bluuebunny/crossref_metadata_2025 huggingface dataset:
Kinetics of sulfur and pyrite oxidation by Thiobacillus thiooxidans. Competitive inhibition by increasing concentrations of cells
Authors: Lizama Hector M. , Suzuki Isamu
Published: May 2010

The oxidation of elemental sulfur by two strains of Thiobacillus thiooxidans was studied by measuring the rate of O2 consumption at various concentrations of substrate and cells. In both the laboratory strain ATCC 8085 and the mine isolate SM-6, sulfur oxidation was competitively inhibited by T. thiooxidans cells; the Ki values were 0.65 and 0.05 mg wet cells∙mL−1, respectively. The rate constants were 500 and 143 μM O2∙min−1∙mg wet cells−1∙mL−1 and the Km values for sulfur concentration were 7.5 and 0.32% pulp density, respectively. Mine isolate SM-6 was used also to study pyrite (FeS2) oxidation by measuring the rate of O2 consumption. Oxidation of both washed and unwashed pyrite samples was competitively inhibited by increasing concentrations of cells; with each sample the Ki values was 0.05 mg wet cells∙mL−1. The rate constants for each sample were also the same (100 μM O2∙min−1∙mg wet cells−1∙mL−1), but the Km values were different (1.11% pulp density for washed pyrite and 2.81% pulp density for unwashed pyrite). Based on the rate of Fe solubilization from the washed pyrite sample, T. thiooxidans cells oxidized the sulfide released from pyrite dissolution beyond the oxidation state of elemental sulfur. Key words: Thiobacillus thiooxidans, sulfur, pyrite, oxidation, kinetics.
Serum antibody response of gnotobiotic athymic and euthymic mice following alimentary tract colonization and infection with Candida albicans
Authors: Balish Edward , Filutowicz Hanna
Published: May 2010

Colonization and infection evoked specific immunoglobulin responses to Candida albicans antigens in gnotobiotic nu/+mice which appeared to correlate with clearance of infected mucosal surfaces (tongue and stomach). Conversely, colonized and infected nu/nu mice formed some IgM but no detectable IgG or IgA antibodies against C. albicans antigens. Although chronic mucosal infections of tongue and stomach persisted in nu/nu mice, they were able to resist overwhelming mucosal and systemic infections with C. albicans. Thus, C. albicans specific antibodies may play a role in clearance of mucosal candidiasis (tongue and stomach), but these antibodies do not appear to be necessary for protecting athymic mice against systemic candidiasis of endogenous origin. Key words: candidiasis, antibody response, mucosal candidiasis, murine candidiasis.
A comparative study of malolactic enzyme and malic enzyme of different lactic acid bacteria
Authors: Battermann Gerd , Radler Ferdinand
Published: May 2010

Malolactic enzyme of lactic acid bacteria catalyzes the decarboxylation of L-malate to L-lactate. The appropriate enzyme of Lactobacillus casei, Leuconostoc oenos, and Leuconostoc mesenteroides, as well as the malic enzyme of Lactobacillus casei, were purified to electrophoretic homogeneity by salmine sulphate precipitation, ion-exchange chromatography, hydrophobic chromatography, and gel filtration. The malolactic enzymes investigated were similar and showed only minor variations in the isoelectric point and the temperature optimum. The molecular weight of the subunit of all malolactic enzymes was about 65 000. Aggregates were formed, depending on the pH. The optimum activity of malolactic enzyme was observed at pH 5.8–6.0, and at this pH the dimer was stable. In addition to Mn2+ and NAD, the malolactic enzyme required K+, which was replaceable by NH4+, for maximum activity. The Km values for L-malate were 10.9 mM (Leuconostoc mesenteroides B116) and 3 mM (Leuconostoc oenos). The Km values for Mn2+ were 0.1 mM (Leuconostoc mesenteroides B116) and 0.017 mM (Leoconostoc oenos). Malic enzyme oxidatively decarboxylates L-malate to pyruvate. This enzyme consists of a 37 000 subunit that forms dimers and tetramers. The NAD-dependent malic enzyme of Lactobacillus casei decarboxylates oxalacetate and is therefore regarded as a L-malate:NAD+ oxidoreductase (oxalacetate decarboxylating), EC 1.1.1.38. Key words: malolactic enzyme, malic enzyme, Lactobacillus, Leuconostoc.
Induction of lethal infection with indigenous Escherichia coli in mice by fluorouracil
Authors: Nomoto Koji , Yokokura Teruo , Yoshikai Yasunobu , Mitsuyama Masao , Nomoto Kikuo
Published: May 2010

A single administration of fluorouracil (5-FU), a well-used cancer chemotherapeutic agent, at high doses (338–800 mg/kg) to specific pathogen free mice induced a lethal infection with Escherichia coli. The infection was manifested in all the mice treated with 5-FU 7–14 days after administration of the drug, when the number of E. coli in liver reached levels ranging from 108 to 1010 colony-forming units, and the type of the infecting bacteria was limited to E. coli. The infection was accompanied with the increase in the population levels of E. coli in the intestinal tract which reached levels about 103 to 104 times as high as those of normal mice. Administration of tegafur, a less toxic derivative of 5-FU, to mice at a lethal dose of 1280 mg/kg induced infection with E. coli similar to that induced by 5-FU. Multiple administration of both streptomycin sulfate and cephalothin to mice after treatment with 5-FU protected the mice completely from the lethal infection induced by 5-FU, suggesting that the lethality of 5-FU was due to the indigenous bacterial infection. Key words: fluorouracil, Escherichia coli, mice, indigenous infection.
Interaction of chalcopyrite and sphalerite with pyrite during leaching by Thiobacillus ferrooxidans and Thiobacillus thiooxidans
Authors: Lizama Hector M. , Suzuki Isamu
Published: May 2010

The interaction of chalcopyrite and sphalerite with pyrite during leaching by Thiobacillus ferrooxidans and Thiobacillus thiooxidans was studied in shake-flask leaching experiments and in respirometer experiments with resting cells. Two samples of pyrite (Nos. 1 and 2) were used. In shake-flask experiments in the absence of bacteria, the copper and zinc extraction rates increased in the presence of No. 1 pyrite from 1.6 to 10.2 and 13%, respectively, and in the presence of No. 2 pyrite from 1.6 to 3.5 and 5.8%, respectively. Thus the effect of pyrite was greater with sphalerite than with chalcopyrite and the No. 1 pyrite was more effective than the No. 2 pyrite. Thiobacillus ferrooxidans increased the leaching rates of Cu from chalcopyrite (from 1.6 to 11.1%), of Zn from sphalerite (from 1.6 to 36%), and of Fe from pyrite (from 7.3 to 29.9% (No. 1) and from 5.1 to 49.3% (No. 2)), although a period of adaptation was required for sphalerite leaching. Thiobacillus thiooxidans did not leach Cu form chalcopyrite, but increased leaching of Zn from sphalerite (from 1.6 to 8.3%) and some Fe from pyrite (from 7.3 to 9.5% (No. 1) and from 5.1 to 13.1% (No. 2)). In the chalcopyrite–pyrite mixture, Cu leaching was further stimulated by T. ferrooxidans (from 10.2 to 14.5% (No. 1) and from 3.5 to 12.2% (No. 2)) and by T. thiooxidans (from 3.5 to 5.8% (No. 2)). The Zn leaching from the sphalerite–pyrite combination increased further with T. ferrooxidans (from 13.0 to 61.7% (No. 1) and from 5.8 to 65.8% (No. 2)) and T. thiooxidans (from 13.0 to 22.4% (No. 1) and from 5.8 to 14.7% (No. 2)). The Fe solubilization from pyrite was inhibited by the presence of chalcopyrite or sphalerite with or without bacteria. Short-term respirometer studies generally supported the leaching results. Oxygen consumption was faster for chalcopyrite or sphalerite in the presence of pyrite. The effect was stronger for sphalerite, although the rapid pyrite oxidation by T. ferrooxidans was inhibited by the interaction. Chalcopyrite alone was oxidized by T. ferrooxidans but not by T. thiooxidans, while sphalerite alone was oxidized only by the latter. It is concluded that shake-flask leaching and Warburg respirometer experiments complement each other in elucidating the complex processes involved in bacterial metal leaching of sulfide ores. Key words: Thiobacillus, sulfide ores, oxidation, mineral leaching.
Calcium binds to and is required for biological activity of the 104-kilodalton hemolysin produced by Actinobacillus pleuropneumoniae serotype 1
Authors: Devenish J. , Rosendal S.
Published: May 2010

Actinobacillus pleuropneumoniae serotype 1, strain Shope 4074, was grown on agar medium containing 10 mM Ca2+ and under Ca2+ limiting conditions by addition of 2 and 5 mM EGTA to the growth medium. Hemolysis of washed bovine erythrocytes was observed from the culture grown in Ca2+ excess but not from the two cultures where Ca2+ was chelated from the growth medium by using EGTA. However, the hemolytic activity of these latter two cultures could be restored if 10 mM Ca2+ was added to the dilution buffer. This restored hemolytic activity could be neutralized with a rabbit homologous polyclonal antiserum specific for the 104-kDa hemolysin of serotype 1 but not with preimmune serum from the same rabbit. Stained SDS–PAGE gels and immunoblots showed the 104-kDa protein hemolysin in fractions from each of the three growth conditions. Thus, the restored hemolytic activity was associated with the 104-kDa protein in the three cultures. In addition, the 104-kDa protein, when electroblotted onto nylon membranes, bound 45Ca, indicating that the molecule has binding sites for Ca2+. The results indicate that Ca2+ is required for the biological activity of the 104-kDa hemolysin of A. pleuropneumoniae serotype 1. Key words: Actinobacillus pleuropneumoniae, hemolysin, calcium requirement.
Respiratory metabolism of Azotobacter vinelandii cells at oxygen concentrations that initially range from suboptimal to supraoptimal for nitrogenase activity
Authors: Peterson Jay B.
Published: May 2010

The effects of three low oxygen concentrations on nitrogenase activity, total oxygen uptake, and respiratory parameters (Vmax and Ks(O2) of N2-grown Azotobacter vinelandii were studied in acetylene reduction assays during a 2-h incubation. The cell suspensions were taken from cultures grown at low aeration. Total oxygen uptake was higher with each increment in oxygen concentration. The highest oxygen concentration was initially supraoptimal for nitrogenase activity. The Ks(O2) values, representing the apparent affinity of the respiration system for oxygen, increased during the incubation of cells at the highest oxygen concentration. The Ks(O2) values at the two lower oxygen concentrations decreased and were very similar. A small effect of oxygen on the Vmax was observed. These results show that the metabolism determining the apparent affinity of the system for oxygen responds to the oxygen concentrations. Furthermore, this metabolism did not substantially increase the Ks(O2) unless the oxygen concentration was high enough to inhibit nitrogenase activity, indicating that the two processes may be linked. Key words: Azotobacter, oxygen regulation, nitrogen fixation.
Characterization of tryptophan-requiring auxotrophs of Streptomyces venezuelae ISP5230
Authors: Paradkar Ashish S. , Vining Leo C. , Stuttard Colin
Published: May 2010

