bluuebunny/crossref_metadata_2025 huggingface dataset:
Utilization of heterologous siderophores and rhizosphere competence of fluorescentPseudomonasspp.
Authors: Raaijmakers Jos M. , Sluis Lentse van der , Bakker Peter A. H. M. , Schippers Bob , Koster Margot , Weisbeek Peter J.
Published: October 2009

In this study, the potential of different Pseudomonas strains to utilize heterologous siderophores was compared with their competitiveness in the rhizosphere of radish. This issue was investigated in interactions between Pseudomonas putida WCS358 and Pseudomonas fluoresceins WCS374 and in interactions between strain WCS358 and eight indigenous Pseudomonas strains capable of utilizing pseudobactin 358. During four successive plant growth cycles of radish, strain WCS358 significantly reduced rhizosphere population densities of the wild-type strain WCS374 by up to 30 times, whereas derivative strain WCS374(pMR), harboring the siderophore receptor PupA for ferric pseudobactin 358, maintained its population density. Studies involving interactions between strain WCS358 and eight different indigenous Pseudomonas strains demonstrated that despite the ability of these indigenous isolates to utilize pseudobactin 358, their rhizosphere population densities were significantly reduced by strain WCS358 by up to 20 times. Moreover, rhizosphere colonization by WCS358 was not affected by any of these indigenous strains, even though siderophore-mediated growth inhibition of WCS358 by a majority of these strains was demonstrated in a plate bioassay. In conclusion, it can be stated that siderophore-mediated competition for iron is a major determinant in interactions between WCS358 and WCS374 in the rhizosphere. Moreover, our findings support the common assumption that cloning of siderophore receptor genes from one Pseudomonas strain into another can confer a competitive advantage in interactions in the rhizosphere. Interactions between WCS358 and the selected indigenous rhizosphere isolates, however, indicate that other traits also contribute to the rhizosphere competence of fluorescent Pseudomonas spp.Key words: siderophore, siderophore receptors, root colonization, fluorescent Pseudomonas.
The identification of bacterial gene expression differences using mRNA-based isothermal subtractive hybridization
Authors: Utt Eric A. , Brousal Jeffery P. , Kikuta-Oshima Lynne C. , Quinn Frederick D.
Published: October 2009

We describe a method for isolating and determining differences in gene expression between related bacterial strains. The method is based upon differences in mRNA expression. To demonstrate this procedure, cDNA generated from total RNA of Listeria monocytogenes serotype 1/2a was hybridized to total RNA from a Tn916 mutant of serogroup 1/2a (M3) that was deficient in the production of listeriolysin O, the product of the hly gene. The single-stranded cDNA fragments remaining after hybridization represent the difference in expressed genes between the two strains. These subtraction products were used as hybridization probes to identify the corresponding hly gene in a Southern hybridization.Key words: subtractive hybridization, Listeria monocytogenes, hemolysin, gene expression, isogenic.
Influence of growth rate and precursor availability on spiramycin production inStreptomyces ambofaciens
Authors: Untrau-Taghian Sophie , Lebrihi Ahmed , Germain Pierre , Lefebvre Gérard
Published: October 2009

The development of a culture medium in which the growth rate was limited by initial phosphate concentration permitted spiramycin production during the growth phase. The influence of the growth rate on spiramycin production in this medium was studied. Addition of glycerol before spiramycin production increased the growth rate by 100% and spiramycin production began at a low rate. Spiramycin production yield was decreased by 50%. Addition of fatty acids such as hexanoate before spiramycin production increased the global yield of spiramycin by 47% and a high level of acetate excretion was observed just before spiramycin production. The development of a biphasic growth medium increased the spiramycin global yield. In this biphasic growth medium, in the first phase there was fast growth during which no acetate was excreted and no spiramycin was detected. During a second phase of slow growth, acetate excretion preceded spiramycin production and the spiramycin biosynthetic rate was maintained at a high level.Key words: Streptomyces ambofaciens, spiramycin, electrophoresis, nitrogen source, regulation.
Utilization of glucose and cellobiose byCandida molischiana
Authors: Freer S. N.
Published: October 2009

Some of the factors that influence the biosynthesis of the Candida molischiana β-glucosidase were investigated. The yeast produced maximal enzyme activity when grown at 28 °C in a carbohydrate-containing complex medium (YM) in which the initial pH was adjusted to 6.0. The enzyme appeared to be produced constitutively, as activity was detected when either ethanol, glycerol, xylose, glucitol, mannitol, maltose, trehalose, cellobiose, cellodextrins, or soluble starch was used as the carbohydrate source. The presence of either glucose, mannose, or fructose (> 25 g/L) repressed β-glucosidase expression; however, C. molischiana did produce β-glucosidase when the initial glucose concentration was <25 g/L. When the yeast was grown in YM medium containing glucose plus cellobiose, diauxic utilization of the carbon sources was observed, and β-glucosidase activity was not detected until the glucose was depleted from the medium.Key words: β-glucosidase, glucose repression, fermentation, yeast.
Direct in siut identification of cellulose microfibrils associated with Rhizobium leguminosarum biovar trifolii attached to the root epidermis of white clover
Authors: Mateos Pedro F. , Baker David L. , Philip-Hollingsworth Saleela , Squartini Andrea , Paruffo Angelo D. B. , Nuti Marco P. , Dazzo Frank B.
Published: October 2009

