bluuebunny/crossref_metadata_2025 huggingface dataset:
Frequent occurrence of the ability to utilize octopine in rhizobacteria
Authors: Beauchamp Chantal J. , Kloepper Joseph W. , Lifshitz Ran , Dion Patrice , Antoun Hani
Published: May 2010

Over 200 strains of root-colonizing bacteria were tested for opine catabolism. Of these, 12% utilized octopine, 9% catabolized octopinic acid, and <1% used succinamopine. None grew on mannopine or nopaline. Most of the octopine and octopinic acid utilizers were pseudomonads. Only one Gram-positive bacterium used succinamopine. No strains of Serratia, Enterobacter, Aeromonas, or Bacillus catabolized an opine. All bacteria that were isolated from roots of arctic plants and selected for dinitrogen fixation utilized octopine after enrichment cycles with malate. Malate and glucose were compared for their ability to amplify, when used as selective substrates, the fraction of opine utilizers initially present in a plant sample. With this approach, <5% of 401 rhizobacteria tested utilized octopine, octopinic acid, or both opines. The opine-catabolizing strains belonged to the families Rhizobiaceae and Pseudomonadaceae and to the genera Alcaligenes and Flavobacterium. The relative effect of malate and glucose in the enrichment for opine utilizers varied according to the origin of the sample. In this study, octopine and to a lesser extent octopinic acid were recognized as substrates that were more commonly utilized by rhizobacteria than other opines. These results demonstrate that opine catabolism is not restricted to the genus Agrobacterium. Key words: octopine, rhizobacteria, Pseudomonadaceae, Alcaligenes, Flavobacterium.
Carbohydrate nutrition of Enterobacter cloacae ATCC 39978
Authors: Roberts Daniel P. , Sheets Carol J.
Published: May 2010

Utilization of carbohydrate and production of carbohydrate-degrading enzymes by the plant beneficial bacterium Enterobacter cloacae ATCC 39978 was studied. Enterobacter cloacae did not grow on any of the carbohydrate polymers supplied as carbon and energy sources. However, E. cloacae did grow on all the mono- and oligo-saccharides and β-glucosides tested, with the exceptions of D-arabinose and D-fucose. No carbohydrate depolymerase activities were detected in culture supernatants from E. cloacae. In contrast, a number of glycosidase activities including β-glucosidase, β-N-acetylglucosaminidase, and β-xylosidase were detected. Carbohydrate inhibition experiments suggested that two different β-glucosidases were produced. Key words: glycosidases, nutrition.
Genomic characteristics of strains of Itersonilia: taxonomic consequences and life cycle
Authors: Boekhout Teun , Poot Gé , Hackman Peter , Steensma H. Yde
Published: May 2010

In the basidiomycetous genus Itersonilia three species, viz. I. perplexans, I. pyriformans, and I. pastinacae, have been described. We studied mole percentage G+C, nDNA–nDNA homology, and electrophoretic karyotypes of strains belonging to these species. Our results support the recognition of only one species, viz. I. perplexans. Changes in the electrophoretic karyotypes were observed after the transition from monokaryotic yeast cells to monokaryotic hyphae. The apomictic life cycle is described, and aspects of pathogenicity are discussed. Key words: Itersonilia, DNA, karyotyping, taxonomy.
Rahnella aquatilis, a nitrogen-fixing enteric bacterium associated with the rhizosphere of wheat and maize
Authors: Berge Odile , Heulin Thierry , Achouak Wafa , Richard Claude , Bally Rene , Balandreau Jacques
Published: May 2010

In a study of dominant diazotrophic bacteria present in the rhizosphere of wheat and maize, 28 strains of Enterobacteriaceae were isolated. They were all Voges-Proskauer positive, motile at 28 °C but not at 37 °C, and they produced a Tween-80 esterase and did not exhibit decarboxylase activity. This fits well with the description of Rahnella aquatilis. The ability of these strains to reduce acetylene in pure culture and in association with their host plant and the DNA hybridization with a nifHDK probe are described. This is the first time that R. aquatilis is reported as a rhizosphere-associated bacterium and also a nitrogen fixer. Key words: Rahnella aquatilis, rhizosphere, wheat, maize, nitrogen fixation.
Improved analysis of metabolite uptake by Bradyrhizobium japonicum bacteroids
Authors: Salminen Seppo O. , Streeter John G.
Published: May 2010

Uptake of a variety of metabolites by Bradyrhizobium japonicum bacteroids under aerobic conditions was studied with the goal of identifying factors that would influence the accuracy of kinetic parameters. Saturable and nonsaturable components of absorption were identified, allowing separate analysis of only the active component. A significant proportion of labeled substrate was released as CO2. The CO2 release was linear with time and occurred without a noticeable lag period. The kinetic parameters of saturable, active uptake indicated that if the label converted to CO2 was ignored, this would result in underestimation of the total uptake of malate by more than 50%. The proportion of the labeled substrate converted to CO2 depended on the compound but was high in all cases. Glucose showed the smallest difference, with 13% of the label converted to CO2 in a 5-min incubation. The uptake of glutamate was inhibited by aspartate, whereas no effect by equimolar dicarboxylic acids was found. Succinate or fumarate inhibited malate uptake, whereas amino acids showed no effect. Thus, organic acids appeared to have a common carrier distinct from that for amino acids. Techniques for separation of active and passive uptake components and for collection and analysis of CO2 respired are described; these techniques should be used for accurate analysis of metabolite uptake. Key words: Bradyrhizobium japonicum, bacteroids, metabolite uptake, CO2.
Genetic characterization of partial lactose-fermenting revertants from lactose-negative mutants of lactococci
Authors: Sinha R. P.
Published: May 2010

Partial lactose-positive (Lac+) revertants, designated RS0121 and RS033, were isolated from lactose-negative (Lac−) mutants of Lactococcus lactis subsp. lactis C2 and ML3, respectively. These revertants were found to coagulate 10% reconstituted skim milk, but the rate of lactose fermentation was much slower than that of their parental Lac+ strains. Such partial Lac+ revertants were also isolated from Lac− mutants of L. lactis subsp. Lactis SL712, SH4109, and SL763 and of L. lactis subsp. cremoris ML1 and SC607, showing a generalized phenomenon. The Lac+ characteristic of the revertant strains was conjugally transferred to Lac− variants. When the plasmid profiles of the Lac− variants and their partial Lac+ revertants and transconjugants were analyzed, there were no detectable differences in the plasmid bands. A strain with no plasmids, MG1363, also yielded partial Lac+ revertants, which were devoid of all plasmids. In addition, the Lac+ phenotype of one such revertant, designated RS101, was transferable to other Lac− strains by conjugation. The results indicate that the genetic information for slow lactose metabolism in such partial Lac+ revertants is mediated through chromosomal gene(s) and is under the influence of some suppressor. These observations also suggest the possibility of utilizing this method for isolating slow acid producing variants, which could be used as adjuncts with regular cheese starter cultures for accelerated cheese ripening. Key words: lactococci, lactose-negative mutants, plasmid DNA, lactose-fermenting revertants.
Calcium activity versus "calcium threshold" as the key factor in the induction of yeast flocculation in simulated industrial fermentations
Authors: Masy Charlotte L. , Kockerols Myriam , Mestdagh Michèle M.
Published: May 2010

Yeast flocculation is regulated by two parameters: the free-calcium activity and the "calcium threshold" or the quantity of calcium at which cells flocculate in a turbidimetric test. The study of the influence of different factors such as calcium concentration, pH, and chelating agents on flocculation has led us to put forward the following hypothesis. Flocculation occurs when the calcium threshold becomes equal to free-calcium activity, i.e., when the medium contains the exact quantity of calcium necessary for flocculation to occur. This hypothesis has been confirmed under standard laboratory culture conditions and in simulated industrial fermentations. Key words: flocculation, yeast, Saccharomyces cerevisiae, calcium induction.
Experimental lethal infection of Leptospira interrogans in mice treated with cyclophosphamide
Authors: Masuzawa Toshiyuki , Hashiguchi Yuji , Nakamura Ryuta , Suzuki Ryoma , Shimizu Tadayori , Iwamoto Yoshihisa , Morita Tamotsu , Yanagihara Yasutake
Published: May 2010

After preadministration of cyclophosphamide (300 mg/kg), BALB/c mice were lethally infected with Leptospira interrogans serovar lai and a virulent strain of Leptospira interrogans serovar copenhageni, and leptospiral cells were detected in both kidneys of infected mice by indirect immunofluorescent assay. Nonpathogenic leptospirae, Leptospira biflexa serovar patoc, Leptonema illini, and an avirulent strain of L. interrogans serovar copenhageni, were not parasitic to the mice treated with cyclophosphamide. The cyclophosphamide-treated mice were protected from the homologous leptospiral infection by passive immunization with anti-leptospiral monoclonal antibody or with rabbit antiserum and by active immunization with lyophilized organisms or with protective antigen. The results of active immunization in mice treated with cyclophosphamide agreed well with those in nontreated hamsters, which were sensitive to the organisms. Furthermore, these experiments were reproducible with any lot of cyclophosphamide used. These results indicated that cyclophosphamide-treated mice can be used in the experimental infection of Leptospira in place of hamsters or guinea pigs. Key words: Leptospira interrogans, protective antigen, mice, cyclophosphamide, immunosuppression.
Modulation of Clostridium difficile induced mortality as a function of the dose and the viability of the Saccharomyces boulardii used as a preventative agent in gnotobiotic mice
Authors: Elmer Gary W. , Corthier Gerard
Published: May 2010

The ability of viable and nonviable Saccharomyces boulardii to protect gnotobiotic mice from Clostridium difficile induced mortality was tested. With the exception of irradiated S. boulardii, which retained some activity, only viable yeast protected the mice from lethality. The survival of C. difficile infected mice was dependent on the dose of the yeast provided in the drinking water. Key words: Saccharomyces boulardii, Clostridium difficile, colitis, pseudomembranous colitis, gnotobiotic mice.
Transformation of Neisseria gonorrhoeae: physical requirements of the transforming DNA
Authors: Stein Daniel C.
Published: May 2010

The 1600-bp (base pair) fragment encoding a portion of the nalidixic acid resistant DNA gyrase, subunit B, was characterized to determine what parameters effect transformation in the gonococcus. When this DNA (pSY2) was isolated from Escherichia coli, it was able to transform a variety of gonococcal strains to resistance to nalidixic acid via DNA-mediated transformation, irrespective of their restriction–modification phenotype. Nalidixic acid resistant transformants contained no plasmid DNA sequences that corresponded to the vector, as measured by plasmid screening procedures and colony hybridization techniques. Supercoiled and linear DNA transformed the gonococcus at the same efficiency. DNA fragments as small as 615 bp were able to transform the gonococcus. The presence of a 10-bp uptake sequence enhanced a DNA fragment's ability to transform the gonococcus by four orders of magnitude. When the fragment encoding the nalidixic acid resistant DNA gyrase was subcloned into M13mp18, both the replicative form and the single-stranded form of the phage were able to transform the gonococcus to nalidixic acid resistance. Key words: sequence-specific uptake, gyrase, restriction and modification.
Two new species of Syncephalis (Zoopagales, Piptocephalidaceae)
Authors: Gruhn U. , Petzold H.
Published: May 2010

