摘要:

SummaryVibrio parahaemolyticusdistinguishes between life in a liquid environment and life on a surface. Growth on a surface induces differentiation from a swimmer cell to a swarmer cell type. Each cell type is adapted for locomotion under different circumstances. Swimmer cells synthesize a single polar flagellum (Fla) for movement in a liquid medium, and swarmer cells produce an additional distinct flagellar system, the lateral flagella (Laf), for movement across a solid substratum, called swarming. Recognition of surfaces is necessary for swarmer cell differentiation and involves detection of physical signals peculiar to that circumstance and subsequent transduction of information to affect expression of swarmer cell genes(laf).The polar flagellum functions as a tactile sensor controlling swarmer cell differentiation by sensing forces that restrict its movement. Surface recognition also involves a second signal, i.e. nutritional limitation for iron. Studying surface‐induced differentiation could reveal a novel mechanism of gene control and lead to an understanding of the processes of surface colonization by pathogens and other bacteri

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1990.tb00678.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

SummaryWe discuss the features ofEscherichia colimRNAs which determine where and how efficiently translation is initiated. We have shown that DNA fragments comprising 60–80 nucleotides that bracket the initiation codon of real genes generally promote translation when inserted within a foreign mRNA, while those not corresponding to an authentic gene start do not do so even if they include a Shine‐Dalgarno‐like element followed by AUG or GUG. Therefore, the information that pinpoints the correct start sites, while extending beyond the mere presence of these elements, remains essentially local. The possible nature of this information is discussed. Next, we point out that, in order to remain accessible, translational starts must escape long‐range base‐pairing within large mRNAs, and we argue that the tight coupling between translation and transcription plays an important role in achieving this. Finally, we discuss two intriguing situations in which the initiation frequency should be dependent upon the rate of translation e

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1990.tb00679.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

SummaryIn this review, we describe the outer membrane proteins ofPseudomonas aeruginosaand related strains from thePseudomonas fluorescensrRNA homology group of the Pseudomonadaceae, with emphasis on the physiological function and biochemical characteristics of these proteins. The use ofopr(forouter membraneprotein) is proposed as the genetic designation for theP. aeruginosaouter membrane proteins and letters are assigned, in conjunction with this designation, to known outer membrane proteins. Proteins whose primary functions involve pore formation, transport of specific substrates, cell structure determination and membrane stabilization are discussed. The conservation of selected proteins in the abovePseudomonasspecies is also examined.

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1990.tb00680.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

SummaryExpression ofEscherichia coliouter‐membrane porin proteins (OmpF and OmpC) is regulated by the osmolarity of the medium. EnvZ and OmpR, which are positive regulatory factors for the transcriptional osmotic regulation of theompFandompCgenes, belong to a group of two‐component regulatory factors that respond to a variety of environmental stimuli in bacteria. EnvZ‐OmpR phosphotransfer was revealed to be involved in signal transduction in response to an osmotic stimulus, and to play a crucial physiological role in the consequent osmotic activation of the porin genes. Based on the various lines of experimental evidence, a model is proposed for the molecular mechanism underlying the osmotic regulation through phosphorylation of the activator (OmpR) by the membrane‐locatekinas

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1990.tb00681.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

SummaryEscherichia colitransports inorganic phosphate (Pi) by the low‐affinity transport system, Pit. When the level of the external Pi is lower than 20μM, another transport system, Pst, is induced with a Ktof 0.25μM. An outer‐membrane porin, PhoE, with a Km of about 1μM is also induced. The outer membrane allows the intake of organic phosphates which are degraded to Pi by phosphatases in the periplasm. The Pi‐binding protein will capture the free Pi produced in the periplasm and direct it to the transmembrane channel of the cytoplasmic membrane. The channel consists of two proteins, PstA and PstC, which have six and five transmembrane helices, respectively. On the cytoplasmic side of the membrane the channel is linked to the PstB protein, which carries a nucleotide (probably ATP)‐binding site. PstB probably provides the energy required by the channel to free Pi. The Pst system has two functions inE. coli: (i) the transport of Pi, and (ii) the negative regulation of the phosphate regulon (a complex of 20 proteins mostly related to organic phosphate transport). It is remarkable that these two functions are not related, since the repressibility of the regulon depends on the integral structure of Pst (PiBP + PstA + PstC + PstB) and not on the Pi transported. Another gene of thepstoperon,phoU, produces a protein involved in the negative regulation of the Pho regulon, but the mechanism of this function has not been explained. Thus the regulatory function of the Pst system remains obscure. Its basal level, present when Pi is abundant, is sufficient to repress the Pho regulon but the negative regulatory function is lost upon Pi

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1990.tb00682.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

SummaryRecovery of the host after infection by the intracellular pathogenListeria monocytogenesis dependent on cell‐mediated immunity. Little is known of the nature of listerial antigens that induce cell‐mediated responses in the infected host. In this study we report on the identification and cloning of anEscherichia colirecombinant encoding a listerial antigen, designated ImaA, capable of eliciting a specific delayed‐type hypersensitivity response inListeria‐immune mice. Nucleotide sequencing of theListeriaDNA insert in plasmid pLM10 showed that theIma Agene product consisted of 170 amino acids with a molecular weight of 17994. The predicted amino acid sequence suggests that the protein is localized to the bacterial plasma membrane or cell wall. TheImaAgene was unique to the pathogenic speciesL. monocytogenesandListeria ivanovii; it was not present in any other species of the genusL

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1990.tb00683.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

SummaryHybrid proteins were constructed in whichC‐terminal regions of the bacterial cell surface and extracellular protein pullulanase were replaced by the mature forms of the normally periplasmicEscherichia coliproteins β‐lactamase or alkaline phosphatase. InE. colistrains expressing all pullulanase secretion genes, pullulanase‐β‐lactamase hybrid protein molecules containing anN‐terminal 834‐amino‐acid pullulanase segment were efficiently and completely transported to the cell surface. This hybrid protein remained temporarily anchored to the cell surface, presumably via fatty acids attached to theN‐terminal cysteine of the pullulanase segment, and was subsequently specifically released into the medium in a manner indistinguishable from that of pullulanase itself. These results suggest that theC‐terminal extremity of pullulanase lacks signal(s) required for export to the cell surface. When β‐lactamase was replaced by alkaline phosphatase, the resulting hybrid also became exposed at the cell surface, but exposition was less efficient and specific release into the medium was not observed. We conclude that proteins that do not normally cross the outer membrane can be induced to do so when fused to a permissive site near theC

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1990.tb00684.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

SummaryThepaggene coding for protective antigen (PA), one of the three toxin components ofBacillus anthracis, has been cloned into the mobilizable shuttle vector pAT187 and transferred by conjugation fromEscherichia colitoB. anthracis.Using this strategy, an insertionally mutatedpaggene constructed and characterized inE. coli, was introduced intoB. anthracisSterne strain. This transconjugant was used to select a recombinant clone (RP8) carrying the inactivatedpaggene on the toxin‐encoding piasmid, pXO1. Strain RP8 was deficient for PA while still producing the two other toxin components, i.e. lethal factor (LF) and edema factor (EF). In contrast to spores from the wild‐type Sterne strain, spores prepared from RP8 were totally non‐lethal in mice. These results clearly establish the central role played by PA inB. anthracispathogen

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1990.tb00685.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

SummaryTheinvlocus ofYersinia enterocoliticais sufficient to convert a non‐invasiveEscherichia coliK12 strain into a microorganism that is able to penetrate cultured mammalian cells. The nucleotide sequence ofinvreveals an open reading frame corresponding to an 835‐amino‐acid protein that is homologous to the invasin protein fromYersinia pseudotuberculosis.A polyclonal antiserum elicited by a synthetic peptide corresponding to theC‐terminal 88 amino acids of this open reading frame detected a unique 100kD protein in cell lysates ofY. enterocoliticastrain 8081c and in anE. colistrain harbouring the clonedinvgene. This protein localized to the outer membranes of both microorganisms and was cleaved by low concentrations of extracellular trypsin. HEp‐2 cells were shown to attach to surfaces coated with bacterial outer membranes containing invasin and this attachment was destroyed by treatment of the membranes with trypsin. Thus it appears that the invasin protein fromY. enterocoliticais able to mediate both attachment to and entry of cultured epithel

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1990.tb00686.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

SummaryWe have identified a clone from a λEMBL3 library containing a 19kb insert ofMycoplasma pneumoniaeDNA which includes the genes that encode both subunits of DNA gyrase. ThegyrBgene and the 5’end of thegyrAgene have been subcloned into M13. ThegryBgene is 1953bp in length and overlaps the gryA gene by a single base. The nucleotide sequence of these subclones has significant homology to previously reported gyrase genes. In terms of the size ofgyrBgene and its proximity to thegyrAgene,M. pneumoniaeis more similar toBacillus subtilisthan toEscherichia co

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1990.tb00687.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY