bluuebunny/crossref_metadata_2025 huggingface dataset:
Multidrug- and metal-resistant strains ofKlebsiella pneumoniaeisolated fromPenaeus monodonof the coastal waters of deltaic Sundarban
Authors: Choudhury Papiya , Kumar Ranajit
Published: April 2011

Marine shrimp of the species Penaeus monodon were collected from the coastal region (Haroa) of the deltaic Sundarbans of West Bengal, India during the premonsoon period in 1996. Klebsiella pneumoniae was isolated from the alimentary canal and gills of the shrimp as the sole isolate. All 10 isolated strains were resistant to erythromycin (30 μg/mL), ampicillin (100 μg/mL), furazolidone 100 μg/mL), and penicillin (100 IU). These strains were able to grow in the presence of silver (Ag+), cobalt (Co2+), cadmium (Cd2+), nickel (Ni2+), lead (Pb2+), copper (Cu2+), zinc (Zn2+) at concentrations up to 10 mM. All the strains showed similar plasmid profiles, ranging in sizes from 1.8 to 120 kb. Resistance to lead, cobalt, nickel, and copper was encoded by a 3.5-kb plasmid of K. pneumoniae. Synthesis of a 14-kDa periplasmic protein was increased when they were grown in presence of 10 mM Cu2+.Key words: Klebsiella pneumoniae, drug resistance, metal resistance, periplasmic protein, plasmid, transformation.
Metschnikowia continentalisvar.borealis,Metschnikowia continentalisvar.continentalis, andMetschnikowia hibisci, new heterothallic haploid yeasts from ephemeral flowers and associated insects
Authors: Lachance Marc-André , Rosa Carlos A , Starmer William T , Schlag-Edler Birgit , Baker J Stuart F. , Bowles Jane M
Published: April 2011

Several strains of three new taxa of haploid heterothallic yeasts have been isolated from various ephemeral flowers and associated insects in North and South America and Australia. Metschnikowia continentalis comprises two varieties and is a close relative of Metschnikowia hawaiiensis. Like the latter, it produces giant ascospores and lives in association with the insects that colonize flowers of the family Convolvulaceae. These species exhibit an unusual asymmetrical mating, but their rare asci are sterile. The varieties of M. continentalis undergo unlimited mating, but ascospores are rarely formed. Metschnikowia continentalis var. continentalis was isolated in central Brazil and is thought to occur across South America.Metschnikowia continentalis var. borealis was recovered in the Great Lakes area and may represent a North American population. Metschnikowia hibisci was found in the flowers and insects of various Hibiscus species in the Australian states of New South Wales and Queensland but appeared to be absent in members of the Convolvulaceae growing in the same areas. The latter forms intermediate-sized ascospores and one of its mating types forms conjugation tubes in the presence of cells of other Metschnikowia species. The three taxa share with M. hawaiiensis a large deletion in the D2 region of their large ribosomal DNA subunit, but in M. hibisci, the variable domain of the D2 region shares little, if any, sequence similarity with others. The type cultures are as follows:M. continentalis var. continentalis strains UFMG96-173 (h+, CBS8429) and UFMG96-179 (h-, CBS8430); M. continentalis var. borealis strains UWO(PS)96-104.2 (h+, CBS 8431) and UWO(PS)96-101.1 (h-, CBS8432); and M. hibisci strains UWO(PS)95-797.2 (h+, CBS8433) and UWO(PS)95-805.1 (h-, CBS8434).Key words: Metschnikowia, yeast, Convolvulaceae, Hibiscus, geographic speciation.
TheCampylobacter fetusS layer is not essential for initial interaction with HEp-2 cells
Authors: Graham Lori L , MacDonald K L
Published: April 2011

In vitro adherence assays were used to determine whether the S layer mediated interactions between Campylobacter fetus subsp. venerealis strains and HEp-2 cells. At multiplicity of infection ratios ranging from 0.1:1 through 100:1, quantitation of bacterial adherence by light microscopy revealed that S layer deficient isogenic C. fetus 809K and C. fetus 810K were not less efficient in their attachment to HEp-2 cells; either S layer deficient C. fetus strains interacted with HEp-2 cells in greater numbers than the corresponding wild-type parent strains 809 and 810 or there was no significant difference in adherence levels between wild-type and mutant strains. Adherence of C. fetus strains to HEp-2 cells increased most during the first 2 h of a 22-h incubation period with only a slight increase in C. fetus cell numbers occuring subsequent to 2 h. At each assay point throughout this 22-h time period, equivalent numbers of wild-type and S layer deficient C. fetus strains were observed associated with HEp-2 cells. Prior to 2 h, adherence levels of all C. fetus strains exceeded those of Escherichia coli AB264 and Salmonella typhimurium SL1344. And, unlike S. typhimurium, C. fetus did not undergo significant replication following initial adherence to HEp-2 cells. Campylobacter fetus did not adhere to HEp-2 cells in a localized or aggregative pattern but were randomly distributed over individual HEp-2 cells and at no time during the assay with C. fetus were changes in HEp-2 cell morphology apparent. These data suggest that the S layer is not essential for mediating initial interactions between C. fetus and HEp-2 cells.Key words: Campylobacter fetus, S layer, HEp-2.
Biodegradation of dibenzothiophene by a nodulating isolate of Rhizobium meliloti
Authors: Frassinetti Stefania , Setti Leonardo , Corti Andrea , Farrinelli Paolo , Montevecchi Piercarlo , Vallini Giovanni
Published: April 2011

Rhizobium meliloti Orange 1 was isolated from aerobic sediments of a drainage ditch receiving oil refinery leakage. This bacterium has been shown to be capable of growing on dibenzothiophene as the sole carbon and energy source. This strain can also efficaciously nodulate alfalfa plants. In cultures with dibenzothiophene, Orange 1 produces six degradation intermediates. By means of analyses with UV-visible and GC-MS spectrometry, as well as nuclear magnetic resonance spectroscopy, three of these products were identified as 3-hydroxy-2-formyl-benzothiophene (product A), benzothienopyran-2-one (product B'), and dibenzothiophene-5-oxide (product D). This suggests that R. meliloti Orange 1 metabolizes dibenzothiophene via oxidative cleavage of the aromatic ring with a mechanism analogous to that described for naphthalene degradation.Key words: biodegradation, dibenzothiophene, Rhizobium.
A comparative study of carrot root tissue colonization and cell wall degradation by Pythium violae and Pythium ultimum, two pathogens responsible for cavity spot
Authors: Campion C , Vian B , Nicole M , Rouxel F
Published: April 2011

The process of infection of carrots by Pythium violae and Pythium ultimum, two causes of cavity spot, is described. The first species causes limited root necrosis, the second progressive root rot. Colonization by both species was intracellular and limited within the tissues. Modes of cell wall degradation were studied by staining (PATAg test) and labeling techniques. Pectins were labeled with monoclonal antibodies and cellulose with an exoglucanase-gold complex. Cell wall polysaccharides were degraded differently by the two species. Pythium violae was responsible for degradations, which could be noticeable, especially for high methylesterified pectins, but which occurred after colonization and were localized near the hyphae. The conservation of integrity of diseased tissue was apparently due to the absence of degradation away from the hyphae. In contrast, P. ultimum was responsible for more extensive degradation of pectins and cellulose, which occurred at a relatively greater distance from the hyphae. Degradation of pectins was always more rapid in the cell walls than in the intercellular junctions. This phenomenon led to loss of tissue integrity and could explain the tissue maceration caused by P. ultimum infection. These differences in infection process are discussed in connection with the enzymic potential for degradation of cell wall polysaccharides.Key words: Daucus carota L., Pythium, pectin, cellulose, cytochemistry.
A very rapid enzyme immunoassay for confirmation of rhizobial identity and estimation of cell numbers in fresh broth culture
Authors: Olsen Perry E , Sande Eve S , Keyser Harold H , Singleton Paul W , Rice Wendell A
Published: April 2011

An enzyme immunoassay has been developed that confirms identity and estimates cell numbers of Bradyrhizobium japonicum and Rhizobium leguminosarum bv. viciae in broth culture. Total testing time required is less than 10 min and no specialized equipment is required. The assay involves a simultaneous and brief reaction of cells, primary antibody, and secondary antibody - enzyme conjugate in aqueous suspension, after which the cells are captured on a 0.45- µm-pore-size syringe filter membrane. Upon addition of enzyme substrate, cell-bound antibody-enzyme conjugate converts the substrate to a blue-green reaction product within the transparent body of the syringe filter. The assay can be quantified by stopping the reaction with acid, extracting the coloured substrate reaction product from the syringe filter, and measuring absorbance using a spectrophotometer. The assay was developed using cultures of rhizobia and bradyrhizobia but should be applicable to liquid cultures of most microorganisms.Key words: Bradyrhizobium, enzyme immunoassay, Rhizobium, syringe filter.
Phenotypic variation and survival of genetically marked Pseudomonas tolaasii in mushroom compost
Authors: Wu Rong Mei , Palmer Barry , Cole Anthony
Published: April 2011

The role of Pseudomonas tolaasii as an important pathogen of the common mushroom Agaricus bisporus is difficult to study in the microbially complex growth medium used for mushroom production. Two strains of P. tolaasii that had been marked with kanamycin resistance and xylE genes were introduced individually into casing soil over mushroom compost. Survival studies revealed that P. tolaasii numbers in casing soil over mushroom compost decreased a 1000-fold in the first 9 days and then remained relatively stable over the rest of the monitoring period. The presence of the pathogenic colony form and the nonpathogenic colony variant was monitored on mushroom caps and in mushroom compost to detect any phenotypic variation while incubated in these environments. Reversion from the nonpathogenic to pathogenic form was detected following isolation and culture from diseased mushroom caps. Inoculation of the marked strains directly onto the cap or into compost beds seeded with A. bisporus resulted in the appearance of brown blotch symptoms.Key words: Pseudomonas tolaasii, Agaricus bisporus, phenotypic variation, mushroom disease.
The separation of alginate biosynthesis and acetylation in Pseudomonas syringae
Authors: Lee Jin W , Day F
Published: April 2011

Seaweed alginate was acetylated by resting cells of Pseudomonas syringae subsp. phaseolicola ATCC 19304. Physiological studies on this strain and its UV-induced mutants showed no correlation between bacterial alginate biosynthesis and acetylation. Specific yields of alginate and degree of acetylation in these polymers varied with strain and culture medium. This was indirect evidence that alginate biosynthesis is separate from polysaccharide acetylation. It indicated that the enzyme system involved in alginate biosynthesis was not directly linked to alginate acetylation and explained why microbial acetylation of seaweed alginates was possible.Key words: resting cell, Pseudomonas syringae, acetylation, bacterial alginate, seaweed alginate.
Cloning of clusteredStreptomyces viridosporusT7A lignocellulose catabolism genes encoding peroxidase and endoglucanase and their extracellular expression inPichia pastoris
Authors: Thomas Latha , Crawford Don L
Published: April 2011

