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S A Zaat

Publications and source records attributed to S A Zaat.

34 records · Page 2Linked to original sources
PubMed1999

Isolation and characterization of promoter regions from Streptococcus gordonii CH1.

We aimed to identify transcription signal sequences from Streptococcus gordonii strain CH1 by random chromosomal cloning. Five genomic fragments from a Sau3A digest, which constitutively activated transcription of a promoterless spectinomycin resistance gene in this strain, were isolated and characterized. Additionally, one promoter fragment was isolated that was specifically activated under iron-limiting conditions. A sequence motif with similarity to the consensus for Fur-binding regulatory DNA sequences (Fur box) in Escherichia coli was detected within the putative promoter region. The open reading frame downstream of this region possibly encodes a transmembrane protein involved in iron uptake.

Amino Acid Sequence↗
PubMed1999

Comparison of PCR, culture, and serological tests for diagnosis of Mycoplasma pneumoniae respiratory tract infection in children.

For diagnosis of Mycoplasma pneumoniae infection we compared two rapid tests, PCR and the immunoglobulin M immunofluorescence assay (IgM IFA), with culture and the complement fixation test (CFT), in a prospective study among 92 children with respiratory tract infection and 74 controls. Based on positivity of culture and/or CFT as the diagnostic criterion, nine patients (10%) were diagnosed with M. pneumoniae infection. All patients positive by culture were also positive by PCR. In all controls cultures, PCRs, and serological assays were negative, except in one with a positive IgM IFA. The IgM IFA had a low positive predictive value of 50%. Only a combination of PCR (seven patients) and CFT (seven patients) allowed diagnosis of all cases.

Adolescent↗
PubMed1998

Controlled delivery of antibacterial proteins from biodegradable matrices.

Prosthetic valve endocarditis is an infrequent, but serious complication of cardiac valve replacement. The infection is caused by the adherence of bacteria to the prosthetic valve or to tissue at the site of implantation. Recently it was shown that antibacterial peptides from blood platelets are involved in clearance and killing of bacteria adhering to vegetations induced in a model for prosthetic valve endocarditis using rabbits. The application of these antibacterial proteins in a release system, incorporated in the Dacron sewing ring of the prosthetic heart valve would diminish the incidence of endocarditis. In this study a release system for small cationic proteins based on cross-linked gelatin was developed and characterised. Furthermore, the system was evaluated with respect to the uptake and in vitro release of lysozyme, a small cationic protein that was chosen as a model protein for small cationic antibacterial proteins. Variation of gelatin type (A and B), and cross-link density resulted in differences in swelling, thermal behaviour, and number of charged groups. Lysozyme uptake was proportional to swelling, but was governed by the number of anionic groups. The latter was also observed for the release profiles: when the amount of free carboxylic acids is higher (gelatin B compared to gelatin A), the lysozyme release lasts for a longer time period. The release into solidified agarose medium, as a model for heart muscle tissue, was measured. After 50 h, 40-100% of the lysozyme was released, which is in accordance with the aimed release period of 24-48 h. The adsorption experiments in vitro suggest an influence of the electrostatic interactions between lysozyme and gelatin. This hypothesis was validated with a mathematical model which takes both diffusion and adsorption interactions into account.

Animals↗
PubMed1996

A simple procedure for isolation of cloning vectors and endogenous plasmids from viridans group streptococci and Staphylococcus aureus.

Isolation of plasmid DNA from viridans group streptococci is difficult, and preparations are often heavily contaminated with chromosomal DNA. We developed a simple protocol to isolate pure plasmid DNA for use in different molecular techniques, including automated sequencing. The protocol is also applicable for plasmid isolation from Staphylococcus aureus. In addition, the protocol allows isolation of pure endogenous plasmids from streptococci and S. aureus.

Cloning, Molecular↗
PubMed1995

Involvement of bactericidal factors from thrombin-stimulated platelets in clearance of adherent viridans streptococci in experimental infective endocarditis.

