scholarly journals Suppressors of recB mutations in Salmonella typhimurium.

Genetics ◽  
1994 ◽  
Vol 138 (1) ◽  
pp. 11-28 ◽  
Author(s):  
N R Benson ◽  
J Roth
Keyword(s):  
Escherichia Coli ◽  
Salmonella Typhimurium ◽  
Mitomycin C ◽  
Ultraviolet Light ◽  
Genetic Background ◽  
Deletion Mutants ◽  
Wild Type ◽  
Insertion And Deletion ◽  
Type Strains ◽  
Tandem Duplications

Abstract Using a screen that directly assesses transductional proficiency, we have isolated suppressors of recB mutations in Salmonella typhimurium. The alleles of sbcB reported here are phenotypically distinct from those isolated in Escherichia coli in that they restore recombination proficiency (Rec+), resistance to ultraviolet light (UVR), and mitomycin C resistance (MCR) in the absence of an accompanying sbcCD mutation. In addition the sbcB alleles reported here are co-dominant to sbcB+. We have also isolated insertion and deletion mutants of the sbcB locus. These null mutations suppress only the UVS phenotype of recB mutants. We have also isolated sbcCD mutations, which map near proC. These sbcCD mutations increase the viability, recombination proficiency and MCR of both the transductional recombination suppressors (sbcB1 & sbcB6) and the sbcB null mutations. S. typhimurium recB sbcB1 sbcCD8 strains are 15-fold more recombination proficient than wild-type strains. The increase in transductants in these strains is accompanied by a loss of abortive transductants suggesting that these fragments are accessible to the mutant recombination apparatus. Using tandem duplications, we have constructed sbcB merodiploids and found that, in a recB mutant sbcCD+ genetic background, the sbcB+ allele is dominant to sbcB1 for transductional recombination but co-dominant for UVR and MCR. However, in a recB sbcCD8 genetic background, the sbcB1 mutation is co-dominant to sbcB+ for all phenotypes. Our results lead us to suggest that the SbcB and SbcCD proteins have roles in RecBCD-dependent recombination.

scholarly journals Identification ofvib-1, a Locus Involved in Vegetative Incompatibility Mediated byhet-cinNeurospora crassa

Genetics ◽  
2002 ◽  
Vol 162 (1) ◽  
pp. 89-101 ◽  
Author(s):  
Qijun Xiang ◽  
N Louise Glass
Keyword(s):  
Acid Phosphatase ◽  
Recognition System ◽  
Deletion Mutants ◽  
Wild Type ◽  
Vegetative Incompatibility ◽  
Death Rates ◽  
Self Recognition ◽  
Allelic Differences ◽  
Native Gel ◽  
Type Strains

AbstractA non-self-recognition system called vegetative incompatibility is ubiquitous in filamentous fungi and is genetically regulated by het loci. Different fungal individuals are unable to form viable heterokaryons if they differ in allelic specificity at a het locus. To identify components of vegetative incompatibility mediated by allelic differences at the het-c locus of Neurospora crassa, we isolated mutants that suppressed phenotypic aspects of het-c vegetative incompatibility. Three deletion mutants were identified; the deletions overlapped each other in an ORF named vib-1 (vegetative incompatibility blocked). Mutations in vib-1 fully relieved growth inhibition and repression of conidiation conferred by het-c vegetative incompatibility and significantly reduced hyphal compartmentation and death rates. The vib-1 mutants displayed a profuse conidiation pattern, suggesting that VIB-1 is a regulator of conidiation. VIB-1 shares a region of similarity to PHOG, a possible phosphate nonrepressible acid phosphatase in Aspergillus nidulans. Native gel analysis of wild-type strains and vib-1 mutants indicated that vib-1 is not the structural gene for nonrepressible acid phosphatase, but rather may regulate nonrepressible acid phosphatase activity.

scholarly journals Isolation of a gene required for programmed initiation of development by Aspergillus nidulans.

1992 ◽  
Vol 12 (9) ◽  
pp. 3827-3833 ◽  
Author(s):  
T H Adams ◽  
W A Hide ◽  
L N Yager ◽  
B N Lee
Keyword(s):  
Life Cycle ◽  
Aspergillus Nidulans ◽  
Optimal Growth ◽  
Growth Conditions ◽  
Nutrient Deprivation ◽  
Deletion Mutants ◽  
Wild Type ◽  
Microbial Development ◽  
Type Strains ◽  
Posttranscriptional Level