A 4.1-kb fragment of chromosomal DNA from the lignocellulose-decomposing actinomycete Streptomyces viridosporus T7A was previously found to encode a lignin peroxidase gene. However, when cloned into Escherichia coli in pBSKS+, peroxidase activity was not expressed. When cloned in pIJ702 in Streptomyces lividans, the gene was expressed in a peroxidase positive background, owing to the production by S. lividans of its own extracellular peroxidases. To circumvent these problems, the DNA was cloned into the commercial expression vector pIC9 for extracellular expression in the yeast Pichia pastoris. Yeast transformants, however, expressed two activities, extracellular peroxidase and an extracellular endoglucanase. The enzymes were not expressed by the yeast cells alone or by yeast cells with pIC9 without the insert. Expression of the enzymes by only those transformants expressing the 4.1-kb DNA was confirmed by Western blot analyses, by nondenaturing activity gel staining, and by spectrophotometric enzyme assays of extracellular culture filtrates. Activity gel staining showed that the two activities resided in different proteins and the peroxidase expressed was similar to ALip-P3, one of the isoenzymes of lignin peroxidase of the S. viridosporus T7A wildtype. Other evidence indicated that in the transformants, the peroxidase and endoglucanase genes in the 4.1-kb insert were controlled by the methanol-inducible AOX1 yeast promoter in pIC9, since their expression was induced by methanol. In the best transformants, extracellular production of peroxidase by recombinant P. pastoris cultures was significantly higher than typically observed in S. viridosporus. The results also indicate that lignocellulose catabolism genes may be clustered on the S. viridosporus chromosome.Key words: lignocellulose, degradation, Streptomyces, peroxidase, endoglucanase, cloning, pIC9, Pichia pastoris.
Biometric analysis of physiologically structured pure bacterial cultures recovering from starvation
Authors: Wilhelm Ralf , Heller Olaf , Bohland Manuela , Tomaschewski Cordula , Klein Inge , Klauth Peter , Tappe Wolfgang , Groeneweg Joost , Soeder Carl Johannes , Jansen Paul , Meyer Wolfgang
Published: April 2011

Cell volume distribution patterns were used to characterize the status of physiologically heterogeneous monospecific populations of bacteria. Such physiologically structured populations typically consist of subpopulations of cells in different metabolic and regulatory states. During recovery from starvation the differentiation of active (growing, proliferating) and quiescent (nonproliferating) subpopulations becomes detectable. Since cell volume distributions may be distorted by background noise or debris, we developed a method to extrapolate size distributions from a reduced set of reliable data. The extrapolation procedure is based upon a lognormal distribution of cell sizes. By the same approach we were able to differentiate between subpopulations even when their size ranges overlapped. The analyses of size distributions were also used, partly in combination with fluorescence microscopy, to investigate the population dynamics of Pseudomonas fluorescens and Nitrosomonas europaea during recovery from energy deprivation.Key words: physiologically heterogeneous populations, cell volume distribution, population dynamics, Pseudomonas fluorescens, Nitrosomonas europaea.
ThephbC(poly-β-hydroxybutyrate synthase) gene ofRhizobium(Sinorhizobium)melilotiand characterization ofphbCmutants
Authors: Willis Laura B , Walker Graham C
Published: April 2011

Defined insertion mutations have been constructed in theRhizobium (Sinorhizobium) meliloti phbC gene, which encodes poly-β-hydroxybutyrate (PHB) synthase. The locus was isolated and subcloned from a genomic library of R. meliloti Rm1021 by complementation of a phbC mutation of Alcaligenes eutrophus. PHB production was detected in wild-type R. meliloti under nutrient-limited conditions but not in rich medium. No PHB production was detected in the R. meliloti phbC mutants. The DNA sequence of the R. meliloti phbC gene was determined. The deduced polypeptide sequence is homologous to previously identified PhbCs from other bacteria. The R. meliloti phbC locus maps to pRmeSU47a, the smaller of the two megaplasmids in this strain.Key words: Rhizobium meliloti, PHB, PHA, poly-β-hydroxybutyrate, phbC.
Chitin as an indicator of the biomass of two wood-decay fungi in relation to temperature, incubation time, and media composition
Authors: Nilsson Kent , Bjurman Jonny
Published: April 2011

Cell wall chitin was determined in the mycelia of the brown rot fungus Neolentinus lepideus (Lentinus lepideus) and an isolate of the soft rot fungus Phialophora sp. to study the correlation to mycelial dry mass. The fungi were incubated as liquid cultures for three incubation periods at three temperatures in six nutrient media with varying levels and combinations of carbon and nitrogen. The glucosamine yield was found to be maximized by hydrolysis at 90°C for 48 h. The chitin content in the studied fungi varied from 8.3 to 39.8 μg.mg-1for N. lepideus and 7.7 to 46 μg.mg-1for the Phialophora isolate. The chitin concentration was remarkably constant, about 10 μg.mg-1, in mycelia growing on the low nitrogen malt extract medium. An experiment with wood blocks indicated that chitin may be a good marker for total fungal biomass production, including living and dead mycelia, in early stages of wood decay (dry weight loss <6%). At higher dry weight losses, the chitin content reaches a plateau or decreases despite continuing degradation as determined by the dry weight loss. The chitin content of visible mycelia growing on wood was determined for both fungi and found to be 19.1 and 12.9 μg.mg-1for N. lepideus and the Phialophora isolate, respectively.Key words: chitin, wood-decay fungi, utility poles, brown rot, soft rot, glucosamine, colorimetry.
Incidence of enteroviruses in Mamala Bay, Hawaii using cell culture and direct polymerase chain reaction methodologies
Authors: Reynolds Kelly A , Roll Kimberly , Fujioka Roger S , Gerba Charles P , Pepper Ian L
Published: April 2011