Two new species of Syncephalis, Syncephalis torpedospora and Syncephalis parvula, are described. They were isolated from agricultural soil in Germany and have been maintained as haustorial mycoparasites on Mortierella alpina. Syncephalis torpedospora bears one-spored merosporangia, S. parvula two-spored merosporangia on the upper hemisphere of the globose fertile vesicle. Both are relatively small members of the genus Syncephalis. Key words: Mucorales, mycoparasitism, Piptocephalidaceae, Syncephalis, Zygomycetes.
Characterization of interspecific hybrids within the Aspergillus nidulans group by isoenzyme analysis
Authors: Kálmán Éva Tóth , Varga János , Kevei Ferenc
Published: May 2010

A comparison of interspecific hybrids within the Aspergillus nidulans species group was made by isoenzyme analysis. The gel electrophoretic patterns of the parental species were distinct for most of the enzymes tested. The hybrids were distinguishable from their parents by isoenzyme patterns. The appearance of novel bands in all the interspecific hybrids indicated that nuclear fusion could have occurred. In most hybrids the appearance of the parental bands showed nonpreferential, partial chromosome loss or repressive interaction between the genomes. The isoenzyme composition of the haploid segregants of the Aspergillus nidulans × Aspergillus rugulosus hybrid differed for some of the enzymes studied from that of the hybrid, suggesting that during segregation further interaction of the chromosomes took place. The results indicate a certain degree of genetic homology among the members of the Aspergillus nidulans species group. Key words: Aspergillus, isoenzyme analysis, hybridization.
Cell-free and cell-bound hemolytic activities of Proteus penneri determined by different Hly determinants
Authors: Łukomski Sławomir , Różalski Liliana Serwecińska Antoni , Dziadek Jarosław , Staczek Paweł , Jaworski Adam
Published: May 2010

A collection of 45 Proteus penneri strains was characterized with respect to their hemolytic activity and representative cell-free or only cell-bound hemolysin possessing strains were chosen for further study. Extracellular Proteus penneri hemolysin, which was investigated earlier by hybridization, reacted with monospecific antiserum against α-hemolysin of Escherichia coli. In this paper we also show, using the colony hybridization technique, that the α-hemolysin-like determinant is widely distributed among Proteus penneri strains. Because one of the strains tested, which expressed a high activity of cell-bound hemolytic factor, did not carry such a Hly determinant, the presence of a second hemolysin is postulated. We cannot demonstrate any difference in hybridization patterns of α- and β-hemolytic Proteus penneri strains and accumulation of the toxin molecule inside the cells was also not observed. The existence of another control mechanism, external to the hly operon, for hemolysin gene is suggested. Key words: Proteus penneri, hemolytic activity.
Changes in antigenic reactivity of Borrelia burgdorferi, the Lyme disease spirochete, during persistent infection in mice
Authors: Schwan Tom G. , Karstens Robert H. , Schrumpf Merry E. , Simpson Warren J.
Published: May 2010

Adult laboratory mice, Mus musculus, were shown to be suitable experimental animals for studying infectivity, persistent infection, and in vivo antigenic changes of Borrelia burgdorferi. Sixteen mice were inoculated intraperitoneally with a low-passage culture of an uncloned strain of B. burgdorferi and 16 months later spirochetes were reisolated from the urinary bladder of 15 (94%) of the mice. Spirochetes recovered from the urinary bladder of one persistently infected mouse were tested for infectivity and found to be infectious when passaged into four laboratory mice. Western blot analysis of immune serum from each of the persistently infected mice demonstrated that spirochetes used to infect the mice reacted differently when compared with the spirochetes subsequently reisolated from the mice, demonstrating for the first time that changes in antigenic reactivity had occurred in the spirochete populations during persistent infection. Key words: Borrelia burgdorferi, Lyme disease, antigenic changes.
Rôle du bactérioplancton en milieu lacustre pélagique : prépondérance des plus grosses bactéries
Authors: Letarte Yvon , Pinel-Alloul Bernadette
Published: May 2010

Bacterioplankton abundance (AB), heterotrophic production (PB) (thymidine incorporation) and renewal time (tr = AB/PB) were determined in eight Canadian Shield lakes in two size classes of bacteria (< 1 μm and > 1 μm). Although large bacteria (> 1 μm) were often less than 50% in numbers, they produced most of the new cells in 20 out of 21 trials. Large bacteria had a tr shorter than that of small ones (< 1 μm). Large bacteria not only represent much of the biomass, but seem to be the principal site of carbon and energy flow within the bacterial community. There was a significant positive correlation between PB of the whole bacterial community and primary production (PP), but we found no correlation between PB and chlorophyll a concentration (CHL). Similar results were obtained for the large bacteria. On the opposite, we found no correlation between PB of the small bacteria and PP, but a significant positive correlation between PB and CHL. Only the small bacteria showed a significant correlation between PB and AB, as well as a more constant rate of reproduction. Our results modify the importance of AB values found in the literature, give a good reason for the weak correlation between PB and AB found in other studies, and change the generally accepted scheme of organic and energy flow in planktonic systems. Key words: bacterioplankton, size class, productivity, correlation.
Stability of plasmids in lactococci during extended incubation in growth media
Authors: Sinha R. P.
Published: May 2010

The stability of plasmids in Lactococcus lactis ssp. lactis strains C2 and ML3, and L. lactis ssp. cremoris strains ML1 and SC607, was investigated by extended incubation of bacterial cells in low nutrient media under acidic conditions. Strains were grown overnight (16–18 h) in skim milk and unbuffered medium (M17−) at 32 °C and subsequently held at that temperature for extended periods (≥ 96 h). Lac− variants were obtained from each strain in milk and (M17−) broth. The plasmid profiles of Lac− variants when compared with their parental Lac+ strains showed loss of one or more plasmid bands. None of the Lac− mutants showed loss of smaller plasmids (< 5 MDa) indicating that smaller plasmids in lactococci are more stable under these conditions than larger plasmids (> 10 MDa). Concomitant loss of the Lac+ phenotype and plasmids by the method used in the present investigation may have application for isolating mutants devoid of one or more plasmids.
Symbiotic interactions of Phaseolus acutifolius and P. acutifolius × P. vulgaris hybrid progeny in symbiosis with Bradyrhizobium spp. And Rhizobium leguminosarum bv. phaseoli
Authors: Somasegaran Padma , Hoben Heinz J. , Lewinson Lisa
Published: May 2010

The rhizobial requirements and the N2-fixing potential of Phaseolus acutifolius and P. acutifolius × P. vulgaris hybrid progeny were investigated in glasshouse experiments. Although P. acutifolius was promiscuous, effective nodulation and N2 fixation occurred only with a few Bradyrhizobium isolates, especially those that were isolated from P. acutifolius, P. limensis, P. penduratus, P. lunatus, Canavalia ensiformis, Calopogonium mucunoides, and Psophocarpus tetragonolobus. Strong host × Bradyrhizobium interactions were detected in four genotypes of P. acutifolius tested against eight isolates of bradyrhizobia and a commercial mixed inoculant. All seven progeny tested nodulated with Bradyrhizobium isolates and Rhizobium leguminosarum bv. phaseoli, but there was a highly specific rhizobial requirement for effective nodulation and N2 fixation. The progeny × rhizobial interaction accounted for 83% of the total phenotypic variation. Two (P-6 and P-7) and five (P-1, P-2, P-3, P-4, and P-5) progeny nodulated and fixed N2 effectively with R. l. bv. phaseoli and Bradyrhizobium spp., respectively. The R. l. bv. phaseoli – progeny symbiosis had a greater N2-fixing potential than the Bradyrhizobium isolate – progeny symbiosis. In a soil (oxisol) test, progeny P-6 and P-7 showed significant response to inoculation with R. l. bv. phaseoli. Strain R. l. bv. phaseoli TAL 182 was the most competitive strain, occupying 84% of the nodules in both the progeny. Key words: rhizobial requirements, Phaseolus acutifolius × Phaseolus vulgaris hybrids.
Sulfur-oxidizing bacteria as plant growth promoting rhizobacteria for canola
Authors: Grayston Susan J. , Germida James J.
Published: May 2010

Canola (Brassica napus) has a high sulfur requirement during vegetative growth and exhibits symptoms of sulfur deficiency when cropped on Saskatchewan soils low in plant available sulfur. Elemental sulfur (S0) is frequently used as a fertilizer to alleviate this deficiency. The potential of sulfur-oxidizing microorganisms to enhance the growth of canola in S0 fertilized soils was assessed. Sulfur-oxidizing bacteria and fungi were isolated from the rhizosphere and rhizoplane of canola grown in four different Saskatchewan soils under growth chamber conditions. Of 273 bacterial isolates, 245 (89.7%) oxidized S0 to thiosulfate or tetrathionate in vitro, and 133 (48.7%) oxidized S0 to sulfate; 70 fungal isolates oxidized S0 to sulfate. Eighteen bacterial isolates demonstrating the highest in vitro sulfur oxidation were tested as seed inoculants under growth chamber conditions, with S0 as sulfur source. Fourteen isolates increased canola leaf size measured at the bud stage of growth, and seven isolates increased root and pod dry weights at maturity. Three of the 14 isolates were also able to stimulate canola leaf area in the presence of plant available sulfate. The shoot material from canola inoculated with two of these isolates contained more iron, sulfur, and magnesium than uninoculated canola. Three of the 14 isolates inhibited the growth of the canola fungal pathogens, Rhizoctonia solani AG2-1, R. solani AG4, and Leptosphaeria maculans "Leroy." Another isolate was antagonistic towards both R. solani strains and another inhibited the growth of R. solani AG2-1 and L. maculans "Leroy." Thus some sulfur-oxidizing isolates appear to stimulate canola growth due to the enhancement of mineral nutrient uptake, whereas in other cases antibiosis towards canola pathogens may also be involved. Key words: elemental sulfur, oxidation, canola, rhizosphere, plant growth promoting rhizobacteria.
Transposition and copy number of insertion sequence ISRm1 are not correlated with symbiotic performance of Rhizobium meliloti from two field sites
Authors: Barran L. R. , Bromfield E. S. P. , Rastogi V. , Whitwill S. T. , Wheatcroft R.
Published: May 2010

The insertion sequence ISRm1 frequently occurs in Rhizobium meliloti and is a potential mutagen. Data for the frequency of ISRm1 transposition in the commercial inoculant strain SU47 (containing eight copies of IsRm1) indicate that this insertion sequence does not significantly affect the ability of SU47 to occupy nodules of alfalfa (Medicago sativa L.) grown at two field sites. Thirty representative isolates from the indigenous population of R. meliloti at each of these sites contained from 0 to 10 copies of IsRm1; there was no significant correlation between insertion sequence copy number and nodulating competitiveness, symbiotic effectiveness, or frequency of occurrence of indigenous rhizobia in nodules of plants grown at these sites. Collectively, these data suggest that ISRm1 has little impact on the stability of agriculturally important properties of R. meliloti from the two field sites, despite its potential as a mutagen. Key words: insertion element, symbiotic effectiveness, competitiveness, Rhizobium meliloti, indigenous populations.
Thermal susceptibility of Streptococcus faecium strains isolated from frankfurters
Authors: Gordon C. L. André , Ahmad M. H.
Published: May 2010

The heat resistance of nine strains of Streptococcus faecium isolated from frankfurters was determined at 63 and 68 °C in brain heart infusion broth. Exponential-phase cultures (approximately 107 colonies/mL) were used as inoculants. The heat resistance of S. faecium DP2181, a moderately resistant isolate, was further examined in broth (55, 63, and 68 °C) and frankfurter emulsion (63 and 68 °C). The decimal reduction times (D values) were determined by regression. In broth, both time–temperature combinations resulted in a 3–4 log decline in bacterial numbers for the nine S. faecium strains tested. For S. faecium DP2181, the survivor curves deviated from the logarithmic order of death at all three heating temperatures. An initial slow period of death was evident at 55 °C and a resistant tail of organisms was observed at 55, 63, and 68 °C. The D55D63, and, D68 values for the logarithmic portion of the corresponding survivor curves were 105.6, 9.36, and 3.34 min, respectively. The survival of DP2181 was enhanced by the frankfurter emulsion. The results indicate that populations of S. faecium existed that were very heat resistant and could survive normal frankfurter processing if initially present in high numbers. Key words: heat resistance, enterococci, D value, resistant tail.
Siderophore synthesis by mucoid Pseudomonas aeruginosa strains isolated from cystic fibrosis patients
Authors: Haas Barbara , Murphy Eileen , Castignetti Domenic
Published: May 2010

Nonmucoid Pseudomonas aeruginosa responds to iron deprivation by synthesizing the siderophores pyochelin and pyoverdine. When grown in iron-deficient medium, six mucoid P. aeruginosa strains isolated from cystic fibrosis patients synthesized copious amounts of the exopolysaccharide alginate. A procedure that eliminated the interference of alginate was developed so that siderophores could be extracted from the growth medium. All six isolates were then noted to produce both pyoverdine and pyochelin. This report thus confirms that mucoid P. aeruginosa, like its nonmucoid counterparts, elicits the siderophores commonly cited as those of the microbe. Key words: mucoid Pseudomonas aeruginosa, siderophores, pyoverdine, pyochelin.
The biotransformation of tranylcypromine by Cunninghamella echinulata
Authors: Foster B. C. , Litster D. L. , Zamecnik J. , Coutts R. T.
Published: May 2010

When incubated alone for 7 days with the fungus Cunninghamella echinulata, tranylcypromine was extensively metabolized. As observed in mammalian systems, N-acetyltranylcypromine was the major metabolite recovered along with lesser amounts of 4-hydroxytranylcypromine, as its N,O-diacetyl derivative. The rate and extent of tranylcypromine biotransformation was affected by whether incubation was on either 30° or flat brackets with a gyratory shaker. There is a strong association between the rate of biotransformation and the utilization of glucose, formation of ammonia, and pH. The slowest rates of biotransformation and metabolic response were observed with the large fungal pellets formed during incubation on flat brackets. These findings raise the possibility that, as in mammalian systems, fungal metabolism of xenobiotics can be affected by nutrient and environmental conditions. Key words: Cunninghamella echinulata, tranylcypromine, biotransformation, toxicity model.
In vitro sporulation of Frankia strain HFPCcI3 from Casuarina cunninghamiana
Authors: Burleigh Stephen H. , Dawson Jeffrey O.
Published: May 2010

Optimization of the in vitro sporulation of Frankia is a prerequisite for the development of spore preparations as a practical inoculum for actinorhizal plants. The in vitro sporulation of Frankia strain HFPCcI3 previously isolated from Casuarina cunninghamiana was increased from 0 to 12 million spores per millilitre of culture medium when nitrogen and phosphorus were excluded from a defined nutrient medium. The same medium did not increase sporulation of Frankia isolates HFPAr13 from Alnus rubra and HFPCpI1 from Comptonia peregrina. The addition of 10 mM aliphatic L amino acids increased the in vitro sporulation of HFPCcI3 by as much as 39% when grown in a defined nutrient medium with 1 mM potassium phosphate lacking ammonium chloride, whereas the addition of 10 mM acidic, basic, aromatic, and sulfur amino acids decreased sporulation. The in vitro sporulation of HFPCcI3 was inhibited by culture at 33 °C relative to culture at 23 and 28 °C. Rotary shaking at 100 rpm increased sporulation at the low culture temperatures. Key words: actinorhizal, Casuarina, Frankia, HFPCcI3, sporulation.
Seasonal changes in mineralization of xenobiotics by stream microbial communities
Authors: Palmisano Anna C. , Schwab Burney S. , Maruscik Dorothy A. , Ventullo Roy M.
Published: May 2010

Seasonal changes in the mineralization of mixed amino acids (MAA), an anionic surfactant (linear alkylbenzene sulfonate; LAS), a detergent builder (nitrilotriacetic acid; NTA), and a herbicide (2,4-dichlorophenoxyacetic acid; 2,4-D) by microbial communities were studied in two streams in southwestern Ohio. Radiolabeled (14C) test compounds were added to samples of seston, leaf litter, periphyton, and sediment collected from Briarly Creek, a waste water impacted stream, and Little Indian Creek, a relatively unimpacted stream. Mean values for NH3, orthophosphate, dissolved organic carbon, and total organic nitrogen were significantly higher in Briarly Creek than Little Indian Creek. However, there was no significant difference in the mean values for esterase activity, chlorophyll a, and bacterial numbers in the respective habitats of the two streams. Mineralization was a significant method for removal of MAA, LAS, and NTA in Briarly Creek, and MAA in Little Indian Creek throughout the year. Mineralization of 2,4-D by microbial communities in both streams was very limited. The importance of temperature as an environmental variable affecting mineralization was indicated by (i) lower first-order rate constants in winter samples as compared with summer samples in some habitats; (ii) an increase in the first-order rate constants when temperatures were increased from 4 to 22 °C; and (iii) a positive correlation of LAS mineralization with ambient temperature. Key words: streams, xenobiotics, biodegradation, leaf litter, seston, periphyton, sediments.
Comparative analysis of five methods for recovering rhizobacteria from cotton roots
Authors: Kloepper Joseph W. , Mahaffee Walter F. , McInroy John A. , Backman Paul A.
Published: May 2010

A variety of methods have been used for recovering introduced bacteria from plant roots. The objective of this study was to compare systematically five methods: agitation in buffer, agitation with glass beads in buffer, mixing in a StomacherR lab-blender, sonication, and trituration with mortar and pestle. Cotton seeds were treated with two previously reported rhizobacterial strains, Pseudomonas fluorescens strain Pf-5 and Bacillus subtilis strain GB03. The efficiency of recovery by each method was determined 3 weeks later by comparing average bacterial populations from whole root systems, single 2.0-cm root segments, and two root regions (the uppermost 5 cm of taproot and the lowermost 5 cm). Treatment with the StomacherR blender yielded significantly higher (P = 0.05) mean populations of GB03 compared with all other methods and significantly higher mean populations of Pf-5 compared with agitation with glass beads. From the lowermost 5 cm of taproot, populations of Pf-5 recovered by the StomacherR treatment were significantly higher than all other methods. The inclusion of glass beads for agitation treatments resulted in neither consistently higher absolute numbers of recovered bacteria nor reductions in variability. The mean standard error of each recovery method varied among root sources, and no single method consistently had the highest or lowest mean standard error. Mean standard errors for strain GB03 were generally lower than those for Pf-5 with each root source and each method of recovery. When viewed in composite, the data suggest that the StomacherR treatment was the best for recovering the greatest absolute numbers of rhizobacteria; however, this treatment had high mean standard errors. Investigations of root colonization by introduced rhizobacteria should include several recovery methods to optimize recovered numbers or to decrease variability, depending on the experimental objectives. Key words: root colonization, rhizobacteria, Pseudomonas fluorescens, Bacillus subtilis, cotton.
Induction of C4-dicarboxylate transport genes by external stimuli in Rhizobium meliloti
Authors: Batista S. , Castro S. , Aguilar O. M. , Martínez-Drets G.
Published: May 2010

We have characterized two mutants of Rhizobium meliloti L5-30 obtained by random mutagenesis using Mu–lacZ that were defective in transport of C4-dicarboxylic acids. These mutants induced ineffective nodules on alfalfa. Mutations in the two strains appeared to be located in a dctA gene. Levels of dctA gene expression were determined under different environmental conditions using dctA–lacZ fusions, and β-galactosidase activities increased in response to osmotic stress and also when the cells were incubated in medium low in calcium. The transcriptional induction of the dctA gene by environmental signals was decreased by DNA gyrase inhibitors such as novobiocin and coumermycin. Key words: Rhizobium meliloti, nitrogen fixation, dicarboxylate transport.
A general method of isolating high molecular weight DNA from methanogenic archaea (archaebacteria)
Authors: Jarrell Ken F. , Faguy David , Hebert Anne M. , Kalmokoff Martin L.
Published: May 2010

High molecular weight DNA was readily isolated from all methanogens treated, as well as from thermophilic anaerobic eubacteria, by grinding cells frozen in liquid N2, prior to lysis with SDS. DNA can subsequently be purified by the usual phenol–chloroform extractions. The procedure yields DNA readily cut by restriction enzymes and suitable for oligonucleotide probing, as well as for mole percent G + C content determination by thermal denaturation. The method routinely yields DNA of high molecular weight and is an improvement over DNA isolation methods for many methanogens, which often involve an initial breakage of the cells in a French pressure cell. Key words: methanogens, archaebacteria, archaea, DNA isolation.
Growth morphology of Streptomyces akiyoshiensis in submerged culture: influence of pH, inoculum, and nutrients
Authors: Glazebrook M. A. , Vining L. C. , White R. L.
Published: May 2010

Most media in which the growth of shaken submerged cultures of Streptomyces akiyoshiensis was examined did not support the formation of well-dispersed mycelial suspensions. Investigation of the culture conditions promoting dispersed growth showed the pH of the culture medium to be of critical importance; an initial value of 5.5 minimized aggregation of the mycelium while supporting adequate biomass production. In cultures started at this pH, spore inocula gave better mycelial dispersal than did vegetative inocula; with spore inocula, growth morphology was also less affected by inoculum size. The composition of the nutrient solution influenced the extent of mycelial dispersal; slow growth was often associated with clumping but no clear correlation was observed between pellet formation and the ability of carbon or nitrogen sources to support rapid growth. Increasing the phosphate concentration from 0.5 to 15 mM caused a modest decrease in mycelial aggregation. Conditions promoting a well-dispersed mycelium suitable for studying the physiological control of secondary metabolism also supported the formation of 5-hydroxy-4-oxonorvaline by S. akiyoshiensis. Key words: Streptomyces akiyoshiensis, mycelial aggregation, growth conditions.
Evaluation of filamentous fungi isolated from petals of bean and rapeseed for suppression of white mold
Authors: Inglis G. D. , Boland G. J.
Published: May 2010

The influence of filamentous fungi isolated from petals of bean and rapeseed on white mold caused by Sclerotinia sclerotiorum was evaluated. In laboratory trials, macerates of agar plugs containing hyphal fragments of the pathogen in combination with individual fungi were applied onto celery petioles, and subsequent lesion diameters were recorded. The efficacy of 10 fungi exhibiting a spectrum of lesion suppression on celery was correlated with the efficacy of the same fungi in growth-room (r = 0.78, P = 0.005) and greenhouse (r = 0.68, P = 0.032) trials. From 315 isolates of fungi evaluated in the laboratory trials, the 10 most suppressive isolates were selected and evaluated in growth-room trials. Spores of the test fungi were applied onto flowers simultaneously with, and up to 24 h after, inoculation with ascospores of S. sclerotiorum. The most suppressive fungi included isolates of Alternaria alternata, Drechslera sp., Epicoccum purpurascens, Fusarium graminearum, Fusarium heterosporum, and Myrothecium verrucaria. These fungi did not provide consistent control of white mold of bean in a field test repeated four times in 1988. However, Drechslera sp. and E. purpurascens significantly reduced the incidence of white mold in one and two trials, respectively. Combination treatments of A. alternata and Benlate (1.1 kg active ingredient ha−1) suppressed white mold significantly more than either treatment alone in one of four trials. Key words: Sclerotinia sclerotiorum, biological control, fungicide interaction.
Modulation of murine macrophage responses stimulated with influenza glycoproteins
Authors: Arora D. Jit S. , Houde Michel
Published: May 2010

Previously it was reported that influenza virus stimulated, nonspecific resistance was largely due to its glycoproteins, hemagglutinin (HA) and neuraminidase (NA). The enhancement of natural killer cell activity was the intrinsic property of NA and HA. In the present study, the stimulatory effect of these glycoproteins on the murine peritoneal macrophages was studied. Electrophoretically purified glycoproteins, NA and HA, of influenza virus A/USSR/90/77 (H1N1) were administered intraperitoneally to C3H/HeN mice, with or without stearyl tyrosine (ST). Macrophages were isolated and were restimulated with phorbol myristate acetate. H2O2 secretion was determined by horseradish peroxidase dependent oxidation of phenol red assay. HA enhanced H2O2 secretion only in the presence of ST (60 nmol∙mg−1∙h−1), whereas NA alone stimulated H2O2 secretion (83 nmol∙mg−1∙h−1), by 6-fold over control (13 nmol∙mg−1∙h−1), and this stimulation was further increased (136 nmol∙mg−1∙h−1) in the presence of ST. Interleukin 1 (IL-1) activity was determined by using D10.G4.1 cells. There was a little stimulation of IL-1 activity (<1 U/mL) of macrophages isolated from HA-primed or HA+ST-primed mice restimulated with HA. On the other hand, IL-1 activity of macrophages isolated from NA-primed mice restimulated with NA significantly increased (102 U/mL) over control (<1 U/mL), and an additional 2-fold increase (231 U/mL) resulted when macrophages from NA + ST-primed mice were used. Tumor necrosis factor (TNF) activity was examined by using L929 cells. Negligible TNF activity was observed in macrophages isolated from either HA-primed or HA + ST-primed mice restimulated with HA. Macrophages from NA-primed mice restimulated with NA increased TNF activity from 2.1 (control) to 20 U/mL, and this activity increased further to 536 U/mL in macrophages from NA + ST-primed mice. NA of N2 subtype also possessed the potential to stimulate TNF activity. ST had an enhancing effect on the stimulatory potential of proteins. Our present results supported by our earlier findings show that NA, even though enzymatically inactive, can stimulate nonspecific resistance mechanisms and probably plays an important role in the control of early influenza infection. Key words: influenza, glycoproteins, modulation, macrophages.
Cloning of tetracycline-resistance genes from various strains of Clostridium perfringens and expression in Escherichia coli
Authors: Saksena Nitin K. , Truffaut Nicole
Published: May 2010

One hundred strains of Clostridium perfringens and 52 strains of other Clostridia of human and animal origins were screened for tetracycline resistance. Fifty-six strains were resistant to tetracycline in the C. perfringens group. Ten strains were selected for their high level of resistance. In all of them, the tetracycline-resistance genes were found to be residing in large plasmids of about 50 kb, all showing homologies. Several tetracycline-resistance genes from plasmids of various strains of C. perfringens were cloned in plasmid pUC19 and the resistance was expressed in Escherichia coli. Hybridization analysis showed these genes to be homologous among themselves and also to tetP gene from the PCW3-type plasmid. Key words: tetracycline resistance, Clostridium perfringens, gene cloning, recombinant plasmids.
Mutational analysis of genes determining antagonism of Alcaligenes sp. strain MFA1against the phytopathogenic fungus Fusarium oxysporum
Authors: Martinetti Gladys , Loper Joyce E.
Published: May 2010

Alcaligenes sp. strain MFA1 inhibits microconidial germination and germination-tube elongation of Fusarium oxysporum f.sp. dianthi and reduces the severity of fusarium wilt of carnation, presumably as a result of its production of a siderophore (G.Y. Yuen and M.N. Schroth. 1986. Phytopathology, 76: 171–176). Derivative strains of MFA1, deficient in antagonism against F. oxysporum and in iron-limited growth, were obtained by Tn5 mutagenesis. The presence of a single Tn5 insertion in the genomic DNA of each derivative strain was detected by Southern analysis. Marker-exchange mutagenesis of strain MFA1 with DNA fragments, containing Tn5 and flanking sequences cloned from representative mutants, confirmed the association of single Tn5 insertions with the loss of antifungal activity and iron-independent growth of MFA1. These results are consistent with the involvement of siderophore biosynthesis by MFA1 in the inhibition of F. oxysporum. Key words: suppression, suppressive soils, biocontrol, siderophore.
Influence de la monensine sur la composition des parois de quelques champignons filamenteux
Authors: Koulali Yahya , Fonvieille Jean-Louis , Touze-Soulet Jane-Marie , Benizri Émile , Dargent Robert
Published: May 2010