Firm attachment of Rhizobium species to the legume root epidermis involves the elaboration of extracellular microfibrils extending from the bacteria and contacting the root surface at multiple sites. We investigated the nature of these extracellular microfibrils associated in situ with Rhizobium leguminosarum bv. trifolii colonized on the root epidermal surface of its legume host, white clover (Trifoiium repens L.). Scanning electron microscopy of seedling roots inoculated with the wild-type strain ANU843 showed that these extracellular microfibrils were associated with the bacteria attached not only to root hairs but also to the non-root-hair epidermis and the external environment under the influence of the developing root. Polystyrene microspheres adsorbed to the root surface did not accumulate similar microfibrils, ruling out their formation by nonspecific deposition of mucigel or self-assembly of rhizoplane fibrils of plant origin. An isozyme of cellulase was purified from Streptomyces sp. strain A20, shown to exhibit high substrate specificity for β-1,4-glucans, and used in enzyme cytochemistry to investigate the nature of these extracellular microfibrils. Combined scanning electron microscopy and computer-assisted image analysis indicated that the extracellular microfibrils associated with attached bacteria were degraded by a brief exposure to the purified cellulase but not by a broad-spectrum protease. These results provide direct in situ evidence of the cellulosic nature of the extracellular microfibrils associated with cells of R. leguminosarum bv. trifolii that have colonized the root environment of its legume host, white clover.Key words: Rhizobium, clover, cellulose microfibrils, enzyme cytochemistry, surface ecology, rhizoplane.
The plasmid profiles of fish pathogenic isolates of Aeromonas salmomcida, Vibrio anguillarum, and Vibrio ordalii from the Atlantic and Pacific coasts of Canada
Authors: Giles Janice S. , Hariharan Harry , Heaney Susan B.
Published: October 2009

The plasmid profiles of oxytetracycline- and streptomycin-resistant isolates of Aeromonas salmonicida, Vibrio anguillarum, and Vibrio ordalii were examined by agarose gel electrophoresis. Bacterial isolates were from disease outbreaks in fish on the Atlantic and Pacific coasts. Resistant isolates were examined when grown in the presence and absence of antibiotic. Alkaline lysis methods were used for plasmid isolation. Vibrio spp. were predominantly plasmidless, except for a 47-kilobase (kb) plasmid. Atlantic coast isolates of A. salmonicida possessed four or six plasmids, with four smaller plasmids ranging in size from 4.3 to 8.1 kb being consistently observed. The plasmid profiles of antibiotic-sensitive ATCC strains were identical. The plasmid profiles of the Pacific coast isolates of A. salmonicida varied slightly from those of the Atlantic coast isolates with six plasmids observed, ranging in size from 4.2 to 8.9 kb. Resistance to the antibiotics was not altered following plasmid curing experiments and resistance was not transferable to Escherichia coli. Thus, resistance to oxytetracycline and streptomycin did not appear to be plasmid mediated.Key words: plasmids, antibiotics, Aeromonas, Vibrio, fish.
Genetic diversity of N2-fixing bacteria associated with rice roots by molecular evolutionary analysis of a nifD library
Authors: Ueda T. , Suga Y. , Yahiro N. , Matsuguchi T.
Published: October 2009

The rhizosphere of wetland rice has significant N2-fixing activity. It has been suggested that N2 fixation in the rice root zone is associated with the activity of various N2-fixing heterotrophic bacteria that inhabit the rice rhizosphere. Because of the generic diversity, many different isolation media and conditions are required to count and isolate these bacteria. In an attempt to overcome any bias from culture-dependent methods we amplified nifD segments from crude rice root DNA by the polymerase chain reaction. The nifD fragments were then cloned into a pT7 BlueT-vector to construct a nifD library. Sixteen cloned nifD genes chosen at random from the library were sequenced. A comparison with published sequences indicated the presence of seven novel groups of NifD proteins, which implies the existence of at least seven components in the diazotrophic community of rice roots, dominated mainly by proteobacteria. We also observed genetic variability within the clusters, which suggests the coexistence of many closely related bacterial lineages. However, we did not find Azospirillum-like nifD clones, although many reports indicated the widespread presence of Azospirillum spp. Therefore, it remains to be clarified whether Azospirillum species are the widespread N2-fixing bacteria in rice roots.Key words: N2 fixation, molecular evolution, nifD, rice rhizosphere.
Wood degradation by Phellinus noxius: ultrastructure and cytochemistry
Authors: Nicole M. , Chamberland H. , Rioux D. , Xixuan X. , Ouellette G. B. , Blanchette R. A. , Geiger J. P.
Published: October 2009

An ultrastructural and cytochemical investigation of the development of Phellinus noxius, a white-rot fungus, in wood chips of Betula papyrifera was done to gain insight into the cellular mechanisms of wood cell wall degradation. Extracellular sheaths and microhyphae were seen to be involved in wood colonization. Close association was observed between these fungal structures and wood cell walls at both early and advanced stages of wood alteration. Fungal sheaths were often seen deep inside host cell walls, sometimes enclosing residual wood fragments. Investigations using gold probes indicated the occurrence of β-1,3-glucans within the fungal sheaths, while β-1,4-glucans were detected only within the fungal septa. The positive reaction with the PATAg test revealed that polysaccharides such as β-1,6-glucans were important components of the sheath. Chitin, pectin, β-glucosides, galactosamine, mannose, sialic acid, fucose, and fimbrial proteins were not found to be present in the sheath. Our data suggest that extracellular sheaths and microphyphae produced by P. noxius during wood cell wall colonization play an important role in wood degradation.Key words: cellulose, Phellinus, sheath, wood degradation.
A Bacillus phage that is a living fossil
Authors: Ackermann Hans-W. , Yoshino Sadazo , Ogata Seiya
Published: October 2009