The growth supplement requirements in minimal medium, the identity of metabolic intermediates accumulated, and the activity of tryptophan biosynfhetic enzymes detectable in cell extracts allowed the trp mutations in 10 auxotrophic strains of Streptomyces venezuelae ISP5230 to be determined. Three strains contained lesions in the trpA and two in the trpB subunits of tryptophan synthetase; two other strains were either double (trpA, trpB) mutants or contained a polar mutation in one of the subunit genes. Two strains with trpC mutations and one with a trpD mutation were also identified. When considered with information about the relative location of the auxotrophic markers obtained in this and earlier studies, the results indicated that trpA, trpB, and trpC are clustered near hisA and hisB, while trpD is in a separate position near nicB. The arrangement resembles that of the comparable genes in Streptomyces coelicolor A3(2). Key words: tryptophan auxotrophs, Streptomyces venezuelae, mutation loci, tryptophan biosynthesis genes.
Use of monoclonal antibodies in a colony immunoblot analysis of viable Rhizobium cell numbers in legume inoculants and on preinoculated seed
Authors: Olsen Perry E. , Rice Wendell A.
Published: May 2010

A colony immunoblot assay using monoclonal antibodies was developed to permit rapid Rhizobium strain identification and quantification in alfalfa inoculants and preinoculated seed produced for the Canadian market. Plate-count colonies were pressed onto nitrocellulose membranes and then allowed to react with specific monoclonal antibodies. The monoclonal antibody reaction was then amplified by reaction with goat anti-mouse antibody and the goat antibody reaction further amplified and detected with rabbit anti-goat antibody conjugated to alkaline phosphatase. A precipitating substrate for alkaline phosphatase was used to form purple spots on the membrane surface corresponding to positive reactions between the monoclonal antibody and the colony imprint. Results of analysis of 13 peat-base inoculants and 20 preinoculated seed samples by traditional most probable number and by immunoblot analysis indicated that the colony immunoblot test could be used as a reliable initial screen for viable Rhizobium cell numbers. Key words: Rhizobium, monoclonal antibody, immunoblot, Rhizobium inoculant analysis.
The role of Na+ in membrane transport and respiration in the marine bacterium Deleya aesta 134
Authors: Berthelet Marc , MacLeod Robert A.
Published: May 2010

Deleya aesta required Na+ for the uptake of 8 of 11 metabolites tested; the other three were transported at low rates in the absence of Na+ but at much higher rates in its presence. The optimal concentration of Na+ for maximum rate of transport of all the metabolites was 200 to 300 mM. Higher concentrations added as NaCl inhibited transport to the same extent as equiosomolar concentrations of other salts and sucrose. Li+ but not K+ could replace Na+ for the uptake of some metabolites but was only one-half as effective. Competition studies indicated that a number of different transport systems were involved in uptake. Inhibitor studies of succinate, L-alanine, and D-glucose accumulation (the last in both the presence and absence of Na+) suggested that for each a membrane potential was required. The relationship between rates of transport and oxidation of succinate by intact cells at various Na+ concentrations indicated that the Na+ requirement for oxidation reflected the Na+ requirement for transport. For D-glucose, the relationship was more complex, sinced over a narrow, low concentration range, Na+ inhibited respiration but not transport. Evidence for the presence in D. aesta 134 of a Na+-activated NADH–quinone acceptor oxidoreductase was obtained. Key words: Deleya aesta, marine bacteria, sodium, membrane transport, respiration.
Biodegradation of pentachlorophenol in soil: the response to physical, chemical, and biological treatments
Authors: Seech Alan G. , Trevors Jack T. , Bulman Terri L.
Published: May 2010

The effects of physical, chemical, and biological treatments on biodegradation of pentachlorophenol (PCP) were studied in a silt-loam soil contaminated with 175 mg PCP/kg and uniformly 14C-labelled PCP. Biodegradation of 14C-labelled PCP and technical-grade PCP were monitored over 210 days incubation. Mineralization of labelled PCP was significantly (p = 0.05) influenced by soil treatments. Negligible biodegradation occurred in either the sterile control soil or the uninoculated control soil, with less than 1% of added 14C recovered as 14CO2. Inoculation of unamended soil with a strain of Flavobacterium (ATCC 39723) known to degrade PCP increased biodegradation of PCP; approximately 60% of the [14C]PCP was recovered as 14CO2. Increased soil water content (60% versus 30%, w/w) enhanced biodegradation (67% recovery of 14C as CO2), while increased chloride ion concentration and anoxic conditions were inhibitory (20 and 1% recoveries, respectively). Residual soil PCP concentrations were also influenced by various treatments. In the sterile control soil and noninoculated control, after 210 days incubation, concentrations of PCP were 143 and 123 mg/kg, respectively, while the PCP concentration in the inoculated soil was 21 mg/kg. When soil organic matter was increased by adding finely ground red clover leaf and stem material, the residual PCP concentration was reduced to 6 mg/kg after 210 days. Increased soil water content resulted in a residual PCP concentration of 5 mg/kg. High-pressure liquid chromatography of soil extracts revealed no accumulation of partial PCP degradation products. These results indicated that biodegradation of PCP in soil was significantly influenced by various soil amendments. Key words: biodegradation, pentachlorophenol, soil, Flavobacterium.
The production of antibacterial tubing, sutures, and bandages by in situ precipitation of metallic salts
Authors: Farrah Samuel R. , Erdos Gregory W.
Published: May 2010