Walls of young hyphae of Achlya bisexualis, Botrytis cinerea, and Sclerotium rolfsii growing in the presence or the absence of monensin were isolated and their chemical content was determined. Monensin induced modified proportions of various monomers resulting in a reduction of the (neutral sugars + uronic acid)/amine sugar ratio of B. cinerea and S. rolfsii (species of group chitin–glucans), and of cellulose in A. bisexualis (species of group cellulose-glucans).The walls of hyphae grown in presence of monensin also contained less total lipids and proteins. These modificationsin chemical composition are related to changes in cytological structure. Key words: fungi, monensin, wall.
Nitrogenase activity and growth of Frankia in batch and continuous culture
Authors: Harris Sharon , Silvester Warwick
Published: May 2010

Frankia grown in batch culture was unable to maintain a high rate of nitrogenase activity and, once a peak level was reached, activity rapidly declined. Addition of 5 mM carbon source of cultures or transfer to fresh medium was followed by brief recovery of nitrogenase activity. The extent of recovery decreased as additions or transfers were made to progressively older cultures. Daily addition of fresh medium (dilution rate = 0.125 day−1) allowed Frankia to be maintained in continuous, derepressed culture with stable rates of growth and nitrogenase activity for more than 30 days. The proportion of active, mature vesicles also remained constant in continuous culture but decreased with time inbatch culture. Key words: Frankia, batch culture, continuous culture, nitrogenase activity.
Synthesis of the ferredoxin-like protein FdxN from Rhizobium meliloti bacteroids as a fusion protein in Escherichia coli
Authors: Riedel Kai-Uwe , Masepohl Bernd , Klipp Werner , Pühler Alfred
Published: May 2010

To analyze the overexpression of the Rhizobium meliloti fdxN gene in Escherichia coli, different translational and transcriptional fusions were constructed. The translational signals of R. meliloti fdxN were recognized in E. coli as demonstrated by the use of in-frame lac fusions. Translational fusions consisting of the lacZ or the lpp gene fused in frame to the 3′ end of the entire fdxN gene were expressed at high levels in E. coli. In contrast, the wild-type R. meliloti FdxN protein without a C-terminal fusion could only be detected using the very sensitive T7 promoter–polymerase system and not in immunoblots with antibodies against an FdxN–LacZ hybrid protein. Evidently, translational fusions to the 3′ end of fdxN had a stabilizing effect on the expression of the fdxN gene. A constitutively expressed transcriptional fdxN fusion, which did not mediate detectable amounts of FdxN protein either in E. coli or in free-living R. meliloti cells, complemented the Fix− phenotype of an R. meliloti fdxN::[Tc] mutant strain to wild-type levels. Therefore, either low amounts of the wild-type FdxN protein are sufficient for symbiotic nitrogen fixation or there are stabilizing factors, which are present only in R. meliloti bacteroids but not in free-living R. meliloti cells. Fusion proteins consisting of FdxN and LacZ or a partial Lpp protein restored the Fix− phenotype of an R. meliloti fdxN mutant to 3 and 11%, respectively, indicating that a C-terminal fusion did not completely abolish the function of FdxN. Key words: overexpression, protein stability, immunoblot, complementation.
Ethanol-extractable substrate pools and the incorporation of thymidine, L-leucine, and other substrates by bacterioplankton
Authors: Hollibaugh James T. , Wong Patricia S.
Published: May 2010

Bacterioplankton productivity measurements based on [methyl-3H]-thymidine (TdR) or L-[3,4,5-3H]leucine (L-leu) incorporation typically depend on cold trichloroacetic acid (TCA) precipitation to separate 3H uptake from incorporation. An additional rinse with cold 80% ethanol (EtOH) removed an average of 22 (L-leu) and 32% (TdR) of 3H "incorporated" by San Francisco Bay samples and decreased the between-duplicate difference by a factor of 3.5. Similar results were obtained with samples from Tomales Bay, Calif., and Palmer Station, Antarctica. Varying amounts of cold TCA insoluble radiolabel from six other substrates were removed by the EtOH rinse. Regression analysis showed relationships between the effect of the EtOH rinse and a group of environmental variables and derived parameters. The percentage of 3H removed was generally independent of filter type; however, there were often large differences in the amount of 3H retained by Millipore versus Nuclepore or Poretics filters. The results strongly suggest that an EtOH rinse or other organic extraction should be included in protocols to determine incorporation of radiolabeled substrates into macromolecules. Furthermore, sequestering low molecular weight substrates in some sort of lipid-bound pool may represent a general storage mechanism employed by bacterioplankton. Key words: bacterioplankton, production, San Francisco Bay, filtration, incorporation.
Mechanism and regulation of synthesis of aerobactin in Escherichia coli K12 (pColV-K30)
Authors: Neilands J. B.
Published: May 2010

The aerobactin operon of the virulence plasmid pColV-K30 of Escherichia coli K12 consists of four genes for biosynthesis and one for transport of the siderophore. Regulation by iron occurs at the transcriptional level and is mediated by a ferrous iron binding protein designated Fur (ferric uptake regulation). The metallated Fur repressor binds at a palindromic dyad, the "iron box" operator, situated in the vicinity of the RNA polymerase attachment site of the promoter. Evidence suggests that the ferrous iron enters the C-terminal domain of Fur to cause a conformational change in the N-terminal part of the protein. This results in greatly enhanced affinity of the repressor for the operator. Key words: aerobactin, enterobactin, Fur repressor, regulation, siderophores, virulence.