MUTATION SPECTRUM IN THE FUNGUS CONIOCHAETA VELUTINA

1969 ◽  
Vol 11 (4) ◽  
pp. 870-879 ◽  
Author(s):  
M. C. Paterson ◽  
H. Tan ◽  
F. Cooke
Keyword(s):  
The Other ◽  
Mutation Spectrum ◽  
Complete Medium ◽  
Auxotrophic Mutants ◽  
Suppressor Mutations ◽  
Mutant Strains

Auxotrophic, morphological, sensitive and suppressor mutant strains of Coniochaeta velutina are described. Of 1334 auxotrophic mutants isolated, all but 58 have been characterized as to their specific requirements. The mutation spectrum obtained on malt medium differs in several respects from that on complete medium. Arginine, adenine, cysteine, methionine, histidine and pyrimidine requiring mutants were most frequently isolated. Of 12 diauxotrophs tested genetically, 7 proved to be double mutants, but the remaining 5 behaved genetically as single mutants with a double requirement. Four of these required both adenine and histidine for growth and the other both phenylalanine and tyrosine. Cysteine-sensitive mutants and histidine-sensitive strains are described. Other mutants isolated included a variety of morphological, conidial and colour variants, UV-sensitive strains, canavanine-sensitive strains and arginine-suppressor mutations.

scholarly journals Anthranilate synthase/anthranilate 5-phosphoribosyl 1-pyrophosphate phosphoribosyltransferase from Aerobacter aerogenes

1972 ◽  
Vol 130 (3) ◽  
pp. 847-859 ◽  
Author(s):  
A. F. Egan ◽  
F. Gibson
Keyword(s):  
Escherichia Coli ◽  
Kinetic Studies ◽  
Competitive Inhibitor ◽  
Active Enzyme ◽  
The Other ◽  
Anthranilate Synthase ◽  
Aerobacter Aerogenes ◽  
Auxotrophic Mutants ◽  
Mutant Strains ◽  
Sequential Mechanism

1. Anthranilate synthase and phosphoribosyltransferase from Aerobacter aerogenes purify simultaneously and sediment together on sucrose gradients, showing that they occur as an enzyme aggregate. Both activities of the intact aggregate are subject to inhibition by tryptophan. 2. By using appropriate auxotrophic mutants it was shown that an intact active enzyme aggregate is formed when the components come from separate mutant strains. An intact active aggregate can also be formed when one component is from Escherichia coli and the other from A. aerogenes. 3. Phosphoribosyltransferase of A. aerogenes is active when not in an aggregate with anthranilate synthase, but is not subject to tryptophan inhibition, indicating that the inhibitor site is on the anthranilate synthase component. 4. Anthranilate synthase can be active and sensitive to tryptophan inhibition when complexed with an inactive phosphoribosyltransferase. 5. Kinetic studies on the anthranilate synthase activity show that tryptophan is a competitive inhibitor with respect to chorismate and a non-competitive inhibitor with respect to either glutamine or NH4+ ions. This is consistent with a sequential mechanism of the ordered type in which chorismate is the first reactant.

scholarly journals act Operon Control of Developmental Gene Expression in Myxococcus xanthus

2002 ◽  
Vol 184 (4) ◽  
pp. 1172-1179 ◽  
Author(s):  
Thomas M. A. Gronewold ◽  
Dale Kaiser
Keyword(s):  
Fruiting Body ◽  
Myxococcus Xanthus ◽  
The Other ◽  
Loss Of Function ◽  
Wild Type ◽  
Developmental Gene ◽  
Developmental Gene Expression ◽  
Mutant Strains ◽  
Genes Encoding ◽  
Signal Production

ABSTRACT Cell-bound C-signal guides the building of a fruiting body and triggers the differentiation of myxospores. Earlier work has shown that transcription of the csgA gene, which encodes the C-signal, is directed by four genes of the act operon. To see how expression of the genes encoding components of the aggregation and sporulation processes depends on C-signaling, mutants with loss-of-function mutations in each of the act genes were investigated. These mutations were found to have no effect on genes that are normally expressed up to 3 h into development and are C-signal independent. Neither the time of first expression nor the rate of expression increase was changed in actA, actB, actC, or actD mutant strains. Also, there was no effect on A-signal production, which normally starts before 3 h. By contrast, the null act mutants have striking defects in C-signal production. These mutations changed the expression of four gene reporters that are related to aggregation and sporulation and are expressed at 6 h or later in development. The actA and actB null mutations substantially decreased the expression of all these reporters. The other act null mutations caused either premature expression to wild-type levels (actC) or delayed expression (actD), which ultimately rose to wild-type levels. The pattern of effects on these reporters shows how the C-signal differentially regulates the steps that together build a fruiting body and differentiate spores within it.