Two procedures were used to modify gauze bandages, polyester sutures, silicone tubing, and polyvinyl chloride tubing. In one procedure, the materials were first modified by in situ precipitation of metallic hydroxides and then used to adsorb silver ions. In the second procedure, the materials were soaked in sodium pyrophosphate or sodium chloride, dried, and then soaked in silver nitrate. These procedures produced materials with silver deposited on the surface of the tubing and sutures and both on the surface and within the gauze fibers. The modified materials inhibited the growth of Pseudomonas aeruginosa, Escherichia coli, and Staphylococcus aureus in vitro. Key words: tubing, sutures, bandages, antibacterial.
The use of methanol extract of Leptospira interrogans in complement fixation tests for leptospirosis
Authors: Koury Matilde Cota , Cisalpino Eduardo Osòrio , Rangel Humberto de Araùjo
Published: May 2010

Methanol extracts were obtained from L. interrogans serovars icterohaemorrhagiae and canicola and L. biflexa serovar patoc. Human sera from 167 normal individuals and 40 patients with different infectious diseases tested by complement fixation tests showed negative reactions. Sera from 100 patients with a suspicion of leptospirosis were tested by complement fixation tests and microscopic agglutination reactions. Agreement of 84% was found for those two reactions. Positive microscopic agglutination tests at a dilution 1:20–1:400 with negative complement fixation tests were observed in 5% of patients and negative microscopic agglutination with complement fixation tests in the range of 1:20–1:1280 were observed in 11% of the cases. Key words: diagnostic, methanol extract, complement fixation test.
Spiroplasma cells utilize carbohydrates via the phosphoenolpyruvate-dependent sugar phosphotransferase system
Authors: Tarshis Mark
Published: May 2010

Ten Spiroplasma species tested were found capable of fermenting glucose, mannose, fructose, and sucrose, but not ribose, maltose, 2-deoxyglucose, xylose, sorbitol, glactose, lactose, and arabinose. Sugar utilization was measured by a direct measurement of the changes in pH of a washed cell suspension upon the addition of the various sugars. Sulfhydryl reagents, uncouplers, and glycolysis inhibitors prevented the sugar-induced pH shifts. The spiroplasmas were capable of phosporylating α-methylgucoside in a reaction that required phosphoenolypyruvate, but not ATP, as a phosphate donor, suggesting that Spiroplasma species possess a phosphoenolpyruvate-dependent sugar phosphotransferase system. Key words: Spiroplasma, carbohydrate utilization, pH changes, phosphenolpyruvate-dependent sugar phosphotransferase system.
Aromatic hydroxylation and sulfation of phenazopyridine by Cunninghamella echinulata
Authors: Foster Brian C. , Thomas Barry H. , Zamecnik Jiri , Dawson Brian A. , Wilson D. Lynden , Duhaime Randy , Solomonraj G. , McGilveray Iain J. , Lodge Bruce A.
Published: May 2010

The metabolism of phenazopyridine was studied in the filamentous fungus Cunninghamella echinulata (synonym C. bainieri) ATCC 9244. Metabolic products were initially isolated by HPLC and TLC, with further characterization achieved by a combination of GLC, NMR, mass spectrum (MS), and GC–MS analyses. Selected samples of the incubation broths were treated with (β-glucuronidase–arylsulfatase. In addition to the reported mammalian metabolites p-aminophenol, acetaminophen, 2′-hydroxyphenazopyridine, 4′-hydroxyphenazopyridine, and parent drug, a novel metabolite was unequivocally identified as the sulfate monoester of 4′-hydroxyphenazopyridine.para-Hydroxylation of the aromatic ring with subsequent sulfoconjugation were observed as the major routes of metabolism. Ethanol, carbon monoxide, and quinidine had inhibitory effects on the C. echinulata metabolism of phenazopyridine, suppressing formation of 4′-hydroxyphenazopyridine and its sulfate monoester. Key words: Cunninghamella echinulata, biotransformation, GLC analysis of phenazopyridine, HPLC analysis of phenazopyridine, phenazopyridine, sulfate conjugate.
Excretion of ammonium by Azospirillum brasilense mutants resistant to ethylenediamine
Authors: Machado H. B. , Funayama S. , Rigo L. U. , Pedrosa F. O.
Published: May 2010

Several spontaneous ethylenediamine-resistant mutants of Azospirillum brasilense strain FP2 (Sp7, NalR SmR) were isolated. Four mutants, HM053, HM14, HM26, and HM210, were found to fix nitrogen constitutively in the presence of high concentration of NH4+ and to excrete NH4+ derived from nitrogen fixation. They also showed lower rates of NH4+ uptake than the wild-type strain, FP2. All of the mutants were prototrophic for glutamine or glutamate. Their glutamate synthase and glutamate dehydrogenase activities were similar to those of the wild-type strain. However, they presented different patterns of glutamine synthetase activity. Mutant HM14 showed low levels of normally regulated glutamine synthetase activity, while the other mutants showed low levels (HM053) or wild-type levels (HM26 and HM210) of constitutively adenylylated glutamine synthetase activity. The mutants are probably defective in the adenylylation system. Key words: Azospirillum brasilense, ammonium excretion, ethylenediamine resistance, glutamine synthetase.
Changes in polyphosphate composition and localization in Propionibacterium acnes after near-ultraviolet irradiation
Authors: Kjeldstad B. , Heldal M. , Nissen H. , Bergan S. , Evjen K.
Published: May 2010

