bluuebunny/crossref_metadata_2025 huggingface dataset:
A nolC-lacZ gene fusion in Rhizobium fredii facilitates direct assessment of competition for nodulation of soybean
Authors: Krishnan Hari B. , Pueppke Steven G.
Published: May 2010

A constitutively expressed chromosomal gene, nolC, regulates the ability of Rhizobium fredii strain USDA257 to nodulate certain agronomically improved soybean cultivars. Other advanced cultivars, as well as unimproved varieties such as 'Peking', form nitrogen-fixing nodules with parental strain USDA257 and with nolC mutants. We have used 257DH512, a derivative of USDA257 that contains a nolC-lacZ fusion, to directly measure strain competition for nodule occupancy. Seedlings of the soybean cultivar 'Peking' were inoculated with mixtures containing various ratios of 257DH512 and R. fredii USDA208; nodules were harvested 14 days later and stained histochemically with X-gal, a chromogenic substrate for the β-galactosidase product of lacZ. We were able to stain and evaluate batches of nearly 500 nodules in just 4 h, without the use of expensive equipment. Under the conditions of these experiments, USDA208 was considerably more competitive than 257DH512, even when it had been present in the inoculum at a numerical disadvantage. We suggest that gene fusions can be used to greatly simplify the assessment of nodulation competitiveness in rhizobia. Key words: competition, nolC-lacZ fusion, soybean – Rhizobium fredii, nodule occupancy.
Slow rehydration improves the recovery of dried bacterial populations
Authors: Kosanke J. W. , Osburn R. M. , Shuppe G. I. , Smith R. S.
Published: May 2010

Slow rehydration of bacteria from dried inoculant formulations provided higher viable counts than did rapid rehydration. Estimates were higher when clay and peat powder formulations of Rhizobium meliloti, Rhizobium leguminosarum biovar trifolii, and Pseudomonas putida, with water activities between 0.280 and 0.650, were slowly rehydrated to water activities of approximately 0.992 before continuing the dilution plating sequence. Rhizobium meliloti populations averaged 6.8 × 108 cfu/g and 1328 cfu/alfalfa seed greater when slowly rehydrated from bulk powder and preinoculated seeds, respectively. Bulk powder samples were slowly rehydrated to 0.992 water activity by the gradual addition of diluent, followed by a 10-min period for moisture equilibration. Preinoculated seed samples were placed in an environmental chamber at 24 °C with relative humidity greater than 80% for 1 h to allow moisture absorption. "Upshock," osmotic cellular stresses that occur during rehydration, was reduced when dried microbial formulations were slowly rehydrated and equilibrated before becoming fully hydrated in the dilution plating sequence. These procedures may also be applicable when estimating total viable bacterial populations from dried soil or other dry formulations. Key words: rehydration procedure, microbial rehydration, desiccation, Rhizobium, Pseudomonas.
Similarities between legume–rhizobium communication and steroid-mediated intercellular communication in vertebrates
Authors: Baker Michael E.
Published: May 2010

Regulation of the actions of flavonoids and Nod factors in legume–rhizobia communication has several interesting similarities with that of steroid-mediated actions in vertebrates. Oxidation or reduction of flavonoids and Nod factors modifies their biological activity just as, for example, oxidation of an alcohol at C11 on hydrocortisone regulates its biological activity. Second, some flavonoids are anti-inducers, functioning like steroid antagonists to negate the actions of inducer flavonoids. Amino acid sequence analyses show that human 17β-hydroxysteroid dehydrogenase, which catalyzes the interconversion of the alcohol and ketone at C17 on estrogens and androgens, and rat 11β-hydroxysteroid dehydrogenase, which catalyzes the interconversion of the alcohol and ketone at C11 of glucocorticoids, and Rhizobium meliloti NodG and Bradyrhizobium japonicum. FixR are derived from a common ancestor. Just as steroid-metabolizing enzymes can regulate steroid-mediated gene transcription, enzymes that modify substituents on flavonoids and Nod factors may have a similar role in regulating signalling between legumes and rhizobia. The enzymes that modify flavonoids and Nod factors have not yet been identified. However, NodG and FixR are two likely candidates to have this role in regulating legume–rhizobia signalling. Key words: NodG function, FixR function, steroid–flavonoid similarities, steroids and nitrogen fixation.
Response of cowpea (Vigna unguiculata) to inoculation with co-selected vesicular–arbuscular mycorrhizal fungi and Rhizobium strains in field trials
Authors: Thiagarajan T. R. , Ames R. N. , Ahmad M. H.
Published: May 2010

