bluuebunny/crossref_metadata_2025 huggingface dataset:
Genomic analysis of a virulent and a less virulent strain of the entomopathogenic fungus Beauveria bassiana, using restriction fragment length polymorphisms
Authors: Kosir John M. , MacPherson James M. , Khachatourians George G.
Published: May 2010

The genomic DNA of two strains of the entomopathogenic fungus Beauveria bassiana, strain GK2016, a "wild type" (virulent), and strain GK2051, a less virulent mutant to grasshoppers, was digested with 12 restriction endonucleases. Gel electrophoresis conditions were established to show restriction fragment length patterns visually in the digested DNA stained with ethidium bromide. The less virulent mutant was generated by ultraviolet illumination of conidiospores at a 95% lethal dose. Both strains of the fungi were identical in morphology as well as in 16 of 22 API-ZYM kit enzyme assays. Differences in levels of total enzyme activity were observed for esterase, esterase–lipase, (β-galactosidase, chitinase, and protease. A Neurospora crassa β-tubulin gene (heterologous gene) and two homologous DNA probes (pJK16 and pJK18) hybridized to several specific DNA bands in B. bassiana strain GK2016 but not in strain GK2051. Strain GK2051 gave different restriction fragment length patterns when compared with its parent strain. Taken together, the data show restriction fragment length differences between the genomic DNA of the two strains, including the loss of some DNA sequences from the mutant strain, which may be involved in pathogenicity. Finally, B. bassiana GK2016 contains a β-tubulin gene with at least partial homology to that of N. crassa. Key words: restriction fragment length polymorphism, entomopathogen, Beauveria bassiana, bioinsecticide, filamentous fungi.
Calcium regulates growth of Rhizobium fredii and its ability to nodulate soybean cv. Peking
Authors: Balatti Pedro A. , Krishnan Hari B. , Pueppke Steven G.
Published: May 2010

We investigated the role of calcium in growth of Rhizobium fredii USDA208 and its influence on nodulation of cv. Peking soybean. The placement and numbers of nodules on soybean roots in growth pouches is relatively insensitive to levels of Ca2+ in the root zone. In contrast, adequate Ca2+ in the Rhizobium culture media is essential for induction of a normal distribution of nodules on the taproot and lateral roots. Ca2+-deprived rhizobia attach in reduced numbers to soybean roots, do not initiate nodules in the most infectible region of the taproot, and induce nodules almost exclusively on lateral roots. Ca2+ starvation also greatly reduces growth of USDA208 in culture, but it has little effect on exopolysaccharide production. Strain USDA208 produces two detectable 45Ca2+-binding proteins in culture. A major 38-kDa bacterial protein is regulated by the availability of Ca2+, but this protein does not itself bind 45Ca2+. Key words: autoregulation, nodule regulation, nodule initiation.
Study of the methanogenic degradation of phenol via carboxylation to benzoate
Authors: Bisaillon Jean-Guy , Lépine François , Beaudet Réjean
Published: May 2010

An anaerobic bacterial consortium carboxylating phenol to benzoate by cometabolism in the presence of proteose peptone under methanogenic conditions was studied. Yeast extract or a mixture of tryptophan and lysine could replace proteose peptone without affecting the carboxylating activity, whereas glucose, glycerol, pyruvate, volatile fatty acids, and sodium bicarbonate could not. The carboxylating microorganism could not be obtained pure from the phenol culture supplemented with tryptophan and lysine; six different morphological types of microorganisms were able to grow in this medium. The results obtained with potential intermediates of benzoate degradation given as substrates to the consortium suggest that benzoate is transformed to 1-cyclohexene carboxylate and to heptanoate. Part of 1-cyclohexene carboxylate was transformed to an apparent dead-end product identified as cyclohexane carboxylate. Key words: phenol, carboxylation, benzoate, methanogenic conditions.
Characteristics of nonpathogenic strains of Listeria monocytogenes
Authors: Farber J. M. , Speirs J. I. , Pontefract R. , Conner D. E.
Published: May 2010

Five strains of nonpathogenic Listeria monocytogenes were characterized for (i) hemolysin production, (ii) cytolysis of Chinese hamster ovary (CHO) cells, and (iii) ability to attach and enter intestine 407 cells. Four of the five strains produced variable hemolysis and were weakly cytolytic for Chinese hamster ovary cells, whereas the other isolate was consistently hemolytic and strongly cytolytic for CHO cells. None of the strains was able to penetrate intestine 407 cells. In addition, two of the five strains were found to be nonmotile. Key words: Listeria monocytogenes, nonpathogenic, attachment, motility, hemolysis.
Comparing vegetative compatibility and protein banding patterns for identification of Fusarium oxysporum f.sp. apii race 2
Authors: Toth K. F. , Lacy M. L.
Published: May 2010

Vegetative compatibility grouping and electrophoretic separation of total proteins were compared as possible techniques for identifying isolates of Fusarium oxysporum f.sp. apii race 2, the cause of fusarium yellows of celery. Vegetative compatibility grouping was determined by pairing chlorate-tolerant, nitrate-nonutilizing mutants on a minimal medium containing nitrate as the sole nitrogen source. Heterokaryon formation, which resulted in wild-type growth, occurred only between mutants from vegetatively compatible isolates. All isolates of F. oxysporum f.sp. apii race 2 examined were placed within a unique vegetative compatibility group that excluded F. oxysporum f.sp. apii race 1 and the 11 other formae speciales of F. oxysporum tested. Few differences were observed in protein banding patterns among isolates of F. oxysporum f.sp. apii race 2, F. oxysporum f.sp. apii race 1, 11 other formae speciales of F. oxysporum, and 2 formae speciales of F. solani on 12% polyacrylamide gels. No banding pattern unique to F. oxysporum f.sp. apii race 2 was observed. Vegetative compatibility grouping could be accomplished more rapidly than greenhouse pathogenicity tests and more accurately identified race 2 isolates in a population of isolates of F. oxysporum from muck soils than did greenhouse pathogenicity tests or electrophoretic protein banding patterns. Key words: celery, fusarium yellows, nitrate-nonutilizing mutants, polyacrylamide gel electrophoresis.
Effect of tungsten on nitrate and nitrite reductases in Azospirillum brasilense Sp7
Authors: Chauret Christian , Knowles Roger
Published: May 2010

Tungstate, at concentrations that completely suppressed nitrate reductase activity in Paracoccus denitrificans, caused only partial inhibition of nitrate reductase in Azospirillum brasilense Sp7. Nitrate reductase activity in cell-free extracts was much more sensitive than whole cells to tungstate, suggesting that there may be a barrier to its transport. Nitrite reductase activity was partially inhibited by tungstate in both whole cells and cell-free extracts. Azospirillum brasilense apparently scavenged enough contaminating molybdenum from molybdenum-limited medium to allow maximum nitrate reductase activity, which was not stimulated by added molybdate. Cells grown in molybdenum-depleted medium could not reduce nitrate. Nitrate concentrations less than 0.25 mM inhibited activity, but not synthesis, of nitrite reductase and caused significant accumulation of nitrite during reduction of nitrate. Key words: Azospirillum brasilense, Paracoccus denitrificans, nitrate reductase, nitrite reductase, tungsten, molybdenum, denitrification.
Purification, characterization, and biological effects of a second bacteriocin from Enterococcus faecalis ssp. liquefaciens S-48 and its mutant strain B-48-28
Authors: López-Lara I. , Gálvez A. , Martínez-Bueno M. , Maqueda M. , Valdivia E.
Published: May 2010

Enterococcus faecalis ssp. liquefaciens S-48 (producer of the peptide antibiotic AS-48) and its mutant B-48-28 (AS-48−) secrete the bacteriocin Bc-48. This substance has been purified to homogeneity from culture supernatants of strain B-48-28; it consists of a protein (80 kDa) stable from pH. 5.5 to 9.0 and sensitive to temperatures above 45 °C and to proteases. Its inhibitory spectrum is restricted to strains of Enterococcus faecalis. Bc-48 inhibits protein synthesis but does not affect amino acid uptake. A partial reduction of cell viability, together with autolysis, is also observed. Bc-48 differs from peptide AS-48 in both its molecular properties and mode of action. Key words: Enterococcus faecalis, bacteriocin, bacteriolytic.
Biological consequences of plasmid transformation of the plant growth promoting rhizobacterium Pseudomonas putida GR12-2
Authors: Hong Yuwen , Pasternak J. J. , Glick Bernard R.
Published: May 2010

Pseudomonas putida GR12-2, a plant growth promoting rhizobacterium, was transformed with the broad host range plasmid pGSS15. The presence of the plasmid caused (i) a decrease in cell generation times, (ii) an altered pattern of cell proteins, (iii) an inhibition of the enhancement of canola root elongation, (iv) impairment of nitrogen fixation, and (v) a decrease in siderophore production. Strains that were cured of pGSS15, on the other hand, re-established growth rates, levels of siderophore production, and canola root elongation capabilities equivalent to nontransformed P. putida GR12-2. Thus, the transforming plasmid imposes a metabolic load on the recipient bacteria that impacts on a number of different energy-dependent processes. Key words: plant growth promoting rhizobacteria, nitrogen fixation, Pseudomonas, transformation, metabolic load.
Changes in membrane potential of intact soybean root elongation zone cells induced by Azospirillum brasilense
Authors: Bashan Yoav
Published: May 2010

Inoculation of soybean seedlings with Azospirillum brasilense significantly reduced the membrane potential of root cells and made it less negative. The effect was most pronounced in the cells of the elongation zone. Three A. brasilense strains reduced the membrane potential of elongation zone cells to a similar extent. Dead cells or cells of an associative nonbeneficial Pseudomonas species caused no effect. Reduction of membrane potential of root cells was directly related to the physiological status of the bacterial cells. Active bacteria reduced the membrane potential. Stressed bacteria, i.e., bacteria exposed to either starvation, anaerobic conditions, or a high level of streptomycin prior to inoculation, failed to affect membrane potential. Continuous perfusion of the roots immediately after inoculation, while maintaining the bacterial cells surrounding the roots, cancelled the effect of live bacteria on membrane potential. Regardless of bacterial cell treatment or effect on membrane potential of root cells, root colonization levels of all A. brasilense strains were similar throughout all experiments. In addition, all strains positively affect the growth of soybean seedlings. It is suggested that inoculation of soybean plants with live A. brasilense strains, possessing an active metabolism, reduced the membrane potential of root cells probably through the release of an, as yet, unidentified bacterial signal(s). Key words: Azospirillum, beneficial bacteria, Glycine max, membrane potential, plant–bacteria interaction, rhizosphere bacteria, soybean.
Purification and characterization of an extracellular exopolygalacturonase from Geotrichum lactis
Authors: Pardo C. , Lapeña M. A. , Gacto M.
Published: May 2010