Bacillus cereus phage Bace-11 has an isometric head and a contractile tail of about 500 nm in length, and is one of the two largest bacterial viruses known. Its tail, characterized by three long, whiplike fibers, is identical to giant phage tails produced by a Clostridium strain. These particles may represent phages of ancient origin that arose before the divergence of Clostridia and bacilli.Key words: Bacillus, bacteriophages, evolution.
Biodegradation of trichloroethylene byMycobacterium vaccae
Authors: Vanderberg Laura A. , Burback Brian L. , Perry Jerome J.
Published: October 2009

Nonproliferating cells of Mycobacterium vaccae that were grown on propane could mineralize limited amounts of trichloroethylene. Intermediates in the biodegradation of trichloroethylene were 2,2,2-trichloroethanol and 2,2,2-trichloroacetaldehyde. Trichloroethanol was completely degraded when added to a nonproliferating cell suspension of Mycobacterium vaccae. Addition of toluene to the reaction mixtures effected a 50% increase in the mineralization of [14C]trichloroethylene.Key words: trichloroethylene, cometabolism, Mycobacterium vaccae.
Diversity of lactate metabolism in halophilic archaea
Authors: Oren Aharon , Gurevich Peter
Published: October 2009

D-Lactate is readily used as a substrate for the growth of species of halophilic archaea belonging to the genera Haloferax and Haloarcula. L-Lactate was used by Haloferax species (Haloferax volcanii, Haloferax mediterranei) only when a substantial concentration of the D-isomer was also present in the medium. On the enzymatic level, considerable diversity was found in the lactate metabolism of the different representatives of the Halobacteriaceae. At least three types of lactate dehydrogenases were detected in halophilic archaea. A high level of activity of an NAD-linked enzyme was present constitutively in Haloarcula species, and a low level of activity was also detected in Haloferax mediterranei. NAD-independent lactate dehydrogenases, oxidizing L-lactate and D-lactate with 2,6-dichlorophenol-indophenol as electron acceptor, were detected in all nine species tested, but L-lactate dehydrogenase activity in Halobacterium species was very low, and Haloarcula species, which possess a high level of activity of NAD-linked lactate dehydrogenase, showed very low activities of both NAD-independent D- and L-lactate dehydrogenase. An inducible lactate racemase, displaying an unusually high pH optimum, was found in Haloferax volcanii. Lactate racemase activity was found constitutively in Haloarcula species, but no activity was detected in Halobacterium species and in Haloferax mediterranei.Key words: lactate dehydrogenase, lactate racemase, Halobacterium, Haloferax, Haloarcula.
Physiological control of trophophase–idiophase separation in streptomycete cultures producing secondary metabolites
Authors: Liao Xiaowen , Vining Leo C. , Doull Janice L.
Published: October 2009

Cultures of Streptomyces coelicolor A3 (2) produced actinorhodin in defined media with various carbon and nitrogen sources. Production occurred during biomass accumulation if assimilation of either the carbon or the nitrogen source limited the rate of growth. High growth rates tended to delay product synthesis until after biomass accumulation was complete, but fully biphasic fermentation profiles were achieved only with media supporting very rapid growth. The onset of actinorhodin production then coincided with a decline in the growth rate during transition of carbon-sufficient cultures to stationary phase. In cultures with maltose as a growth-limiting carbon source, depletion of phosphate increased the rate of actinorhodin biosynthesis, but did not alter the timing of its initiation. With defined media, the use of spores rather than vegetative mycelium as inocula reduced the overlap between trophophase and idiophase. The general guidelines for achieving biphasic production of actinorhodin in S. coelicolor A3 (2) cultures could be used to obtain trophophase–idiophase separation in cultures of Streptomyces venezuelae producing chloramphenicol. However, the conditions needed to be modified to give optimized biphasic fermentations with individual strains. Under conditions favouring chloramphenicol production in a distinct idiophase, aromatic amine secondary metabolites in the same cultures of S. venezuelae were produced in a pattern that overlapped the trophophase, suggesting that conditions need to be tailored also to meet differences in the regulation of secondary metabolites.Key words: Streptomyces coelicolor A3 (2), Streptomyces venezuelae, actinorhodin, biphasic fermentations, chloramphenicol, inoculum shift down.
Différences structurales des peptidomannanes pariétaux chez le Kluyvetomyces lactis, entre souches floculante et non floculante
Authors: Bellal M. , Benallaoua S. , Elfoul L. , Bonaly R.
Published: October 2009

Two strains, flocculating and nonflocculating, of the yeast Kluyveromyces lactis were grown in a Sabouraud's liquid medium containing 0.07 mM Ca. Treatment by ethylenediamine of isolated cell walls yielded three fractions: A, B, and C. Fraction A, soluble in ethylenediamine, contained phosphopeptidomannan-like hydrosoluble polymers; these constituted the external wall of the parietal layer. Phosphopeptidomannans have also been extracted from entire yeast cells autoclaved at 140 °C in a citrate buffer at pH 7.0. The flocculating and nonflocculating states of yeasts showed structural and quantitative variations in phosphopeptidomannans. The walls of the flocculating yeast cells contained higher amounts of peripheral polymers, the molecular masses of which were greater than those of nonflocculating yeast cells. These are the result of a more complex structure, due to the presence of a greater number of ramifications containing three or four mannose units. Analysis of the acetolysis products revealed in fact the release esentially of phosphorylated mannotriose and mannotetraose units by the flocculating yeast phosphopeptidomannans, while polymers of the nonflocculating yeast were characterized by the presence of mannobiose units. When such polymers were submitted to a β-elimination reaction, mannobiose and mannose units were liberated in such a ratio that mannobiose units appeared to be more numerous in flocculating yeast cells. A lectin extracted from the flocculating strain was incubated with erythrocytes activated by phophopeptidomannans derived from flocculating and nonflocculating yeasts and showed clearly that the more agglutinated erythrocytes were those activated by polymers derived from the flocculating yeast. The C fraction, insoluble in ethylenediamine, corresponded to the wall rigid matrix. The study of its chemical composition revealed no significative difference between the flocculating and the nonflocculating strains.Key words: Kluyveromyces lactis, phosphopeptidomannans, flocculation.[Journal translation]not available
A stydy of Rhizobium leguminosarum biovar trifolii populations from soil extracts using randomly amplified polymorphic DNA profiles
Authors: Dye Malcolm , Sket Leif , Mytton Lance R. , Cresswell Ann , Harrison Stephen P. , Dooley John J.
Published: October 2009

This study has shown that isolates of Rhizobium leguminosarum biovar trifolii can be grouped on the basis of their randomly amplified polymorphic DNA (RAPD) fragment patterns. Evidence is presented that these groups are not entirely arbitrary but are consistent with other genetic and phenotypic characteristics. RAPD analysis has been used to assess the efficiency of a dispersion and differential centrifugation procedure used to extract bacteria from soil. Whilst the major groups of Rhizobium isolates in soils were also found in the extracts, some of the others were missing. This is also reflected in the finding, made by measuring abundance of organisms, that as many Rhizobium isolates are left in the residue as appear in the supernatant; more dispersion steps, possibly with different dispersants, are needed to maximize extraction. The technique has also demonstrated that dispersing soil by simply shaking it in water not only underestimates the numbers of Rhizobium isolates present but also masks much of their diversity.Key words: Rhizobium, DNA amplification, random primers, bacterial extraction.
Development of a practical method for inducing white-rot fungi to grow into and degrade organopollutants in soil
Authors: Boyle C. David
Published: October 2009

White-rot fungi degrade many hazardous organic compounds that are not readily degraded by other microorganisms. Some of these compounds are soil contaminants, so methods for using these fungi to decontaminate soil through either land farming or composting technologies are being developed. White-rot fungi normally colonize plants or plant residues (e.g., wood) and do not grow well in unamended soil, particularly if it is not sterilized. A practical method to promote their growth in soil, without the use of large quantities of amendments or inoculum, is presented. A variety of assays showed that growth of white-rot fungi in steamed soil is limited by availability of carbon and nitrogen sources, but not other nutrients. Ground alfalfa straw was a more effective inexpensive source of these nutrients than the other amendments that were tested. However, the fungi only sometimes colonized alfalfa-amended nonsterile soil, as a result of competition from other microorganisms. Consistently high growth of the white-rot fungi in alfalfa-amended soil could be induced by adjusting the moisture content, adding the fungicide benomyl, and inoculating with benomyl-resistant fungi. In soil so treated, degradation (mineralization) of pentachlorophenol was much more rapid than in untreated soil.Key words: white-rot fungi, bioremediation, growth, pentachlorophenol.
A biosensor based on Thiobacillus thioparus for measuring thiosulfate and methanethiol
Authors: Kubo Izumi , Karube Isao , Takeuchi Toshifumi , Furusawa Masako , Arikawa Yoshiko , Kanagawa Takahiro
Published: October 2009

A biosensor based on Thiobacillus thioparus was developed for the determination of thiosulfate and methanethiol. Thiobacillus thioparus is a chemoautotrophic bacterium and it oxidizes sulfur compounds to sulfuric acid. The sensor consisted of an oxygen electrode and immobilized T. thioparus. When the sensor was used to determine thiosulfate, a linear relation between sensor output and concentration was obtained for the concentration range from 1 to 100 μM in a batch system and from 1 to 10 mM in a flow injection system. Output of the sensor was stable for more than 1 month. For methanethiol, the response of the sensor was measured for the concentration range from 0.2 to 3 mM in a flow injection system.Key words: microbial sensor, thiosulfate, methanethiol, Thiobacillus thioparus TK-m.
Analysis of fowlpox virus DNA replication and mapping
Authors: Zantinge Jennifer L. , Nagy Éva , Derbyshire J. Brian , Krell Peter J.
Published: October 2009

A physical map was generated for the fowlpox virus Chick-N-Pox vaccine strain DNA genome for EcoRI, BamHI, NcoI, and PstI. The gel profiles resulting from EcoRI, BamHI, BglII, NcoI, StyI, PstI, and PvuII digestions were analyzed by agarose and polyacrylamide gel electrophoresis. The size of the fowlpox virus genome was estimated from these digests to be 289–301 kb. Replication of fowlpox virus DNA in QT-35 cells was followed and indicated that viral DNA replication initiated at 6–8 h postinfection in these cells.Key words: physical mapping, fowlpox virus, QT-35 cells, DNA replication.
Dependence on reporter gene of apparent activity in gene fusions of a Streptomyces griseus streptomycin biosynthesis promoter
Authors: Lindley Helen K. , Deeble V. Jayne , Peschke Ursula , O'Neill Mary , Baumberg Simon , Cove Jonathan
Published: October 2009

The adjacent genes strR–strA–strB1 lie within the large cluster of genes of streptomycin biosynthesis and resistance in Streptomyces griseus. sirR encodes a pathway-specific activator StrR, suggested by previous work to be either an antiterminator or a conventional activator, binding to its DNA target via a helix-turn-helix motif. strB1 is transcribed in an StrR-dependent fashion from a promoter (PstrB1) that lies downstream from strA; between PstrB1 and sirB1 there is a 300-bp leader region containing numerous inverted repeats that could represent modulatable transcription termination sites. Hybrid plasmids were constructed in vitro with transcriptional fusions in which fragments containing PstrB1 and either the entire leader region ("long" fragments) or a small part of it (the "short" fragment) were cloned upstream of (i) aph as reporter gene, in a high copy number plasmid background, or (ii) xylE as reporter gene, in a low copy number plasmid background. The short fragment directed high levels of APH (aminoglycoside 3′-phosphotransferase) whether StrR was present or not, while the long fragments did not do so in the absence of StrR; one long fragment directed high levels in wild-type S. griseus, in which StrR would be present. Insertion of an extraneous fragment into PstrB1 in the short fragment construct led to loss of APH activity, demonstrating that no adventitious promoter had been formed in the short construct. In vitro deletion of part of the leader region in a long fragment construct led to high APH expression with or without StrR present. Although these results are consistent with the target of StrR being within the leader region, and thus with an antiterminator role, it was found that both long and short fragments in the low copy number background failed to direct high expression of catechol oxygenase (the product of xylE) unless strR was also present on a compatible plasmid. Transfer of PstrB1-xylE fragments to the high copy number vector did not increase catechol oxygenase expression. We interpret these results in terms of an effect, in the hybrid constructs, of one of the reporter genes on promoter function, possibly by affecting local DNA topology.Key words: gene fusions, reporter genes, Streptomyces, streptomycin, regulation of secondary metabolism.
Microbial degradation of resins fractionated from Arabian light crude oil
Authors: Venkateswaran Kasthuri , Hoaki Toshihiro , Kato Misako , Maruyama Tadashi
Published: October 2009

Sediment samples from Japanese coasts were screened for microorganisms able to degrade resin components of crude oil, and a mixed population that could degrade 35% of 5000 ppm resin in 15 days was obtained. This population also metabolized 50% of saturates and aromatics present in crude oil (5000 ppm) in 7 days. A Pseudomonas sp. isolated from the mixed population emulsified and degraded 30% of resins. This strain also degraded saturates and aromatics (30%) present in crude oil (5000 ppm). This is the first report describing organisms that are able to grow on the resin fraction of crude oil as a sole source of carbon and energy.Key words: resin, crude oil, biodegradation, Iatroscan.
Reduced recovery of a Cryptococcus neoformans adherence mutant from a rat model of cryptococcosis
Authors: Merkel Glenn J. , Scofield Barbara A. , Rescorla Frederick J. , Yang Rong , Grosfeld Jay L.
Published: October 2009

Stable mutants of Cryptococcus neoformans (strain CSF-1) induced by treatment with ultraviolet light and nitrosoguanidine were isolated that demonstrated reduced adherence to glial cells in culture. Adherence of the mutants, as measured by a radiometric assay, was reduced by 50–70% of that attained for the parent CSF-1 strain. The adherence mutants appeared to be phenotypically similar to the CSF-1 strain. However, all but one mutant (designated as CSF-23) demonstrated slightly slower growth rates than the wild-type strain. The CSF-1 and CSF-23 strains were injected intravenously and intratracheally into normal rats and rats immunosuppressed by cyclophosphamide treatment, and the organ distribution and recovery of viable yeasts determined over 2–96 h. During this relatively short period of observation the majority of the yeasts were localized in the lungs. By either route of injection, the recovery of the CSF-23 adherence mutant was reduced by as much as 90% of that obtained for the wild-type strain. The results indicated that host cell adherence may be important for the persistence of cryptococci in tissue and that further studies with the adherence mutants are warranted.Key words: Cryptococcus, adherence, cryptococcosis, yeast.
Environmental scanning electron microscopic observation of the hyphal sheath and mycofibrils in Postia placenta
Authors: Connolly Jon H. , Chen Ying , Jellison Jody
Published: October 2009

Environmental scanning electron microscopic observations of Postia placenta grown on a defined medium and on red spruce wood allowed for the examination of the hydrated sheath of P. placenta. In the wood environment, mature hyphae that were not adhering to the substrate were observed to have a mycofibrillar morphology whereas hyphal tips and branch points had a smooth sheath morphology. A mycofibrillar adhesive matrix was observed on the hyphae growing on glass slides in the defined medium. These morphologies for hyphal sheaths in P. placenta are similar to those previously described by investigators from other laboratories who have used traditional electron microscopic preparative protocols that include dehydration steps. The potential future usefulness of environmental scanning electron microscopic technology in the study of the fine details of extracellular matrices is briefly discussed.Key words: mycofibrils, hyphal sheath, environmental scanning electron microscopy, extracellular matrix.
Enzymes from Pseudomonas sp. strain NCIB 11097 participating in biotransformation of acetaldehyde and glycine to threonine isomers
Authors: Diaz-Diaz M. , Ward O. P. , Honek J. , Lajoie G.
Published: October 2009

