nifHDK or nifK deletion mutants showed N/sub 2/-dependent growth only in the presence of V/sup 2/O/sub 5/. The only mutant in the fourth class shows wild-type nitrogenase activity under Mo sufficiency, but only 10% of the acetylene reduction activity of the wild type in the presence of 50 nM V/sub 2/O/sub 5/. The acetylene reduction rates of whole cells of this mutant are identical in Mo-deficient medium and in medium containing V/sub 2/O/sub 5/. The conventional nitrogenase subunits are expressed in this mutant even under Mo deficiency or in the presence of V/sub 2/O/sub 5/; however, the NH/sub 4//sup +/-and Mo-repressible proteins normally seen under these conditions could not be detected on two-dimensional gels.

• Research Organization: North Carolina State Univ., Raleigh
• OSTI ID: 6897056
• Journal Information: J. Bacteriol.; (United States), Vol. 168:2
• Country of Publication: United States
• Language: English

Related Subjects

63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
59 BASIC BIOLOGICAL SCIENCES
AZOTOBACTER
NITROGEN FIXATION
MOLYBDENUM
BIOLOGICAL EFFECTS
VANADIUM
ENZYME ACTIVITY
GENETICS
HYBRIDIZATION
MUTANTS
NITROGENASE
PHENOTYPE
PLASMIDS
VANADIUM OXIDES
BACTERIA
BIOLOGY
CELL CONSTITUENTS
CHALCOGENIDES
ELEMENTS
ENZYMES
METALS
MICROORGANISMS
NITRO-GROUP DEHYDROGENASES
OXIDES
OXIDOREDUCTASES
OXYGEN COMPOUNDS
TRANSITION ELEMENT COMPOUNDS
TRANSITION ELEMENTS
VANADIUM COMPOUNDS
560300* - Chemicals Metabolism & Toxicology
550400 - Genetics