Geotrichum lactis ATCC 48590 produced extracellular polygalacturonase (EC 3.2.1.67) in media containing pectate, pectin, or galacturonic acid as inducers. The synthesis of the enzyme was strongly repressed by glucose. The polygalacturonase was purified 80-fold by ammonium sulphate precipitation, Sephadex G-100 filtration, and DEAE Sephadex ion-exchange chromatography. Polyacrylamide gel electrophoresis with copolymerized substrate indicated that the isolated material was a single enzyme with polygalacturonase activity. The main product of enzyme action was galacturonic acid. The enzyme shows a molecular weight close to 53 000 by gel filtration and degrades preferentially de-esterified substrates. Km values for pectate and pectin (64% esterified) were 0.09 and 0.49 mg mL−1, respectively. The optimum pH for enzyme activity was 5.0, while the optimum temperature was 40 °C. The polygalacturonase was precipitated by concanavalin A – Sepharose, and treatment with endoglycosidase H reduced its precipitation by the lectin, suggesting that the enzyme is a glycoprotein. In addition to being found extracellularly, the polygalacturonase is also present in the periplasm of the cells. A different form of the polygalacturonase showing a lower molecular weight was located inside the cells. Key words: polygalacturonase, pectic enzymes, Geotrichum lactis.
Photosynthesis gene superoperons in purple nonsulfur bacteria: the tip of the iceberg?
Authors: Wellington C. L. , Bauer C. E. , Beatty J. T.
Published: May 2010

The purple, nonsulfur phototrophic bacterium Rhodobacter capsulatus has recently been found to contain several pigment biosynthetic operons that exhibit marked transcription read through into downstream operons that encode polypeptide components of photosynthetic pigment-protein complexes. This phenomenon has been found to be phenotypically significant for adaptation to changes in environmental conditions, and the term superoperon has been proposed to describe this sort of coupled transcriptional arrangement. We summarize the data that led to recognition of this novel transcriptional arrangement and suggest that superoperons might be more prevalent in prokaryotes than has heretofore been recognized. Key words: superoperons, overlapping transcription units, photosynthesis genes.
Microcarrier culture of fish cells and viruses in cell culture bioreactor
Authors: Chen Zhihong , Chen Yinliang , Shi Yuan , Yie Xuepin , Yang Guangzi
Published: May 2010

This article deals with the culture of grass carp (Ctenopharyngodon idellus) lip and embryo cells on Cytodex 3 and GT-2 microcarriers in a 1.5-L cell culture bioreactor to propagate grass carp hemorrhage virus. The cells and viruses were successfully cultivated at 26 °C, pH 7.0, and dissolved oxygen 40% of air saturation. The cell density achievedwas as high as 7.4 × 106 cells/mL, and the virus titre reached 6.75 log LD50/0.5 mL from an initial 3.00 log LD50/0.5 mL. The results present broad prospects for fish virus vaccine production. Key words: fish cell, hemorrhage virus, microcarrier, cell culture.
Recovery of Bacteroides fragilis group from clinical specimens following antimicrobial therapy
Authors: Brook Itzhak , Frazier Edith H.
Published: May 2010

Over a period of 14 years (1973–1987), 3165 specimens submitted to the microbiology laboratory demonstrated the recovery of anaerobic bacteria. A total of 988 Bacteroides fragilis group isolates were recovered (0.3 isolates per specimen). Bacteroides fragilis accounted for 62% of the total of all B. fragilis group isolates, Bacteroides thetaiotaomicron for 15%, Bacteroides vulgatus for 8%, Bacteroides ovatus for 7%, Bacteroides distasonis for 6%, and Bacteroides uniformis for 2%. Of the 988 B. fragilis group isolates, 310 (31%) were recovered after the administration of antimicrobial therapy, and 129 (13%) were the single isolate recovered from the infected site at that time. The recovery rate of all members of B. fragilis group after the administration of antimicrobial therapy, when isolated alone or when mixed with other bacteria, was similar. The data illustrate the equal ability of all members of the B. fragilis group to persist in and to contribute to the inflammatory process; and provide further support for their pathogenic role. Key words: Bacteroides fragilis, bacteremia, abscesses, antimicrobials.
Characterization of an O-antigen bacteriophage from Aeromonas hydrophila
Authors: Merino Susana , Camprubí Silvia , Tomás Juan M.
Published: May 2010

A unique bacteriophage of Aeromonas hydrophila serotype O:34 was isolated, purified, and characterized. The bacterial surface receptor was shown to be the O-antigen polysaccharide component of lipopolysaccharide specific to serotype O:34, which was chemically characterized. The high molecular weight lipopolysaccharide fraction (a fraction enriched in O antigen) was fully able to inactivate bacteriophage PM1. Phage-resistant mutants of A. hydrophila O:34 were isolated and found to be specifically devoid of lipopolysaccharide O antigen. No other cell-surface molecules were involved in phage binding. The host range of bacteriophage PM1 was found to be very narrow, producing plaques only on A. hydrophila strains from serotype O:34. Key words: Aeromonas hydrophila, serotype O:34, bacteriophage PM1, lipopolysaccharide.
Effect of nitrogen sources on oxidoreductive enzymes and ethanol production during D-xylose fermentation by Candida shehatae
Authors: Palnitkar Sanjay , Lachke Anil
Published: May 2010