Platelets activated with thrombin release bactericidal factors. We studied the role of the susceptibility of viridans streptococci to these bactericidal factors in the development of infective endocarditis (IE). By using the experimental endocarditis rabbit model, the initial adherence and the development of IE were assessed for 10 viridans streptococcal strains differing in their susceptibilities to releasate (material released) from thrombin-activated platelets. Six strains were susceptible and four strains were resistant to these releasates. The numbers of vegetations (VGs) colonized at 5 min and 48 h after intravenous challenge with 10(4) CFU were determined. At 5 min after challenge, significantly more VGs were colonized with bacteria of the six platelet releasate-susceptible strains than with bacteria of the four releasate-resistant strains (P < 0.005). In the releasate-susceptible group of strains, the number of colonized VGs decreased significantly between 5 min and 48 h after intravenous inoculation (P < 0.001). Such a decrease was not observed with the releasate-resistant strains. As a result, the final developments of IE due to releasate-susceptible and -resistant strains were not significantly different. The releasate-susceptible strain 1 and the releasate-resistant strain 2 were selected for more detailed experiments. Rabbits were killed at 5 and 30 min and 2, 4, and 48 h after inoculation. The number of culture-positive VGs as well as the number of adherent bacteria on the individual VGs were determined. The 90% infective dose for each strain was 10(5) CFU. At low inoculum concentrations (10(3) and 10(4) CFU) a larger proportion of the inoculated bacteria of both strains was found to be adherent on VGs than at higher challenge doses. The number of culture-positive VGs as well as the number of adherent bacteria per VG decreased rapidly in the first 30 min after challenge with strain 1 but not after challenge with strain 2. Additional experiments with the platelet releasate-susceptible strain S224 and the platelet releasate-resistant stain S182 confirmed the data obtained with strains 1 and 2 and indicated that releasate-susceptible strains disappeared from the VGs with time, whereas releasate-susceptible strains persisted. In vitro studies with VGs excised 5 min after challenge with stain 1 or 2 showed that clearance of the releasate-susceptible strain 1 was not caused by complement bactericidal activity or surface phagocytosis by polymorphonuclear cells. Bacterial cells of strain 1 adherent on excised VTGs were rapidly cleared by exposure to fresh clotting blood or to releasates from thrombin-stimulated platelet suspension.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1994

Construction of phoE-caa, a novel PCR- and immunologically detectable marker gene for Pseudomonas putida.

In this paper we describe the construction and use in Pseudomonas putida WCS358 of phoE-caa, a novel hybrid marker gene, which allows monitoring both at the protein level by immunological methods and at the DNA level by PCR. The marker is based on the Escherichia coli outer membrane protein gene phoE and 75 bp of E. coli caa, which encode a nonbacteriocinic fragment of colicin A. This fragment contains an epitope which is recognized by monoclonal antibody (MAb) 1C11. As the epitope is contained in one of the cell surface-exposed loops of PhoE, whole cells of bacteria expressing the protein can be detected by using the MAb. The marker gene contains only E. coli sequences not coding for toxins and therefore can be considered environmentally safe. The hybrid PhoE-ColA protein was expressed in E. coli under conditions of phosphate starvation, and single cells could be detected by immunofluorescence microscopy with MAb 1C11. Using a wide-host-range vector the phoE-caa gene was introduced into P. putida WCS358. The gene appeared to be expressed under phosphate limitation in this species, and the gene product was present in the membrane fraction and reacted with MAb 1C11. The hybrid PhoE-ColA protein could be detected on whole cells of WCS358 mutant strains lacking (part of) the O-antigen of the lipopolysaccharide but not on wild-type WCS358 cells, unless these cells had previously been washed with 10 mM EDTA. In addition to immunodetection, the phoE-caa marker gene could be specifically detected by PCR with one primer directed to a part of the phoE sequence and a second primer that annealed to the caa insert.

Base Sequence↗
PubMed1993

Recognition of the colicin A N-terminal epitope 1C11 in vitro and in vivo in Escherichia coli by its cognate monoclonal antibody.