After initial screening in sterilized and nonsterilized soils, two vesicular–arbuscular mycorrhizal (VAM) fungi (Glomus pallidum Hall and Sclerocystis microcarpa Iqbal & Bushra) and two compatible cowpea rhizobial strains (JRC14 and JRC29) have been co-selected. The response of cowpea (Vigna unguiculata (L.) Walp) to inoculation with co-selected pairs of VAM fungus and Rhizobium strains was field tested in Jamaica at two locations (soil types sandy clay loam and bauxitic silt loam). Dual inoculations of cowpea increased the pod yield, mycorrhizal infection, nodule formation, and shoot P and N content compared with single inoculations of either VAM fungus or Rhizobium. However, JRC14 when paired with G. pallidum or S. microcarpa showed maximum yield increase (45%) in both soil types. Our work suggests that appropriate pairing of VAM fungus – Rhizobium should be used for field inoculation. Key words: cowpea, rhizobia, mycorrhizal fungi.
Bactericidal properties of peracetic acid and hydrogen peroxide, alone and in combination, and chlorine and formaldehyde against bacterial water strains
Authors: Alasri Anouar , Roques Christine , Michel Georges , Cabassud Corinne , Aptel Philippe
Published: May 2010

The bactericidal properties of peracetic acid, hydrogen peroxide, chlorine, and formaldehyde were compared in vitro using a rapid micromethod. A combination of peracetic acid and hydrogen peroxide was also tested to assess interactions. The activities of these agents, which are widely used as disinfectants, were evaluated against water isolates and culture collection strains. Peracetic acid and chlorine exhibited an excellent antimicrobial activity, with a relatively rapid destruction of 105 bacteria/mL. The time-dependent bactericidal activities of hydrogen peroxide and formaldehyde were the lowest. The combination of peracetic acid and hydrogen peroxide, tested by a checkerboard micromethod, was found to be synergistic. The minimal bactericidal concentration was established in terms of time for a given mixture of peracetic acid and hydrogen peroxide. Determination of bactericidal concentrations showed that synergy was maintained with increasing contact time. Concentrations for minimal times of treatment by chemicals that provided interesting activities in vitro were tested for disinfection of ultrafiltration membranes. The bactericidal activities of peroxygen compounds were confirmed and synergism was maintained in working conditions. Chlorine showed a loss of efficacy when used on membranes. Key words: peracetic acid, hydrogen peroxide, chlorine, formaldehyde, minimal bactericidal concentration, ultrafiltration membranes.
A modification of the method using cellulose overlay agar to isolate and purify cellulolytic cytophagas from enrichment culture
Authors: Drijber R. A. , McGill W. B.
Published: May 2010

We report here on a modification of the cellulose overlay agar method for isolating and purifying cellulolytic cytophagas from enrichment cultures. We call it the "back-door" method, and it overcomes two existing problems. First, it prevents recontamination with organisms growing on the agar surface. Second, it permits purification of cellulolytic cytophagas that are unable to utilize glucose or that are accompanied by a rapidly growing contaminant with spreading habit. Pure cultures of cellulolytic cytophagas were obtained from five enrichment cultures of nine soil samples examined. Two limitations are that (i) the cytophaga must be able to penetrate the overlay and (ii) some noncellulolytic cytophagas may also penetrate the overlay to yield cocultures. In conclusion, the back-door method can be used both to isolate and purify cellulolytic cytophagas from soils, using only a cellulose-based medium. Key words: back-door method, cellulolytic cytophagas, cellulose overlay agar, cellulolysis.
Survie du Salmonella paratyphi B et du Pseudomonas aeruginosa dans l'eau de mer après incubation ou lavage en présence d'osmolytes
Authors: Bakhrouf Amina , Jeddi Moncef , Gauthier Michel J.
Published: May 2010