In contrast to many other cases in microbial development, Aspergillus nidulans conidiophore production initiates primarily as a programmed part of the life cycle rather than as a response to nutrient deprivation. Mutations in the acoD locus result in "fluffy" colonies that appear to grow faster than the wild type and proliferate as undifferentiated masses of vegetative cells. We show that unlike wild-type strains, acoD deletion mutants are unable to make conidiophores under optimal growth conditions but can be induced to conidiate when growth is nutritionally limited. The requirement for acoD in conidiophore development occurs prior to activation of brlA, a primary regulator of development. The acoD transcript is present both in vegetative hyphae prior to developmental induction and in developing cultures. However, the effects of acoD mutations are detectable only after developmental induction. We propose that acoD activity is primarily controlled at the posttranscriptional level and that it is required to direct developmentally specific changes that bring about growth inhibition and activation of brlA expression to result in conidiophore development.

scholarly journals In Vivo Titration of Mitomycin C Action by Four Escherichia coli Genomic Regions on Multicopy Plasmids

2001 ◽  
Vol 183 (7) ◽  
pp. 2259-2264 ◽  
Author(s):  
Yan Wei ◽  
Amy C. Vollmer ◽  
Robert A. LaRossa
Keyword(s):  
Escherichia Coli ◽  
Mitomycin C ◽  
Transcriptional Activation ◽  
Efflux Pump ◽  
Wild Type ◽  
Potent Inducer ◽  
E Coli ◽  
Genomic Regions

ABSTRACT Mitomycin C (MMC), a DNA-damaging agent, is a potent inducer of the bacterial SOS response; surprisingly, it has not been used to select resistant mutants from wild-type Escherichia coli. MMC resistance is caused by the presence of any of four distinctE. coli genes (mdfA, gyrl, rob, andsdiA) on high-copy-number vectors. mdfAencodes a membrane efflux pump whose overexpression results in broad-spectrum chemical resistance. The gyrI (also called sbmC) gene product inhibits DNA gyrase activity in vitro, while the rob protein appears to function in transcriptional activation of efflux pumps. SdiA is a transcriptional activator of ftsQAZ genes involved in cell division.

scholarly journals Natural Genetic Transformation of Clinical Isolates of Escherichia coli in Urine and Water

2002 ◽  
Vol 68 (1) ◽  
pp. 440-443 ◽  
Author(s):  
Markus Woegerbauer ◽  
Bernard Jenni ◽  
Florian Thalhammer ◽  
Wolfgang Graninger ◽  
Heinz Burgmann
Keyword(s):  
Escherichia Coli ◽  
Antibiotic Resistance ◽  
Current Knowledge ◽  
Antibiotic Resistance Genes ◽  
Aquatic Environments ◽  
Wild Type ◽  
E Coli ◽  
Naturally Occurring ◽  
Natural Genetic Transformation ◽  
Type Strains

ABSTRACT Transfer of plasmid-borne antibiotic resistance genes in Escherichia coli wild-type strains is possible by transformation under naturally occurring conditions in oligotrophic, aquatic environments containing physiologic concentrations of calcium. In contrast, transformation is suppressed in nitrogen-rich body fluids like urine, a common habitat of uropathogenic strains. Current knowledge indicates that transformation of these E. coli wild-type strains is of no relevance for the acquisition of resistance in this clinically important environment.

scholarly journals Comparison of the Proteomes of Three Yeast Wild Type Strains: CEN.PK2, FY1679 and W303

2001 ◽  
Vol 2 (4) ◽  
pp. 207-225 ◽  
Author(s):  
Adelina Rogowska-Wrzesinska ◽  
Peter Mose Larsen ◽  
Anders Blomberg ◽  
Angelika Görg ◽  
Peter Roepstorff ◽  
...  
Keyword(s):  
Gel Electrophoresis ◽  
Genetic Background ◽  
Function Analysis ◽  
Spectrometric Analysis ◽  
Yeast Mutant ◽  
Wild Type ◽  
Phenotypic Differences ◽  
Mutant Phenotypes ◽  
Gene Function Analysis ◽  
Type Strains

Yeast deletion strains created during gene function analysis projects very often show drastic phenotypic differences depending on the genetic background used. These results indicate the existence of important molecular differences between the CEN.PK2, FY1679 and W303 wild type strains. To characterise these differences we have compared the protein expression levels between CEN.PK2, FY1679 and W303 strains using twodimensional gel electrophoresis and identified selected proteins by mass spectrometric analysis. We have found that FY1679 and W303 strains are more similar to each other than to the CEN.PK2 strain. This study identifies 62 proteins that are differentially expressed between the strains and provides a valuable source of data for the interpretation of yeast mutant phenotypes observed in CEN.PK2, FY1679 and W303 strains.

scholarly journals A Combination of Three Mutations, dcd,pyrH, and cdd, Establishes Thymidine (Deoxyuridine) Auxotrophy in thyA+ Strains of Salmonella typhimurium