Enzyme activities involved in L-threonine bioconversions present in cells of Pseudomonas sp. strain NCIB 11097 were separated by phenyl-Sepharose hydrophobic chromatography. The separation of the two main activity components was monitored by discontinuous polyacrylamide gel electrophoresis. Threonine aldolase catalyzed the conversion of glycine and acetaldehyde to a mixture of isomers, L-threonine and L-allothreonine, in a biotransformation reaction having pH and temperature optima of 7.5 and 25–30 °C, respectively. The fraction containing serine hydroxymethyltransferase converted acetaldehyde and glycine specifically to L-allothreonine in a biotransformation reaction having pH and temperature optima of 7.4 and 37 °C, respectively.Key words: L-threonine aldolase, serine hydroxymethyltransferase, Pseudomonas, L-allothreonine, biotransformation.
Dynamics of non-O1 Vibrio choletae and fecal coliforms in experimental stabilization ponds in the arid region of Marrakesh, Morocco, and the effect of pH, temperature, and sunlight on their experimental survival
Authors: Mezrioui N. , Oufdou K. , Baleux B.
Published: October 2009

We studied the spatial-temporal dynamics of non-O1 Vibrio cholerae numbers at a stabilization pond treatment plant. This bacterium's seasonal dynamics were the inverse of those of fecal coliforms, with high levels in hot periods and low levels in cold periods. Stabilization pond treatment did not significantly reduce non-O1 V. cholerae numbers between the system's inflow and outflow points. In contrast, fecal coliforms were reduced by 98.95% in hot periods and by 94.91% in cold periods. Significant rho coefficient values for the Spearman correlation between numbers of non-O1 V. cholerae and temperature and pH of 0.91 and 0.76, respectively, were found at the system's outflow point. An experimental study of the effects of pH, temperature, and sunlight on the survival of non-O1 V. cholerae and fecal coliforms confirmed the inverse behaviour of the two bacterial groups noted in the stabilization ponds. Alkaline pH values of 8 and 8.8 promoted the survival of non-O1 V. cholerae and inhibited that of Escherichia coli. Low temperatures (8 °C) prolonged E. coli survival (k = 0.002/h), while a temperature of 23 °C reduced it markedly (k = 0.022/h). Non-O1 V. cholerae did not survive as well as E. coli at 8 °C (k = 0.009/h). The effect of temperature on non-O1 V. cholerae appeared to be closely linked to nutrient levels. Non-O1 V. cholerae appeared to be less sensitive to sunlight than E. coli whose survival was markedly reduced, particularly during summer periods. Non-O1 V. cholerae and E. coli did not behave in the same way in water subjected to stabilization pond treatment. The use of fecal coliforms as an indicator of the potential health hazard of the effluent may not be adequate for this treatment procedure.Key words: stabilization pond, non-O1 Vibrio cholerae, Escherichia coli, pH, temperature, sunlight.
Transformation of formaldehyde by a Halomonas sp.
Authors: Azachi Malkit , Henis Yigal , Oren Aharon , Gurevich Peter , Sarig Shlomo
Published: October 2009

A halotolerant Gram-negative eubacterium was isolated from soil collected at a storage site for formaldehyde near a chemical plant that uses formaldehyde in the production of glue. The strain, designated MA-C and identified as Halomonas sp. (DSM 7328), grew at salt concentrations from zero to above 20%. Halomonas sp. strain MA-C was found to be highly tolerant to formaldehyde and grew well in the presence of up to 75–100 mg/L formaldehyde. The isolate transformed formaldehyde at a high rate by means of a constitutive NAD- and glutathione-dependent formaldehyde dehydrogenase (EC 1.2.1.1). Previous exposure to formaldehyde resulted in an increase in formaldehyde dehydrogenase activity from 280–480 to 650–850 nmol∙mg protein−1∙min−1. Formate did not accumulate in culture media enriched with formaldehyde, and formate added to cultures was rapidly metabolized. An inducible NAD-dependent formate dehydrogenase (EC 1.2.1.2) was detected (activity between 14 and 34 nmol NAD reduced∙mg protein−1∙min−1). Radioactive labelling experiments showed that neither formaldehyde nor formate was incorporated into cell material to a significant extent.Key words: formaldehyde, formate, Halomonas, halotolerant.
Sphalerite oxidation by Thiobacillus fertooxidans and Thiobacillus thiooxidans
Authors: Garcia Jr. Oswaldo , Bigham Jerry M. , Tuovinen Olii H.
Published: October 2009

Sphalerite (ZnS) oxidation was monitored in Thiobacillus ferrooxidans and Thiobacillus thiooxidans cultures and in abiotic controls by X-ray diffraction (XRD) analysis of solid phases and by chemical analysis of solution composition. X-ray diffraction data revealed no solid-phase reaction products in unsupplemented sphalerite media, whereas minor amounts of S0 accumulated in FeSC4-amended sphalerite media with or without T. ferrooxidans inoculum. Jarosite ((K,Na,H3O,NH4)Fe3(SO4)2(OH)6) also precipitated in the amended T. ferrooxidans cultures. When sphalerite media inoculated with T. thiooxidans were amended with S0, acid production was enhanced, decreasing the pH to 1.1, but Zn dissolution was not accelerated. By comparison with T. thiooxidans, T. ferrooxidans was more efficient in the oxidation of sphalerite.Key words: bioleaching of sphalerite, sphalerite oxidation, Thiobacillus ferrooxidans, Thiobacillus thiooxidans, zinc sulfide oxidation.
Effects of leader sequences upon the heterologous expression of restrictocin in Aspergillus nidulans and Aspergillus niger
Authors: Brandhorst Tristan , Kenealy William R.
Published: October 2009

