Phenotypes of
 lexA
 Mutations in
 Salmonella enterica
 : Evidence for a Lethal
 lexA
 Null Phenotype Due to the Fels-2 Prophage

Bunny, Kim L.; Liu, Jing; Roth, John R.

doi:10.1128/jb.184.22.6235-6249.2002

Cited by 58 publications

(47 citation statements)

References 59 publications

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“…In this study, we investigated how constitutive expression of the DNA damage-inducible LexA regulon would affect the mutation rate for four different types of mutations. These experiments were performed in a S. typhimurium strain lacking the prophages Gifsy-1, Gifsy-2, and Fels-2 to prevent cellular killing caused by LexA inactivation and resulting phage induction (Bunny et al 2002). Depending on the mutation types examined, constitutive derepression of the LexA regulon [due to a lexA(def) mutation] caused 3.5-fold (chlorate resistance), 8-fold (rifampicin resistance), and 11-fold (nalidixic acid resistance) increases in mutation rates, whereas Lac 1 reversion rates remained unaltered (Figure 1).…”

Section: Resultsmentioning

confidence: 99%

Effect of Translesion DNA Polymerases, Endonucleases and RpoS on Mutation Rates inSalmonella typhimurium

Koskiniemi¹,

Hughes

Andersson³

2010

Genetics

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It has been suggested that bacteria have evolved mechanisms to increase their mutation rate in response to various stresses and that the translesion DNA polymerase Pol IV under control of the LexA regulon and the alternative sigma factor RpoS are involved in regulating this mutagenesis. Here we examined in Salmonella enterica serovar Typhimurium LT2 the rates for four different types of mutations (rifampicin, nalidixic acid, and chlorate resistance and Lac 1 reversion) during various growth conditions and with different levels of four translesion DNA polymerases (Pol II, Pol IV, Pol V, and SamAB) and RpoS. Constitutive derepression of the LexA regulon by a lexA(def ) mutation had no effect on Lac 1 reversion rates but increased the other three mutation rates up to 11-fold, and the contribution of the translesion DNA polymerases to this mutagenesis varied with the type of mutation examined. The increase in mutation rates in the lexA(def ) mutant required the presence of the LexA-controlled UvrB protein and endonucleases UvrC and Cho. With regard to the potential involvement of RpoS in mutagenesis, neither an increase in RpoS levels conferred by artificial overexpression from a plasmid nor long-term stationary phase incubation or slow growth caused an increase in any of the four mutation rates measured, alone or in combination with overexpression of the translesion DNA polymerases. In conclusion, mutation rates are remarkably robust and no combination of growth conditions, induction of translesion DNA polymerases by inactivation of LexA, or increased RpoS expression could confer an increase in mutation rates higher than the moderate increase caused by derepression of the LexA regulon alone.

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Section: Resultsmentioning

confidence: 99%

Effect of Translesion DNA Polymerases, Endonucleases and RpoS on Mutation Rates inSalmonella typhimurium

Koskiniemi¹,

Hughes

Andersson³

2010

Genetics

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“…Gifsy 1 and 2 were originally identified in S. enterica serovar Typhimurium and have been implicated in Salmonella virulence (19). Fels-2 has been identified in S. enterica (7). Sequences with homology to a number of other hypothetical genes were observed.…”

Section: Resultsmentioning

confidence: 99%

Partial Analysis of the Genomes of Two Nontypeable Haemophilus influenzae Otitis Media Isolates

et al. 2004

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In 1995, The Institute for Genomic Research completed the genomic sequence of a rough derivative of Haemophilus influenzae serotype d, strain KW20. This sequence, though extremely useful in understanding the basic biology of H. influenzae, has yet to provide significant insight into our understanding of disease caused by nontypeable H. influenzae (NTHI), because serotype d strains are not generally pathogens. In contrast, NTHI strains are frequently mucosal pathogens and are the primary pathogens of chronic otitis media as well as a significant cause of acute otitis media in children. Thus, it is of great importance to further understand their biology. We used a DNA-based microarray approach to identify genes present in a clinical isolate of NTHI that were absent from strain Rd. We also sequenced the genome of a second NTHI isolate from a child with chronic otitis media to threefold coverage and then used an array of bioinformatics tools to identify genes present in this NTHI strain but absent from strain Rd. These methods were complementary in approach and results. We identified, in both strains, homologues of H. influenzae lav, an autotransported protein of unknown function; tnaA, which encodes tryptophanase; as well as a homologue of Pasteurella multocida tsaA, which encodes an alkyl peroxidase that may play a role in protection against reactive oxygen species. We also identified a number of putative restriction-modification systems, bacteriophage genes and transposon-related genes. These data provide new insight that complements and extends our ongoing analysis of NTHI virulence determinants.