We demonstrate that the 1C10 monoclonal antibody (mAb) directed against the N-terminal domain of the colicin A recognizes a 13 residue-region (13Thr-Gly-Trp-Ser-Ser-Glu-Arg-Gly-Ser-Gly-Pro- Asp-Pro25). When this peptide is inserted into a protein in the amino-terminal or an internal position, the tagged protein is efficiently detected by the 1C11 mAb either by immunoblotting or immunoprecipitation. In vitro, the minimal structure required for detection using the pepscan system is 19Arg-Gly-Ser-Gly-Pro-Glu-Pro25, indicating that in vivo the proper exposure of the epitope requires additional residues. The construction of a versatile vector allowing overproduction of tagged proteins is described. Various applications of the 1C11 epitope are mentioned. This epitope did not alter the function of any of the proteins so far tested.

Amino Acid Sequence↗
PubMed1989

Analysis of the major inducers of the Rhizobium nodA promoter from Vicia sativa root exudate and their activity with different nodD genes.

Root exudate of Vicia sativa contains 7 inducers for the nodA promoter of Rhizobium leguminosarum biovar viciae. Six of these inducers are flavanones. One inducer was identified as 3,5,7,3'-tetrahydroxy-4'-methoxyflavanone, and a second inducer most likely is 7,3'-dihydroxy-4'-methoxyflavanone. The inducing activity of these compounds and the other inducers depends on the nodD gene present in the test strains, which originated either from R. leguminosarum biovars viciae or trifolii, or from R. meliloti. Three inducers are 'common', three others almost exclusively induce the nodA promoter in the presence of the R. leguminosarum biovar viciae nodD gene, and the last one is active with the noD genes of either R. leguminosarum biovar viciae or that of R. meliloti. Testing of a large number of flavonoids revealed two classes of structural features required for inducing ability: (i) features required for induction in general, and (ii), features restricting the inducing ability to (a) specific nodD gene(s). These features are discussed in relation to current models of the process of nodD-mediated transcription activation of the inducible nod genes.

Fabaceae↗
PubMed1988

Root Exudates of Various Host Plants of Rhizobium leguminosarum Contain Different Sets of Inducers of Rhizobium Nodulation Genes.

Rhizobium promoters involved in the formation of root nodules on leguminous plants are activated by flavonoids in plant root exudate. A series of Rhizobium strains which all contain the inducible Rhizobium leguminosarum nodA promoter fused to the Escherichia coli lacZ gene, and which differ only in the source of the regulatory nodD gene, were recently used to show that the regulatory nodD gene determines which flavonoids are able to activate the nodA promoter (HP Spaink, CA Wijffelman, E Pees, RJH Okker, BJJ Lugtenberg 1987 Nature 328: 337-340). Since these strains therefore are able to discriminate between various flavonoids, they were used to determine whether or not plants that are nodulated by R. leguminosarum produce different inducers. After chromatographic separation of root exudate constituents from Vicia sativa L. subsp. nigra (L.), V. hirsuta (L.) S.F. Gray, Pisum sativum L. cv Rondo, and Trifolium subterraneum L., the fractions were tested with a set of strains containing a nodD gene of R. leguminosarum, R. trifolii, or Rhizobium meliloti, respectively. It appeared that the source of nodD determined whether, and to what extent, the R. leguminosarum nodA promoter was induced. Lack of induction could not be attributed to the presence of inhibitors. Most of the inducers were able to activate the nodA promoter in the presence of one particular nodD gene only. The inducers that were active in the presence of the R. leguminosarum nodD gene were different in each root exudate.

Journal Article↗
PubMed1987

Induction of the nodA promoter of Rhizobium leguminosarum Sym plasmid pRL1JI by plant flavanones and flavones.