The effects of altered leader sequences on the secretion and localization of restrictocin expression in Aspergillus nidulans and Aspergillus niger were investigated. The region encoding the leader sequence of the Aspergillus resirictus restrictocin (res) gene was altered and variants were expressed under the glucoamylase (glaA) promoter in A. nidulans and A. niger. The entire restrictocin leader sequence was replaced by the glaA leader sequence in one variant. In another, the signal sequence of restrictocin was replaced with the glaA signal, leaving a hybrid with the putative restrictocin pro region in place of the glaA pro region. The putative pro region was deleted from the restrictocin leader of a third variant. Toxic effects, such as reduced transcript levels and cellular lysis, were minimal when restrictocin was expressed with the native leader sequence, but became more pronounced as the leader sequence was varied. These toxic effects were inversely proportional to the level of restrictocin secreted. In all transformed strains, restrictocin secretion appeared at the periphery of colonies and was observed to occur at the tips of hyphae. Localization of restrictocin to differentiated structures (conidiophores), as occurs in A. resirictus, was observed only in transformed strains containing the complete restrictocin leader sequence.Key words: localization, secretion, targeting, translocation, development.
Replication of measles virus in human monocytes and T cells
Authors: Vydelingum S. , Salmi A. A. , Suryanarayana K. , Marusyk R. G.
Published: October 2009

Replication of measles virus (MV) in populations of peripheral blood mononuclear cells enriched for T cells and monocytes was studied using a temperature-sensitive mutant, MV ts38, and the parent counterpart, MV Lee. Stimulation of the cells was required for a full cycle of virus replication in both cell types. More infectious virus was released after stimulation from MV-infected populations enriched for T cells, T cell-enriched than from monocyte-enriched populations. However, similar amounts of viral mRNA, genomic RNA, and viral proteins of the expected size were found in both cell populations. The results indicate that MV-specific macromolecular synthesis is similar in both T cells and monocytes, but the assembly and (or) release of infectious virus is greatly reduced in monocytes as compared with T cells.Key words: Measles virus replication.
Overcoming the metabolic load associated with the presence of plasmid DNA in the plant growth promoting rhizobacteriumPseudomonas putidaGR12-2
Authors: Hong Yuwen , Pasternak J. J. , Glick Bernard R.
Published: October 2009

When the broad host range plasmid vector pGSS15 was used to genetically transform the plant growth promoting rhizobacterium Pseudomonas putida GR12-2, the transformants were physiologically debilitated. It was postulated that the expression of the β-lactamase gene of pGSS15 caused a metabolic load resulting in the impaired functioning of the bacterium. To test this hypothesis, derivatives of pGSS15 that either lack the β-lactamase gene (pYH122) or in which a β-glucosidase gene was substituted for the β-lactamase gene (pYH124) were constructed and examined to see whether their presence also impaired the functioning of P. putida GR12-2. On the basis of growth rates, siderophore production, and the ability to stimulate canola root elongation in sterile growth pouches, neither of the newly constructed plasmids debilitated P. putida GR12-2. In addition, P. putida GR12-2 transformed with pYH124 facilitated the proliferation of the bacterium in minimal medium containing cellobiose at low temperature. This latter trait may enable P. putida GR12-2 to persist in the soil in competition with other microorganisms.Key words: plant growth promoting rhizobacteria, PGPR, bacterial fertilizer, soil bacteria, metabolic load, β-glucosidase
Molecular techniques and their potential application in monitoring the microbiological quality of indoor air
Authors: MacNeil L. , Kauri T. , Robertson W.
Published: October 2009

Health effects associated with poor indoor air quality have created a need for accurate, reproducible methods of monitoring the microbiological content of indoor air. Improved methods of detection may allow researchers to clarify the effect of individual species present in the indoor environment on human health. This review discusses the shortcomings of current methods of identification and detection and focuses on the potential for molecular techniques in this emerging field. Probe techniques, restriction endonuclease analysis, karyotyping, and DNA and polymerase chain reaction fingerprinting methods available to detect and identify bacteria and fungi significant in the indoor air environment are discussed. Problems that may be encountered using these techniques are also considered. The authors have included a brief discussion on current air sampling techniques as well as adapting these techniques for use with molecular detection methods.Key words: indoor air microbiology, microbiological air sampling, molecular detection methods.
In situ analysis of the bacterial community in the gut of the earthwormLumbricus terrestrisL. by whole-cell hybridization
Authors: Fischer Kathrin , Hahn Dittmar , Daniel Otto , Zeyer Josef , Amann Rudolf I.
Published: October 2009