The consequence of point and nonpoint pollution sources, discharged into marine waters, on public recreational beaches in Mamala Bay, Hawaii was evaluated using virus cell culture and direct reverse transcriptase - polymerase chain reaction (RT-PCR). Twelve sites, nine marine, two freshwater (one stream and one canal), and one sewage, were assessed either quarterly or monthly for 1 year to detect the presence of human enteric viruses. Water samples were concentrated from initial volumes of 400 L to final volumes of 30 mL using Filterite electronegative cartridge filters and a modified beef extract elution procedure. Cell culture was applied using the Buffalo Green Monkey kidney cell line to analyze samples for enteroviruses. Positive samples were also evaluated by RT-PCR, using enterovirus-specific primers. Levels of RT-PCR inhibition varied with each concentrated sample. Resin column purification increased PCR detection sensitivity by at least one order of magnitude in a variety of sewage outfall and recreational marine water samples but not in the freshwater canal samples. Using cell culture, viable enteroviruses were found in 50 and 17% of all outfall and canal samples, respectively. Samples were positive at beaches 8% of the time. These data illustrate the potential public health hazard associated with recreational waters. Using direct PCR, viruses were detected at the outfall but were not found in any beach or canal samples, in part, owing to substances that inhibit PCR. Therefore, conventional cell culture is the most effective means of detecting low levels of infectious enteroviruses in environmental waters, whereas direct RT-PCR is rendered less effective by inhibitory compounds and low equivalent reaction volumes.Key words: enteroviruses, RT-PCR, cell culture, marine waters.
Production of metabolites from chlorobiphenyls by resting cells ofPseudomonasstrain LB400 after growth on different carbon sources
Authors: Billingsley K A , Backus S M , Ward O P
Published: April 2011

Cells of Pseudomonas strain LB400, grown on biphenyl, glucose, or glycerol, transformed polychlorinated biphenyl (PCB) congeners into chlorobenzoic acid (CBA) metabolites. Transformation of the PCB congeners, 2,3-chlorobiphenyl (CBP), 2,2'-CBP, 2,5,4'-CBP, and 2,4,2',4'-CBP, produced the metabolites, 2,3-CBA, 2-CBA, 4-CBA, and 2,4-CBA, respectively. Rates and extents of PCB transformation and metabolite formation were highest with biphenyl-grown cells. Intermediate rates of metabolite production were observed with glycerol-grown cells, and lowest rates of production were found with glucose-grown cells. Regardless of carbon source, the rate of degradation of congeners was faster than the rate of production of CBAs. Relative rates of PCB transformation and metabolite production from different congeners with cells grown on a particular substrate followed the same general order, 2,3-CBA (from 2,3-CBP) > 2-CBA (from 2,2'-CBP) > 4-CBA (from 2,5,4'-CBP) > 2,4-CBA (from 2,4,2',4'-CBP). Pseudomonas strain LB400 appeared unable to grow on any of the chlorobenzoic acids. However, Pseudomonas strain LB400 cells grown on biphenyl appeared capable of degrading 2-CBA and 2,3-CBA but not 4-CBA nor 2,4-CBA. Cells grown on glycerol appeared unable to metabolize any CBAs.Key words: polychlorinated biphenyls, metabolites, Pseudomonas LB400.
Kodamaea kakaduensisandCandida tolerans, two new ascomycetous yeast species from AustralianHibiscusflowers
Authors: Lachance Marc-André , Bowles Jane M , Starmer William T , Barker J Stuart F.
Published: April 2011

Two new yeast species were isolated from flowers of Hibiscus species in Eastern and Northern Australia. Kodamaea kakaduensis is heterothallic, haploid, and similar to other Kodamaea species and to Candida restingae. Buds are often produced on short protuberances, and a true mycelium is formed. The new species differs from others by the assimilation of trehalose, melezitose, and xylitol, and is reproductively isolated. The cells of Candida tolerans are small and a pseudomycelium is formed. The carbon and nitrogen assimilation pattern is reminiscent of that of Zygosaccharomyces rouxii but the two are not closely related. Sequences of the D1/D2 domain of large subunit ribosomal DNA confirm the membership of K. kakaduensis in the genus Kodamaea and indicate that C. tolerans belongs to the Clavispora-Metschnikowia clade, with a moderate relatedness to Candida mogii. The type strains are: K. kakaduensis, UWO(PS)98-119.2 (h+, holotype, CBS 8611) and UWO(PS)98-117.1 (h-, isotype, CBS 8612); and C. tolerans, UWO(PS)98-115.5 (CBS 8613).Key words: Kodamaea, Candida, new yeast species, ribosomal DNA, whole-cell PCR.
Parenteral immunization with a glycoconjugate vaccine containing the O157 antigen ofEscherichia coliO157:H7 elicits a systemic humoral immune response in mice, but fails to prevent colonization by the pathogen
Authors: Conlan J Wayne , Cox Andrew D , KuoLee Rhonda , Webb Ann , Perry Malcolm B
Published: April 2011

The results of the present study show that whereas both BALB/c and C57BL/6 mice parenterally inoculated with a horse serum albumin - Escherichia coli O157 antigen conjugate vaccine develop systemic, specific antibodies to the carrier protein, only the former mice routinely develop antibodies to the carbohydrate O157 moiety. However, little convincing evidence was found to show that these antibodies transuded into the intestinal tract either naturally or in response to an oral inoculum of the pathogen. Moreover, this vaccination procedure failed to protect mice against intestinal colonization following oral challenge with the pathogen. Thus, the results of this study suggest that parenteral vaccination might be an unsuitable strategy for combatting E. coli O157:H7 organisms located in the gut.Key words: Escherichia coli, glycoconjugate vaccine, mice.
Utilization of low molecular weight aromatic compounds by heterobasidiomycetous yeasts: taxonomic implications
Authors: Sampaio J P
Published: April 2011