Electron microscopy showed that electron-dense granules accumulated in Propionibacterium acnes in larger amounts when the bacteria were grown on a phosphate-rich medium. X-ray microanalysis demonstrated that the granules contained mostly phosphorus and potassium, indicating that the cells contained polyphosphate granules. When cells were grown on a complex Bacto-agar medium, the amount and the size of the polyphosphate granules were reduced. Polyphosphate was also detected with 31P nuclear magnetic resonance (31P-NMR). Of the polyphosphates observed with 31P-NMR, 20% seemed to be located outside the cell membrane. Broad-band near-ultraviolet irradiation (emission maximum 366 nm) corresponding to doses that killed 37% of the cells increased the amount of polyphosphate in cells grown on the phosphate-rich medium. The fluorescent chromophore 4′,6-diamidino-2-phenylindole (DAPI) shifted the fluorescence emission from 478 to 538 nm when bound to polyphosphate and excited at 340 nm. DAPI was used to detect polyphosphates generated after near-ultraviolet irradiation of the cells. Nonirradiated cells showed no increased fluorescence at 538 nm, indicating no polyphosphates, even if polyphosphate is present in the cells. We conclude that DAPI did not have "access" to the intracellular polyphosphate as long as the cells were not light damaged. This observation is important for the interpretation of near-UV damage to cells. Key words: electron and X-ray microscopy, fluorescence, DAPI, 31P-NMR, granule.
Characterization of a Salmonella choleraesuis mutant that cannot multiply within epithelial cells
Authors: Finlay B. Brett , Chatfield Steve , Leung Ka Yin , Dougan Gordon , Falkow Stanley
Published: May 2010

A mutant of Salmonella choleraesuis was identified that could invade (enter) and penetrate through polarized monolayers of Caco-2 and MDCK epithelial cells at normal levels but was defective for intracellular multiplication within these cells. It was also able to survive inside cultured J774 macrophage cells. These bacteria remained inside membrane-bound vacuoles, which coalesced at later times in the perinuclear region of the epithelial cell. This mutant exhibited slightly slower growth rates in rich or minimal media than the parental strain but was normal for iron usage, phosphate usage, and anaerobic growth and was a prototroph. The mutant was completely avirulent when administered orally or intravenously to susceptible mice. These results suggest that the ability to multiply within eukaryotic cells may contribute to S. choleraesuis virulence. Key words: Salmonella choleraesuis, virulence, pathogenesis, intracellular, multiplication.
Production and characterization of murine monoclonal antibodies against staphylococcal enterotoxins A and E
Authors: Shinagawa Kunihiro , Nishimura Emiko , Mitsumori Makoto , Matsusaka Naonori , Sugii Shunji
Published: May 2010

Six murine monoclonal antibodies (MAbs) against staphylococcal enterotoxin A (SEA) and enterotoxin E (SEE) were prepared by fusion of myeloma cells with mouse spleen cells immunized with SEA and SEE. Of five MAbs to SEA tested, two MAbs were reactive with only SEA, whereas three were specific for both SEA and SEE. On the other hand, one MAb to SEE was found to be specific for only SEE. To study specificities of the combining sites of these MAbs, competitive binding assays with either SEA or SEE and horseradish peroxidase conjugated MAbs were performed using unconjugated MAbs as inhibitors. The results obtained in the assays suggest that different epitopes may be located on SEA and that some of them may be cross-reacting epitopes between SEA and SEE. Key words: enterotoxins, monoclonal antibodies, Staphylococcus aureus.
Genotypic diversity of an indigenous Rhizobium meliloti field population assessed by plasmid profiles, DNA fingerprinting, and insertion sequence typing
Authors: Hartmann A. , Amarger N.
Published: May 2010

One hundred and twenty-five Rhizobium meliloti isolates nodulating field-grown Medicago sativa cv. Europe were evaluated for plasmid content and for symbiotic effectiveness with this host. Relative to the strain used commercially in France (RCR2011), isolates showed a comparable level of symbiotic effectiveness, although two isolates were poorly effective. Twenty-four distinct plasmid profiles were observed among these isolates, with a plasmid number varying between one and five per isolate. All isolates but one harboured a plasmid equivalent in size to that of the R. meliloti 41 megaplasmid. Sizes of the other plasmids varied from 45 to >600 kb. The major plasmid group (representing 30% of the whole population) consisted of isolates carrying a megaplasmid plus a large plasmid with an average size of 230 kb. To assess the validity of plasmid grouping, 32 isolates representative of 12 plasmid groups were further characterized on the basis of their genomic DNA restriction patterns and their insertion sequence (IS) fingerprints, using the indigenous insertion sequence ISRm1 as a probe. The DNA restriction patterns and IS fingerprints were highly distinctive among the 32 isolates examined since 20 and 16 types, respectively, were observed. These two characteristics are strongly correlated with the plasmid profiles of the strains, confirming the validity of plasmid grouping in assessing diversity of natural populations of R. meliloti. Plasmid profile analysis, although less discriminating than DNA restriction patterns or IS fingerprinting, is the method of choice when many isolates need to be typed. Key words: Rhizobium meliloti, ecology, diversity, field population, symbiotic effectiveness.
Serotypes and subtypes of Neisseria meningitidis serogroup B strains associated with meningococcal disease in Canada, 1977–1989
Authors: Ashton F. E. , Mancino L. , Ryan A. J. , Poolman J. T. , Abdillahi H. , Zollinger W. D.
Published: May 2010

Typing of Neisseria meningitidis serogroup B disease isolates was carried out using a panel of serotype- and subtype-specific monoclonal antibodies (MAbs) in enzyme-linked immunosorbent assays (ELISA). Three hundred and sixty-two strains isolated from 1977 to 1986 were typed using five serotyping and seven subtyping reagents and outer membrane vesicles as antigens. Serotype 2b accounted for 30% of the disease isolates. The most common subtype was P1.2, which occurred on 18.5% of all strains or 48.6% of the serotype 2b strains. Of the 362 strains typed, 135 (37.3%) were serotyped and 122 (33.7%) were subtyped. Overall, 185 (51.1%) of the strains could be assigned a serotype and (or) subtype. Strains (221) isolated during the years 1987–1989 were typed using a panel of 6 serotyping and 12 subtyping reagents by whole-cell ELISA. Strains of serotypes 4 (21.7%) and 15 (20.8%) were the most common and carried a wide variety of subtypes. The most common subtypes were P1.2 (11.8%) and P1.16 (9.5%). Of the 221 strains analyzed, 132 (59.7%) were assigned a serotype and 123 (55.7%) a subtype and with all 18 MAbs, 192 (86.9%) of the strains were serotyped and (or) subtyped. Two different MAbs to the four epitopes 2a, 15, P1.2, and P1.16 gave discordant reactions of 0.3, 6.6, 2.6, and 2.2%, respectively, when used to analyze over 300 strains of N. meningitidis. Key words: meningococcal serotypes, subtypes.
Deletion mutant analysis of the Staphylococcus aureus plasmid pI258 mercury-resistance determinant
Authors: Babich Kenneth , Engle Mike , Skinner Jeffery S. , Laddaga Richard A.
Published: May 2010

