摘要:

SummarySporulation begins coincidentally with the expression of several stationary‐phase‐associated gene products during the transition state of a culture from exponential to stationary phase. Mutations in the stage 0 sporulation genes prevent the expression of these gene products in addition to blocking sporulation. Suppressor mutations in theabrBgene, in aspo0background, restore stationary‐phase‐associated gene expression but not sporulation. The nature of theabrBgene product was investigated by isolating and sequencing theabrBgene. TheabrBgene coded for a 96‐amino‐acid protein (molecular weight 10773) and contained a helix‐turn‐helix structure common to DNA binding proteins. Analysis of expression of theabrBgene usinglacZtranscription fusions and direct measurement of mRNA content by hybridization showed that thespo0Agene repressed transcription of theabrBgene. Primer extension analysis ofabrBgene mRNA revealed two initiation sites. The downstream site was dramatically repressed inspo0A+strains, while the upstream site appeared not to be regulated byspo0A.FiveabrBmutant alleles were cloned and sequenced. One mutation,abrB4, resided within the structural gene and continued to overexpressabrBmessenger RNA from both promoters. A promoter mutation,abrB15, reduced transcription from the downstream promoter but not the upstream promoter. Thus, the phenotype ofabrBmutations results from inactivation of theabrBgene product or by prevention of its overexpression. The results suggest that theabrBgene codes for a regulator which controls several genes whose products are normally produced during the transition phase between active growth and sporulation. The level of this regulator is, in turn, controlled by thespo0Agene. The pleiotropic phenotypes ofspo0Amutants result from uncontrolled overexpression of t

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1988.tb00079.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

SummaryThe FNR protein ofEscherichia coliis a regulatory protein that activates the transcription of its target genes in response to oxygen limitation. Site‐directed mutagenesis was used to show that a 28‐residueN‐terminal segment containing three cysteines is essential for normal FNR function. The cysteine residue which is centrally located in the three‐cysteine cluster (Cys‐Ala‐Ile‐His‐Cys‐Gln‐Asp‐Cys) was also shown to be essential for FNR activity. Possible mechanisms by which this cysteine residue might function in the response of FNR to anaer

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1988.tb00080.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

SummaryAminoglycoside 2″‐O‐nucleotidyltransferase (AAD(2″)) mediates bacterial resistance to dibekacin, gentamicin, kanamycin, sisomicin and tobramycin. Its coding sequence,aadB, is part of Tn21‐related transposon, Tn4000. Nucleotide sequence analysis revealed the presence of an open reading frame capable of specifying a protein of 177 amino acids with a calculated molecular weight of 21240. The predicted amino acid sequence revealed up to 27% homology to that of three nucleotidyltransferases of type AAD(3″), which are widely distributed among Gram‐negatives, and to the AAD(9) fromStaphylococcus aureustransposon Tn554. The regions flankingaadBsuggest that its insertion into Tn21 arose from a site‐specific recombination event adjacent t

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1988.tb00081.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

SummaryThe Enzymes II of the PEP:carbohydrate phosphotransferase system (PTS) specific forN‐acetylglucosamine (IINag) and β‐glucosides (IIBgl) containC‐terminal domains that show homology with Enzyme IIIGlcof the PTS. We investigated whether one or both of the Enzymes II could substitute functionally for IIIGlc. The following results were obtained: (i) Enzyme IINag, synthesized from either a chromosomal or a plasmidencodednagE+gene could replace IIIGlcin glucose, methyl α‐glucoside and sucrose transport via the corresponding Enzymes II. An Enzyme IINagwith a large deletion in theN‐terminal domain but with an intactC‐terminal domain could also replace IIIGlcin IIGlc‐dependent glucose transport, (ii) After decryptification of theEscherichia coli bgloperon, Enzyme IIBglcould substitute for IIIGlc. (iii) Phospho‐HPr‐dependent phosphorylation of methyl α‐glucoside via IINag/IIGlcis inhibited by antiserum against IIIGlcas isN‐acetyl‐glucosamine phosphorylation via IINag. (iv) In strains that contained the plasmid which coded for IINag, a protein band with a molecular weight of 62000 D could be detected with antiserum against IIIGlc. We conclude from these results that the IIIGlc‐like domain of Enzyme IINagand IIBglcan replace IIIGlcin IIIGlc‐dependent carbohydrate

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1988.tb00082.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

SummaryAntibodies were raised against purified germinationspecific cortex‐lytic enzyme (GSLE) from spores ofBacillus megateriumKM which neutralized the ability of GSLE to germinate permeabilized spores. Western blotting of dormant spore and vegetative cell fractions separated by SDS‐PAGE demonstrated that GSLE is spore‐specific and that>90% of the GSLE is associated with the dormant spore cortex peptidoglycan as a phosphorylated 63 kD pro‐form, which could only be visualized after lysozyme digestion of the peptidoglycan. During germination, the 63 kD pro‐form of GSLE is processed to release the active enzyme, which had an apparent molecular weight of 30 kD. Inhibitor studies demonstrated that GSLE activation occurs as part of the commitment reaction and thus represents the first‐identified enzymatic event to occur during germination triggering. Proteins that cross‐react with anti‐GSLE sera are present in spore fractions o

