摘要:

SummaryA method Is described here that can be used to identify operons whose expression Is controlled by any particular regulator protein. This method was used to Identify operons whose expression is negatively regulated by Spo0A inBacillus subtilis.Twenty‐eight strains were identified, each of which contains an operon‐lacZ transcriptional fusion, negatively regulated, either directly or Indirectly, by Spo0A. In one of these strains (CSA8), thelacZgene is fused to theargC‐Foperon positioned at 100° on theB. subtilischromosome. The regulated expression of this operon by Spo0A ∼ P is mediated indirectly through the transition state regulator AbrB and is manifest only during growth on solid medium. In a second strain (CSA15), thelacZgene is fused to an operon encoding a transport system which displays features characteristic of the ABC group of transporters, and which has a very high level of identity to the ribose transport system fromEscherichia coliExpression of the ribose transport operon is directed by a single SigA‐type promoter. Transcription from this promoter is repressed by the phosphorylated form of Spo0A during the late‐exponential/transition phase of the growth cycle and this control is not mediated through the transition‐state r

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1994.tb00292.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

SummaryWe previously identified three well‐dispersed mutations, E978‐K, F989‐L and D1009‐R within the haemolysin A signal region, located at positions –46, –35 and –15, with respect to the C‐terminus, respectively. Each mutation reduces the efficiency of secretion two‐ to threefold leaving 30–45% of the wild‐type activity. We have constructed byin vitromanipulations double mutants of HlyA carrying all combinations of these mutations and a triple mutant carrying all three mutations. The effects on secretion were determined and the results, including residual levels of secretion with the triple mutant of only 0.6%, compared with the wild type, indicated that these residues may interact to form a single function in the wild‐type signal. To test this further, we developed a secretion competition assay in order to classify signal mutations. We demonstrated that a CIZ‐HlyA fusion protein, containing the C‐terminal 81 kDa of HlyA fused to virtually the whole LacZ protein, strongly inhibits the secretion of the wild‐type HlyA co‐expressed In the same cell. The properties of the fusion indicate that it blocks the translocator. The three mutations singly and in combinations were recombinedin vitrointo the 3′‐end of the hybrid gene. In every case, the presence of a mutation in the secretion signal of the hybrid protein alleviated the inhibition of secretion of the co‐expressed HiyA. All the mutations are therefore essentially recessive and we propose that they all affect an early function, probably recognition of the translocator, rather than a subsequent step involved in translocation or final release of the toxin to the medium. This would indicate that resi

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1994.tb00293.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

SummaryMutations affecting DNA topoisomerase I(topA)inSaimonella typhimuriumwere isolated and graded on the basis of their ability to reverse the effects ofgyrBmutations onhisoperon expression. DifferenttopAandgyrBalleles (in otherwise isogenic strains) were used to gather insights into the transcription‐dependent variability of plasmid DNA‐linking deficit in growing bacteria. This study showed that modulation of DNA supercoiling by transcription results from the action of two components: one is highly dependent on the coupling of translation to RNA‐chain elongation; and the other is unrelated to protein synthesis and entirely dependent on promoter determinants. The former greatly predominates In DNA topoisomerase I mutants (topAandtopA gyrB) while the latter is the sole contributor to plasmid DNA‐linking deficit in wild‐type cells. Altogether, these data suggest that whereas translation acts by enhancing the formation of twin supercoiled domains during elongation, the promoter‐dependent effects bear no relation to the twin‐supercoiled‐domain model and are latter explained by a mechanism which responds to the binding/unwinding of template DNA by

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1994.tb00294.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

SummaryTheinvgene encodes the protein invasin, which is the primary invasion factor forYersinia enterocolitica in vitroandin vivo.Previous studies ofYersiniaspecies have shown thatinvexpression and entry into mammalian cells are temperature regulated. Invasin production is reduced at the host temperature of 37°C as compared to production at ambient temperature; consequently, this study was initiated to determine whether other host environmental signals might induceinvexpression at 37°C. Aninv::phoAtranslational fusion was recombined on to theY. enterocoliticachromosome by allelic exchange to monitorinvexpression. Molecular characterization of expression of the wild‐typeinvgene and theinv phoAfusion showed that invasin is not produced until early stationary phase in bacteria grown at 23°C.Y. enterocoliticagrown at 37°C and pH 5.5 showed levels ofinvexpression comparable to those observed in bacteria grown at 23 C. An increase in Na+ions caused a slight increase in expression at 37 C. However, expression at 37°C was unaffected by anaerobiosis, growth’medium, calcium levels, or iron levels. Additionally,Y. enterocoliticaexpressed invasin in Peyer's patches two days after being introduced intragastrically into BALB/c mice. These results suggest that invasin expression inK enterocoliticamay remain elevated eariy during interaction with the intestinal epithelium, a site at which invasin was shown to be n

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1994.tb00295.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