The utilization of low molecular weight aromatic compounds implies the operation of complex metabolic pathways. In order to investigate the taxonomic relevance of this property among heterobasidiomycetous yeasts, both at the species level and at higher taxonomic ranks, the capacity to assimilate twenty such compounds was tested in a total of 332 strains representing approximately 200 species. The substrates most frequently utilized were protocatechuic, caffeic, and p-hydroxybenzoic acids, whereas cinnamic, sinapic, and syringic acids and guaiacol were never assimilated. The assimilation of the majority of the aromatic compounds investigated correlated with the utilization of protocatechuic acid. Among the Urediniomycetes, the members of the Sporidiales and those of the Naohidea - Rhodotorula minuta clade showed a good ability to utilize aromatic compounds, whereas the members of the Agaricostilbum - Kondoa group were more heterogeneous, in agreement with the four subclades known. Among the Tremellomycetidae, the members of the Cystofilobasidium and Tremella clades showed a reduced or null ability to utilize aromatic compounds. In contrast, the members of the Trichosporon clade were able to utilize phenol and similar substrates, and the representatives of the Filobasidium clade assimilated various aromatic compounds, including those requiring more complex catabolic routes. Assimilation tests using, as sole carbon and energy sources, low molecular weight aromatic compounds appear to be potentially useful in taxonomic studies of basidiomycetous yeasts. In those species in which a considerable number of strains was investigated, variable assimilation patterns were frequently observed. The possibility that such discrepant results indicate an incorrect species delimitation is discussed.Key words: aromatic compounds, yeasts, heterobasidiomycetes, systematics.
Microbial degradation of nitrobenzene and mono-nitrophenol by bacteria enriched from municipal activated sludge
Authors: Zhao Jian-Shen , Ward Owen P
Published: April 2011

Using a mixture of three mono nitrophenols as sole carbon, nitrogen and energy sources, mixed cultures were enriched from municipal activated sludge to degrade both nitrophenols and nitrobenzene. Bacterial growth and degradation rate could be increased by supplementing the medium with 0.1% YE. Microorganisms were isolated from the nitrophenols enrichment, and they were identified as strains of Comamonas testosteroni and Acidovorax delafieldii. These strains showed broad degradation ability toward nitrophenols and nitrobenzene.Key words: biodegradation, nitrobenzene, nitrophenol, Comamonas testosteroni, Acidovorax delafieldii, mixed cultures.
Use of RAPD (random amplified polymorphic DNA) to analyse genetic diversity of dematiaceous fungal pathogens
Authors: Caligiorne Rachel B , Resende Maria A , Paiva Edilson , Azevedo Vasco
Published: April 2011

Thirteen strains of chromoblastomycosis and phaeohyphomycosis etiologic agent fungi were obtained from different geographical origins. These strains were genotypically compared by means of the RAPD (Random Amplified Polymorphic DNA) technique. The data generated showed a high degree of polymorphism between distinct species and a low polymorphism between strains of the same species. The results generated by these tests were subjected to a numerical taxonomy analysis, using the unweighted pair-group method. A phenogram was constructed for the set of strains studied. Based on its structure, we concluded that genotypical data provide enough information to us to use the unweighted pair-group method to cluster the strains in accordance to their respective species. The phenogram grouped in a single branch the strains of Fonsecaea pedrosoi and F. compacta species, indicating a great similarity between these fungi, and suggesting that the classification as distinct species may not be appropriate for these species of the genus Fonsecaea.Key words: chromoblastomycosis, phaeohyphomycosis, dematiaceous fungi, RAPD,Fonsecaea pedrosoi.
Cresol metabolism by the sulfate-reducing bacteriumDesulfotomaculumsp. strain Groll
Authors: Londry Kathleen L , Suflita Joseph M , Tanner Ralph S
Published: April 2011

The metabolism of cresols under sulfate-reducing conditions was investigated in Desulfotomaculum sp. strain Groll. This strain grows on a variety of aromatic compounds, including para- and meta- but not ortho-cresol. Degradation of p-cresol proceeded by oxidation reactions of the methyl group to yield p-hydroxybenzoate, which was then dehydroxylated to benzoate. The aromatic intermediates expected for this pathway, p-hydroxybenzyl alcohol, p-hydroxybenzaldehyde, p-hydroxybenzoate, and benzoate, were readily metabolized by strain Groll. Utilization of these intermediates generally preceded and inhibited the degradation of p-cresol. p-Hydroxybenzoate and benzoate were detected in culture fluid as metabolites of p-cresol. p-Hydroxybenzaldehyde and p-hydroxybenzoate were detected in cultures degrading p-hydroxybenzyl alcohol. Enzyme activities responsible for utilization of p- and m-cresol, induced by growth on the respective cresol, were detected in cell-free extracts of strain Groll. The compounds detected in culture fluids and the enzyme activities detected in cell-free extracts indicate that the pathways for the degradation of p- and m-cresol converge on benzoate, followed by metabolism to benzoyl-coenzyme A (CoA). Strain Groll can utilize both cresol isomers under sulfate-reducing conditions by similar reactions, but the enzyme activities catalyzing these transformations of the two isomers appear distinct.Key words: anaerobic biodegradation, sulfate reduction, Desulfotomaculum, p-cresol, m-cresol, o-cresol, benzoylCoA.
Defects in pyruvate kinase cause a conditional increase of thiamine synthesis inSalmonella typhimurium
Authors: Christian Todd , Downs Diana M
Published: April 2011

As genomic sequence data become more prevalent, the challenges in microbial physiology shift from identifying biochemical pathways to understanding the interactions that occur between them to create a robust but responsive metabolism. One of the most powerful methods to identify such interactions is in vivo phenotypic analysis. We have utilized thiamine synthesis as a model to detect subtle metabolic interactions due to the sensitivity allowed by the small cellular requirement for this vitamin. Although purine biosynthesis produces an intermediate in thiamine synthesis, mutants blocked in the first step of de novo purine biosynthesis (PurF) are able to grow in the absence of thiamine owing to an alternative synthesis. A number of general metabolic defects have been found to prevent PurF-independent thiamine synthesis. Here we report stimulation of thiamine-independent growth caused by a mutation in one or both genes encoding the pyruvate kinase isozymes. The results presented herein represent the first phenotype described for mutants defective in pykA or pykF, and thus identify metabolic interactions that exist in vivo.Key words: thiamine synthesis, metabolic integration.
An endogenous periodicity exhibited in the activity of a natural bacterioplankton community isolated in mesocosms
Authors: Chatila Khaled , Demers Serge , Mostajir Behzad , Chanut Jean-Pierre , Monfort Patrick
Published: April 2011

In July 1996, bacterial abundance and incorporation of [3H]thymidine (3H-TdR) were determined every 4 h during a mesocosm experiment initially designed to study the effects of different intensities of ultraviolet-B (UVB) radiation on the summer planktonic community of the lower St. Lawrence Estuary. Water was obtained from the quay of the Maurice Lamontagne Institute (Mont-joli, Qué.) and incubated in experimental mesocosms (1500 L total volume, n = 8) with continuous mixing provided by a pumping system. During 72 h, different UVB intensities showed no significant effects on the bacterial incorporation of3H-TdR. This indicates that in the presence of other trophic levels and with continuous mixing, bacterioplankton responses to UVB are substantially different from those reported in axenic bacterial cultures or even whole-water incubations exposed to UVB at fixed depths. In conjunction with this observation,3H-TdR incorporation exhibited a significant periodic variation within all experimental treatments. The periodicity consisted of a 16-h cycle occurring independently of the time of the day. When the3H-TdR incorporation was normalized to cell abundance, the resulting cell-specific thymidine incorporation exhibited the same periodic oscillatory pattern. On the other hand, other factors suspected of inducing such a variability showed no consistent oscillation. In addition to suggesting an endogenously controlled activity of the studied bacterial community, the results of the present study indicate that failure of taking temporal variations of bacterial activity into account may introduce an error of almost 50% in the estimation of the daily thymidine incorporation rates. This represents a considerable error, because several studies rely on this measurement to estimate bacterial carbon production and to establish carbon budgets within different oceanic provinces.Key words: bacterioplankton, [3H]thymidine, ultraviolet-B radiation, periodicity, endogenous cycles, St. Lawrence Estuary.
Recovery of a rhizosphere-colonizing GEM from inside wheat roots
Authors: Nairn James D , Chanway Christopher P
Published: April 2011

Pseudomonas chloroaphis 3732 RN-L11 is a genetically modified bacterial strain that contains the lacZY marker genes in its chromosome. This strain is known to be a vigorous colonizer of plant roots and rhizosphere soil, and has been used as a model to evaluate survival and persistence of field-released genetically engineered microorganisms (GEMs). However, the possibility that strain 3732 RN-L11 may also colonize internal plant tissues has not previously been investigated. Using spring wheat as a model system, we studied the ability of strain 3732 RN-L11 to colonize external and internal root tissues after seed inoculation. Strain 3732 RN-L11 was recovered from rhizosphere soil of 28-, 42-, and 56-day-old seedlings with mean population sizes of 3.3 × 105, 7.5 × 104, and 2.2 × 105CFU·g-1fresh root tissue, respectively. In addition, this strain was consistently recovered from surface-sterilized root tissues of 28- to 56-day-old seedlings with mean population sizes of 1.0 × 102to 6.2 × 103CFU·g-1fresh root tissue. Our results indicate that evaluation of plant-associated GEM populations after field release should include all possible colonization niches, including internal plant tissues.Key words: genetically engineered microorganism, rhizosphere, endophyte.
Induction and development of the oil emulsifying system in an alkane oxidizing Rhodococcus species
Authors: Bredholt Harald , Eimhjellen Kjell
Published: April 2011

The physiological criteria for the development of crude oil emulsifying activity in a Rhodococcus species isolated from sea water was investigated. The bacterium was used as a model organism and all experiments were performed in shake flasks at 30°C. The development of emulsifying activity was inducible, but only under conditions of cell growth. A test was developed for assessing the ability of different chemical compounds to induce the crude oil emulsifying activity in acetate pre-grown cells, and a comprehensive survey of possible inducers carried out. The compounds that gave excellent or good emulsification in the test assay included n-alkanes (C11 to C18), pristane, 1-decene, fatty alcohols (C14 to C18), the fatty aldehydes decanal and dodecanal, some unsaturated fatty acids and some oils containing glycerol esters of unsaturated fatty acids. All these compounds also served as sole carbon and energy sources. Alkanes and fatty acids behaving as solids at 30°C did not function as inducers in the assay. Heptamethylnonane served as a moderate inducer, but not as a growth substrate. The inducers had to be present in the concentration range of 0.01 to 0.05% (w/v) in order to give a detectable emulsion under the conditions of the assay. The development of the emulsifying activity, hypothesised to comprise compounds from the hydrophobic cell surface, is suggested to be coordinated with new cell wall synthesis.Key words: emulsification, crude oil, inducers, alkane-oxidation, bacteria.
Bacterial population dynamics, production, and heterotrophic activity in a recently formed reservoir
Authors: Jugnia Louis B , Tadonléké Rémy D , Sime-Ngando T , Devaux J , Andrivon C
Published: April 2011