scholarly journals Suppressor Mutations in the Study of Photosystem I Biogenesis: sll0088 Is a Previously Unidentified Gene Involved in Reaction Center Accumulation in Synechocystis sp. Strain PCC 6803

2003 ◽  
Vol 185 (13) ◽  
pp. 3878-3887 ◽  
Author(s):  
Jianping Yu ◽  
Gaozhong Shen ◽  
Tao Wang ◽  
Donald A. Bryant ◽  
John H. Golbeck ◽  
...  
Keyword(s):  
Photosystem I ◽  
Point Mutations ◽  
Kanamycin Resistance ◽  
Negative Regulator ◽  
Binding Motif ◽  
Wild Type ◽  
Photoautotrophic Growth ◽  
Suppressor Mutations ◽  
Mutant Strains ◽  
Pcc 6803

ABSTRACT In previous work, some members of our group isolated mutant strains of Synechocystis sp. strain PCC 6803 in which point mutations had been inserted into the psaC gene to alter the cysteine residues to the FA and FB iron-sulfur clusters in the PsaC subunit of photosystem I (J. P. Yu, I. R. Vassiliev, Y. S. Jung, J. H. Golbeck, and L. McIntosh, J. Biol. Chem. 272:8032-8039, 1997). These mutant strains did not grow photoautotrophically due to suppressed levels of chlorophyll a and photosystem I. In the results described here, we show that suppressor mutations produced strains that are capable of photoautotrophic growth at moderate light intensity (20 μmol m−2 s−1). Two separate suppressor strains of C14SPsaC, termed C14SPsaC-R62 and C14SPsaC-R18, were studied and found to have mutations in a previously uncharacterized open reading frame of the Synechocystis sp. strain PCC 6803 genome named sll0088. C14SPsaC-R62 was found to substitute Pro for Arg at residue 161 as the result of a G482→C change in sll0088, and C14SPsaC-R18 was found to have a three-amino-acid insertion of Gly-Tyr-Phe following Cys231 as the result of a TGGTTATTT duplication at T690 in sll0088. These suppressor strains showed near-wild-type levels of chlorophyll a and photosystem I, yet the serine oxygen ligand to FB was retained as shown by the retention of the S ≥ 3/2 spin state of the [4Fe-4S] cluster. The inactivation of sll0088 by insertion of a kanamycin resistance cartridge in the primary C14SPsaC mutant produced an engineered suppressor strain capable of photoautotrophic growth. There was no difference in psaC gene expression or in the amount of PsaC protein assembled in thylakoids between the wild type and an sll0088 deletion mutant. The sll0088 gene encodes a protein predicted to be a transcriptional regulator with sequence similarities to transcription factors in other prokaryotic and eukaryotic organisms, including Arabidopsis thaliana. The protein contains a typical helix-turn-helix DNA-binding motif and can be classified as a negative regulator by phylogenetic analysis. This suggests that the product of sll0088 has a role in regulating the biogenesis of photosystem I.

scholarly journals Regulation of the enzymes converting l-mandelate into benzoate in bacterium N.C.I.B. 8250

1972 ◽  
Vol 130 (4) ◽  
pp. 937-946 ◽  
Author(s):  
A. Livingstone ◽  
C. A. Fewson
Keyword(s):  
Alcohol Dehydrogenase ◽  
Single Cell ◽  
Benzyl Alcohol ◽  
Dehydrogenase Activity ◽  
The Other ◽  
Cell Free Extract ◽  
Mutant Strains ◽  
Benzaldehyde Dehydrogenase ◽  
Kinetics Of