SummaryThe type 4 pill ofPseudomonas aeruginosa areimportant cell‐associated virulence factors that play a crucial role in mediating (i) bacterial adherence to, and colonization of, mucosal surfaces, (ii) a novel mode of fiagetia‐independent surface translocation known as‘twitching motility, and (iii) the initial stages of the infection process for a number of bacteriophages. A new set of loci involved in pilus biogenesis and twitching motility was identified based on the ability of DNA sequences downstream of thepilGgene to complement the non‐piliated(pil)strain, PAO6609. Sequence analysis of a 3.2 kb region directly downstream ofpilGrevealed the presence of three genes, which have been designatedpilH, pill, andpilJ.The predicted translation product of thepilHgene (13 272 Da), like PilG, exhibits significant amino acid identity with the enteric single‐domain response regulator CheY. The putative Pili protein (19933 Da) is 28% identical to the FrzA protein, a CheW homologue of the gliding bacteriumMyxococcus xanthus, and the PMJ protein (72 523 Da) is 26% identical to the enteric methyl‐accepting chemotaxis protein (MCP) Tsr. Mutants containing insertions inpillandpilJwere severely impaired in their ability to produce pili and did not translocate across solid surfaces. ThepilHmutant remained capable of pilus production and twitching motility, but displayed an altered motility pattern characterized by the presence of many doughnut‐shaped swirls. Each of thesepilmutants, however, produced zones that were at least as large as the parent in flagellar‐mediated swarm assays. The sequence similarities between the putativepilG, H, Iand J gene products and several established chemotaxis proteins, therefore, lend strong support to the hypothesis that these proteins are part of a signal‐transduction network that controlsP. aeruginosapilus biosynthesis and t

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1994.tb00296.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

SummaryKiller toxins are polypeptides secreted by some fungal species that kill sensitive cells of the same or related species, in the best‐characterized cases, they function by creating new pores in the ceil membrane and disrupting ion fluxes. Immunity or resistance to the toxins is conferred by the preprotoxins (or products thereof) or by nuclear resistance genes. In several cases, the toxins are encoded by one or more genomic segments of resident double‐stranded RNA viruses. The known toxins are composed of one to three polypeptides, usually present as multimers. We have further characterized the KP4 killer toxin from the maize smut fungusUstilago maydis.This toxin is also encoded by a single viral double‐stranded RNA but differs from other known killer toxins in several respects: it has no N‐linked glycosylation either in the precursor or in the mature polypeptide, it is the first killer toxin demonstrated to be a single polypeptide, and h Is not processed by any of the known secretory protelnases (other than the signal peptidase). It is efficiently expressed in a heterologous fungal

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1994.tb00297.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

SummaryWe identified several linked genes of a lactose regulon inRhizobium meliloti.These werelacZ, the structural gene for β‐galactosidase;lacR, the lactose repressor gene; and two genes encoding proteins of unknown function.lacWandlacX.Insertion mutants inlacWandlacZbelonged to a single genetic compiementation group, andlacWappeared to lie upstream oflacZin an operon. Expression oflacZ, lacWandlacXwas repressed bylacR, and expression oflacZandlacWwas derepressed by lactose.lacZwas not required for Induction oflacW bylactose, suggesting that lactose itself, rather than a processed form of lactose, may be the actual Inducer molecule. Expression of all three genes was repressed by succinate, and thelacRindependence of this repression showed that inducer exciusion could not be the sole mechanism. This pattern oflacgene organization and regulation differs in several ways from that observed in enteric bacter

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1994.tb00298.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

SummaryFive murine epitopes were defined and mapped within IgA1 protease produced byNeisseria meningitidis.Epitopes 1 and 2 were present in IgA1 protease from all strains, and fromNeisseria gonorrhoeae.Epitopes 3 through to 5 varied between subgroups of serogroup A meningococci. but have remained constant over decades within the subgroups, except for epitope 4, which changed between 1983 and 1987 during the spread of subgroup III meningococci from Asia to Africa. Binding of monoclonal antibodies to epitopes 1, 4 and 5 neutralized enzymatic function. Human sera containing antibodies to lgA1 protease as a result of natural infection inhibited binding of monoclonal antibodies to epitope 4 but not to the other epitopes.

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1994.tb00299.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

SummaryWe report a molecular genetic analysis of the region Immediately upstream from theEscherichia coli mutLDNA repair gene at 94.8 min. An open reading frame ending 9bp upstream from the start ofmutLcorresponds to a 48kDa polypeptide detected previously in minicells. The predicted amino acid sequence of this 48kDa polypeptide shows homology to the major N‐acetylmuramoyl‐L‐alanine amidase autolysin ofBacillus subtilis, a known amidase ofBacillus licheniformis, and the product of aSalmonella typhimuriumgene that maps near SO min. Insertions in this upstream gene, which we namedAmiB, or inmutLdid not affect cell shape or viability; however, overexpression of the AmiB potypeptide caused ceil lysis, hypersensitivity to osmotic shock and treatment with water, and temporary autolysis by low levels of antibiotics, which are all consistent with AmiB acting as a cell‐wall hydrolase. Analysis of chromosomal transcription demonstrated thatamiBforms a complex operon withmutLand two additional upstream genes.mutLtranscripts also originated from an internal promoter, designated PmutL, located inamiB312bp upstream from the translational start ofmutL.Together, these results suggest thatE. colicontains a second amidase possibly involved in cell‐wall hydrolysis, septation, or recycling, and that transcription of this amidase is directly linked to a gene central for D

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1994.tb00300.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

SummaryAlthough it has never been reported thatBacillus subtilisis capable of accumulating glycogen, we have isolated a region from the chromosome ofB. subtiliscontaining a glycogen operon. The operon is located directly downstream fromtrnB, which maps at 275 on theB. subtilischromosome, it encodes five poly‐peptides with extensive similarity to enzymes involved in glycogen and starch metabolism in both prokaryotes and eukaryotes. The operon is presumably expressed by an EσE‐controlled promoter, which was previously identified downstream fromtrnB.We have observed glycogen biosynthesis inB. subtilisexclusively on media containing carbon sources that allow efficient sporulation. Sporulation‐independent synthesis of glycogen occurred after integration of an EσAcontrolled promoter upstream of the

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1994.tb00301.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY