Two new mutant loci (smhB and lytD) in Escherichia coli which confer temperature-sensitive growth and lysis phenotypes

1990 ◽  
Vol 36 (12) ◽  
pp. 827-833
Author(s):  
Dexi Dai ◽  
Edward E. Ishiguro
Keyword(s):  
Escherichia Coli ◽  
Key Words ◽  
Linkage Map ◽  
Temperature Sensitive ◽  
Restrictive Temperature ◽  
Suppressor Activity ◽  
Peptidoglycan Synthesis ◽  
Extragenic Suppressor ◽  
Temperature Sensitive Mutation ◽  
Key Words Temperature

A temperature-sensitive mutation in the murH gene of Escherichia coli confers a lysis phenotype at the restrictive temperature. An extragenic suppressor of murH apparently representing a new locus at 12.5 min on the linkage map and designated smhB is described. The smhB mutation by itself also conferred a temperature-sensitive lysis phenotype. A mutation in another new locus designated lytD which arose spontaneously in the smhB mutant was mapped close to smhB at 12.7 min on the linkage map. The lytD mutation by itself conferred a temperature-sensitive lysis phenotype indistinguishable from that of the murH mutant. Thus, the suppression of lysis in the smhB murH and the smhB lytD double mutants suggests a mechanism involving the reciprocal suppression of the two individual lysis-causing mutant alleles. The suppressor activity of smhB was apparently relatively specific in that smhB failed to prevent lysis induced by either mutational (murE or murF) or antibiotic-induced blocks in peptidoglycan synthesis. This suggests that murH, smhB, and lytD may be functionally related. Key words: temperature-sensitive mutation, Escherichia coli, lysis phenotype, suppression.

Genetic mapping of the lytA and lytB loci of Escherichia coli, which are involved in penicillin tolerance and control of the stringent response

1992 ◽  
Vol 38 (9) ◽  
pp. 975-978 ◽  
Author(s):  
Robin E. Harkness ◽  
Wolfgang Kusser ◽  
Bei-jing Qi ◽  
Edward E. Ishiguro
Keyword(s):  
Escherichia Coli ◽  
Genetic Mapping ◽  
Key Words ◽  
Linkage Map ◽  
Stringent Response ◽  
Temperature Sensitive ◽  
Restrictive Temperature ◽  
Temperature Sensitive Mutants ◽  
And Control

The mutations in nine independently isolated temperature-sensitive mutants of Escherichia coli, which exhibited penicillin tolerance and induction of the stringent response at the restrictive temperature, were assigned to two new loci designated lytA (7 alleles) and lytB (2 alleles) at 58 and 0.4 min on the linkage map, respectively. Key words: bacteriolysis, penicillin tolerance, stringent response.

Two new genes (smhA and lytE) apparently functionally related to the murH gene of Escherichia coli

1991 ◽  
Vol 37 (2) ◽  
pp. 122-127
Author(s):  
Dexi Dai ◽  
Edward E. Ishiguro
Keyword(s):  
Escherichia Coli ◽  
Spontaneous Mutation ◽  
Temperature Sensitive ◽  
Restrictive Temperature ◽  
Suppressor Activity ◽  
Peptidoglycan Synthesis ◽  
New Genes ◽  
New Gene ◽  
Extragenic Suppressors ◽  
Derivatives Of

The murH mutant of Escherichia coli exhibits temperature-sensitive growth and lysis at the restrictive temperature. Temperature-resistant derivatives of the mutant occurred at a frequency of about 3 × 10−6. All of the seven independent isolates examined were shown to be pseudorevertants carrying extragenic suppressors of murH, which mapped at 24.5 min on the linkage map. One allele, apparently representing a new locus, designated smhA, was characterized further. The smhA mutation by itself conferred no recognizable phenotype. However, smhA suppressed the temperature-sensitive lysis phenotype of the murH mutant. The smhA mutant acquired a spontaneous mutation in another new gene, designated lytE, which was mapped at 25 min. The lytE mutation by itself conferred a temperature-sensitive lysis phenotype indistinguishable from that of the murH mutant. The lytE mutation was suppressed by smhA as well as by another suppressor of murH designated smhB. The suppressor activity of smhA was apparently relatively specific in that smhA failed to prevent lysis caused by either mutational or antibiotic-induced blocks in peptidoglycan synthesis. The possibility that the smhA and lytE genes are functionally related to murH is considered. Key words: bacteriolysis, peptidoglycan, smhA, lytE.

scholarly journals THE SELECTION OF S. CEREVISIAE MUTANTS DEFECTIVE IN THE START EVENT OF CELL DIVISION

Genetics ◽  
1980 ◽  
Vol 95 (3) ◽  
pp. 561-577 ◽  
Author(s):  
Steven I Reed
Keyword(s):  
Cell Division ◽  
Genetic Analysis ◽  
Linkage Map ◽  
Nuclear Genes ◽  
Temperature Sensitive ◽  
Restrictive Temperature ◽  
Mating Pheromone ◽  
Preliminary Characterization ◽  
Complementation Groups ◽  
Selection Of

