Isolation and characterization of Azospirillum mutants excreting high amounts of indoleacetic acid

1983 ◽  
Vol 29 (8) ◽  
pp. 916-923 ◽  
Author(s):  
A. Hartmann ◽  
Mahavir Singh ◽  
W. Klingmüller
Keyword(s):  
Azospirillum Brasilense ◽  
Indoleacetic Acid ◽  
Acid Metabolism ◽  
Feedback Inhibition ◽  
Growth Patterns ◽  
Wild Type ◽  
Azospirillum Lipoferum ◽  
Isolation And Characterization ◽  
Resistant Mutants

Mutants of Azospirillum brasilense Sp Cd, resistant to 5-fluorotryptophan (FT) excreted 3-indoleacetic acid (IAA), i.e., auxin, producing up to 16 μg/mL which was 30 times greater than the wild-type level. Under conditions of nitrogen fixation, the mutants excreted IAA up to 1 μg/mL, 10 times more than the wild type. However, none of the FT-resistant mutants of Azospirillum lipoferum Sp RG 20a excreted high levels of IAA. This was probably due to differences in the tryptophan and IAA biosynthetic steps between A. brasilense and A. lipoferum strains. Some of the FT-resistant mutants of A. brasilense Sp Cd showed a reduced feedback inhibition of anthranilate synthetase by tryptophan. The increased synthesis of tryptophan could explain the observed excretion of tryptophan and related metabolites. In addition, the IAA-overproducing mutants excreted other amino acids, probably owing to pleiotropic effects of deregulated tryptophan biosynthesis on amino acid metabolism. The growth patterns of some mutants excreting large amounts of IAA were almost identical to those of the wild type.

Isolation and characterization of catabolite repression-resistant mutants of Escherichia coli

1977 ◽  
Vol 23 (10) ◽  
pp. 1384-1393 ◽  
Author(s):  
Glen D. Armstrong ◽  
Hiroshi Yamazaki
Keyword(s):  
Escherichia Coli ◽  
Catabolite Repression ◽  
Coli Strain ◽  
Wild Type ◽  
Phosphotransferase System ◽  
E Coli ◽  
Isolation And Characterization ◽  
In The Wild ◽  
Resistant Mutants

A method has been developed for the isolation of Escherichia coli mutants which are resistant to catabolite repression. The method is based on the fact that a mixture of glucose and gluconate inhibits the development of chemotactic motility in the wild type, but not in the mutants. A motile E. coli strain was mutagenized and grown in glucose and gluconate. Mutants which were able to swim into a tube containing a chemotactic attractant (aspartic acid) were isolated. Most of these mutants were able to produce β-galactosidase in the presence of glucose and gluconate and were normal in their ability to degrade adenosine 3′,5′-cyclic monophosphate. Some of these mutants were defective in the glucose phosphotransferase system.

Isolation and characterization of Azotobacter vinelandii mutant strains with potential as bacterial fertilizer

1983 ◽  
Vol 29 (8) ◽  
pp. 973-978 ◽  
Author(s):  
Joyce K. Gordon ◽  
Marty R. Jacobson
Keyword(s):  
Azotobacter Vinelandii ◽  
Nitrogenase Activity ◽  
Resistant Mutant ◽  
Free Medium ◽  
Wild Type ◽  
Isolation And Characterization ◽  
Mutant Strains ◽  
Resistant Strains ◽  
Resistant Mutants

Mutant strains of Azotobacter vinelandii which might have potential for use as bacterial fertilizer have been isolated and fall into two categories: constitutive mutants that synthesize nitrogenase in the presence of ammonium and mutants that overproduce nitrogenase when grown in nitrogen-free medium. The constitutive mutants described in this paper were isolated from the wild type as methylalanine-resistant strains and express up to 23% of the fully derepressed nitrogenase level when grown in medium containing excess ammonium. By contrast, ammonium-grown cultures of wild type have less than 0.003% of the fully derepressed level. Strains which fix more N2 than the wild type in nitrogen-free medium were isolated as mefhylammonium-resistant mutants. Although the methylammonium-resistant mutant strains fix more N2 than the wild type, they grow no faster. The excess nitrogen produced by these mutants is excreted into the medium, resulting in up to 60% more nitrogen than in the medium of the wild type. Higher nitrogenase activity in the methylammonium-resistant mutant strains was found to be a result of increased levels of nitrogenase protein, suggesting that regulation of nitrogenase synthesis may be altered.

Characterization of Enterococcus faecium mutants resistant to mundticin KS, a class IIa bacteriocin

Microbiology ◽  
2003 ◽  
Vol 149 (10) ◽  
pp. 2901-2908 ◽  
Author(s):  
Youko Sakayori ◽  
Mizuho Muramatsu ◽  
Satoshi Hanada ◽  
Yoichi Kamagata ◽  
Shinichi Kawamoto ◽  
...  
Keyword(s):  
Enterococcus Faecium ◽  
Antimicrobial Agents ◽  
Wild Type Strain ◽  
Unsaturated Fatty Acids ◽  
Class I ◽  
Wild Type ◽  
Food Preservatives ◽  
In The Wild ◽  
Resistant Mutants

The emergence and spread of mutants resistant to bacteriocins would threaten the safety of using bacteriocins as food preservatives. To determine the physiological characteristics of resistant mutants, mutants of Enterococcus faecium resistant to mundticin KS, a class IIa bacteriocin, were isolated. Two types of mutant were found that had different sensitivities to other antimicrobial agents such as nisin (class I) and kanamycin. Both mutants were resistant to mundticin KS even in the absence of Mg2+ ions. The composition of unsaturated fatty acids in the resistant mutants was significantly increased in the presence of mundticin KS. The composition of the phospholipids in the two resistant mutants also differed from those in the wild-type strain. The putative zwitterionic amino-containing phospholipid in both mutants significantly increased, whereas amounts of phosphatidylglycerol and cardiolipin decreased. These changes in membrane structure may influence resistance of enterococci to class IIa and class I bacteriocins.