The effect on D-xylose utilization and the corresponding xylitol and ethanol production by Candida shehatae (ATCC 22984) were examined with different nitrogen sources. These included organic (urea, asparagine, and peptone) and inorganic (ammonium chloride, ammonium nitrate, ammonium sulphate, and potassium nitrate) sources. Candida shehatae did not grow on potassium nitrate. Improved ethanol production (Y(p/s), yield coefficient (grams product/grams substrate), 0.34) was observed when organic nitrogen sources were used. Correspondingly, the xylitol production was also higher with organic sources. Ammonium sulphate showed the highest ethanol:xylitol ratio (11.0) among all the nitrogen sources tested. The ratio of NADH- to NADPH-linked D-xylose reductase (EC 1.1.1.21) appeared to be rate limiting during ethanologenesis of D-xylose. The levels of xylitol dehydrogenase (EC 1.1.1.9) were also elevated in the presence of organic nitrogen sources. These results may be useful in the optimization of alcohol production by C. shehatae during continuous fermentation of D-xylose. Key words: xylose fermentation, Candida shehatae, nitrogen source, oxidoreductive enzymes.
Utilization of chymotrypsin as a sole carbon and (or) nitrogen source by Escherichia coli
Authors: Brecher Arthur S. , Moehlman Timothy A. , Hann William D.
Published: May 2010

α-Chymotrypsin serves as a sole carbon source, sole nitrogen source, and as sole carbon plus nitrogen source for wild-type Escherichia coli in a totally defined medium. Hence, a mammalian host for E. coli may supply the necessary carbon and nitrogen nutrients for the microorganism. Growth is most rapid when chymotrypsin is a sole nitrogen source,and least rapid with chymotrypsin as a carbon source. The approximate doubling times for E. coli utilizing chymotrypsin as a nitrogen source, carbon plus nitrogen source, and carbon source are 1.6, 4.6, and 11.3 h, respectively. The activity of the residual enzyme in the culture supernates falls off asymptotically over the course of time, as followed by cleavage of glutaryl-L-phenylalanine-p-nitroanilide. Chymotrypsin hydrolyzes succinyl-L-ala-L-ala-L-ala-p-nitroanilide, the elastase substrate, to some extent. Peptidases do not appear to be secreted that hydrolyze such model substrates as benzoyl-DL-arginine-p-nitroanilide, the tryptic and cathepsin B substrate, L-leucine-p-nitroanilide, the leucine aminopeptidase substrate, or L-lysine-p-nitroanilide, the aminopeptidase B substrate. Growth of E. coli is generally directly related to the loss of chymotryptic activity in the medium. Hence, autolysis of chymotrypsin, i.e., self-degradation, is an important factor for the availability of degradation products of the enzyme to the bacterium for growth purposes. Accordingly, the degradation of a host protein by autolysis presents an opportunity for E. coli to survive during periods of host nutritional crisis by utilization of the degradation peptides that are produced during autolysis. Key words: chymotrypsin, Escherichia coli, growth, nutrition, peptide source.
Rhizosphere colonization and seedling growth promotion of lodgepole pine by Bacillus polymyxa
Authors: Holl F. B. , Chanway C. P.
Published: May 2010

Lodgepole pine seed was inoculated with Bacillus polymyxa isolate L6-16R, a strain marked with antibiotic resistance to 100 mg rifamycin per litre. Inoculation resulted in statistically significant seedling biomass increases after 8 weeks of pine growth. The L6-16R rhizosphere population declined by an order of magnitude per month, from ca. 106 cfu/g dry weight of pine root tissue 4 weeks past inoculation to ca. 104 cfu/g of root tissue 12 weeks past inoculation. Seed-lings from three of four pine provenances had mean shoot and root dry weight increases of up to 35% due to seed inoculation, but shoot growth of the fourth provenance was inhibited. The size of the L6-16R rhizosphere population was not correlated to the magnitude of the shoot growth response 4 weeks after inoculation, but it showed a strong correlation with shoot growth 8 weeks after inoculation. These results indicate that the promotion of pine seedling growth may be a function of the size of the bacterial rhizosphere population that develops 4 weeks after inoculation, and that B. polymyxa may promote growth of lodgepole pine collected from many, but not all provenances. Key words: Bacillus polymyxa, lodgepole pine, growth promotion, rhizosphere colonization.
Biochemical defects of outermost layer deficient mutants during sporulation of Bacillus megaterium
Authors: Takubo Y. , Inoue T. , Kunimatsu T. , Kondo M. , Nishihsara T.
Published: May 2010

To determine the regulation of morphogenesis of the outermost layer, the thick layer outside the inner coat, of the Bacillus megaterium spore, we isolated 15 outermost layer deficient mutants of B. megaterium using transposon Tn917. Three mutant strains lacked both synthesis of the 48-kDa outermost layer protein and induction of two initial enzymes for galactosamine-6-phosphate polymer synthesis, evidence that these biochemical events are regulated in the cascade system during morphogenesis of the outermost layer. Key words: Bacillus megaterium, outermost layer, morphogenesis, regulation, transposon.
Enzymes associated with metabolism of xylose and other pentoses by Prevotella (Bacteroides) ruminicola strains, Selenomonas ruminantium D, and Fibrobacter succinogenes S85
Authors: Matte Allan , Forsberg Cecil W. , Gibbins Ann M. Verrinder
Published: May 2010

