Isolation and characterization of pyrimidine mutants of Salmonella typhimurium altered in expression of pyrC, pyrD, and pyrE

1985 ◽  
Vol 31 (11) ◽  
pp. 981-987 ◽  
Author(s):  
Rod A. Kelln ◽  
J. Neuhard ◽  
Lisbeth Stauning
Keyword(s):  
Salmonella Typhimurium ◽  
Biochemical Characterization ◽  
Lac Operon ◽  
Structural Genes ◽  
General Applicability ◽  
Cis Acting ◽  
Isolation And Characterization ◽  
Mutant Strains ◽  
The Individual

Parental strains of Salmonella typhimurium having a specific pyr gene (pyrC, pyrD, or pyrE) fused to the structural genes of the lac operon through the specialized transducing phage Mu dl (ApRlac) were used to construct thermostable derivatives for purposes of conducting a genetic and biochemical characterization of the individual pyr genes. The direction of transcription of each pyr gene in relation to the current linkage map was defined with both pyrC and pyrE being transcribed counterclockwise and pyrD exhibiting clockwise transcription. Mutants displaying increased pyr gene expression were isolated employing a genetic strategy which is of general applicability. Among the mutants, only one isolate was found to possess a mutation which was unlinked to the specific pyr gene under study; the other isolates harbored linked mutations which were inferred to be cis-acting. Additional studies demonstrated that in conditions of severe pyrimidine limitation, further derepression could still occur in the mutant strains.

scholarly journals Isolation and Characterization of Two Lytic Bacteriophages Infecting a Multi-Drug Resistant Salmonella Typhimurium and Their Efficacy to Combat Salmonellosis in Ready-to-Use Foods

2021 ◽  
Vol 9 (2) ◽  
pp. 423
Author(s):  
Ahmed Esmael ◽  
Ehab Azab ◽  
Adil A. Gobouri ◽  
Mohamed A. Nasr-Eldin ◽  
Mahmoud M. A. Moustafa ◽  
...  
Keyword(s):  
Salmonella Typhimurium ◽  
Multidrug Resistant ◽  
Viable Count ◽  
Food Storage ◽  
Chicken Breast ◽  
Whole Genome Analysis ◽  
Isolation And Characterization ◽  
Phage Cocktail ◽  
Global Threat

Foodborne salmonellosis is a global threat to public health. In the current study, we describe the isolation and characterization of two broad-spectrum, lytic Salmonella phages: SPHG1 and SPHG3 infecting a multidrug-resistant Salmonella Typhimurium EG.SmT3. Electron microscopy and whole genome analysis identified SPHG1 as a Myovirus, while SPHG3 as a new member of the genus “Kuttervirus” within the family Ackermannviridae. SPHG1 and SPHG3 had a lysis time of 60 min. with burst sizes of 104 and 138 PFU/cell, respectively. The two phages were robust at variable temperatures and pH ranges that match the corresponding values of most of the food storage and processing conditions. A phage cocktail containing the two phages was stable in the tested food articles for up to 48 h. The application of the phage cocktail at MOIs of 1000 or 100 resulted in a significant reduction in the viable count of S. Typhimurium by 4.2 log10/sample in milk, water, and on chicken breast. Additionally, the phage cocktail showed a prospective ability to eradicate and reduce the biofilm that formed by S. Typhimurium EG.SmT3. A phage cocktail of SPHG1 and SPHG3 is considered as a promising candidate as a biocontrol agent against foodborne salmonellosis due to its broad host ranges, highly lytic activities, and the absence of any virulence or lysogeny-related genes in their genomes.

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.

Analysis of the structural genes encoding M-factor in the fission yeast Schizosaccharomyces pombe: identification of a third gene, mfm3

1994 ◽  
Vol 14 (6) ◽  
pp. 3895-3905
Author(s):  
S Kjaerulff ◽  
J Davey ◽  
O Nielsen
Keyword(s):  
Schizosaccharomyces Pombe ◽  
Fission Yeast ◽  
Mutational Analysis ◽  
M Cells ◽  
Gene Products ◽  
Structural Genes ◽  
Triple Mutant ◽  
Isolation And Characterization ◽  
Genes Encoding

We previously identified two genes, mfm1 and mfm2, with the potential to encode the M-factor mating pheromone of the fission yeast Schizosaccharomyces pombe (J. Davey, EMBO J. 11:951-960, 1992), but further analysis revealed that a mutant strain lacking both genes still produced active M-factor. Here we describe the isolation and characterization of a third M-factor gene, mfm3. A mutant lacking all three genes fails to produce M-factor, indicating that all functional M-factor genes now have been identified. The triple mutant exhibits an absolute mating defect in M cells, a defect that is not rescued by addition of exogenous M-factor. A mutational analysis reveals that all three mfm genes contribute to the production of M-factor. Their transcription is limited to M cells and requires the mat1-Mc and ste11 gene products. Each gene is induced when the cells are starved of nitrogen and further induced by a pheromone signal. Additionally, the signal transduction machinery associated with the pheromone response is required for transcription of the mfm genes in both stimulated and unstimulated cells.

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