The authors have compared the survival in seawater of Salmonella paratyphi B and Pseudomonas aeruginosa cells grown at low or high osmolarity, in the presence of organic osmolytes: glycine betaine, choline, proline, and glutamate. The four substrates enhanced the survival potential of S. paratyphi B while only glycine betaine protected P. aeruginosa. In addition only S. paratyphi B cells were more resistant after a preliminary growth at high osmolarity. Both bacteria were sensitive to osmotic down-shock, sensitization of S. paratyphi B being inversely proportional (p ≥ 0.01) to the osmolarity of the medium used to wash cells. The transit in wastewater, at low osmolarity, can therefore modify the behavior of these pathogens in the marine environment. Key words: Salmonella paratyphi B, Pseudomonas aeruginosa, survival, seawater, osmotic shock.
Pathogenicity and molecular genetics of O-specific side-chain lipopolysaccharides of Escherichia coli
Authors: Valvano Miguel A.
Published: May 2010

Lipopolysaccharide (LPS), a glycolipid molecule found on the outer leaflet of outer membranes of gram-negative bacteria, consists of three moieties: lipid A, core oligosaccharide, and the O-specific polysaccharide chain. The O-specific side chain, which extends to the extracellular milieu, plays an important role in pathogenicity, especially during the initial stages of infection, because of its ability to interact with serum complement. In recent years, several laboratories have used recombinant DNA tools to determine, at the molecular level, the organization, expression, and regulation of genes involved in LPS biosynthesis in Salmonella and Escherichia coli. An increased understanding of the molecular aspects of the O-specific side-chain genes will shed light on the intimate details related with the formation of the O-specific side chain, its assembly onto the lipid A – core, and the translocation and insertion of the complete LPS molecule into the outer membrane. It will also contribute to the understanding of the evolution of these genes and the correlation of chemical diversity of O-specific side chains with the genetic diversity of O-specific side-chain genes. In addition, since the O-specific side chains are involved in the pathogenicity of medically important gram-negative bacteria, a basic understanding of the regulation and expression of O-specific side chain LPS genes will contribute to the field of molecular pathogenesis. This article provides an overview of the role of O-specific side chains in septicemic infections and also discusses the current status of molecular genetic studies on O-specific side-chain genes from E. coli. Key words: lipopolysaccharides, O types, molecular genetics, serum resistance.
Role of fimbrial adhesins in the pathogenesis of Escherichia coli infections
Authors: Hacker Jörg
Published: May 2010

Escherichia coli strains are able to cause intestinal (enteritis, diarrhoeal diseases) and extraintestinal (urinary tract infections, sepsis, meningitis) infections. Most pathogenic E. coli strains produce specific fimbrial adhesins, which represent essential colonization factors: intestinal E. coli strains very often carry transferable plasmids with gene clusters specific for fimbrial adhesins, like K88 and K99, or colonization factor antigens (CFA) I and II. In contrast, the fimbrial gene clusters of extraintestinal E. coli strains, such as P, S, or F1C fimbriae, are located on the chromosomes. The fimbrial adhesin complexes consist of major and minor subunit proteins. Their binding specificity can generally be assayed in hemagglutination tests. In the case of fimbrial adhesins of intestinal E. coli strains, the major subunit proteins preferentially represent the hemagglutinating adhesins, whereas minor subunit proteins are the hemagglutinins of extraintestinal E. coli strains. Recently "alternative" adhesin proteins were identified, which have the capacity to bind to eukaryotic structures different from the receptors of the erythrocytes. Fimbrial adhesins are not constitutively expressed but are stringently regulated on the molecular level. Extraintestinal E. coli wild-type strains normally carry three or more fimbrial adhesin determinants, which have the capacity to influence the expression of one another (cross talk). Furthermore the fimbrial gene clusters undergo phase variation, which seems to be important for their contribution to pathogenesis of E. coli. Key words: fimbriae, adhesins, Escherichia coli, pathogenicity.
Sporulation of Streptomyces antibioticus ETHZ 7451 in submerged culture
Authors: Novella Isabel S. , Barbés Covadonga , Sánchez Jesús
Published: May 2010

Streptomyces antibioticus ETHZ 7451 formed spores in cultures grown in a liquid medium from either a spore or a mycelium inoculum. The spores formed were similar to those formed on surface-grown cultures, except for reduced heat resistance. Both types of spores were sensitive to lysozyme, which is unusual for Streptomyces spores. Glucose and other carbon sources, which promoted different growth rates, did not affect sporulation efficiency. Nitrogen sources, such as casamino acids, that allowed high growth rates suppressed the sporulation. A remarkable repression was also observed in media with some nitrogen sources that promoted noticeably lower growth rates. In permissive media, with nitrogen sources that permitted relatively high growth rates, sporulation was conditioned to the consumption of ammonium in the medium, but not to that of other nitrogen sources, such as asparagine. Phosphate did not show a repressive effect on sporulation in the assayed conditions. Key words: Streptomyces antibioticus, sporulation.
Two-phase model for describing the interactions between copper ions and exopolymers from Alteromonas atlantica
Authors: Geesey Gill G. , Bremer Philip J. , Smith James J. , Muegge Michael , Jang Larry K.
Published: May 2010

Interactions between copper ions and exopolymer from the marine film-forming bacterium Alteromonas atlantica were evaluated by a two-phase model that treats the polymer as if it exists in a phase separate from the bulk solution. The model takes into account electrostatic interactions and molecular volume changes within the polymer phase to determine the copper activity in the domain where copper interacts with the ligands on the polymer molecule(s). The volume of the polymer phase varied with pH, ionic strength, and copper ion concentration. Exopolymer recovered from chemostat cultures grown at different dilution rates exhibited unique interligand distances, number of ionizable ligands, and molecular volumes. The variations in physical properties, in part, reflected differences in polymer chemistry. The exopolymer contained a lower density of ionizable groups and a smaller molecular volume per number of ionizable groups than alginic acid. The numerical procedure yielded a stability constant of 1 × 105 L/mol for a type I complex between copper ion and exopolymer produced at a dilution rate of 0.02 h−1 that was valid over a range of hydrogen ion concentrations and ionic strengths. The approach provided useful insight on how environmental variables affect the physicochemical properties of microbial exopolymers. Key words: exopolysaccharide, metal ions, chemostat culture.
Characterization of Azospirillum associated with maize (Zea mays) in France, using biochemical tests and plasmid profiles
Authors: Penot Isabelle , Berges Nathalie , Guinguene Christine , Fages Jacques
Published: May 2010

Thirty Azospirillum strains were isolated from the rhizosphere of 13 maize (Zea mays L.) cultivars grown in 14 French soils, using a new specific method, which has been given the name ROSEA. Among these strains 26 were Azospirillum lipoferum and 4 were Azospirillum brasilense. Their characterization was achieved using biochemical tests and plasmid profiles. Biochemical patterns allowed clear differentiation between the two species. A large diversity in carbon source metabolism was found among the Azospirillum sp. strains regardless of their origin. The A. brasilense were much more closely related, and were found in only two of the rhizospheres studied. The 30 plasmid patterns were all different, and the plasmid-profiling technique can therefore be considered as strain specific. All the A. lipoferum harboured a 150-MDa plasmid, while all the A. brasilense harboured a 90 to 100-MDa plasmid. This result reinforces the hypothesis of the presence of such plasmids as an additional criterion for differentiating these two species. Key words: Zea mays, Azospirillum, ROSEA method, biochemical tests, plasmid profiles.
Interactive effects of salt concentration and temperature on growth and lipid composition in the moderately halophilic bacterium Vibrio costicola
Authors: Adams Rachel L. , Russell Nicholas J.
Published: May 2010

The interactive effects of NaCl concentration and growth temperature on the growth and lipid composition of the moderately halophilic eubacterium Vibrio costicola have been investigated. Vibrio costicola was shown to be capable of growth over the temperature range 4–37 °C. Maximum growth yields were obtained at 30 °C when the optimum NaCl concentration was 1.0 M NaCl. In contrast with some previous studies, at higher or lower growth temperatures both the optimum and lower limit of NaCl concentration were higher, but there was no change in the upper limit of NaCl concentration for growth. There were no differences between the lipid compositions of cultures grown in 1 M NaCl at 30 or 37 °C, but as the growth temperature was lowered from 30 to 10 or 4 °C, the ratio of phosphatidylethanolamine to phosphatidylglycerol increased significantly as a result of the conversion of phosphatidylglycerol to diphosphatidylglycerol; in addition, at the lower growth temperatures the phospholipid fatty acyl composition became more unsaturated and the mean acyl chain length was shorter. It is suggested that the altered salt dependence of V. costicola at temperatures below the optimum for growth is due to a modification in membrane lipid phase behavior and stability brought about by changes in lipid composition, whereas a different mechanism operates above the growth temperature optimum. Key words: salinity, halophilic bacteria, temperature, Vibrio costicola, lipid composition, nonbilayer phases of lipids.
Cytochemical localization of some polysaccharide components in the cell walls of Chalara elegans during its life cycle
Authors: Dumas-Gaudot Eliane , Tahiri-Alaoui Abdessamad , Benhamou Nicole
Published: May 2010

The occurrence of polysaccharides and sugars in the cell walls of the soil-borne pathogenic fungus Chalara elegans (deuteromycete) has been investigated at the electron microscope level, using cytochemical approaches based on the affinity of lectin or enzyme–gold complexes for some carbohydrates. Evidence for the presence of both β-1,4-glucans and chitinous components is reported here for the first time in the cell walls of chlamydospores, endoconidia, and hyphae. A minor component with N-acetyl-D-galactosamine residues is also detected in the cell walls and, as a storage product, in the cytoplasm. The spatial distribution of both cellulosic β-1,4-glucans and N-acetylglucosamine residues differs according to the fungal cells, and the present results give a more accurate description of the multilayered structure of the fungal walls (i.e., chlamydospores and hyphae). Key words: Chalara elegans, fungi, cell walls, gold cytochemistry.
Strain distribution and in planta production of an extracellular polysaccharide depolymerase from Bradyrhizobium japonicum
Authors: Dunn Michael F. , Karr Arthur L.
Published: May 2010

Thirty-four strains of Bradyrhizobium japonicum were screened for the in vitro production of an extracellular polysaccharide depolymerase active against the B. japonicum acidic extracellular polysaccharide that contains mannose, glucose, galactose, and 4-O-methylgalactose as neutral sugar components. Over 90% of tested strains producing this type of extracellular polysaccharide also produced the extracellular polysaccharide depolymerase, whereas strains producing a compositionally different extracellular polysaccharide did not. In addition, representatives of species related to B. japonicum by extracellular polysaccharide composition or host range were also phenotypically depolymerase negative. Depolymerase was also present in soybean root nodules formed by B. japonicum strain 2143. In contrast to the cell-associated depolymerase activity found in free-living cells of this strain, most of the depolymerase activity present in nodules is free of the bacteroids. The widespread occurrence of the depolymerase among B. japonicum strains and the spatiotemporal distribution of its activity in planta are consistent with the enzyme playing a role in the removal of surface extracellular polysaccharide from the microorganism during the infection of nodulation process. Key words: Bradyrhizobium japonicum, soybean, extracellular polysaccharides, extracellular polysaccharide depolymerase, bacteroids.
DNA sequence heterogeneity in the gene encoding a 60-kilodalton extracellular protein of Listeria monocytogenes and other Listeria species
Authors: Gutekunst Karen A. , Holloway Brian P. , Carlone George M.
Published: May 2010

Chromosomal DNA sequences from the 60 kilodalton protein gene of Listeria monocytogenes, amplified by the polymerase chain reaction, were used for restriction fragment length polymorphism differentiation of L. monocytogenes serotypes and other Listeria species. All 24 strains of L. monocytogenes examined produced an extracellular protein of molecular weight 60 000 (p60) as determined by Western blot analysis. Four of six other Listeria species had a protein that cross-reacted to antibodies to p60, but all differed in molecular weight, ranging from approximately 50 000 to 65 000. The gene encoding p60 was amplified from chromosomal DNA in all strains using polymerase chain reaction with a single primer pair. Restriction enzyme digestion with HindIII of the amplified product revealed a restriction pattern that was distinct between serotypes 1/2a and either 4b or 1/2b of L. monocytogenes. Of the other Listeria species, four strains that produced a cross-reacting protein likewise produced a polymerase chain reaction amplification product with the primer pair. Listeria innocua alone had a restriction pattern similar to that of Listeria monocytogenes serotype 4b and 1/2b. Genotypic heterogeneity, as revealed by DNA amplification and restriction endonuclease digestion of the p60 open reading frame, correlates with "electrophoretic type" grouping and may be related to differences in virulence mechanisms of Listeria monocytogenes and other Listeria species. Key words: Listeria monocytogenes, 60-kilodalton extracellular protein, polymerase chain reaction, restriction fragment length polymorphism.
Purification, properties, and partial amino acid sequence of chitinase from a marine Alteromonas sp. strain O-7
Authors: Tsujibo Hiroshi , Yoshida Yukio , Miyamoto Katsushiro , Imada Chiaki , Okami Yoshiro , Inamori Yoshihiko
Published: May 2010

Chitinase (EC 3.2.1.14) was isolated from the culture supernatant of a marine bacterium, Alteromonas sp. strain O-7. The enzyme (Chi-A) was purified by anion-exchange chromatography (DEAE-Toyopearl 650 M) and gel filtration (Sephadex G-100). The purified enzyme showed a single band on sodium dodecyl sulfate polyacrylamide gel electrophoresis. The molecular size and pI of Chi-A were 70 kDa and 3.9, respectively. The optimum pH and temperature of Chi-A were 8.0 and 50 °C, respectively. Chi-A was stable in the range of pH 5–10 up to 40 °C. Among the main cations, such as Na+, K+, Mg2+, and Ca2+, contained in seawater, Mg2+ stimulated Chi-A activity. N-Bromosuccinimide and 2-hydroxy-5-nitrobenzyl bromide inhibited Chi-A activity. The amino-terminal 27 amino acid residues of Chi-A were sequenced. This enzyme showed sequence homology with chitinases from terrestrial bacteria such as Serratia marcescens QMB1466 and Bacillus circulons WL-12. Key words: marine bacterium, Alteromonas sp., chitinase.
Characterization of transcripts expressed from nitrogenase-3 structural genes of Azotobacter vinelandii
Authors: Premakumar R. , Jacobson Marty R. , Loveless Telisa M. , Bishop Paul E.
Published: May 2010

Five major anfH-hybridizing mRNA species accumulated in Azotobacter vinelandii cells derepressed for nitrogenase-3 (an alternative nitrogenase, which appears to lack Mo and V). Using anfH-, anfD-, anfG-, anfK-, and orf1orf2-specific probes and mutant strains of A. vinelandii these mRNA species have been identified as encoding anfHDGKorf1orf2 (6.0 kb), anfHDGK (4.3 kb), anfHD (2.6 kb), vnfHorfFd (1.3 kb), and vnfH and (or) anfH(1.0 kb). A 0.6-kb mRNA species, which hybridized only to the orf1orf2-specific probe, and a 3.5-kb mRNA species, which hybridized to anfD or anfK, also accumulated under these conditions. Northern blot analysis and S1 nuclease mapping indicate that transcription of the anf structural gene cluster initiates at a unique nif consensus promoter situated 127 base pairs upstream from the anfH coding region. Observation of anfH-hybridizing mRNA species that accumulate in strains derepressed for nitrogen fixation demonstrates that transcription of the anfHDGKorf1orf2 cluster is normally repressed by Mo, V, and NH4+, whereas transcription of the vnfHorfFd cluster does not require the presence of V and is repressed only by Mo, but not NH4+. Analysis of the accumulation of mRNAs in a tungsten-tolerant strain revealed that Mo and V repression of anf transcription must occur by different mechanisms. Key words: Azotobacter vinelandii, nitrogenase-3, transcripts, regulation, molybdenum, vanadium.
Croissance de la biomasse azotée du Phaeodactylum tricornutum (Bacillariophyceae) en cultures discontinues dialysante et non dialysante
Authors: Marsot Pierre , Cembella Allan D. , Mouhri Khadija
Published: May 2010

The unique conditions associated with discontinuous (batch) dialysis culture of the diatom Phaeodactylum tricornutum elicit different nutritional responses from those observed in nondialysis culture. Simultaneous determinations of the nitrogen biomass concentration and of the nitrogen nutrients (NO3− + NO2−) in the culture chamber, as well as in the seawater nutrient medium at the entrance and exit of the dialyzer, revealed that nitrogen-biomass production in dialysis cultures is achieved mainly (>90%) during postexponential growth, when the concentration of nutrients is limiting (smaller than Michaelis-Menten constant). Almost half of this biomass is produced at the diffusion limit of the apparatus, i.e., when the mass transfer of nutrient substrates, which determines the total uptake activity of the culture, reaches a maximum. In contrast, in nondialysis discontinuous cultures, in which the postexponential growth phase is short, most of the total cellular nitrogen is accumulated during active growth. Certain physiological indices relating to the active uptake and assimilation of inorganic nitrogen are consistent with the different nutritional responses elicited by these two types of culture techniques and explain the high biomass levels obtained in dialysis culture. Key words: dialysis culture, diatom, nitrogen metabolism.
Genetic mapping of the lytA and lytB loci of Escherichia coli, which are involved in penicillin tolerance and control of the stringent response
Authors: Harkness Robin E. , Kusser Wolfgang , Qi Bei-jing , Ishiguro Edward E.
Published: May 2010

The mutations in nine independently isolated temperature-sensitive mutants of Escherichia coli, which exhibited penicillin tolerance and induction of the stringent response at the restrictive temperature, were assigned to two new loci designated lytA (7 alleles) and lytB (2 alleles) at 58 and 0.4 min on the linkage map, respectively. Key words: bacteriolysis, penicillin tolerance, stringent response.
Effects of diphenols on the growth of three entomopathogenic fungi
Authors: Hsiao Wen-Feng , Bidochka Michael J. , Khachatourians George G.
Published: May 2010

The growth of three entomopathogenic fungi, Verticillium lecanii, Beauveria bassiana, and Metarhizium anisopliae, was determined in a yeast extract – peptone – dextrose (YPD) medium or a defined medium supplemented with dihydro-xyphenylalanine, dopamine, dopamine-HCl, norepinephrine-HCl, dihydroxyphenylacetic acid, or catechol. These diphenols may be found as part of the insect cuticle or hemolymph. Without diphenols YPD medium afforded generally higher growth of the fungi when compared with defined medium. Least growth was observed for B. bassiana and M. anisopliae in defined medium supplemented with dopamine, dopamine-HCl, or norepinephrine-HCl. Best growth for B. bassiana and M. anisopliae in defined medium was observed in unsupplemented medium or medium supplemented with dihydroxyphenylacetic acid, dihydroxyphenylalanine, or catechol. Best growth for V. lecanii was observed in a defined medium supplemented with dopamine, dopamine-HCl, or norepinephrine-HCl. In YPD medium, catechol inhibited growth of B. bassiana and M. anisopliae, whereas dihydroxyphenylalanine stimulated growth. The results showed similarities in M. anisopliae and B. bassiana response to various diphenols, whereas V. lecanii was different. Key words: diphenols, entomopathogenic fungi, Beauveria bassiana, Metarhizium anisopliae, Verticillium lecanii, fungal growth.
Microbial "footprints" and the general ability of microorganisms to label interfaces
Authors: Neu Thomas R.
Published: May 2010