Deletion mutant analysis of the mercury-resistant determinant (mer operon) from the Staphylococcus aureus plasmid pI258 was used to verify the location of the merA and merB genes and to show the existence of mercuric ion transport gene(s). ORF5 was confirmed to be a transport gene and has an amino acid product sequence homologous to the merT gene products from several gram-negative bacteria and a Bacillus species. Deletion analysis established that inactivation of merA on a broad-spectrum mer resistance determinant resulted in a mercury-hypersensitive phenotype. Gene dosage had no apparent effect on the level of resistance conferred by the intact mer operon or on the expression of an inducible phenotype, except that when the intact pI258 mer operon was on a high copy number plasmid, uninduced cells possessed a volatilization rate that was at most only 3.5-fold less than that observed for induced cells. There was no need for mercury ion transport proteins for full resistance when the mer operon was expressed in a high copy number plasmid. Key words: mercury resistance, Staphylococcus aureus plasmid.
Detection of Escherichia coli cytotoxins by enzyme-linked immunosorbent assays
Authors: Speirs Joan I. , Akhtar Mumtaz
Published: May 2010

Sandwich enzyme-linked immunosorbent assays (ELISAs) were developed to detect Escherichia coli cytotoxins. Wells were coated with monoclonal antibodies from hybridomas 13C4 and (or) 11E10, and biotin conjugates of these antibodies were used for detecting verotoxin 1 and Shiga-like toxin II, respectively. Sensitivities were about 100 and 200 cytotoxic doses, respectively. Verotoxin 2 was detected by ELISA with monoclonal antibody 11E10, but at a sensitivity of only about 4000 cytotoxic doses. ELISA results of polymyxin-treated cell extracts from cultures of 67 E. coli strains were in agreement with Vero cell assay as regards the presence and type of toxin. Key words: Escherichia coli, cytotoxin, ELISA.
Effect of ultraviolet-induced mutants of Trichoderma harzianum with altered antibiotic production on selected pathogens in vitro
Authors: Graeme-Cook K. A. , Faull J. L.
Published: May 2010

Mutants of Trichoderma harzianum with altered antibotic production were isolated using ultraviolet light mutagenesis. These included strains whose activity in a Fusarium oxysporum spore germination assay was greater than twice that of the parental strain and one that had no detectable antifungal activity. Characterisation of extracellular metabolites of these strains using thin-layer chromatography and gas–liquid chromatography showed that the strains with high activity produced not only elevated levels of a 6-n-pentyl pyrone, the antibiotic produced by the parental strain, but two new antifungal compounds. One of these has been identified as an isonitrile antibiotic. The nature of the interactions of the mutants with Fusarium oxysporum, Rhizoctonia solani, and Pythium ultimum was examined in an in vitro dual-plating assay using two media. High antibiotic production by two T. harzianum strains, BC10 and BC63, did increase inhibition of hyphal growth of R. solani and P. ultimum, but there was no correlation between increased antibiotic production and colonisation ability. In some cases the increased antibiotic levels appeared to impede colonisation of F. oxysporum and R. solani by the mutants. Slow growth rate also affected colonising ability. The types of interactions showed great variability depending on the nature of the T. harzianum isolate and on the test fungus. Key words: Trichoderma harzianum, antibiotics, mutants, colonisation ability.
Immunogold–silver staining of extracellular ligninases secreted by Phanerochaete chrysosporium
Authors: Lackner Richard , Srebotnik Ewald , Messner Kurt
Published: May 2010

The secretion of ligninases by Phanerochaete chrysosporium was investigated with polyclonal antibodies, followed by immunogold–silver staining and light microscopy. After growing fungal mycelium on nitrocellulose, extracellular ligninases were detected around old, plasmaless hyphae, but not at arthrospores, chlamydospores, or blastoconidia. Labeling of fungal hyphae on cover-slip cultures was observed only when the cell wall was highly porous and translocation of cell material occurred. These experiments suggested that there is a correlation between hyphal lysis and the release of extracellular ligninases from hyphae. Key words: ligninase secretion, immunogold–silver staining, Phanerochaete chrysosporium.
Surface hydrophobicity of acidophilic heterotrophic bacterial cells in relation to their adhesion on minerals
Authors: Chakrabarti B. K. , Banerjee P. C.
Published: May 2010

The cell-surface hydrophobicity of acidophilic heterotrophic bacteria originating from mines varied with the pH of the suspending medium and with the growth temperature. Adhesion of these bacterial cells on mineral particles depended upon the hydrophobic (or hydrophilic) nature of both the cells and the minerals. A strong correlation between these properties was usually observed at different pH values of the suspending medium. At a certain pH value, bacterial attachment depended upon the particle size of the minerals. Key words: hydrophobicity, acidophilic bacteria, Acidiphilium cryptum, Acidiphilium symbioticum, adhesion, manganese nodule, chalcopyrite, iron pyrite.
Genetic transformation of Chainia and heat attenuation of its restriction system
Authors: Chauthaiwale Vijay M. , Vyas Pranav R. , Deshpande Vasanti V.
Published: May 2010