Prevotella (Bacteroides) ruminicola strains B14 and S23 and Selenomonas ruminantium strain D used xylose as the sole source of carbohyrate for growth, whereas Fibrobacter succinogenes was unable to metabolize xylose. Prevotella ruminicola strain B14 exhibited transport activity for xylose. In contrast, F. succinogenes lacked typical xylose uptake activity but did exhibit low binding potential for the sugar. Prevotella ruminicola strains B14 and S23 as well as S. ruminantium D showed low xylose isomerase activities but higher xylulokinase activities, using assays that gave high activities for these enzymes in Escherichia coli. Xylose isomerase appeared to be produced constitutively in these ruminal bacteria, but xylulokinase was induced to varying degrees with xylose as the source of carbohydrate. Fibrobacter succinogenes lacked xylose isomerase and xylulokinase. All three species of ruminal bacteria possessed transketolase,xylulose-5-phosphate epimerase, and ribose-5-phosphate isomerase activities. Neither P. ruminicola B14 nor F. succinogenes S85 showed significant phosphoketolase activity. The data indicate that F. succinogenes is unable to either actively uptake or metabolize xylose as a result of the absence of functional xylose permease, xylose isomerase, and xylulokinase activities, although it and both P. ruminicola and S. ruminantium possess the essential enzymes of the nonoxidative branch of the pentose phosphate cycle. Key words: Fibrobacter succinogenes, Prevotella, Selenomonas, xylose metabolism, rumen bacteria, pentose phosphate cycle.
Effects of culture conditions and biofilm formation on the iodine susceptibility of Legionella pneumophila
Authors: Cargill Kari L. , Pyle Barry H. , Sauer Richard L. , McFeters Gordon A.
Published: May 2010

The susceptibility of Legionella pneumophila to iodination was studied with cultures grown in well water, on rich agar media, and attached to stainless-steel surfaces. Legionella pneumophila grown in water cultures in association with other microorganisms were less sensitive to disinfection by chlorine and iodine than were agar-passaged cultures. Differences in sensitivity to disinfection between water-cultured and agar-grown legionellae were determined by comparing C × T values (concentration in milligrams per litre multiplied by time in minutes to achieve 99% decrease in viability)and CM × T values (concentration in molarity). Iodine (1500×) gave a greater difference in CM × T values than did chlorine (68×). Iodine was 50 times more effective than chlorine when used with agar-grown cultures but was only twice as effective when tested against water-grown Legionella cultures. C × T × S values (C × T multiplied by percent survivors), which take into consideration the percent surviving bacteria, were used to compare sensitivities in very resistant populations, such as those in biofilms. Water cultures of legionellae associated with stainless-steel surfaces were 135 times more resistant to iodination than were unattached legionellae, and they were 210 000 times more resistant than were agar-grown cultures. These results indicate that the conditions under which legionellae are grown can dramatically affect their susceptibility to some disinfectants and must be considered when evaluating the efficacy of a disinfecting agent. Key words: Legionella pneumophila, iodine, disinfection, growth conditions, biofilms, water.
Phenotypic characterization of sym8 and sym9, two genes conditioning non-nodulation in Pisum sativum 'Sparkle'
Authors: Markwei Carol M. , LaRue Thomas A.
Published: May 2010

Two non-nodulating and non-allelic mutants of P. sativum (L.) 'Sparkle', R25 (sym8) and R72 (sym9), were obtained by γ-radiation. Non-nodulation in each mutant was conditioned by a single recessive gene. Growth analysis indicated that if the mutants were provided with adequate fixed nitrogen, they both had the same growth rate as their nodulating parent, 'Sparkle'. Reciprocal grafts between mutants and parent plants indicated that non-nodulation was controlled by the root genotype. Both mutants induced the common nod genes in rhizobia, and had either higher or similar numbers of rhizobia attached to their roots as had 'Sparkle'. Microscopic studies indicated that root hairs of R72 deformed after inoculation, whereas root hairs of R25 did not show such deformation. In both mutants hair curling, infection thread formation, and nodule meristem initiation did not occur. Key words: mutants, sym genes, nodulation stages, symbiosis.
Relative contributions to nitrogenase (acetylene reducing) activity of stem and root nodules in Sesbania rostrata
Authors: Ladha J. K. , Garcia Minviluz , Pareek R. P. , Rarivoson G.
Published: May 2010

Six experiments, two each in the phytotron, greenhouse, and field, were conducted to assess the contribution of nitrogenase activity (acetylene reduction) by stem nodules in the presence and absence of root nodules of Sesbania rostrata (Brem & Oberm). In a greenhouse experiment, the effect of detaching already formed aerial stem nodules on the restoration of root nodules and nitrogenase activity was studied. The field experiment compared nodulation and acetylene-reduction activity by dual-nodulating S. rostrata and root-nodulating Sesbania cannabina. Acetylene-reduction activity expressed per gram of nodule dry weight was higher for stem nodules than for root nodules. Root nodule dry weight and acetylene-reduction activity failed to increase after stem inoculation, but root nodule dry weight and acetylene-reduction activity increased several fold within 15 days of detachment of aerial stem nodules. Stem nodulation, which occurred without inoculation under lowland field condition, suppressed root nodulation, thus accounting for more than 75% of total nitrogenase activity. Sesbania rostrata showed higher acetylene-reduction activity than S. cannabina. In dual-nodulating plants, root and stem nodules appeared to strike a balance in competition for energy, which may be controlled by stem nodulation. Key words: Sesbania rostrata, Azorhizobium caulinodans, stem nodule, root nodule, acetylene-reducing activity.
Effect of numbers of Bradyrhizobium japonicum applied in commercial inoculants on soybean seed yield in Ontario
Authors: Hume D. J. , Blair D. H.
Published: May 2010