ABSTRACT Thirty-three temperature-sensitive mutations defective in the start event of the cell division cycle of Saccharomyces cereuisiae were isolated and subjected to preliminary characterization. Complementation studies assigned these mutations to four complementation groups, one of which, cdc28, has been described previously. Genetic analysis revealed that these complementation groups define single nuclear genes, unlinked to one another. One of the three newly identified genes, cdc37, has been located in the yeast linkage map on chromosome IV, two meiotic map units distal to hom2.—Each mutation produces stage-specific arrest of cell division at start, the same point where mating pheromone interrupts division. After synchronization at start by incubation at the restrictive temperature, the mutants retain the capacity to enlarge and to conjugate.

Genetic exploration of interactive domains in RNA polymerase II subunits

1990 ◽  
Vol 10 (5) ◽  
pp. 1908-1914
Author(s):  
C Martin ◽  
S Okamura ◽  
R Young
Keyword(s):  
Escherichia Coli ◽  
Saccharomyces Cerevisiae ◽  
Rna Polymerase ◽  
Rna Polymerase Ii ◽  
Temperature Sensitive ◽  
Suppressor Mutations ◽  
Region I ◽  
Temperature Sensitive Mutation ◽  
Allele Specific ◽  
Separate Protein

The two large subunits of RNA polymerase II, RPB1 and RPB2, contain regions of extensive homology to the two large subunits of Escherichia coli RNA polymerase. These homologous regions may represent separate protein domains with unique functions. We investigated whether suppressor genetics could provide evidence for interactions between specific segments of RPB1 and RPB2 in Saccharomyces cerevisiae. A plasmid shuffle method was used to screen thoroughly for mutations in RPB2 that suppress a temperature-sensitive mutation, rpb1-1, which is located in region H of RPB1. All six RPB2 mutations that suppress rpb1-1 were clustered in region I of RPB2. The location of these mutations and the observation that they were allele specific for suppression of rpb1-1 suggests an interaction between region H of RPB1 and region I of RPB2. A similar experiment was done to isolate and map mutations in RPB1 that suppress a temperature-sensitive mutation, rpb2-2, which occurs in region I of RPB2. These suppressor mutations were not clustered in a particular region. Thus, fine structure suppressor genetics can provide evidence for interactions between specific segments of two proteins, but the results of this type of analysis can depend on the conditional mutation to be suppressed.

scholarly journals The mechanism of recA polA lethality: suppression by RecA-independent recombination repair activated by the lexA(Def) mutation in Escherichia coli.

Genetics ◽  
1995 ◽  
Vol 139 (4) ◽  
pp. 1483-1494 ◽  
Author(s):  
Y Cao ◽  
T Kogoma
Keyword(s):  
Escherichia Coli ◽  
Dna Replication ◽  
Dna Polymerase ◽  
Reca Protein ◽  
Minor Role ◽  
Temperature Sensitive ◽  
Restrictive Temperature ◽  
Dna Polymerase I ◽  
Recombination Repair ◽  
Polymerase I

Abstract The mechanism of recA polA lethality in Escherichia coli has been studied. Complementation tests have indicated that both the 5'-->3' exonuclease and the polymerization activities of DNA polymerase I are essential for viability in the absence of RecA protein, whereas the viability and DNA replication of DNA polymerase I-defective cells depend on the recombinase activity of RecA. An alkaline sucrose gradient sedimentation analysis has indicated that RecA has only a minor role in Okazaki fragment processing. Double-strand break repair is proposed for the major role of RecA in the absence of DNA polymerase I. The lexA(Def)::Tn5 mutation has previously been shown to suppress the temperature-sensitive growth of recA200(Ts) polA25::spc mutants. The lexA(Def) mutation can alleviate impaired DNA synthesis in the recA200(Ts) polA25::spc mutant cells at the restrictive temperature. recF+ is essential for this suppression pathway. recJ and recQ mutations have minor but significant adverse effects on the suppression. The recA200(Ts) allele in the recA200(Ts) polA25::spc lexA(Def) mutant can be replaced by delta recA, indicating that the lexA(Def)-induced suppression is RecA independent. lexA(Def) reduces the sensitivity of delta recA polA25::spc cells to UV damage by approximately 10(4)-fold. lexA(Def) also restores P1 transduction proficiency to the delta recA polA25::spc mutant to a level that is 7.3% of the recA+ wild type. These results suggest that lexA(Def) activates a RecA-independent, RecF-dependent recombination repair pathway that suppresses the defect in DNA replication in recA polA double mutants.

Sign in / Sign up

Export Citation Format

Share Document