Isolation and Characterization of Apoptosis-Resistant Mutants from a Radiosensitive Mouse Lymphoma Cell Line

1998 ◽  
Vol 149 (1) ◽  
pp. 41 ◽  
Author(s):  
Hidehiko Kawai ◽  
Yukika Kitamura ◽  
Osamu Nikaido ◽  
Masaaki Tatsuka ◽  
Hiroko Hama-Inaba ◽  
...  
Keyword(s):  
Cell Line ◽  
Lymphoma Cell ◽  
Lymphoma Cell Line ◽  
Isolation And Characterization ◽  
Resistant Mutants ◽  
Mouse Lymphoma

scholarly journals Isolation and characterization of the SPT2 gene, a negative regulator of Ty-controlled yeast gene expression.

1985 ◽  
Vol 5 (7) ◽  
pp. 1543-1553 ◽  
Author(s):  
G S Roeder ◽  
C Beard ◽  
M Smith ◽  
S Keranen
Keyword(s):  
Gene Product ◽  
Regulatory Region ◽  
Negative Regulator ◽  
Transcriptional Level ◽  
Wild Type ◽  
Isolation And Characterization ◽  
Mutant Strains ◽  
Insertion Mutations ◽  
His4 Gene

The his4-917 mutation of Saccharomyces cerevisiae results from the insertion of the Ty element Ty917 into the regulatory region of the HIS4 gene and renders the cell His-. The hist4-912 delta mutant, which carries a solo delta in the 5'-noncoding region of HIS4, is His+ at 37 degrees C but His- at 23 degrees C. Both these mutations interfere with HIS4 expression at the transcriptional level. The His- phenotype of both insertion mutations is suppressed by mutations at the SPT2 locus. The product of the wild-type SPT2 gene apparently represses HIS4 transcription in these mutant strains; this repression is relieved when the SPT2 gene is destroyed by mutation. The repression of transcription by SPT2 presumably results from an interaction between the SPT2+ gene product and Ty or delta sequences. In this paper, we report the cloning and DNA sequence analysis of the wild-type SPT2 gene and show that the gene is capable of encoding a protein of 333 amino acids in length. In addition, we show that a dominant mutation of the SPT2 gene results from the generation of an ochre codon which is presumed to lead to a shortened SPT2 gene product.

Isolation and characterization of Schizosaccharomyces pombe mutants with defective NAD-dependent malic enzyme

1986 ◽  
Vol 32 (6) ◽  
pp. 481-486 ◽  
Author(s):  
C. Osothsilp ◽  
R. E. Subden
Keyword(s):  
Schizosaccharomyces Pombe ◽  
Malic Enzyme ◽  
Pool Analysis ◽  
Starch Gel Electrophoresis ◽  
Wild Type ◽  
Isolation And Characterization ◽  
Starch Gel ◽  
Colony Color ◽  
Color Indicator

To obtain NAD-dependent malic enzyme mutants of Schizosaccharomyces pombe, a colony color indicator screening system was developed. Mutants defective for malic acid utilization (mau mutants) are yellow, while wild-type colonies are blue on the defined bromcresol green based indicator medium. NAD-dependent malic enzyme mutants were distinguished from other mau mutants by subsequent, starch gel electrophoresis, spectrophotometry, complementation tests, and intermediate pool analysis with cell-free extracts.

Isolation and characterization of dominant mutations resistant to carbon catabolite repression of galactokinase synthesis in Saccharomyces cerevisiae

1981 ◽  
Vol 1 (2) ◽  
pp. 83-93
Author(s):  
K Matsumoto ◽  
A Toh-e ◽  
Y Oshima
Keyword(s):  
Partial Resistance ◽  
Carbon Catabolite Repression ◽  
Glucose Repression ◽  
Isocitrate Lyase ◽  
Isolation And Characterization ◽  
Enhanced Resistance ◽  
Leloir Pathway ◽  
Resistant Mutants ◽  
A Site

Seven dominant mutations showing greatly enhanced resistance to the glucose repression of galactokinase synthesis have been isolated from GAL81 mutants, which have the constitutive phenotype but are still strongly repressible by glucose for the synthesis of the Leloir enzymes. These glucose-resistant mutants were due to semidominant mutations at either of two loci, GAL82 and GAL83. Both loci are unlinked to the GAL81- gal4, gal80, or gal7 X gal10 X gal1 locus or to each other. The GAL83 locus was mapped on chromosome V at a site between arg9 and cho1. The GAL82 and GAL83 mutations produced partial resistance of galactokinase to glucose repression only when one or both of these mutations were combined with a GAL81 or a gal80 mutation. The GAL82 and GAL83 mutations are probably specific for expression of the Leloir pathway and related enzymes, because they do not affect the synthesis of alpha-D-glucosidase, invertase, or isocitrate lyase.

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