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1988.tb00083.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

SummaryTherodC1 mutation ofBacillus subtilisis a temperature‐sensitive marker which affects the orientation of the plane of cell division. We have cloned therodCgene and have localized the site of therodC1 lesion. To identify therodCgene product, we have subjected several plasmid clones containingB. subtilischromosomal DNA from therodCregion to maxicell analysis inEscherichia coli.A 68 kiloDalton protein has been identified as therodCgene product. This is the initial cloning of a cell division gene and the identification of its product fromB. subtilis.TherodCgene has also been implicated as being directly associated with the synthesis of glycerol teichoic aci

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1988.tb00084.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

SummaryThe chemotactic behaviour of a strain ofRhizobium leguminosarumbiovarviciaewas investigated. The flavanoids apigenin and naringenin, inducers of transcription of the nodulation (nod) genes, were both potent attractants but hesperitin, another flavonenodgene inducer, was not. The response of strains containing the Sym plasmid pRL1JI to apigenin and naringenin was significantly greater than the response of a strain cured of the plasmid, although both strains gave a positive response. Addition of the flavanol kaempferol, an antagonist ofnodgene induction, had no detectable effect on the chemotactic response to naringenin or aplgenin, but was itself found to be an attractant. The attractant response to a variety of amino acids and sugars was not affected by the presence of the Sym plasmid. Homoserine, the most abundant nitrogenous compound in legume exudates, was also found to be an attractant. However, although the Sym plasmid is required for the biovar to metabolize homoserine as a carbon source, it was not required for the chemotactic response. A group of membrane proteins showed increased methylation in response to stimulation with serine. There was no measurable change in methylation after stimulation with apigenin.

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1988.tb00085.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

SummaryTheputPgene encodes the major proline permease inSalmonella typhimuriumthat couples transport of proline to the sodium electrochemical gradient. To identify residues involved in the cation binding site, we have isolatedputPmutants that confer resistance to lithium during growth on proline. Wild‐type S.typhimuriumcan grow well on proline as the sole carbon source in media supplemented with NaCl, but grows poorly when LiCl is substituted for NaCl. In contrast to the growth phenotype, proline permease is capable of transporting proline via Na+/proline or Li+/proline symport. Therefore, we selected mutants that grow well on media containing proline as the sole carbon source in the presence of lithium ions. All of the mutants assayed exhibit decreased rates of Li+pro‐line and Na+/proline cotransport relative to wild type. The location of each mutation was determined by deletion mapping: the mutations cluster in two small deletion intervals at the 5′ and 3′ termini of theputPgene. The map positions of these lithium resistance mutations are different from the locations of the previously isolated substrate specificity mutations. These results suggest that Lirmutations may define domains of the protein that fold to form the cation binding site of proline p

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1988.tb00086.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

SummarySurface protein mutants of the invasiveSalmonellaspecies,S. choleraesuis, were generated using the transposonTnphoA.626 alkaline phosphatase (PhoA+) fusion mutants were identified and screened for their ability to pass through (transcytose) polarized epithelial monolayers of Madin Darby canine kidney (MDCK) cells grown on membrane filters. Forty two mutants were unable to pass through this barrier. All of these transcytosis mutants were unable to adhere to or invade MDCK monolayers, yet these mutations were not in the genes encoding type 1 pili or mannose‐resistant haemagglutination (MRHA). These transcytosis mutants could be grouped into six classes. Class 1 mutants had altered lipopolysaccharide (LPS) O side‐chain structures while Class 2 mutants had defects in their LPS core. Mutants belonging to Classes 5 and 6 did not decrease the transepithelial electrical resistance of polarized MDCK cell mono‐layers, in contrast to the parental strain and the other mutants (Classes 1, 2, 3 and 4). Mutants belonging to Class 1 were less virulent in mice, while Class 2 (defective core) and Classes 4 and 5 (normal LPS) mutant strains were avirulent in mice. Mutants from Classes 3 and 6 were as virulent in mice as S.choleraesuis.These results suggest that the ability to pass through epithelial barriers may be an important virulence characteristic ofSalmonella.These data indicate that bacterial adherence, internalization and monolayer transcytosis are closely linked events. It was also demonstrated that a mutant with decreased rates of intracellular replication still passed through the monolayer at rates similar to wild‐typeS. chole

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1988.tb00087.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

SummaryThe nucleotide sequence of theugpgenes ofEscherichia ColiK‐12, which encode a phosphate‐limitation inducible uptake system for sn‐glycerol‐3‐phosphate and glycerophosphoryl diesters, was determined. The genetic organization of the operon differed from previously published results. A single promoter, containing a putativephobox, was detected by S1‐nuclease mapping. The promoter is followed by four open reading frames, designatedugpB, A, EandC, which encode a periplasmic binding protein, two hydrophobic membrane proteins and a protein that is likely to couple energy to the transport system, respectively. The sequences of the proteins contain the characteristics of several other binding protein‐dependent transport systems, but they seem to be particularly closely related to the m

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1988.tb00088.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY