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  • 1
    ISSN: 1432-072X
    Keywords: Escherichia coli ; lon mutant ; tif mutant ; Pantolactone ; Butyrolactone ; SOS functions ; Filament formation ; Phage induction ; Lysogenization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Pantolactone and butyrolactone, known to suppress cell filament formation in the lon mutant of Escherichia coli, were found also to be capable of partially correcting other anomalies of the mutant including impaired lysogenization with bacteriophages lambda and Pl and increased synthesis of colanic acid. In contrast to pantolactone, which inhibited thermal induction of cell filament formation and lambda prophage in the tif mutant as previously described, butyrolactone enhanced these phenomena. It was inferred that whereas these substances exert their effects through acting upon the tif-recA protein in the tif bacterium, there is a distinct target for their characteristic actions in the lon mutant.
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  • 2
    ISSN: 1617-4623
    Keywords: Escherichia coli ; recQ gene ; Nucleotide sequence ; SOS regulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A 2,695 bp chromosomal segment of Escherichia coli K12 containing the recQ gene was sequenced. Analysis of the sequence revealed an open reading frame thought to represent recQ, with a clockwise direction of transcription relative to the standard genetic map of E. coli K12 and having a coding capacity for a protein of M r 68,350. The—10 region of the presumptive recQ promoter overlapped the putative terminator for the upstream gene pldA, and was immediately followed by a 15 bp stretch of DNA bearing a strong resemblance to the reported sequences of LexA repressor binding sites. This latter finding suggested the possibility of SOS regulation of recQ gene expression, which was substantiated by experiments with recQ-lacZ fusions.
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  • 3
    ISSN: 1617-4623
    Keywords: Excision repair ; Incision enzyme ; DNA damage ; Nucleotide sequence ; Micrococcus luteus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Restriction fragments ofMicrococcus luteus DNA containing the gene affected by a mutation in the UV-sensitive mutant DB7 were cloned both from the wild type and from the mutant in anEscherichia coli host-vector system. The wild-type fragment was able to reverse the multiple sensitivity of the mutant to UV, mitomycin C, and 4-nitroquinoline 1-oxide by a one-step transformation. Determination of the nucleotide sequences revealed a potential open reading frame coding for a protein of 992 (tentative) amino acid residues, within which the DB7 mutation was identified as a CG-to-TA transition causing a translation termination. The putative product of the open reading frame shares an extensive amino acid sequence homology with theE. coli UvrA protein comprising 940 residues. The homology extends over the greater part of both polypeptides except for two extra sequences of 31 and 24 amino acid residues located at the amino-terminal and in the interior, respectively, of theM. luteus protein. In the homologous region, 56.7% and 16.7% of the 933 pairs of the aligned amino acids were accounted for by conserved residues and conservative substitutions, respectively. These results indicate that the gene defined by the mutation in DB7 represents a homolog of theE. coli uvrA gene. Hence, it has to be concluded that DB7, known for its deficiency in UV endonuclease (pyrimidine dimer DNA glycosylase/apurinic-apyrimidinic endonuclease) activity, is a double mutant which is also defective in an enzyme complex similar to theE. coli UvrABC excinuclease.
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  • 4
    ISSN: 1617-4623
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The recQ gene of Escherichia coli K12 was subcloned from plasmid pKO1 (Oeda et al. 1981) by monitoring the capacity of the resulting recombinant plasmids partially to reverse the increased ultraviolet (UV) sensitivity of a recF143 recQ1 double mutant. We were able to trace this complementation activity to a 3.4 kilobase (kb) SalI-PvuII fragment. Furthermore, analysis of the Tn3 insertion mutations that abolished the complementation revealed the exclusive localisation of such insertions in the same 3.4 kb segment. This segment was situated about 4 kb clockwise from corA on the chromosome, a result consistent with the transductional data previously reported. In addition, a comparison of our restriction endonuclease cleavage map with the published data has placed recQ between pldA and pldB. When relocated to the recQ site on the chromosome, the recQ::Tn3 mutations conferred partial resistance to thymineless death (TLD) or, in the case of a recBC sbcB background, recombination deficiency and increased UV sensitivity. This has provided the firm evidence that both the TLD resistance and the deficiency in the RecF recombination pathway result from loss of the functional recQ gene. We also identified the recQ gene product as a 74 kilodalton polypeptide by using the maxicell technique.
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  • 5
    ISSN: 1617-4623
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The expression of the Escherichia coli uvrD gene was studied with a uvrD::Mud(Apr lac) insertion mutant. The results indicate that it is inducible by DNA damaging agents in a recA + gene-dependent manner.
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  • 6
    ISSN: 1617-4623
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary An Escherichia coli K12 mutant resistant to thymineless death (TLD) was isolated, and its genetic analysis led us to identify a new mutation (recQ1) located between corA and metE on the standard linkage map. The mutation was found to result in increased sensitivity to ultraviolet light and deficiency in conjugational recombination when placed in the recBC sbcB background, indicating that it blocked the RecF pathway of recobbination. It seemed likely that this mutation is also capable of causing partial resistance to TLD, but we reserve the possibility of a separate mutation closely linked to recQ1 giving rise to this phenotype. The original mutant was shown to carry an additional mutation probably in the vicinity of the uhp locus, which was also required for the full TLD resistance of the mutant to be expressed.
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  • 7
    ISSN: 1617-4623
    Keywords: Micrococcus luteus ; Excision repair ; UV damage ; Endonuclease ; Nucleotide sequence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Restriction fragments of Micrococcus luteus DNA that contained the gene defined by the mutation of an excision repair-deficient mutant, UVsN1, were cloned from both the parental and mutant strains with the Escherichia coli host-vector system. The wild-type fragment was able to reverse the multiple sensitivity of the mutant to ultraviolet, mitomycin C, and 4-nitroquinoline-1-oxide by one-step transformation. Determination of the nucleotide sequences revealed an open reading frame potentially coding for a protein of 709 amino acid residues, within which the mutation was identified as a CG→TA transition causing a change from serine to phenylalanine. The putative product of the open reading frame showed an extensive amino acid sequence homology to the E. coli UvrB protein comprising 673 residues; the homologous region extended over the greater parts of both polypeptides, in which 55% and 17% of the 659 pairs of aligned amino acids were accounted for by conserved residues and conservative substitutions, respectively. This indicates that the gene defined by the UVsN1 mutation represents a homolog of the E. coli uvrB gene, implying the presence in M. luteus of an enzyme complex homologous to the E. coli UvrABC excinuclease.
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  • 8
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: In penicillin-susceptible bacteria, penicillin causes growth of a small fraction of cells as wall-deficient forms if an appropriate osmoprotection is provided (unstable L-forms). A subfraction of human serum high density lipoprotein (HDL3) was shown to have the ability to inactivate unstable L-forms of Staphylococcus aureus. The active principle was distinguishable from the well-documented trypanosome lytic factor 1 with respect to density, size, and other properties. This L-form cytotoxicity therefore seems to represent a novel antimicrobial entity in human serum.
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  • 9
    ISSN: 1573-0832
    Keywords: C. albicans ; C. stellatoidea ; DNA homology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Genetic relatedness between strains of C. albicans and C. stellatoidea was studied by measuring G + C content and overall sequence homology. G + C contents determined by high-performance liquid chromatography were 32.6 to 34.2% for 26 strains of C. albicans and 33.0 to 33.9% for eight strains of C. stellatoidea. DNA-DNA hybridization with two C. albicans and two C. stellatoidea probes revealed that all 34 test strains formed a single cluster in which the extents of hybridization with the heterologous probes ranged between 77.9 and 105.6% of those with the homologous probes. These results give support to the unification of C. albicans and C. stellatoidea into a single species.
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  • 10
    ISSN: 1436-5073
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Summary A series of new sensitive resin spot tests for the detection of fluoride is proposed based on the decolorization of the coloured metal chelates by substitution with fluoride as well as the colour change by the formation of ternary fluorocomplexes on the beads of pale-coloured anion-exchange resins. Limits of identification are determined to be 85 ng, 57 ng and 80 ng of fluoride for the tests using beryllium(II)-Chrome Azurol S, aluminium(III)-haematoxylin and cerium(III)-Alizarincomplexone, respectively. Influences of the interfering ions are also studied.
    Notes: Zusammenfassung Eine Reihe neuer und empfindlicher Harztüpfelmethoden zum Nachweis von Fluoridspuren wird vorgeschlagen. Die Entfärbung farbiger Metallchelate durch Substitution mit Fluorid sowie der Farbwechsel durch Bildung fluorhaltiger ternärer Komplexe an Anionenaustauscherkügelchen schwacher Eigenfarbe lassen sich erfolgreich anwenden. Die Erfassungsgrenze beträgt 85 ng F− bei der Beryllium(II)-Chromazurol-S-Methode, 57 ng F− bei der Aluminium-(III)-Hämatoxylin-Methode und 80 ng F− bei der Cer(III)-Alizarin-komplexon-Methode. Einflüsse störender Begleitionen werden beschrieben.
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