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“…Plasmid pBLSK (Stratagene, La Jolla, Calif.) and pET15b (Invitrogen, Carlsbad, Calif.) manipulations were performed by using E. coli NF1829 and XL-1-Blue (Stratagene), respectively, and pET15b expression constructs were induced by IPTG (isopropyl-␤-D-thiogalactopyranoside) in E. coli BL21 (DE3). Plasmid FЈ128 derivatives were constructed by the strategy described by Bunny et al (11). The P 22 -lacZ reporter constructs were made as follows.…”

Section: Methodsmentioning

confidence: 99%

The pKO2 Linear Plasmid Prophage ofKlebsiella oxytoca

et al. 2004

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Temperate bacteriophages with plasmid prophages are uncommon in nature, and of these only phages N15 and PY54 are known to have a linear plasmid prophage with closed hairpin telomeres. We report here the complete nucleotide sequence of the 51,601-bp Klebsiella oxytoca linear plasmid pKO2, and we demonstrate experimentally that it is also a prophage. We call this bacteriophage KO2. An analysis of the 64 predicted KO2 genes indicate that it is a fairly close relative of phage N15; they share a mosaic relationship that is typical of different members of double-stranded DNA tailed-phage groups. Although the head, tail shaft, and lysis genes are not recognizably homologous between these phages, other genes such as the plasmid partitioning, replicase, prophage repressor, and protelomerase genes (and their putative targets) are so similar that we predict that they must have nearly identical DNA binding specificities. The KO2 virion is unusual in that its phage -like tails have an exceptionally long (3,433 amino acids) central tip tail fiber protein. The KO2 genome also carries putative homologues of bacterial dinI and umuD genes, both of which are involved in the host SOS response. We show that these divergently transcribed genes are regulated by LexA protein binding to a single target site that overlaps both promoters.Temperate bacteriophages usually physically integrate their prophage DNAs into the host bacterium's chromosome when they establish lysogeny. However, a few prophages, such as those of phages P1, N15, LE1, 20, and BB-1, are not integrated but replicate in the lysogen as low-copy-number plasmids (32,38,52,53,84). Of these, the Escherichia coli doublestranded DNA (dsDNA) tailed-phage N15 has an unusual linear prophage plasmid that has covalently closed hairpin telomeres (67, 68). Although N15 has been studied in some detail (83,85,87), few other phages with similar linear DNA prophages have been described. While this paper was being prepared, another linear plasmid prophage, PY54, was reported for Yersinia enterocolitica (48). Furthermore, the linear, hairpin-ended plasmids Lp28-2 and Lp54 in the spirochete Borrelia burgdorferi B31-MI carry sequence similarities to dsDNA phage virion assembly genes (19, 33); however, they have not yet been shown to be bone fide prophages. Linear plasmids are very rare in the ␥-Proteobacteria, but it has been reported that Klebsiella oxytoca strain CCUG 15788 (a nickelresistant bacterium isolated from the mineral oil-water coolant-lubricant emulsion of a metal working machine in Göte-borg, Sweden, in 1989 [69]) harbors a linear plasmid, pKO2, of about 50 kbp (95). Since this is close to the size of the N15 linear plasmid prophage, we were prompted to investigate the possibility that this plasmid could be a prophage. We report here the complete nucleotide sequence of pKO2, a linear plasmid prophage that encodes the synthesis of a tailed-phage particle, and the analysis of some of its properties. MATERIALS AND METHODSBacterial strains and plasmid construction. The bacterial st...

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Phenotypes of lexA Mutations in Salmonella enterica : Evidence for a Lethal lexA Null Phenotype Due to the Fels-2 Prophage

Cited by 58 publications

References 59 publications

Effect of Translesion DNA Polymerases, Endonucleases and RpoS on Mutation Rates inSalmonella typhimurium

Effect of Translesion DNA Polymerases, Endonucleases and RpoS on Mutation Rates inSalmonella typhimurium

Partial Analysis of the Genomes of Two Nontypeable Haemophilus influenzae Otitis Media Isolates

The pKO2 Linear Plasmid Prophage ofKlebsiella oxytoca

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