Seasonal and spatial fluctuations in abundance, biomass production, and potential heterotrophic activity (i.e., 14C-glucose uptake) of bacterioplankton assemblages in a 1-year-old reservoir (the Sep Reservoir, Puy-de-Dôme, France) were examined concurrently with water temperature, phytoplankton chlorophyll a concentration, and primary production (PP). Based on the values observed for these biological variables, the Sep Reservoir was considered to have evolved to an oligo-mesotrophic state. Spatiotemporal variations of bacterial variables were a consequence of the seasonal evolution of the reservoir coupled with the resource availability. Multivariate regression analyses suggest that about 14 and 26% of the variance in bacterial standing stock and activity may be explained by the physical environment (i.e., temperature) and a resource availability index (chlorophyll a concentration or primary production), respectively. A carbon budget indicated that 4-126% (mean = 20%) of the ambient PP may be channeled through the microbial loop via bacterial biomass production. Heterotrophic bacterial production in the Sep Reservoir may therefore, on occasion, represent a significant source of carbon for higher order consumers.Key words: reservoirs, plankton, bacteria, heterotrophic uptake, primary and bacterial production.
Phylogenetic analyses of Bradyrhizobium strains nodulating soybean (Glycine max) in Thailand with reference to the USDA strains of Bradyrhizobium
Authors: Ando Shotaro , Yokoyama Tadashi
Published: April 2011

To elucidate the phylogenetic relationships between Thai soybean bradyrhizobia and USDA strains of Bradyrhizobium, restriction fragment length polymorphism (RFLP) analysis using the nifDK gene probe and sequencing of the partial 16S rRNA gene were performed. In our previous work, Thai isolates of Bradyrhizobium sp. (Glycine max) were separated clearly from Bradyrhizobium japonicum and Bradyrhizobium elkanii based on the RFLP analysis using the nodDYABC gene probe. RFLP analysis using the nifDK gene probe divided 14 Thai isolates and eight USDA strains of B. japonicum into different groups, respectively, but categorized into the same cluster. All of seven strains within these Thai isolates had the same sequence of the partial 16S rRNA gene, and it was an intermediate sequence between those of B. japonicum USDA 110 and B. elkanii USDA 76T. Furthermore, three USDA strains of B. japonicum, USDA 6 (B. japonicum ATCC 10324T), USDA 115 and USDA 129, had the same partial 16S rRNA gene sequence that seven Thai isolates had. These results suggest that Thai isolates of Bradyrhizobium sp. (Glycine max) are genetically distinct from USDA strains of B. japonicum and B. elkanii, but also indicate a close relationship between Thai isolates and USDA strains of B. japonicum.Key words: Bradyrhizobium, 16S rRNA gene, nif gene, soybean, Thailand.
Cloning and analysis of the aroB gene encoding dehydroquinate synthase from Corynebacterium glutamicum
Authors: Han Min-Ah , Lee Heung-Shick , Cheon Choong-Ill , Min Kyung-Hee , Lee Myeong-Sok
Published: April 2011

The aroB gene encoding dehydroquinate synthase of Corynebacterium glutamicum has been cloned by complementation of an aro auxotrophic mutant of Escherichia coli with the genomic DNA library. The recombinant plasmid contained a 1.4-kb fragment that complemented the Escherichia coli dehydroquinate-synthase-deficient mutant. The nucleotide sequences of the subcloned DNA has been determined. The sequences contain an open reading frame of 360 codons, from which a protein with a molecular mass of about 38 kDa could be predicted. This is consistent with the size of the AroB protein expressed in E. coli. Alignment of different prokaryotic and eukaryotic aroB gene products reveals an overall identity ranging from 29 to 57% and the presence of several highly conserved regions.Key words: Corynebacterium glutamicum, aromatic amino acid biosynthetic gene, dehydroquinate synthase, aroB gene.
Effects of low temperature on growth parameters in the entomopathogenic fungus Metarhizium anisopliae
Authors: Amritha De Croos J N , Bidochka Michael J
Published: April 2011

The effects of temperature (8°C, 15°C, and 22°C) on germination, growth rate and conidia production in thirty-two isolates of the entomopathogenic fungus Metarhizium anisopliae were assessed. Most isolates were obtained from various locations in Ontario, Canada. Ten out of thirty-two (31.3%) isolates were deemed cold-active because of their ability to grow at 8°C. Growth rates in all isolates increased as the incubation temperature was increased. There were significant differences in growth rates and conidia production among isolates. However, conidia production had no relationship with a growth rate. With respect to the geographical origin, there was no general relationship between latitude and growth rates. However, we found that all the cold-active isolates were isolated from the more northern sites and no isolate originating below 43.5° latitude showed cold activity. Cold-active germination and growth of this biocontrol fungus have implications for strain selection and application in Canadian insect control efforts.Key words: Metarhizium anisopliae, cold activity, entomopathogen.
Immunosuppression by a corticosteroid fails to exacerbate Helicobacter pylori infection in a mouse model of gastric colonization
Authors: Conlan J Wayne , KuoLee Rhonda , Webb Ann , Perry Malcolm B
Published: April 2011