An expression vector containing the Rhizobium leguminosarum nodA promoter cloned in front of the Escherichia coli lacZ gene was used to characterize the properties of the R. leguminosarum nodA gene-inducing compound(s) present in sterile root exudate of the host plant Vicia sativa L. subsp. nigra (L.). The major inducing compound was flavonoid in nature, most likely a flavanone. The commercially available flavonoids naringenin (5,7,4'-trihydroxyflavanone), eriodictyol (5,7,3'4'-tetrahydroxyflavanone), apigenin (5,7,4'-trihydroxyflavone), and luteolin (5,7,3',4'-tetrahydroxyflavone) induced the nodA promoter to the same level as the root exudate. On the basis of chromatographic properties, it was concluded that none of these compounds is identical to the inducer that is present in root exudate. The induction of the nodA promoter by root exudate and by the most effective inducer naringenin was very similar, as judged from the genetic requirements and the kinetics of induction.

Escherichia coli↗
PubMed1987

Flavonoids induce Rhizobium leguminosarum to produce nodDABC gene-related factors that cause thick, short roots and root hair responses on common vetch.

Rhizobium leguminosarum produced a factor(s) that caused thick, short roots (Tsr phenotype) as well as root hair induction (Hai phenotype) and deformation (Had phenotype) in Vicia sativa plants upon incubation with root exudate or with one of the nod gene inducers naringenin or apigenin; this was a nodDABC gene-dependent process. Detection of the Hai and Had phenotypes was much more sensitive than that of the Tsr phenotype.

Fabaceae↗
PubMed1986

Role of plant root exudate and Sym plasmid-localized nodulation genes in the synthesis by Rhizobium leguminosarum of Tsr factor, which causes thick and short roots on common vetch.

In a previous paper it was shown that cocultivation of Rhizobium leguminosarum with the plant Vicia sativa subsp. nigra on solid medium causes a changed mode of growth of the plant roots, resulting in thick and short roots (Tsr). The Sym plasmid present in the bacterium appeared to be essential for causing Tsr (A. A. N. van Brussel, T. Tak, A. Wetselaar, E. Pees, and C. A. Wijffelman, Plant Sci. Lett. 27:317-325, 1982). In the present paper, we show that a role in causing Tsr is general for Sym plasmids of R. leguminosarum and Rhizobium trifolii. Moreover, mutants with transposon insertions in the Sym plasmid-localized nodulation genes nodA, B, C, and D are unable to cause Tsr, in contrast to nodulation mutants localized in other parts of the Sym plasmid. The observation that Tsr could also be brought about in liquid medium enabled us to show that Tsr is caused by a soluble factor. Experiments in which plants and bacteria were grown separately in the sterile supernatant fluids of each other resulted in establishing the following sequence of events. (i) The plant produces a factor, designated as factor A. (ii) Factor A causes the Sym plasmid-harboring bacteria to produce Tsr factor. (iii) Growth of young plants in the presence of Tsr factor results in the Tsr phenotype. Models explaining this example of molecular signalling between bacteria and plants are discussed.

Phenotype↗
PubMed1985

Bacteriocin small of fast-growing rhizobia is chloroform soluble and is not required for effective nodulation.

Small bacteriocin is a low-molecular-weight bacteriocin which is common in fast-growing rhizobia. As its activity could not be detected in chloroform-sterilized culture supernatants (P.R. Hirsch, J. Gen. Microbiol. 113:219-228, 1979), the bacteriocin could not be purified in order to study its mechanism of action. We report here that small is soluble in chloroform, an observation which led to effective and simple (partial) purification. Other properties of small are its low molecular weight, which is estimated to be between 700 and 1,500, its resistance to proteolytic enzymes, pectinase, and lysozyme, and its heat stability at pH 5.5 but not at pH 7.0. Its bactericidal action on exponentially growing sensitive cells was not detected until 11 h after its addition. The bactericidal action was preceded by inhibition of cell division. To determine whether small activity is required for nodulation or nitrogen fixation, a transposon Tn5-induced small-negative mutant was isolated. The observation that this strain formed normal, acetylene-reducing root nodules showed that small production is not a prerequisite for the formation of effective nodules.

Bacteriocins↗