l-Mandelate is oxidized to benzoate by the enzymes l-mandelate dehydrogenase, phenylglyoxylate carboxy-lyase and benzaldehyde dehydrogenase I. Conditions have been established for measuring these three enzymes as well as benzyl alcohol dehydrogenase, benzaldehyde dehydrogenase II and catechol 1,2-oxygenase in a single cell-free extract prepared from bacterium N.C.I.B. 8250. The kinetics of induction of all these enzymes have been measured under a variety of conditions. l-Mandelate dehydrogenase, phenylglyoxylate carboxy-lyase and benzaldehyde dehydrogenase I appear to be co-ordinately regulated because (a) their differential rates of synthesis are proportional to one another under various conditions of induction and repression, (b) they are specifically and gratuitously induced by thiophenoxyacetate and a number of other compounds, and (c) mutant strains have been isolated that lack all three enzymes. Phenylglyoxylate is the primary inducer of the regulon as mutant strains lacking phenylglyoxylate carboxy-lyase form the other two enzymes in the presence of l-mandelate or phenylglyoxylate, whereas in mutant strains devoid of l-mandelate dehydrogenase activity only phenylglyoxylate induces phenylglyoxylate carboxy-lyase and benzaldehyde dehydrogenase I.

scholarly journals Analysis of the movement of Chlamydomonas flagella:" the function of the radial-spoke system is revealed by comparison of wild-type and mutant flagella.

1982 ◽  
Vol 92 (3) ◽  
pp. 722-732 ◽  
Author(s):  
C J Brokaw ◽  
D J Luck ◽  
B Huang
Keyword(s):  
Recovery Phase ◽  
Wild Type ◽  
Radial Spoke ◽  
Suppressor Mutations ◽  
Mutant Strains ◽  
Type Pattern ◽  
Dynein Arms ◽  
Beta Frequency ◽  
Amplitude Pattern ◽  
Asymmetric Bending

The mutation uni-1 gives rise to uniflagellate Chlamydomonas cells which rotate around a fixed point in the microscope field, so that the flagellar bending pattern can be photographed easily. This has allowed us to make a detailed analysis of the wild-type flagellar bending pattern and the bending patterns of flagella on several mutant strains. Cells containing uni-1, and recombinants of uni-1 with the suppressor mutations, suppf-1 and suppf-3, show the typical asymmetric bending pattern associated with forward swimming in Chlamydomonas, although suppf-1 flagella have about one-half the normal beta frequency, apparently as the result of defective function of the outer dynein arms. The pf-17 mutation has been shown to produce nonmotile flagella in which radial spoke heads and five characteristic axonemal polypeptides are missing. Recombinants containing pf-17 and either suppf-2 or suppf-3 have motile flagella, but still lack radial-spoke heads and the associated polypeptides. The flagellar bending pattern of these recombinants lacking radial-spoke heads is a nearly symmetric, large amplitude pattern which is quite unlike the wild-type pattern. However, the presence of an intact radial-spoke system is not required to convert active sliding into bending and is not required for bend initiation and bend propagation, since all of these processes are active in suppfpf-17 recombinants. The function of the radial-spoke system appears to be to convert the symmetric bending pattern displayed by these recombinants into the asymmetric bending pattern required for efficient swimming, by inhibiting the development of reverse bends during the recovery phase of the bending cycle.

scholarly journals Genetic Characterization of DNA Region Containing the trh and ure Genes of Vibrio parahaemolyticus

2000 ◽  
Vol 68 (10) ◽  
pp. 5742-5748 ◽  
Author(s):  
Kwon-Sam Park ◽  
Tetsuya Iida ◽  
Yoshiharu Yamaichi ◽  
Tomohito Oyagi ◽  
Koichiro Yamamoto ◽  
...  
Keyword(s):  
Vibrio Parahaemolyticus ◽  
Open Reading Frames ◽  
The Other ◽  
Close Proximity ◽  
Mutant Strains ◽  
Thermostable Direct Hemolysin ◽  
Urease Production ◽  
Reading Frames ◽  
Type Nickel

ABSTRACT We have demonstrated that possession of the gene for thermostable direct hemolysin-related hemolysin (trh) coincides with the presence of the urease gene among clinical Vibrio parahaemolyticus strains and that the location of the two genes are in close proximity on the chromosome. Here, we cloned and sequenced the 15,754-bp DNA region containing the trh gene and the gene cluster for urease production from the chromosome of clinicalV. parahaemolyticus (TH3996). We found 16 open reading frames (ORFs) and a lower G+C content (41%) compared with the total genome of this bacterium (46 to 47%). The ure cluster consisted of eight genes, namely, ureDABCEFG andureR. ureR was located 5.2 kb upstream of the other seven genes in the opposite direction. The genetic organization and sequences of the ure genes resembled those found in Proteus mirabilis. Between ureR and the other uregenes, there were five ORFs, which are homologous with the nickel transport operon (nik) of Escherichia coli. We disrupted each of the ureR, ureC, andnikD genes in TH3996 by homologous recombination and analyzed the phenotype of the mutants. In the presence of urea these mutant strains had dramatically less urease activity than the strain they were derived from. Disruption of ureR,nikD, or ureC, however, had no effect on TRH production. The DNA region containing the trh,nik, and ure genes was found in onlytrh-positive strains and not in Kanagawa phenomenon-positive and environmental V. parahaemolyticusstrains. At the end of the region, an insertion sequence-like element existed. These results suggest that the DNA region was introduced intoV. parahaemolyticus in the past through a mechanism mediated by insertion sequences. This is the first reported case that the genes for an ATP-binding cassette-type nickel transport system, which may play a role in nickel transport through bacterial cytoplasmic membrane, are located adjacent to the ure cluster on the genome of an organism.

scholarly journals A suppressor of a mating-type limited zygotic lethal allele also suppresses uniparental chloroplast gene transmission in Chlamydomonas monoica.

Genetics ◽  
1994 ◽  
Vol 136 (3) ◽  
pp. 867-877
Author(s):  
K VanWinkle-Swift ◽  
R Hoffman ◽  
L Shi ◽  
S Parker
Keyword(s):  
Chloroplast Dna ◽  
Mating Type ◽  
Uniparental Inheritance ◽  
Chloroplast Gene ◽  
Suppressor Mutations ◽  
Chloroplast Genomes ◽  
Mutant Strains ◽  
Resistance Markers ◽  
Lethal Allele ◽  
Chlamydomonas Monoica

Abstract Uniparental inheritance of Chlamydomonas chloroplast genes is thought to involve modification of maternal (mt+) chloroplast genomes to protect against a nuclease that is activated after gamete fusion. The mating-type limited mtl-1 mutant strain of Chlamydomonas monoica is unable to protect mt(+)-derived chloroplast DNA. Zygotes homozygous for mtl-1 lose all chloroplast DNA and fail to germinate. We have selected for suppression of this zygote-specific lethality, and have obtained 20 mutant strains that produce viable homozygotes despite the continued presence of the mtl-1 allele. Genetic analysis indicates that the suppressor mutations are all recessive alleles at a single locus (sup-1) which is unlinked to mtl-1. Crosses between sup-1 strains carrying distinctive chloroplast antibiotic resistance markers also show predominantly biparental chloroplast gene transmission. Chloroplast nucleoids of both parental origins (stained with the DNA-specific fluorochrome, DAPI) are retained in the zygotes homozygous for sup-1. The data are compatible with the idea that the sup-1 (suppressor of uniparental inheritance) locus may encode a chloroplast DNA nuclease that is expressed from both parental genomes.

scholarly journals ISOLATION AND GENETIC ANALYSIS OF MUTANT STRAINS OF CHLAMYDOMONAS REINHARDI DEFECTIVE IN GAMETIC DIFFERENTIATION

Genetics ◽  
1976 ◽  
Vol 82 (2) ◽  
pp. 169-186
Author(s):  
Ursula W Goodenough ◽  
Carol Hwang ◽  
Howard Martin
Keyword(s):  
Genetic Analysis ◽  
Cell Fusion ◽  
Mating Type ◽  
Normal Growth ◽  
The Other ◽  
Genetic Dissection ◽  
Structural Studies ◽  
Tetrad Analysis ◽  
Mating Structure ◽  
Mutant Strains

ABSTRACT Impotent mutant strains of Chlamydomonas reinhardi, mating-type (mt) plus, are described that have normal growth and motility but fail to differentiate into normal gametes. Procedures for their isolation and their genetic analysis are described. Five of the imp strains (imp-2, imp-5, imp-6, imp-7, and imp-8) exhibit no flagellar agglutination when mixed with mt  - or mt  + gametes; these strains have been induced to form rare zygotes with mt  - gametes and the mutations are shown to be unlinked to the mt locus (with the possible exception of imp-7). Two of the strains (imp-3 and imp-4) carry leaky mutations that affect cell fusion; neither mutation is found by tetrad analysis to be linked to mt or to the other. Cells of the imp-1 strain agglutinate well with mt  - gametes and active agglutination continues for up to 48 hours, but cell fusion occurs only very rarely. Analysis of these rare zygotes indicates that imp-1 is closely linked to the mt  + locus, and fine-structural studies reveal that imp-1gametes produce a mutant mating structure involved in zygotic cell fusion. The development of sexuality in C. reinhardi therefore appears amenable to genetic dissection.

scholarly journals EPISTATIC GROUPING OF REPAIR-DEFICIENT MUTANTS IN NEUROSPORA: COMPARATIVE ANALYSIS OF TWO uvs-3 ALLELES, uvs-6 AND THEIR mus DOUBLE MUTANT STRAINS

Genetics ◽  
1983 ◽  
Vol 105 (1) ◽  
pp. 19-33
Author(s):  
Etta Käfer
Keyword(s):  
Comparative Analysis ◽  
Double Mutant ◽  
Extracellular Enzyme ◽  
The Other ◽  
Methyl Methanesulfonate ◽  
Lower Sensitivity ◽  
Sensitive Mutant ◽  
X Ray ◽  
Mutant Strains ◽  
Dnase A

ABSTRACT The nuclease halo mutant, nuh-4, of Neurospora crassa was identified conclusively as an allele of uvs-3, a gene involved in error-prone DNA repair. Like uvs-3, nuh-4 showed spontaneous mutator effects, and any previous contradictory findings were found to be due to newly arisen mutants. In normal strains the two alleles are noncomplementing and indistinguishable for sensitivity to UV and methyl methanesulfonate (MMS). Like uvs-3, nuh-4 lacked secretion of the extracellular enzyme, DNase A, a Ca++-dependent strand-nonspecific endonuclease which was found to be phosphate repressible. However, nuh-4 differed from uvs-3 in showing much higher conidial viability and lower sensitivity to ionizing radiation and mitomycin C.——Epistatic relationships of the two uvs-3 alleles with seven other MMS-sensitive mutants were determined and compared with those of the highly X-ray-sensitive mutant, uvs-6. Three epistatic groups were found, based on survival of double mutant strains relative to that of their component single mutant strains after treatment with MMS. Both, uvs-3 and nuh-4, were epistatic to mus-9 which also is a mutator. None of the three produced viable double mutants in crosses to uvs-6. On the other hand, uvs-6, but not the uvs-3 alleles, was found to be epistatic to mus-7 and mus-10. The excision-defective uvs-2 and mus-8 both showed synergism with the uvs-3 alleles and with uvs-6, forming a third, separate epistatic group.

Suppression of dual-effect mutants of the L-ribulokinase structural gene of Escherichia coli B/r

1971 ◽  
Vol 17 (8) ◽  
pp. 1105-1114
Author(s):  
Morad Abou-Sabe
Keyword(s):  
Enzyme Level ◽  
The Other ◽  
Wild Type ◽  
Dual Effect ◽  
Wild Type Level ◽  
Suppressor Mutations ◽  
Extragenic Suppressors ◽  
Escherichia Coli B ◽  
Distinct Increase ◽  
Arabinose Isomerase

A number of extragenic suppressors for two-dual effect, polarity, and hyperinducible L-ribulokinaseless mutants were isolated and enzymatically characterized. The effect of the suppressors on L-arabinose isomerase and L-ribulokinase enzyme activities was tested using a variety of arar suppressor-carrying strains. The effect of these suppressor mutations on T4 amber and ocher mutants was also studied. Results show that low-dual-effect, i.e. polarity, araB− suppressor-carrying strains invariably have a distinct increase in the L-arabinose isomerase enzyme level, above the wild-type level, irrespective of the restoration of the L-ribulokinase enzyme activity. High-dual-effect, hyperinducible, suppressed mutants, on the other hand, were not significantly altered in their L-arabinose isomerase enzyme level. It is also found that four different T4 amber mutants were suppressible by all tested suppressor-carrying strains, while T4 ocher mutants were not. It is concluded that the suppressor mutations studied are amber-like suppressors acting at the translation level, and that both polarity mutant araB68 and hyperinducible mutant araBA87 are nonsense mutants. The phenomenon of hyperinducibility is also discussed.

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