In the absence of Bradyrhizobium japonicum populations in the soil, yields of field-grown soybean (Glycine max (L.) Merrill) usually respond to inoculation with B. japonicum. The objective of this research was to determine the relationship between numbers of B. japonicum per seed in inoculants and soybean nodulation and yield. A total of six field experiments were conducted in 1989 and 1990 on new soybean soils. In dilution trials, Grip inoculant was applied to provide approximately 106, 105, 104, and 103B. japonicum per seed at two locations in 1989. Nodule number and mass, as well as seed yield, increased curvilinearly upward with increasing log10 most probable numbers (MPNs) of B. japonicum. The yield response curve was best fit by a cubic equation, which accounted for 97% of the variation in yield. Seed yields increased 19% (1.83 to 2.13 Mg/ha) from 105 to 106B. japonicum per seed. In field experiments involving 8 commercial inoculants in 1989 and 10 in 1990, and conducted at two locations in each year, responses to increasing log MPNs in the inoculants also were concave upwards and cubic. In the two years, 78 and 46% of the yield variation was accounted for by log MPN per seed. Increasing MPN per seed from 105 to 106 improved yields in first-time fields by an average of 24%, indicating the present minimum standard of 105B. japonicum per seed should be increased. Key words: most probable numbers, response to inoculation, nodulation, Glycine max (L.) Merrill.
Eradication of biofilm cells of Staphylococcus aureus with tobramycin and cephalexin
Authors: Anwar H. , Strap J. L. , Costerton J. W.
Published: May 2010

The kinetics of growth and formation of biofilm by Staphylococcus aureus were investigated under iron-limited conditions in the chemostat. The population of planktonic cells reached 5.5 × 109 cells/mL 24 h after inoculation (D = 0.05 h−1) and remained constant throughout. The number of biofilm cells of S. aureus colonizing the silicone tubing increased exponentially from 6 × 104 to 2.7 × 107 cells/cm2 (6 days later) and continued to increase at a reduced rate to 2.7 × 108 cells/cm2 on day 13. Planktonic cells of S. aureus were susceptible to tobramycin and cephalexin. The planktonic cells could be successfully eradicated with a combination of 5 μg tobramycin plus 100 μg cephalexin per millilitre. Exposure of young biofilm cells of S. aureus to 5 μg tobramycin plus 100 μg cephalexin per millilitre resulted in a rapid loss of cell viability. The percentage of survival dropped to less than 0.0001% after exposure to these concentrations of antibiotics for 3 h. Old biofilm cells of S. aureus were found to be extremely resistant to these antibiotics. The cell viability was reduced to 0.09% after exposure to 10 μg tobramycin plus 100 μg cephalexin per millilitre. The results suggest that it is possible to eradicate S. aureus infection at the early stage with tobramycin plus cephalexin. Any delay in implementing antibiotic therapy is likely to result in the failure of the treatment. It is important to note that the concentrations of antibiotics required for the eradication of young biofilm cells must be determined for the treatment of device-associated infections. Key words: chemostat, biofilm, tobramycin, cephalexin, Staphylococcus aureus.
Effects of intact rhizosphere microbial communities on the mineralization of surfactants in surface soils
Authors: Knaebel David B. , Vestal J. Robie
Published: May 2010

This work addressed the impact that the rhizosphere has on the biodegradation of foreign organic compounds. This was examined with live plants grown in a sewage sludge amended agricultural soil and a woodlot soil. Microcosms were designed that contained soil, roots, and microbial biomass in a compartment that excluded most of the plant stem and all of the leaf biomass. Control microcosms contained soils without plants and had no plant-induced rhizosphere microbial communities. Microbial mineralization of 14C-labelled organic compounds (anionic, cationic, and nonionic surfactants) was measured by quantifying cumulative production of 14CO2 over a 40- to 55-day period. Regardless of the treatment, the surfactants were mineralized without lag periods. The mineralization results were fitted to mineralization models by nonlinear regression techniques. A mixed-order (3/2 order) mineralization model best fit the data. This model is similar to a first-order rate model but contains additional parameters that describe growth events or the mineralization of 14C that has been incorporated or bound by the microorganisms. Of the compounds tested, sodium stearate was mineralized to the greatest extent (65% conversion to 14CO2) in the sludge-amended agricultural soil. A cationic surfactant, dodecyltrimethylammonium chloride, was mineralized to the least extent (8%) by the microbes associated with corn roots in the sludge-amended soil. Linear alcohol ethoxylate was mineralized at the highest initial rate (1.5 day−1) in the presence of a soybean-induced rhizosphere in the woodlot soil. Overall, the rhizosphere treatments significantly increased the initial rates of mineralization by a factor of 1.1–1.9. However, there was no significant difference between the rhizosphere treatments and the soil-alone controls in the asymptotic yields of 14CO2. The results suggest that rhizosphere microbial communities enhanced the biodegradation of surfactants in soils in terms of their effects on the initial rates of mineralization. However, because the total amounts of 14CO2 production were the same as in the no-plant controls, the extents of biodegradation of xenobiotic compounds may be limited by other factors, such as chemical and (or) physical interactions between the soil and the chemicals. Key words: rhizosphere, biodegradation, surfactants, soils, kinetics.
Capsules of Escherichia coli, expression and biological significance
Authors: Jann Klaus , Jann Barbara
Published: May 2010

Escherichia coli may cause intestinal or extraintestinal infections. Generally, extraintestinal E. coli are encapsulated. The capsules are important virulence determinants, which enable the pathogenic bacteria to evade or counteract the unspecific host defense during the early (preimmune) phase of infection. They interfere with the action of complement and phagocytes. This effect is generally transient and overcome by capsule-specific antibodies in the immune phase of the host defense. In some cases, capsules are not or only poorly immunogenic, as a result of structural relationship or identity with host material. Strains with such capsules (e.g., K1 or K5) are very virulent. Bacterial capsules consist of acidic polysaccharides, which are made up from oligosaccharide repeating units. The capsules of E. coli are divided into two groups, which differ in chemistry, biochemistry, and genetic organization. All capsular polysaccharides are chromosomally determined: those of group I close to his and those of group II close to serA. The biosynthesis and surface expression have been extensively studied with representatives of group II capsular polysaccharides. It could be shown that their biosynthesis is directed from a gene block that determines the synthesis of the polysaccharide, its translocation across the cytoplasmic membrane, as well as its surface expression in a coordinate process. The chemical nature of group II capsular polysaccharides, as well as the mechanism(s) of their biosynthesis and expression, is presented. Key words: Escherichia coli, capsular polysaccharides, structure, genetics, biology.
Modification des caractères culturaux et biochimiques du Salmonella paratyphi B après incubation dans l'eau de mer
Authors: Bakhrouf Amina , Jeddi Moncef , Gauthier Michel J.
Published: May 2010

After incubation in seawater Salmonella paratyphi B cells rapidly became unable to grow on bacteriological media. Previous adaptation to high osmolarity conditions greatly slowed down this process. Strains isolated from seawater microcosms after varying incubation periods were qualitatively different and showed changes in some of their growth (colony shape and size) and biochemical properties (acidification of some sugars, gelatinase activity, acetoin production, nitrate reduction). Because of these modifications, the bacteria showed atypical profiles and could not be identified as members of the Salmonella genus. The alteration of the phenotype, although reversible, could explain some of the false-negative results obtained upon isolation and identification of these bacteria in seawater samples. Key words: Salmonella paratyphi B, seawater, survival, acetoin production. [Journal translation]
Myofibrillar cell wall extensions in the hyphal sheath of Postia placenta
Authors: Larsen Michael J. , Green III Frederick
Published: May 2010

Evidence is provided for the existence of linear extracellular fibrillar elements in the brown-rot fungus Postia placenta. These elements appear as structural components of the hyphal sheath and more closely resemble mycofibrils than fungal fimbriae. Mycofibrils are associated with and appear to originate from the hyphal surface when hyphae are grown on wood or inert substrates, such as glass cover slips and polycarbonate filters. These extracellular structures have a nominal diameter of 10–50 nm and are up to 25 μm in length. We conclude that mycofibrils are linear structural extensions of the hyphal cell wall. The precise function of mycofibrils in the brown-rot decay process of wood remains to be elucidated. Key words: Postia placenta, mycofibrils, fungal fimbriae, hyphal sheath, electron microscopy.
Glyphosate degradation by immobilized bacteria: laboratory studies showing feasibility for glyphosate removal from waste water
Authors: Heitkamp Michael A. , Adams William J. , Hallas Laurence E.
Published: May 2010

To evaluate immobilized bacteria technology for the removal of low levels of glyphosate (N-phosphonomethylglycine) from aqueous industrial effluents, microorganisms with glyphosate-degrading activity obtained from a fill and draw enrichment reactor inoculated with activated sludge were first exposed to glyphosate production wastes containing 500–2000 mg glyphosate/L. The microorganisms were then immobilized by adsorption onto a diatomaceous earth biocarrier contained in upflow Plexiglas® columns. The columns were aerated, maintained at pH 7.0–8.0, incubated at 25 °C, supplemented with NH4NO3 (50 mg/L), and exposed to glyphosate process wastes pumped upflow through the biocarrier. Glyphosate degradation to aminomethylphosphonic acid was initially >96% for 21 days of operation at flows yielding hydraulic residence times (HRTs) as short as 42 min. Higher flow rate studies showed >98% removal of 50 mg glyphosate/L from the waste stream could be achieved at a HRT of 23 min. Glyphosate removal of >99% at a 37-min HRT was achieved under similar conditions with a column inoculated with a pure culture of Pseudomonas sp. strain LBr, a bacterium known to have high glyphosate-degrading activity. After acid shocking (pH 2.8 for 18 h) of a column of immobilized bacteria, glyphosate-degrading activity was regained within 4 days without reinoculation. Although microbial growth and glyphosate degradation were not maintained under low organic nutrient conditions in the laboratory, the low levels of degradable carbon (45–94 mg/L) in the industrial effluent were sufficient to support prolonged glyphosate-degrading activity. The results demonstrated that immobilized bacteria technology is effective in removing low levels of glyphosate in high-volume liquid waste streams. Key words: glyphosate, degradation, immobilized bacteria technology.
Purification and properties of alcohol dehydrogenase from a mutant strain of Candida guilliermondii deficient in one form of the enzyme
Authors: Indrati Retno , Ohta Yoshiyuki
Published: May 2010

Alcohol dehydrogenase (ADH1) was purified from Candida guilliermondii strain B10-05 to homogeneity, using affinity chromatography on triazine dyes and gel filtration. The enzyme was tetrameric, with a subunit molecular weight of 38 000. The purified enzyme oxidized primary and secondary alcohols, although it preferred primary alcohols. Its activity toward secondary alcohols was better than those of other yeast ADH; however, the enzyme was less sensitive toward inhibitors. Kinetic studies indicated that C. guilliermondii ADH1 oxidized ethanol by an ordered bi–bi mechanism, with NAD as the first substrate fixed. Key words: Candida guilliermondii, alcohol dehydrogenase, ADH1, tetrameric.
Molybdenum incorporation in denitrifying Azospirillum brasilense Sp7
Authors: Chauret Christian , Barraquio Wilfredo L. , Knowles Roger
Published: May 2010

