- Volume 135, Issue 3, 1989
Volume 135, Issue 3, 1989
- Biochemistry
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Monoclonal Antibodies Reacting with the Exopolysaccharide Xanthan from Xanthomonas campestvis
More LessWe have prepared murine hybridomas secreting monoclonal antibodies against the exopolysaccharide xanthan from Xanthomonas campestris pv. campestris 646 after fusing NSO myeloma cells and spleen cells from BALB/c mice immunized with xanthan. Four hybridomas, secreting antibodies designated A6 (IgMk), B3 (IgMk), D1 (IgMk), and D3 (IgG2 A K) were selected for further studies. All antibodies reacted with a range of different xanthans. Competition studies using variants of the exopolysaccharide as competitors suggested that specificity was mainly against the side-chain. One of the antibodies (B3) appeared to require the fully acylated side-chain with the pyruvylated terminal mannose as the immunodominant part. The three others were assumed to be directed against the nonsubstituted trisaccharide with the inner mannose-glucuronic acid being immunodominant. None of the antibodies reacted with cellulose (the xanthan backbone). Using immunoblotting techniques on nitrocellulose paper both a mixture of monoclonal antibodies, and also polyclonal ascitic fluid, could detect xanthan quantities of approximately 0·1 μg.
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Degradation of Fungal Cell Walls by Lytic Enzymes of Trichoderma harzianum
Alex Sivan and Ilan ChetIn in vitro tests, two strains of Trichoderma harzianum failed to parasitize colonies of Fusarium oxysporum f. sp. vasinfectum and F. oxysporum f. sp. melonis. However, these strains were strongly mycoparasitic on Rhizoctonia solani and Pythium aphanidermatum. When grown in liquid cultures containing laminarin, chitin or fungal cell walls as sole carbon sources, both strains of T. harzianum released, 1-3-β-glucanase and chitinase into the medium. Higher levels of these enzymes were induced in strain T-203 than in T-35 by hyphal cell walls of F. oxysporum. When the lytic enzymes produced by T-35 were incubated with hyphal cell walls of the test fungi, more glucose and N-acetyl-d-glucosamine was released from cell walls of R. solani and Sclerotium rolfsii than from those of F. oxysporum. Treatment of F. oxysporum cell walls with 2 m-NaOH, protease or trypsin prior to their incubation with the lytic enzymes of T. harzianum significantly increased the release of glucose and N-acetyl-d-glucosamine. The effect of these treatments on R. solani and S. rolfsii cell walls was much lower. These results suggest that proteins in the cell walls of F. oxysporum may make these walls more resistant than those of R. solani or S. rolfsii to degradation by extracellular enzymes of T. harzianum.
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Metabolism of Mollicutes: the Embden—Meyerhof—Parnas Pathway and the Hexose Monophosphate Shunt
More LessCell-free extracts of eighteen fermentative and nonfermentative Mollicutes were examined for enzyme activities associated with the hexose monophosphate shunt (HMS) and Embden---Meyerhof---Parnas (EMP) pathway. All Acholeplasma spp. had glucose-6-phosphate (G6P) dehydrogenase (EC 1.1.1.49), 6-phosphogluconate (6PG) dehydrogenase (EC 1.1.1.44) and hexokinase (EC 2.7.1.1) activity. Of these three enzyme activities, hexokinase was also detected in Mycoplasma sp. Let. 1 but in no other fermentative or nonfermentative Mycoplasma spp. The Acholeplasma and fermentative Mycoplasma spp. possessed all other HMS and EMP activities examined. All Acholeplasma spp. possessed a pyrophosphate (PPi)-dependent phosphofructokinase (PFK) (EC 2.7.1.90) while fermentative Mycoplasma spp. possessed an ATP-dependent PFK (EC 2.7.1.11). Transaldolase (EC 2.2.1.2) activity was detected in some, but not all Acholeplasma and fermentative Mycoplasma spp. 2-Deoxyribose-5-phosphate aldolase (EC 4.1.2.4) activity was present in all mollicute extracts tested except for Mycoplasma gallisepticum and Mycoplasma sp. Let. 1. The two nonfermentative Mycoplasma spp. lacked all enzyme activities of the HMS pathway except for ribulose-5-phosphate epimerase activity, and of the EMP pathway only phosphoglucose isomerase and the enzymes converting glyceraldehyde 3-phosphate (G3P) to phosphoenolpyruvate (PEP) were detected. We believe that the three major observations of this study are: (1) all Mycoplasma spp. lack G6P and 6PG dehydrogenase activities, suggesting a reduction in their NADPH pool, which may relate to the lipid growth requirement of this genus; (2) the fermentative Mycoplasma spp. have an ATP-dependent PFK activity, while the fermentative Acholeplasma spp. have a PPi-dependent PFK activity; and (3) the nonfermentative Mycoplasma spp. lack ATP and PPi-dependent PFK and fructose-1,6-bisphosphate aldolase activities but, like the fermentative Mollicutes, can convert three-carbon compounds, G3P to PEP through the three-carbon arm of the EMP pathway.
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A Novel, Fully Saturated Menaquinone from the Thermophilic, Sulphate-reducing Archaebacterium Archaeoglobus fulgidus
More LessA recently described extremely thermophilic, sulphate-reducing archaebacterium, Archaeoglobus fulgidus, was investigated for the presence of respiratory lipoquinones. Initial screening using thin-layer chromatography and UV spectroscopy indicated that naphthoquinones were present. A more detailed study, using a combination of HPLC, mass spectroscopy and NMR techniques, indicated that the major respiratory lipoquinone present in this organism is a menaquinone with a fully saturated heptaprenyl side chain (MK-7H14).
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Purification and Properties of Glycerol: NADP+ 2-Oxidoreductase from Schizosaccharomyces pombe
More LessGlycerol: NADP+ 2-oxidoreductase (EC 1.1.1.156) was isolated from Schizosaccharomyces pombe, purified and characterized. It had an M r of 57000, and SDS-PAGE revealed two polypeptides, of M r 25000 and 30000. Its coenzyme requirement was satisfied exclusively by NADP. The pH optimum for glycerol oxidation was 9·5, for dihydroxyacetone reduction 6·0. Rates of oxidation with some structurally related diols were three- to six-fold lower than for glycerol, while glyceraldehyde and other carbonyl compounds showed negligible rates of reduction. Neither monovalent nor divalent cations activated the enzyme. Apparent K m and V max values were determined. The enzyme is similar to glycerol dehydrogenases isolated from Mucor javanicus and from Dunaliella parva but differs considerably from the glycerol: NAD+ 2-oxidoreductase of S. pombe.
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Generalized Distribution and Common Properties of Na+-dependent NADH: Quinone Oxidoreductases in Gram-negative Marine Bacteria
More LessEffects of Na+ on respiratory NADH oxidase were studied in membranes prepared from Gram-negative marine bacteria belonging to the genera Alcaligenes, Alteromonas, Flavobacterium and Vibrio. NADH oxidases of 9 out of the 10 strains examined were found to require Na+ for maximum activity. Without exception, the Na+-dependent site was located at the level of the NADH: quinone oxidoreductase region of the respiratory chain and was highly sensitive to 2-heptyl-4-hydroxyquinoline-N-oxide (HQNO). NADH dehydrogenases in the Na+-dependent segment were sensitive to Ag+ and able to oxidize reduced nicotinamide hypoxanthine dinucleotide as a substrate. Since the NADH dehydrogenase was neither dependent on Na+ nor sensitive to HQNO, it was suggested that reduction of quinone by the NADH: quinone oxidoreductase involves the formation of an intermediate, presumably semiquinone, and that electron transfer from the intermediate requires Na+ and is sensitive to HQNO. These results showed a striking similarity to those obtained with the Na+-dependent NADH: quinone oxidoreductase, the Na+ pump, of Vibrio alginolyticus, indicating that this enzyme is widely distributed among Gram-negative marine bacteria and shares common properties.
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- Development And Structure
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Location of a Single β-Tubulin Gene Product in Both Cytoskeletal and Mitotic-spindle Microtubules in Physarum polycephalum
More LessIn the mutant BEN210 of Physarum polycephalum several β-tubulins are detectable. β1-tubulin is unique to the myxamoeba, β2-tubulin is unique to the plasmodium, and the mutant β1-210 tubulin encoded by the benD210 allele is present in both cell types. In order to analyse the subcellular distribution of the β1-210 polypeptide, we prepared cytoskeletons from myxamoebae and mitotic spindles from plasmodia, and examined the tubulin polypeptide composition of these microtubular organelles by two-dimensional gel electrophoresis and immunoblotting. The results show that the β1-210 tubulin is present in microtubules of both the cytoskeleton and the intranuclear mitotic spindle. Thus a single β-tubulin gene product can participate in multiple microtubular organelles in distinct cellular compartments.
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- Ecology
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Factors Affecting the Migration and Sequestration of Rumen Protozoa in the Family Isotrichidae
More LessA chemotactic migration of Isotrichidae, primarily Isotricha and Dasytricha, into sheep rumen contents was observed at feeding time, followed by an abrupt decrease in relative numbers, presumably as a result of sequestration. An increase in the numbers of isotrichids was also observed before feeding, and was not a response to handling or sampling of the animals. When feeding was delayed for 4·5 h, isotrichid numbers increased markedly, falling again when feed was provided. The size of the decrease in numbers after feeding was directly related to feed intake. In general, chemotactic migration of the Isotrichidae was observed 12 h after feeding, while migration without feeding occurred after 22–24 h. In animals normally fed once daily, the relative number of isotrichids in the rumen contents of an unfed animal about 3 h after the regular feeding time is probably the best estimate of total isotrichid numbers. Two migrations of the same isotrichids appeared to occur in animals fed twice a day. It is proposed that feeding level controls the amount of storage polysaccharide in the protozoan cell, which in turn controls migration of Isotrichidae into the rumen. The isotrichids appeared to sequester by settling in the ventral rumen.
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The Use of Gel-stabilized Model Systems for the Study of Microbial Processes in Polluted Sediments
More LessGel-stabilized model sediment ecosystems were prepared using agar and colloidal silica as gelling agents and were employed in studies of the effects and degradation of xenobiotics in marine and freshwater sediments. All models produced physicochemical and microbiological profiles characteristic of sediments. The fate of 3-nitrophenol was studied in a freshwater system and the compound was found to be readily distributed through the gel column and to be rapidly degraded. The release of the nitro-group during metabolism resulted in the accumulation of nitrate in the aerobic portion of the gel column. The fate of a 1:1 hexadecane/naphthalene mixture was investigated using a seawater model system. The metabolism of these compounds resulted in oxygen depletion in the gel column and in a decrease in the population size of aerobic heterotrophic bacteria. Conversely, the populations of anaerobic heterotrophic bacteria and sulphate-reducing bacteria were significantly increased. The data are discussed with particular respect to the practical uses of gel-stabilized model ecosystems in research into the microbiology of sediments.
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- Genetics And Molecular Biology
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Location and Characterization of Two Functions on RP1 That Inhibit the Fertility of the IncW Plasmid R388
More LessTwo fertility-inhibition functions which reduce R388 (IncW) transfer were detected on RP1 (60 kb, IncP). The respective genes, fiwA and fiwB, were mapped by transposon insertion mutagenesis to the regions between coordinates 32·8 to 31·7 kb (fiwA), and 59·8 to 0·8 kb (fiwB). The fiwA function occurs in a non-essential region of RP1 whereas fiwB is straddled by essential plasmid-maintenance and host-range determinants and apparently coincides (or overlaps) with the gene for tellurite-resistance.
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Distribution of Virulence Plasmids within Salmonellae
More LessThe virulence region of the Salmonella dublin 50 MDa plasmid shared homology with 678 of 1021 salmonellae tested in colony hybridization experiments. The majority of S. dublin, S. typhimurium and S. enteritidis isolates tested hybridized with the region whereas, with the exception of S. hessarek, S. pullorum and S. gallinarum, other serotypes did not. Homologous virulence regions were plasmid encoded. In S. typhimurium a common 60 MDa plasmid was present in all phage types tested but not in DT4, DT37 and DT170. Smaller plasmids showing partial homology were found in DT12, DT18, DT193 and DT204C. In S. enteritidis a distinct plasmid profile for each of eight phage types was observed. Hybridizing plasmids were found in DT3, DT4, DT8, DT9 and DT11 whereas DT7, which was plasmid free, and DT10 and DT14, which harboured plasmids, did not hybridize. The extent of homology shared between S. dublin, S. typhimurium and S. enteritidis virulence plasmids was about 10 MDa and appeared conserved. Virulence plasmids from S. typhimurium and S. enteritidis did not show homology with a region of the S. dublin 50 MDa plasmid which was not associated with virulence functions whereas plasmids of about 24 MDa and 38 MDa in some S. typhimurium phage types did. The association of conserved virulence regions upon differing plasmids within salmonellae is discussed with reference to possible mechanisms of distribution and evolution of virulence genes.
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Aeromonas salmonicida Plasmids: Plasmid-directed Synthesis of Proteins in vitro and in Escherichia coli Minicells
More LessPlasmid DNAs from 25 Aeromonas salmonicida strains (14 ‘typical’ and 11 so-called ‘atypical’ strains) were analysed using two plasmid isolation techniques in conjunction with restriction enzyme digestion and agarose gel electrophoresis. ‘Atypical’ strains carried two to four plasmid species, which were different from the plasmids carried by ‘typical’ strains, and corresponded to isolate source and biotype, suggesting that plasmid content may be a useful epidemiological marker for ‘atypical’ A. salmonicida. The ‘typical’ group was extremely homogeneous in plasmid content. In addition to a single large (70–145 kb) structurally related plasmid species, all strains carried a highly conserved group of three low-M r plasmids (pAsa1, 5·0 kb; pAsa2, 5·2 kb; pAsa3, 5·4 kb). The pAsa plasmids had different restriction maps, and directed the synthesis of four polypeptides when assayed in vitro using a transcription/translation system and [3 5S]methionine radiolabelling. A partially conserved 6·0 kb plasmid directed synthesis of an additional polypeptide. Total cellular plasmid DNA from virulent ‘typical’ strain A. salmonicida A449 was also cloned in Escherichia coli, using the vector pBR322. When analysed using a minicell expression system, 17 plasmid-encoded proteins, ranging in size from 12 to 90 kDa, were identified, including two putative exported proteins, and a chloramphenicol acetyltrans-ferase which was encoded by the 145 kb conserved, non-conjugative, plasmid.
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Arsenical Resistance of Growth and Phosphate Control of Antibiotic Biosynthesis in Streptomyces
More LessTwenty-six wild-type Streptomyces strains tested for resistance to arsenate, arsenite and antimony(III) could be divided into four groups: those resistant only to arsenite (3) or to arsenate (2) and those resistant (8) or sensitive (13) to both heavy metals. All strains were sensitive to antimony. The structural genes for the ars operon of Escherichia coli were subcloned into various Streptomyces plasmid vectors. The expression of the whole ars operon in streptomycetes may be strain-specific and occurred only from low-copy-number plasmids. The arsC gene product could be expressed from high-copy plasmids and conferred arsenate resistance to both E. coli and Streptomyces species. The ars operon expressed in S. lividans and the arsC gene expressed in S. noursei did not render the synthesis of undecylprodigiosin and nourseothricin, respectively, phosphate-resistant. In addition in wild-type strains of Streptomyces phosphate sensitivity of antibiotic biosynthesis did not show strong correlation with resistance of growth to arsenicals.
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Heat Shock at an Elevated Temperature Improves Transformation Efficiency of Protoplasts from Podospora anserina
More LessWe have developed an improved transformation procedure for the filamentous fungus Podospora anserina. This procedure is based on the observation that a heat shock at an elevated temperature (48 °C) improves the competence of P. anserina protoplasts for transformation 5- to 10-fold. This is observable only if the heat shock is applied before the addition of transforming DNA. An increase in competence is observed immediately after the heat shock, and heat-shocked cells are still competent after 20–30 min. The mechanism by which heat shock improves competence remains unclear. The modified transformation procedure gives as many as 200–500 stable transformants per μg of plasmid DNA containing the P. anserina ura5 gene. This should allow direct cloning of P. anserina genes from a cosmid library.
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Chlorate-resistant, Nitrate-utilizing (crn) Mutants of Fusarium moniliforme (Gibberella fujikuroi)
More LessFive crn loci have been identified in Fusarium moniliforme. Mutants at these loci were chlorate resistant and able to utilize nitrate. The crnl locus was closely linked to, and may be allelic with, nit3, a regulatory gene controlling induction of the nitrate reductase pathway. The crn2 locus was linked to, but distinct from, the nit5 gene coding for a molybdenum-containing cofactor. The crn3 and crn4 loci were unlinked to any known gene affecting nitrate reduction. The crn5 locus was clearly linked to the nit1 gene coding for the nitrate reductase enzyme. Mutants of crn1 and crn5 had low but detectable levels of nitrate reductase activity; these mutations may be leaky alleles of nitrate reduction genes. crn2 mutants had normal nitrate reductase activity, and may be altered in nitrate uptake.
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- Immunology
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Demonstration of Membrane Association and Surface Location of Mycoplasma pneumoniae Antigens Using Monoclonal Antibodies
More LessWe examined 10 monoclonal antibodies (mAbs) directed against Mycoplasma pneumoniae proteins of 200, 170, 67, 46 and 42 kDa, and one mAb directed against a glycolipid component. The membrane association of the antigens reacting with our mAbs was investigated, in particular by phase-fractionation involving use of the detergent Triton X-114. The 170 kDa protein was shown to be membrane-associated, and surface exposure of this antigen was demonstrated by its disappearance from SDS-PAGE patterns after treatment of intact mycoplasmas with proteolytic enzymes. Cross-reactions with protein antigens of Mycoplasma genitalium were also shown. A mAb directed against a component of a lipid extract, prepared by the methods used for preparation of the antigen used in the complement fixation (CF) test for serological diagnosis of M. pneumoniae infection, reacted with one major and a few minor bands in thin-layer chromatography (TLC) of the crude extract. The glycolipid character of this major antigen was demonstrated by treatment of the extract with sodium periodate, and by development of the TLC with orcinol/ferric chloride. These reactive bands were the same as those detected by the use of polyclonal mouse antiserum and a human convalescent serum, a result showing that the CF antigen contains a glycolipid moiety reacting with our mAb. The surface exposure of this antigen was demonstrated by binding of mAbs to intact cells.
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- Pathogenicity And Medical Microbiology
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Electron Microscopy of Adhesive Interactions between Gardnerella vaginalis and Vaginal Epithelial Cells, McCoy Cells and Human Red Blood Cells
More LessExfoliated vaginal epithelial cells with attached bacteria, termed ‘clue cells’, which were procured from a patient with non-specific vaginitis, were stained with ruthenium red and examined by transmission electron microscopy. The attached bacteria appeared to adhere by means of an outer fibrillar coat. An epithelial tissue culture cell line (McCoy) and human red blood cells to which strains of Gardnerella vaginalis attached were similarly examined. The adherence of G. vaginalis to the epithelial cell line appeared to be mediated by an outer fibrillar coat while adherence to red cells appeared to be mediated by fimbriae. Transmission electron microscopy was performed on the Gardnerella strains used. Thin sections of tissue-culture-adherent strains revealed a dense outer fibrillar coat whereas the surface of the haemagglutinating strains showed fine fimbriae. Negative staining of haemagglutinating strains demonstrated fimbriae on a minority of organisms.
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Production of Thiol-dependent Haemolysins by Listeria monocytogenes and Related Species
More LessTwenty-six strains belonging to the five main species of the genus Listeria were examined for production of thiol-dependent exotoxins. All strains of L. monocytogenes cultured in charcoal-treated broth secreted a haemolytic factor at a level ranging from 200 to 800 haemolytic units (HU) ml-1, except for the strain EGD (1500 HU ml−1) and the type strain CIP 82110T (10 HU ml−1). The haemolytic activity reached a maximum level by 8–10 h and then rapidly declined as soon as bacterial exponential growth ceased. The titres of haemolytic activity were markedly reduced when bacteria were grown in charcoal-untreated broth. The haemolytic factor produced by L. monocytogenes strains was characterized as listeriolysin O (M r about 60000), a member of the group of thiol-dependent exotoxins. Strains of Listeria ivanovii also produced high levels of thiol-dependent exotoxin (about 2500 HU ml−1), in both charcoal-treated and untreated broth. Small amounts of haemolytic factor (about 9–30 HU ml−1) were also produced by Listeria seeligeri in charcoal-treated broth. The haemolysin produced by L. seeligeri was identified for the first time as a thiol-dependent exotoxin of M r about 60000, antigenically related to listeriolysin O. As expected, we failed to detect thiol-dependent exotoxin in the two nonhaemolytic species, Listeria innocua and Listeria welshimeri.
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The Role of Surface Components of the Entomopathogenic Fungus Entomophaga aulicae in the Cellular Immune Response of Galleria mellonella (Lepidoptera)
More LessLarvae of Galleria mellonella (Lepidoptera) displayed a strong cellular reaction to the walled-stage hyphal bodies of the entomopathogenic fungus Entomophaga aulicae (Entomophthorales). In contrast, no reaction was observed against the wall-less protoplasts. This phenomenon was not due to an inhibition of the cellular response by secretion of a toxin by protoplasts. Furthermore, no molecular mimicry was observed between host and protoplast antigens. Host macromolecules which could protect them from being recognized as foreign did not attach to the protoplasts. Ultrastructural and chemical studies of hyphal body and protoplast surfaces of E. aulicae demonstrated the presence of 1,3-β-glucan and chitin on the hyphal wall, whereas these components were absent on the protoplast surface. Since purified 1,3-β-glucan and chitin isolated from E. aulicae and from another entomophthoralean species, Conidiobolus obscurus, induced their haemocytic encapsulation in vitro, it is suggested that these wall components are responsible for the recognition of hyphal body elements, and that their absence accounts for the ability of protoplasts to escape encapsulation.
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Cloning and Expression of an Adhesin Antigen of Streptococcus sanguis G9B in Escherichia coli
A genomic library of Streptococcus sanguis, strain G9B, was constructed and expressed in Escherichia coli using a λgt11 expression vector. The amplified library was probed with polyclonal anti-G9B IgG and 13 antigen-positive clones were isolated. A lysate of one clone, designated PP39, absorbed the adhesion-inhibitory activity of anti-G9B IgG. This clone contained an insert of approximately 2000 bp and expressed unique 200 and 53 kDa proteins that reacted with monospecific anti-adhesin antibody. The 200 kDa protein also reacted with anti-β-galactosidase IgG, indicating that it is a fusion protein of which 84 kDa represents the streptococcal adhesin. The 84 and 53 kDa proteins are similar in size to the major polypeptides in a streptococcal antigen complex which is associated with the adhesion of G9B to salivacoated hydroxyapatite. The 53 kDa fragment may result from post-translational cleavage of the recombinant polypeptide.
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Production of Cell-bound and Vesicle-associated Trypsin-like Protease, Alkaline Phosphatase and N-Acetyl-β-glucosaminidase by Bacteroides gingivalis Strain W50
More LessBacteroides gingivalis strain W50 was grown in batch and continuous culture on complex medium with haemin. In batch culture, cell-bound levels of trypsin-like protease (EC 3.4.21.4), alkaline phosphatase (EC 3.1.3.1) and N-acetyl-β-glucosaminidase (EC 3.2.1.30) increased during the exponential phase of growth. These enzyme activities were also detected in extracellular vesicles and in extracellular soluble forms in the supernatant fluid, but in lower amounts per unit biomass compared to cell-bound levels. In continuous culture, at high relative growth rates (0·7–0·9 μ rel), the highest proportions of enzyme activities were cell-bound. In contrast, at low relative growth rates (0·1–0·2 μ rel), highest enzyme levels were detected in the extracellular vesicle fraction. Levels of extracellular soluble enzymes were always low compared to cell-bound or extracellular vesicle levels, but were highest at low relative growth rates. All three enzymes appeared to be relatively stable in their soluble forms. Vesicle production appeared to be associated with actively growing cells but was influenced by growth rate. The results are consistent with the hypothesis that cell-bound periplasmic enzymes are encapsulated into vesicles which are subsequently released by the cells. Therefore, levels of total extracellular enzyme (extracellular vesicle plus extracellular soluble) may depend on the rate of vesicle formation superimposed on the rates of production of periplasmic enzymes in the cell.
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Changes in Progesterone, Oestradiol 17β, and Intrauterine Prostaglandin E2 during Late Gestation in Sheep Experimentally Infected with an Ovine Abortion Strain of Chlamydia psittaci
The placenta is the primary site of infection of Chlamydia psittaci and is also intimately involved in the control of parturition. Changes in the pattern of placental hormone secretion were investigated in ewes infected with C. psittaci and in saline-injected controls. The concentration of progesterone in peripheral plasma of infected sheep was significantly lower than in control sheep (P < 0·01). A gradual decline in plasma progesterone occurred in Chlamydia-infected sheep, beginning on day 125 of gestation, in comparison with the sharper decline commencing on day 139 of gestation in the control population. The release of oestradiol 17β, which was greatest on the day of parturition in control sheep, was significantly (P < 0·02) increased on the day before parturition in Chlamydia-infected sheep. The concentrations of prostaglandin E2 in amniotic and allantoic fluids were low during late pregnancy in 12 control sheep, but were significantly raised (P < 0·05) in four out of 12 samples obtained from Chlamydia-infected sheep over the same period. The changes in progesterone and prostaglandin E2 were temporally related to the morphological and histochemical changes characteristic of trophoblast infection. These findings suggest that C. psittaci infection may precipitate premature labour by altering placental steroid and prostaglandin release.
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- Physiology And Growth
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Relationship between the Production of Spirosomes and Anaerobic Glycolysis Activity in Escherichia coli B
More LessThe effects of culture conditions (aerobic or anaerobic) and glucose in the medium on the production of spirosomes in Escherichia coli B were studied by SDS-PAGE and electron microscopy. The M r of the spirosome of E. coli B was estimated to be 97000. Electron microscopy revealed that the amount of spirosomes derived from anaerobic cultures was about eightfold larger than that from aerobic cultures. In SDS-PAGE, the bands of spirosome protein derived from anaerobic cultures were more intense than those derived from aerobic cultures, either in peptone water or in Davis-Mingioli’s minimal medium. With increased glucose concentration under aerobic conditions, the intensity of the band of spirosome protein was similar to that observed under anaerobic conditions in basal media. These results suggest that spirosome production by E. coli B is related to its anaerobic glycolysis activity.
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Some Properties of Two Erythromycin-dependent Strains of Escherichia coli
More LessStrains of Escherichia coli can be isolated that require erythromycin for growth. With one strain, AM, a range of antibiotics, including chloramphenicol, tetracycline, spectinomycin, kasugamy-cin and rifampicin, will substitute for erythromycin on solid and in liquid media; nalidixic acid supports growth in liquid but not on solid media. With a second strain, 103, chloramphenicol, tetracycline and spectinomycin support growth in liquid media but on solid medium only chloramphenicol substitutes for erythromycin. In media of higher than normal ionic strength, strain AM, but not strain 103, can grow in the absence of antibiotics. Possible reasons for these complex phenotypes are discussed.
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Induction of d-Amino-acid Oxidase by d-Alanine in Rhodotorula gracilis Grown in Defined Medium
More LessThe obligate aerobe yeast Rhodotorula gracilis was grown in batch culture on a chemically defined, pH-controlled medium containing glucose or d-alanine as carbon sources, ammonium or d-alanine as nitrogen sources, and d-alanine as a sole carbon and nitrogen source. Under these conditions, d-alanine induced the synthesis of d-amino-acid oxidase (EC 1.4.3.3) to an extent depending on the nutrients, the highest specific activity of the enzyme [up to 0·6 U (mg protein)−1] being detected when both d-alanine and glucose were present in the growth medium. In contrast, enzyme activity was negligible when both ammonium and glucose were present in the growth medium, even in the presence of d-alanine. The racemic mixture dl-alanine was also utilized as a source of both carbon and nitrogen for the growth of R. gracilis, but the enzyme activity appeared only after the depletion of l-alanine from the medium. Data on transmembrane transport of d-alanine in the presence of different nutrients clearly indicated that the l-isomer prevented induction by d-alanine through inhibition of the transport of the d-amino acid into cells. However, such an effect was not exerted by ammonium, indicating that this compound probably acts at the level of enzyme synthesis.
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Regulation of Glutamine Synthetase Isoenzymes in Rhizobium leguminosarum biovar viceae
Ammonia assimilation in Rhizobium leguminosarum biovar viceae strain RCR1001 (hereafter called R. leguminosarum) appears to take place only through the glutamine synthetase/glutamate synthase pathway since (a) no glutamate dehydrogenase was detected in crude extracts of bacteria grown in different nitrogen sources, and (b) the growth rate on glutamine as a nitrogen source was faster than that observed on NH4Cl. In contrast to reports for other Rhizobium species, R. leguminosarum can definitely utilize NH4C1 for growth. R. leguminosarum contains two glutamine synthetase isoenzymes, GSI and GSII, which can be detected in the presence of each other by differential heat stability, or separated by affinity chromatography or immunoabsorption with an antiserum raised against pure GSI. GSII does not cross-react with an anti-GSI antiserum. GSI was shown to be reversibly adenylylated and it was also shown that adenylylation inhibits the biosynthetic activity of this enzyme, in a similar way to that reported for Escherichia coli glutamine synthetase and in contrast to that observed for glutamine synthetase of Rhizobium sp. strain ANU289. The apparent adenylylation level in different growth conditions changes from 21% to 99%, indicating a physiological role of this post-translational modification in the in vivo regulation of GSI activity. The intracellular concentration of GSI varies very little when R. leguminosarum is grown on different nitrogen sources (twofold when measured by the transferase assay, or fourfold when measured by ELISA). In addition, the concentration of mRNA specific for GSI in different nitrogen sources does not show appreciable differences. The intracellular concentration of GSII varies from a specific activity value higher than 1000 when R. leguminosarum is grown on glutamate or nitrate, to an undetectabie level when grown on NH4C1. When NH4C1 is added to a culture growing in glutamate, GSII activity is rapidly diluted out, suggesting a post-translational mechanism of enzyme inhibition or inactivation. Chloramphenicol prevents the disappearance of GSII activity, thus suggesting that protein synthesis is required for this process.
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Inhibition of the Binding of Penicillin to the Pneumococcal Penicillin-binding Proteins (PBPs) by Exogenous Cell Wall Peptides
More LessIncubation of pneumococci with d-alanine-containing peptides naturally occurrins in peptidoglycan protected cells against lysis and killing by β-lactam antibiotics near MIC. Such peptides caused decreased binding of the antibiotic to penicillin-binding proteins (PBPs), primarily PBP 2B. This provides direct evidence in vivo for the hypothesis that β-lactams act as substrate analogues and identifies PBP 2B as a killing target in pneumococci.
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Cell Wall Assembly in Bacillus subtilis: Visualization of Old and New Wall Material by Electron Microscopic Examination of Samples Stained Selectively for Teichoic Acid and Teichuronic Acid
More LessUranyl actetate staining of thin sections allowed a distinction to be made between cell wall material that contains teichoic acid and that which contains teichuronic acid. The stain was used to study the pattern of wall assembly in Bacillus subtilis undergoing transitions between growth conditions leading to incorporation of the different anionic polymers. The results showed that new material is incorporated along the inner surface of the cylindrical region of the wall confirming, by a more direct method, results obtained earlier with teichoic acid specific phages. New material appears to be evenly distributed along the inner surface and no evidence was obtained for the presence of specific zones of incorporation.
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Cell Wall Assembly in Bacillus subtilis: Partial Conservation of Polar Wall Material and the Effect of Growth Conditions on the Pattern of Incorporation of New Material at the Polar Caps
More LessThe use of phage SP50 as marker for cell wall containing teichoic acid in Bacillus subtilis showed clear differences in the rates at which new wall material becomes exposed at polar and cylindrical regions of the wall, though the poles were not completely conserved. Following transition from phosphate limitation to conditions that permitted synthesis of teichoic acid, old polar caps fairly rapidly incorporated enough teichoic acid to permit phage binding. Electron microscopy suggested that the new receptor material spread towards the tip of the pole from cylindrical wall so that phages bound to an increasing proportion of the pole area until only the tip lacked receptor. Eventually, receptor was present over the whole polar surface. Direct electron microscopic staining of bacteria collected during transitions between magnesium and phosphorus limitations showed that new material was incorporated at the inner surface of polar wall and later became exposed at the outer surface by removal of overlying older wall. The apparent partial conservation of the pole reflected a slower degradation of the overlying outer wall at the pole than at the cylindrical surface, the rate being graded towards the tip of the pole. The relative proportions of the new wall material incorporated into polar and cylindrical regions differed in bacteria undergoing transitions that were accompanied by upshift or downshift in growth rate. These differences can be explained on the basis that growth rate affected the rate of synthesis of cylindrical but not septal wall.
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Cell Wall Composition and Surface Properties in Bacillus subtilis: Anomalous Effect of Incubation Temperature on the Phage-binding Properties of Bacteria Containing Varied Amounts of Teichoic Acid
More LessAdsorption of bacteriophage SP50 to walls and heat-killed cells of Bacillus subtilis 168 appeared to be irreversible at both 37 and 0 °C. Few, if any, active phage were desorbed when phage-wall complexes, formed at either temperature, were suspended in fresh medium. Bacteria rich in wall teichoic acid (TA) bound phage rapidly at both 0 and 37 ¼C, binding at the higher temperature being approximately twice as fast. Bacteria containing diminished proportions of TA showed less rapid phage adsorption but the reduction in rate was greater at 37 than at 0 °C and bacteria containing only small proportions of TA bound phage more rapidly at 0 °C than they did at 37 °C. These findings show that at low phage receptor density the temperature affects some component(s) involved in the phage-bacterium interaction such that the collision efficiency is increased at the lower temperature. The possible effect of temperature on the organization of bacterial surface components is discussed.
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Comparison of Nucleoside Triphosphate Levels in the Wild-type Strain with Those in Sporulation-deficient and Solvent-deficient Mutants of Clostridium acetobutylicum P262
More LessThe role of GTP and other ribonucleoside phosphates in the differentiation of Clostridium acetobutylicum and two sporulation-deficient mutants was investigated. The clostridial stage (cls-1) mutant was unable to produce the clostridial stage, solvents, granulose, capsules or endospores, whereas the sporulation-deficient (spo-1) mutant produced the clostridial stage, solvents, granulose and capsules, but did not form a forespore septum. The nucleoside triphosphate profiles of the wild-type and spo-1 mutant were similar and were characterized by a trough in nucleotide levels which occurred just prior to the pH break point, the onset of the stationary growth phase, clostridial stage formation and the transition from the acidogenic to the solventogenic phase. The nucleoside triphosphate concentrations during the exponential growth phase were much lower than those found during the stationary phase. The nucleotide levels in the cls-1 mutant during the exponential phase were comparable to those observed in the wild-type and spo-1 mutant. However, the nucleotide levels in the cls-1 mutant did not increase during the stationary growth phase. The involvement of nucleotide levels, particularly that of GTP, in the differentiation of C. acetobutylicum was indicated by the effect of inhibitors, which have been shown to decrease ribonucleotide levels in other organisms and cause an increase in sporulation.
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