A PEG-mediated transformation system for Chainia (NCL 82-5-1) was develolped using a broad host range Streptomyces vector, pIJ702. Protoplasts prepared from Chainia (NCL 82-5-1) were regenerated with 5% efficiency. Transformation of the protoplasts with pIJ702 gave 10–20 transformants/μg DNA. The low efficiency of transformation is attributed to a restriction system in Chainia; this could be inhibited by treating the protoplasts at 42 °C for 10 min just before transformation. The yield of transformants increased 100-fold when pIJ702 was modified by passage in Chainia. Because the plasmid replicon was functional in Chainia and the modified plasmid was stably maintained, the transformation system should be useful for self-cloning in Chainia NCL 82-5-1 of the many commercially important enzymes this strain is known to produce. Key words: Chainia, transformation, Streptomyces, pIJ702 restriction modification, heat attenuation.
Pyridine metabolism by a denitrifying bacterium
Authors: Ronen Zeev , Bollag Jean-Marc
Published: May 2010

A denitrifying bacterium capable of pyridine degradation was isolated from contaminated soil. The Gram-negative bacterium, which was identified as an Alcaligenes sp., rapidly metabolized pyridine under anaerobic conditions with nitrate as electron acceptor. [14C]Pyridine was converted to 14CO2, unidentified polar metabolic products, and labeled biomass. During pyridine metabolism, nitrate was reduced to nitrogen gas via nitrite and nitrous oxide. The molar ratio of pyridine to nitrate strongly affected pyridine metabolism. Maximum pyridine degradation occurred at a nitrate concentration above 5 mM, a temperature of 22–36 °C, and a pH of 6.8–8.0. Key words: pyridine, anaerobic metabolism, denitrifying bacteria, Alcaligenes sp.
Bacterial culture history affects the attachment of Bradyrhizobium japonicum to host Glycine max roots
Authors: Smith Geoffrey B. , Wollum II A. G.
Published: May 2010

To understand the physiological control of attachment of Bradyrhizobium japonicum, bacterial growth and preincubation conditions were varied before exposing the bacteria (104 cfu mL−1) to excised soybean root segments. The attachment rate of strain USDA 110 was constant through a 7-h exposure (0.9% of the population attached per hour). Maximal attachment of strain USDA 110 occurred during log phase and for strains USDA 76 and USDA 31, during early stationary phase. The ability of log-phase cultures to attach to roots was significantly correlated with their competitive ability to nodulate soybean. Cells of strains USDA 110 attached to roots were isolated and reexposed to roots 15 times over a 6-month period. No significant increase in attachment ability of these serially exposed bacteria was observed (a mean of 1.4% of the population attached at each 2-h exposure). Attachment was stimulated 2.4- to 7-fold when cells of strains USDA 110 or USDA 31 were preincubated in a minus-nitrogen plant nutrient solution and on new cell growth. The stimulation of attachment could not be mimicked by preconditioning cells in solutions of NaCl, CaCl2, or CaSO4 of the same normality as the nutrient solution. The ability of B. japonicum strains to attach to host roots is a dynamic property affected by growth medium, culture age, and cell pretreatment conditions. The progeny of attached cells adhered to roots in the same low proportions as cells not previously exposed to roots. Key words: rhizobia, adhesion, competition, bacterial pretreatment.
Growth characteristics and expression of iron-regulated outer-membrane proteins of chemostat-grown biofilm cells of Pseudomonas aeruginosa
Authors: Anwar H. , Strap J. L. , Costerton J. W.
Published: May 2010

An in vitro chemostat system was used to study the growth and the expression of iron-regulated outer-membrane proteins (IROMPs) by biofilm cells of Pseudomonas aeruginosa cultivated under conditions of iron limitation. The population of the planktonic cells decreased when the dilution rate was increased. At a dilution rate of 0.05 h−1 the populations of planktonic cells of both mucoid and nonmucoid P. aeruginosa were 3 × 109 cells/mL. This value dropped to 5 × 106 cells/mL when the dilution rate was increased to 1.0 h−1. The reverse was observed for the biofilm cells. The number of biofilm cells colonising the silicone tubing increased when the dilution rate was increased. The number of biofilm cells of the mucoid strain at steady state was 2 × 108 cells/cm (length) when the dilution rate was fixed at 0.05 h−1. The figure increased to 8 × 109 cells/cm when the dilution rate was increased to 1.0 h−1. The population of biofilm cells of the nonmucoid strain was 9 × 107 cells/cm (length) when the dilution rate was 0.05 h−1. It increased to 2 × 109 cells/cm when the dilution rate was set at 1.0 h−1. The expression of IROMPs was induced in the biofilm cells of both mucoid and nonmucoid strains when the dilution rates were 0.05 and 0.2 h−1. IROMPs were reduced but still detectable at the dilution rate of 0.5 h−1. However, the expression of IROMPs was repressed when the dilution rate was increased to 1.0 h−1. The data suggest that the biofilm cells of P. aeruginosa switch on the expression of IROMPs to assist iron acquisition when the dilution rate used for the chemostat run is below 0.5 h−1. The high affinity iron uptake system is not required by the biofilm cells when the dilution rate is increased because the trace amount of iron present in the chemostat is sufficient for the growth of adherent biofilm cells. Key words: Pseudomonas aeruginosa, chemostat, iron, outer-membrane proteins, biofilm.
Colicins G and H and their host strains
Authors: Bradley D. E.
Published: May 2010