Nondenaturating disc gel electrophoresis revealed that 99Mo was incorporated into the nitrate reductase of Azospirillum brasilense grown in the absence but not in the presence of tungstate. Under denitrifying conditions, A. brasilense grown in tungsten-free medium steadily accumulated 99Mo for 12 h. In contrast, Paracoccus denitrificans grown under the same conditions ceased uptake after 1 h. However, both bacteria were incapable of accumulating significant amounts of 99Mo in media containing 10 mM tungstate, even though nitrate was reduced by A. brasilense. Aerobically grown A. brasilense cells transported 99Mo more efficiently than anaerobically grown cells. Key words: Azospirillum brasilense, tungsten, molybdenum incorporation, nitrate reduction.
Bacterial conjugation: everybody's doin' it
Authors: Frost Laura S.
Published: May 2010

Recent evidence suggests that bacterial conjugation is ubiquitous in the bacterial world and that DNA transfer between different genera–kingdoms is possible. It has also been demonstrated that many bacterial gene transfer systems resemble each other at the molecular level and that others are a blend of two or more of these systems. Thus, in the absence of a sexual cycle, bacterial conjugation, along with bacteriophages, transposons, and natural transformation systems, forms a potent force for gene dissemination and repair in the eubacteria and simple eukaryotes. Key words: conjugation, gene transfer, pili, relaxation complexes, plasmids.
Protein composition of Methanococcus thermolithotrophicus flagella
Authors: Kostyukova Alla S. , Gongadze Georgi M. , Obraztsova Anna Ya. , Laurinavichus Konstantin S. , Fedorov Oleg V.
Published: May 2010

Sodium dodecyl sulfate – polyacrylamide gel electrophoresis of flagella from the thermophilic methanogen Methanococcus thermolithotrophicus indicated that they were composed of three major proteins, with molecular weights of 62 000,44 000, and 26 000, whereas all previously studied flagella of mesophilic methanogens consisted of two subunits. Proteins were isolated by preparative electrophoresis followed by complete removal of sodium dodecyl sulfate and their renaturation. It was shown that at least two of the proteins contain a thermostable domain whose complete denaturation proceeds only upon prolonged boiling in the presence of sodium dodecyl sulfate. Key words: flagellin, thermostability, archaebacteria, Methanococcus thermolithotrophicus.
Effects of potassium sorbate on growth patterns, morphology, and heat resistance of Zygosaccharomyces rouxii at reduced water activity
Authors: Golden David A. , Beuchat Larry R.
Published: May 2010

A study was made of the effects of potassium sorbate on growth, morphology, and heat sensitivity of an osmotolerant yeast, Zygosaccharomyces rouxii, grown in media (water activity (aw) 0.93) supplemented with glucose and sucrose. Growth patterns of Z. rouxii in YM broth supplemented with glucose (YMBG) and sucrose (YMBS) were similar, although increased potassium sorbate concentration in both media resulted in decreased growth rates. Growth in YMBS containing potassium sorbate was not as prolific as that in YMBG containing potassium sorbate. Inhibition of growth was indicated by decreased absorbance (at 600 nm) of cells grown in YMBS and in YMBG and YMBS supplemented with potassium sorbate at 600 or 1000 μg/mL. Slight decreases in cell size and alteration of cellular morphology were associated with increased potassium sorbate concentration. Plasmolysis increased as potassium sorbate concentration was elevated in YMBS but not in YMBG. Tolerance of Z. rouxii to potassium sorbate was enhanced by previous adaptation of cells in media with elevated potassium sorbate concentrations. Heat resistance of cells unadapted to potassium sorbate showed little or no increase regardless of culture age, but increased substantially in cells grown in media containing potassium sorbate, particularly YMBS. Key words: Zygosaccharomyces rouxii, potassium sorbate, glucose, sucrose, heat resistance.
Phage coating of soybean seed reduces nodulation by indigenous soil bradyrhizobia
Authors: Basit H. Abdel , Angle J. Scott , Salem S. , Gewaily E. M.
Published: May 2010

Inoculation of soybean with Bradyrhizobium japonicum is often unsuccessful owing to the failure of inoculum strains to nodulate soybeans (Glycine max (L.) Merr.) in the presence of indigenous strains of rhizobia in soil. Previous studies have shown that it is possible to reduce nodulation with indigenous strains of rhizobia by amending the soil with a bacteriophage specific for the indigenous strain. The objective of the current study was to determine whether the coating of seed with phage affected nodule occupancy and soybean growth. A phage specific for B. japonicum USDA 469 and a symbiotically superior strain of rhizobium (B. japonicum USDA 110) were coated together onto soybean seed and planted into both greenhouse and field soil previously inoculated with B. japonicum USDA 469. The phage coated onto seed reduced nodulation by B. japonicum USDA 469 to 48% occupancy, compared with 64% for the untreated control value. Nodulation by the superior inoculum strain was increased from 48 to 82% occupancy by coating seed with the homologous phage and B. japonicum USDA 110. The rate of nitrogenase activity (on a per plant basis) was increased by coating seed with the phage and B. japonicum USDA 110. No other plant or symbiotic parameters were affected by phage coating of seed. These results indicate that the nodulation of soybeans can be significantly affected by the coating of seed with phage specific for undesirable strains of rhizobia in soil and the concurrent coating of seed with desirable strains of rhizobia. Key words: competition, rhizobiophage, rhizobia, soybeans.