Helicobacter pylori can colonize the human stomach for prolonged periods of time, and this colonization uniformly leads to the development of chronic active gastritis. In a small percentage of individuals, gastric pathology progresses to peptic ulceration or more rarely certain gastric cancers. In addition to non-specific inflammation, specific systemic and local immunity develops in response to gastric colonization by this pathogen. However, these responses combined appear inadequate for eliminating H. pylori from the gastric mucosa. This is also the case in a mouse model of gastric colonization by H. pylori. In the present study, we attempted to determine whether the mammalian host response to infection with H. pylori exerts any overt antibacterial effects. To this end we examined H. pylori colonization in normal mice, and mice immunosuppressed by treatment with a corticosteroid. Despite obvious suppression of the immune response in the latter mice, H. pylori burdens remained similar in both groups after three months of colonization. This suggests that the murine host response, at least, exerts little obvious protection against H. pylori colonization.Key words: Helicobacter pylori, immunosuppression, mice.
16S rDNA restriction fragment length polymorphism analysis of psychrotrophic vibrios from Japanese coastal water
Authors: Urakawa Hidetoshi , Kita-Tsukamoto Kumiko , Ohwada Kouichi
Published: April 2011

Restriction fragment length polymorphism (RFLP) analysis was carried out for 136 natural isolates belonging to the family Vibrionaceae. These were collected from inshore areas of Japan, mainly in winter. Twenty-eight 16S rDNA genotypes were obtained by digestion with four restriction endonucleases (HhaI, DdeI, RsaI, and Sau3AI). To estimate the genetic relationships, 53 informative fragments were scored by their presence or absence. A dendrogram was constructed using the unweighted pair group method with the arithmetic averages algorithm. Five RFLP groups (groups I to V) were obtained. Group I corresponded to Vibrio splendidus-like strains. It was confirmed that this group was not only found in Otsuchi Bay, but also in broad coastal areas of Japan. Group II strains were not identified as previously known Vibrio species. Group III strains were regarded as members of the Vibrio main group, which is a major phylogenetic group deduced from 16S rRNA gene analysis in the family Vibrionaceae. The RFLP profile indicated that Group IV strains were closely related to V. hollisae. Group V strains showed RFLP patterns which have not been observed previously. From the clustering analysis, it was concluded that group V strains were not Vibrio species. Most of the isolates studied were not identified as previously described species. It suggests that many psychrotrophic vibrios in cold marine environments remain as unknown species.Key words: Vibrio, vibrios, psychrotroph, restriction fragment length polymorphism (RFLP) analysis, Vibrio splendidus.
Three new ascomycetous yeasts from insect-associated arboreal habitats
Authors: Kurtzman C P
Published: April 2011

A new species of Pichia and two new species of Candida are described and were determined to be genetically isolated from all other currently recognized ascomycetous yeasts from their sequence divergence in the species-variable D1/D2 domain of large subunit (26S) ribosomal DNA. The three species were primarily isolated from the frass of wood-boring insects living in pine and spruce trees. The new species and their type strains are the following: Pichia ramenticola NRRL YB-1985 (CBS 8699), mating type alpha (NRRL YB-3835, CBS 8700, mating type a), Candida piceae NRRL YB-2107 (CBS 8701), and Candida wyomingensis NRRL YB-2152 (CBS 8703). Pichia ramenticola and C. piceae assimilate methanol as a carbon source; P. ramenticola is the first known heterothallic ascomycetous yeast to utilize this compound.Key words: Pichia, Candida, new yeast species, ribosomal DNA, molecular systematics, methanol utilization.
Evidence for plasmid-mediated chemotaxis ofPseudomonas putidatowards naphthalene and salicylate
Authors: Samanta Sudip K , Jain Rakesh K
Published: April 2011

A naphthalene (Nap) and salicylate (Sal) degrading microorganism, Pseudomonas putida RKJ1, is chemotactic towards these compounds. This strain carries a 83 kb plasmid. A 25 kb EcoRI fragment of the plasmid contains the genes responsible for Nap degradation through Sal. RKJ5, the plasmid-cured derivative of RKJ1, is neither capable of degradation nor is chemotactic towards Nap or Sal. The recombinant plasmid pRKJ3, which contained a 25 kb EcoRI fragment, was transferred back into the plasmid-free wild-type strain RKJ5, and the transconjugant showed both degradation and chemotaxis. The recombinant plasmid pRKJ3 was also transferred into motile, plasmid-free P. putida KT2442. The resulting transconjugant (RKJ15) showed chemotaxis towards both Nap and Sal. Two mutant strains carrying deletions in pRKJ3 (in KT2442) with phenotypes Nap-Sal+and Nap-Sal-, were also tested for chemotaxis. It was found that the Nap-Sal+mutant strain showed chemotaxis towards Sal only, whereas the Nap-Sal-mutant strain is non-chemotactic towards both the compounds. These results suggest that the metabolism of Nap and Sal may be required for the chemotactic activity.Key words: Pseudomonas putida, plasmid-encoded chemotaxis, naphthalene, salicylate.
Inactivation of maltose permease and maltase in sporulatingSaccharomyces cerevisiae
Authors: Ferreira Julio C , Panek Anita D , de Araujo Pedro S
Published: April 2011

Maltose transport and maltase activities were inactivated during sporulation of a MAL constitutive yeast strain harboring different MAL loci. Both activities were reduced to almost zero after 5 h of incubation in sporulation medium. The inactivation of maltase and maltose permease seems to be related to optimal sporulation conditions such as a suitable supply of oxygen and cell concentration in the sporulating cultures, and occurs in the fully derepressed conditions of incubation in the sporulation acetate medium. The inactivation of maltase and maltose permease under sporulation conditions in MAL constitutive strains suggests an alternative mechanism for the regulation of the MAL gene expression during the sporulation process.Key words: maltase activity, maltose permease activity, sporulation, Saccharomyces cerevisiae.