The bacterial community in the gut of the earthworm Lumbricus terrestris was analyzed by whole-cell hybridization with 16S rRNA targeted oligonucleotide probes. Whole-cell hybridization protocols using fluorescence-, peroxidase-, or digoxigenin-labeled oligonucleotide probes facilitated detection of significant fractions of bacterial cells stained with 4′,6-diamidino-2-phenylindole (DAPI) in the fore-, mid-, and hind-gut and cast of the earthworm. The application of peroxidase- and digoxigenin-labeled probes, however, was hampered by several methodological drawbacks: the requirement of enzymatic permeabilization, the diffuse images of stained cells, and the incompatibility with DAPI staining used as control. Quantitative analysis of the bacterial community was also influenced by its considerable variability in different individual earthworms. Though the number of bacteria detected by DAPI staining as well as by whole-cell hybridization with the fluorescent eubacterial probe Eub338 generally showed a significant increase in the number of bacteria towards the end of the gut, a decrease in bacterial numbers could be found in some earthworms. In situ analysis of the bacterial community in the fore-, mid-, and hind-gut of one individual earthworm by whole-cell hybridization with the fluorescent eubacterial probe Eub338 recorded 15, 30, and 25% of DAPI-stained bacteria, respectively. In the cast 37% of the bacteria were detected. Similar to counts obtained by DAPI and by whole-cell hybridization with probe Eub338, the number of bacteria belonging to the α-, β-, and γ-subgroups of proteobacteria increased significantly towards the end of the gut and remained high in the cast. While the most significant difference in the counts of bacteria belonging to the α-subgroup was obtained between the hind-gut and cast, bacterial populations of the β- and γ- subgroups of proteobacteria increased most prominently between the fore- and hind-gut.Key words: digoxigenin, fluorescent probes, in situ detection, Lumbricus terrestris, rRNA, whole-cell hybridization.
Bacillus oleroniussp.nov., a member of the hindgut flora of the termiteReticulitermes santonensis(Feytaud)
Authors: Kuhnigk Thomas , Borst Eva-Maria , Breunig Alfred , König Helmut , Collins Matthew D. , Hutson Roger A. , Kämpfer Peter
Published: October 2009

A new rod-shaped endospore-forming bacterium is described, which was isolated from the hindgut of the termite Reticulitermes santonensis (Feytaud). The isolate stains Gram negative and its DNA has a guanine-plus-cytosine content of 35 mol%. Despite the Gram-staining reaction, both biochemical and physiological features place the isolate in the genus Bacillus and indicate a phenotypic resemblance to the Bacillus firmus–lentus group of species. On the basis of comparative 16S rRNA analysis and some phenotypic features the isolate clearly represents a new species for which the name Bacillus oleronius is proposed. The type strain is Bacillus oleronius Rt 10 (DSM 9356).Key words: Bacillus, termites, hindgut flora.
Cell surface properties of Aspergillus fumigatus conidia: correlation between adherence, agglutination, and rearrangements of the cell wall
Authors: Tronchin G. , Bouchara J. P. , Ferron M. , Larcher G. , Chabasse D.
Published: October 2009

Culture conditions that lead to swelling and germination dramatically influence cell surface characteristics and properties of Aspergillus fumigatus conidia. Conidial adherence to polystyrene and agglutination markedly increased during swelling, in a time-dependent manner. Agglutination appeared to be sensitive to cycloheximide and calcium. Removal of cell wall polysaccharides by lyticase or sodium metaperiodate suppressed agglutination of conidia. Proteinase K weakly decreased it whereas dithiothreitol strongly dispersed the cells. These observations suggest that both cell surface carbohydrates and proteins are involved in the agglutination process. Electron microscopic observations demonstrated that the cell wall of conidia was subject to some rearrangements during swelling, involving degradation and loss of the external convoluted layer, and subsequent exposure of underlying ligands. This was confirmed using lectins labelled with gold or fluorescein isothiocyanate, which showed that some carbohydrates, particularly those acting as ligands for peanut agglutinin, are largely exposed during the process. Finally, SDS-PAGE revealed major protein changes between resting and swollen conidia. We conclude that the ability of A. fumigatus conidia to aggregate correlates with an increase in adherence and biochemical reorganization of the cell wall.Key words: Aspergillus fumigatus, adherence, agglutination, cell wall rearrangements.
Action de la désertomycine sur la synthèse des polymères pariétaux du Saccharomyces uvarum
Authors: Benallaoua S. , Bellal M. , Bonaly R.
Published: October 2009

The desertomycin action upon Saccharomyces uvarum wall synthesis has been studied. Spheroblast regeneration was carried out in a liquid medium containing labeled glucose to monitor the synthesis of different wall components. In the presence of desertomycin, wall synthesis was affected; this was expressed as a net reduction of insoluble alkali constituents content, more precisely the insoluble acido-alkali fraction that, in yeasts, is constituted by chains of β(1,3)-glucans linked among themselves by β(1,6) bonds. Mannan formation was not inhibited; such polymers that cannot be fixed to the glucan matrix of the wall were liberated in the regeneration medium. Because of desertomycin action, the decrease in insoluble alkali content revealed an interference with the enzymatic systems catalyzing glucan synthesis. In vitro, however, this antifungal had little effect upon glucan synthetase activity: doses 5 times superior to the subinhibiting level used in vivo caused only 30% inhibition. This result can be explained by an indirect action of desertomycin. Parietal disorders were the result of membrane structure disturbance, notably the phospholipids and localized enzymatic systems. This antifungal presents an analogical structure with macrolides with recognized membrane action.Key words: desertomycin, wall, yeast.
Metronidazole uptake in Helicobacter pylori
Authors: Moore Richard A. , Beckthold Brenda , Bryan L. E.
Published: October 2009

Currently, the mechanism of metronidazole resistance is not understood in Helicobacter pylori. We have looked at uptake of metronidazole into a sensitive and a resistant strain of H. pylori. Both strains displayed rapid uptake of [14C]metronidazole, although the resistant strain accumulated the drug at a slower rate and to a lesser amount than the sensitive strain. Uptake was inhibited by KCN and carbonyl cyanide m-chlorophenyl-hydrazone (CCCP) but not by sodium arsenate. Thin-layer chromatography analysis of lysed cell supernatants showed that metronidazole was metabolized in both strains. A variety of related imidazole compounds inhibited metronidazole uptake, consistent with a common transport system for this group of antibiotics. Our data do not support an absence of uptake or metabolism as a cause of resistance in the strain examined.Key words: metronidazole, uptake, Helicobacter.