Escherichia coli strains CA46(pColG) and CA58(pColH) each apparently synthesized two generally similar bactericidal colicin proteins whose molecular weights were approximately 5 500 and 100 000. These proteins were more resistant to trypsin than representative colicins A, D, E1, and V. The smooth wild-type strains harbouring plasmids pColG and pColH were serotyped O169:NM and O30:NM, respectively, being typically associated with nonpathogenic E. coli of human origin. Rough and semirough variants, which were selected using resistance to novobiocin, were intrinsically insensitive to almost as many colicins (10 tested) as their parents. For this reason the wild-type strains would not be useful for identifying colicins G and H on the basis of immunity. The O antigenic side chains of both wild-type strains shielded three of the six bacteriophage protein receptors tested. Key words: colicin, protein, plasmid, O antigen, bacteriophage.
Efficacy of bacteriocinogenic strains of Xanthomonas oryzae pv. oryzae on the incidence of bacterial blight disease of rice (Oryza sativa L.)
Authors: Sakthivel N. , Mew T. W.
Published: May 2010

A total of 144 isolates of Xanthomonas oryzae pv. oryzae were screened for bacteriocin production against 30 indicator strains of X. oryzae pv. oryzae. Forty isolates showed broad-spectrum inhibitory activity against 20–27 indicators, presumably because of the production of bacteriocin compounds. The selected isolates were screened for bacteriocin production at 29 °C and tested for virulence on rice differentials. Since all of the isolates were pathogenic, nonpathogenic bacteria were generated through N-methyl-N-nitro-N-nitrosoguanidine mutagenesis and by repeated subculturing. Epiphytic colonization and survival of pathogens and of nonpathogenic bacteriocin producers on rice plants were monitored, using mutants resistant to streptomycin and rifampicin. An improved method of pathogen inoculation was developed and used to evaluate biological control. Treatment with nonpathogenic bacteriocin-producing bacteria resulted in reductions of bacterial blight incidence up to 31–99% in greenhouse tests and 11–73% in the screenhouse. Bacterial leaf streak severity was reduced 4–20% in the greenhouse and disease incidence was reduced 20–39% in the screenhouse. Key words: bacteriocin, biological control, Xanthomonas oryzae pv. oryzae, mutagenesis, rice.
Reversibility of oxygen switch-off effect on Bacillus polymyxa nitrogenase
Authors: Holzmann Hans-Paul , Berghammer Heinrich A. , Ortner Martin , Haselwandter Kurt
Published: May 2010

The objective of this study was to analyse in vivo the effect of oxygen on the nitrogenase of Bacillus polymyxa. The culture technique employed in this study prevented spore formation by B. polymyxa during the entire period of exposure to acetylene. Under these conditions the acetylene-reduction assay allowed quantification of nitrogenase activity over long incubation periods (44 h). Nitrogenase activity was highest in cells harvested in the late logarithmic phase. At [Formula: see text] of 0.19 and 0.37 kPa, acetylene reduction was inhibited by 80 and 100%, respectively. This switch-off effect could be reversed through oxygen exhaustion, either by flushing the culture with N2 or by cellular respiration, suggesting a respiratory protection mechanism for the nitrogenase complex in B. polymyxa. Oxygen consumption measured by a closed-chamber respirometer showed a linear increase up to a [Formula: see text] of 0.2 kPa. Above 0.3 kPa a saturation in oxygen consumption was observed. Exposure to high oxygen pressures resulted in an irreversible loss of nitrogenase activity. The oxygen inhibition pattern was shown to be similar to that in other microaerophilic and anaerobic nitrogen-fixing microorganisms. Key words: Bacillus polymyxa, nitrogenase, oxygen inhibition, reversibility, respiration.
Optimal growth temperature for the isolation of Plesiomonas shigelloides, using various selective and differential agars
Authors: Huq Anwarul , Akhtar Anwari , Chowdhury M. A. R. , Sack David A.
Published: May 2010

The growth characteristics of known strains of Plesiomonas shigelloides were compared with those of Aeromonas species (the major competing species in environmental waters) on plesiomonas differential agar, inositol brilliant green bile salt, and modified salmonella–shigella agar at incubation temperatures of 37, 42, and 44 °C. Using local isolates from clinical and environmental sources, optimal growth conditions, as determined by colony counts and the colony characteristics, plesiomonas differential agar proved to be ideal when incubated at 44 °C. Contrary to earlier recommendations for 48 h incubation, the colonies could be recognized readily after an incubation of 24 h. Key words: Plesiomonas, growth temperature, growth media.
Corrélations entre l'aptitude de différentes souches de Fusarium à limiter la fusariose vasculaire du lin, leur activité respiratoire et leur développement saprophytique dans un sol désinfecté
Authors: Amir Hamid
Published: May 2010

Correlations between two ecophysiological traits of 13 Fusarium strains (viz., ability to develop saprophytically in a disinfected soil and respiratory activity) and their capacity to protect a flax crop from vascular fusariosis were established for one soil type. The ability of Fusarium strains to reduce the severity of the disease (efficiency) differed greatly. The most competent ones lowered the death rate by 80%, while the least competent had virtually no effect. Classification based on strain efficiency differed depending on whether it was performed on disinfected soil or on soil not heat treated. When the abilities of strains to colonize disinfected soil were estimated by enumeration on agar plates, Fusarium oxysporum strains proved superior to Fusarium solani due to their production of more numerous conidia, and therefore greater numbers of colonies, without significantly increasing biomass. Respiratory activity ranged from moderate to low. A clear, positive correlation was found between the respiratory activity and the efficiency of the strains grown in untreated soil, while the correlation was not significant in the disinfected soil. In the latter case, however, efficiency was correlated with the saprophytic development of the strains. [Journal translation]