1998 ◽  
Vol 180 (22) ◽  
pp. 5891-5895 ◽  
Author(s):  
Nevan J. Krogan ◽  
Michelle L. Zaharik ◽  
Jan Neuhard ◽  
Rod A. Kelln
Keyword(s):  
Salmonella Typhimurium ◽  
Genetic Background ◽  
Kinase Activity ◽  
Null Mutation ◽  
Wild Type ◽  
Gene Encoding ◽  
Deoxycytidine Deaminase ◽  
In The Wild ◽  
Ump Kinase ◽  
Thymidine Auxotrophy

ABSTRACT The dum gene of Salmonella typhimurium was originally identified as a gene involved in dUMP synthesis (C. F. Beck et al., J. Bacteriol. 129:305–316, 1977). In the genetic background used in their selection, the joint acquisition of adcd (dCTP deaminase) and a dum mutation established a condition of thymidine (deoxyuridine) auxotrophy. In this study, we show that dum is identical to pyrH, the gene encoding UMP kinase. The level of UMP kinase activity in thedum mutant was found to be only 30% of that observed for the dum + strain. Thymidine prototrophy was restored to the original dum dcd mutant (KP1361) either by transduction using a pyrH + donor or by complementation with either of twopyrH +-carrying plasmids. Thymidine auxotrophy could be reconstructed in the dum + derivative (KP1389) by the introduction of a mutant pyrH allele. To define the minimal mutational complement necessary to produce thymidine auxotrophy in thyA + strains, adcd::Km null mutation was constructed. In the wild-type background, dcd::Km alone or in combination with a pyrH (dum) mutation did not result in a thymidine requirement. A third mutation, cdd(cytidine-deoxycytidine deaminase), was required together with thedcd and pyrH mutations to impart thymidine auxotrophy.

A Stable 44S Intermediate in the Autodigestion of 50S Ribosomal Subunits

1971 ◽  
Vol 29 ◽  
pp. 430-431
Author(s):  
John H. Nisbet ◽  
Henry S. Slayter
Keyword(s):  
Escherichia Coli ◽  
Molecular Weight ◽  
Ribosomal Rna ◽  
Gel Electrophoresis ◽  
Type Strain ◽  
Wild Type Strain ◽  
Ribosomal Subunit ◽  
Wild Type ◽  
Ribosomal Subunits ◽  
Type Strains

Wild - type strains of Escherichia coli are known to contain as many as four endogenous nucleases (Ref. 1). These are commonly found associated with the ribosomes after extraction from the cell, but may be removed, with the exception of RNase IV, by washing the ribosomes in NH4Cl (at 0.2 M and higher concentrations). We have examined the effect of these nucleases on the 50S ribosomal subunit of one wild-type strain, K12 (Hfr 3000), by incubating the unwashed particles at 37° in the presence of varying magnesium concentrations.At 10-4 molar magnesium (slower at 10-3 molar), the 50S particle is converted to a species sedimenting at about 44S. About 20% of the total O.D260 is liberated at the same time. Continued incubation leads to the release of more O.D260 material while the RNA remaining in the 44S (Fig. 1) particle is progressively cleaved, eventually to the point where it consists of one principal fragment of molecular weight 0.42 x 106 daltons and several lesser fragments. The ribosomal RNA and proteins have been characterized by acrylamide gel electrophoresis.

Colicins G and H and their host strains

1991 ◽  
Vol 37 (10) ◽  
pp. 751-757 ◽  
Author(s):  
D. E. Bradley
Keyword(s):  
Escherichia Coli ◽  
Key Words ◽  
Side Chains ◽  
Human Origin ◽  
Wild Type ◽  
E Coli ◽  
Molecular Weights ◽  
Protein Receptors ◽  
Type Strains ◽  
Host Strains

Escherichia coli strains CA46(pColG) and CA58(pColH) each apparently synthesized two generally similar bactericidal colicin proteins whose molecular weights were approximately 5 500 and 100 000. These proteins were more resistant to trypsin than representative colicins A, D, E1, and V. The smooth wild-type strains harbouring plasmids pColG and pColH were serotyped O169:NM and O30:NM, respectively, being typically associated with nonpathogenic E. coli of human origin. Rough and semirough variants, which were selected using resistance to novobiocin, were intrinsically insensitive to almost as many colicins (10 tested) as their parents. For this reason the wild-type strains would not be useful for identifying colicins G and H on the basis of immunity. The O antigenic side chains of both wild-type strains shielded three of the six bacteriophage protein receptors tested. Key words: colicin, protein, plasmid, O antigen, bacteriophage.

Sign in / Sign up

Export Citation Format

Share Document