In this minireview the expression microbial "footprints", the term used, to date, for adhesive polymers of microorganisms, is discussed. In addition, recent findings on the potential of microorganisms to label interfaces are considered. In conclusion a suggestion is made to distinguish between adsorption footprints and desorption footprints. Key words: adhesion, interfaces, "footprints," labeling, polymers.
Enhanced degradation of ammonium-pretreated wheat straw by lignocellulolytic Streptomyces spp.
Authors: Basaglia Marina , Concheri Giuseppe , Cardinali Stefano , Pasti-Grigsby Maria B. , Nuti Marco P.
Published: May 2010

Eleven actinomycetes, isolated from the gut of worker termites (Macrotermes, Armitermes, Microcerotermes, Odontotermes), were identified as Streptomyces chromofuscus, S. chromogenus, S. diastaticus, and S. rochei. Their ability to grow on natural lignocellulosic substrates was tested in solid state fermentation experiments using wheat straw (C/N = 49.8) as a sole carbon source. Weight loss was 4.7–20.9% of the initial substrate, after 5 weeks at 30 °C; lignin and cellulose content decreased 2.0–16.1 and 3.5–32.9%, respectively. When the 11 Streptomyces were grown on wheat straw pretreated with (NH4)HCO3 (C/N = 28.2), weight loss was 9.3–29.9% of the initial substrate, indicating an overall enhancement of lignocellulose degradation. Weight, lignin, and cellulose losses were enhanced when S. chromofuscus (strain A2 and A11) and S. rochei A4 were grown on pretreated wheat straw instead of the untreated substrate. With S. rochei A10 the weight loss and lignin degradation were enhanced, while cellulolysis was slightly depressed. Weight loss and cellulose degradation were both enhanced when the remaining strains were grown on pretreated wheat straw. In this case, lignin degradation was depressed (S. chromofuscus A6 and A8, S. diastaticus A12, S. rochei A14) or remained essentially the same (S. diastaticus A3 and S. chromogenus A7). Key words: Streptomyces, wheat straw, degradation, lignin, cellulose.
Characterization of catalase activities in a root-colonizing isolate of Pseudomonas putida
Authors: Katsuwon J. , Anderson A. J.
Published: May 2010

Pseudomonas putida, a saprophytic root-colonizing bacterium, produces multiple forms of catalase. Catalase A, which increases in specific activity during growth phase and after treatment with H2O2, is located in the cytoplasm and is inhibited by 3-amino-1,2,4-triazole, EDTA, and cyanide, but not by chloroform–methanol treatment. Catalase B, which is induced by external H2O2 or during stationary phase of growth, is membrane associated and is inhibited by chloroform–methanol, EDTA, and cyanide, but not by aminotriazole. Catalase A has a broad pH optimum, from pH 6.0 to 11.0, with two peaks, at pH 8.0 and 11.0. Catalase B is most active at pH 5.0–11.0. Mutant J-1, generated by ethyl methanesulfonate mutagenesis, lacked catalase A activity in extracts of cells harvested throughout lag to early stationary growth phase in liquid medium. Catalase B was produced by J-1 in stationary phase. Exposure of J-1 to H2O2 caused the production of both catalase A and catalase B. Mutant J-1 was more susceptible to cell death than the wild type upon direct exposure to 2.5 mM H2O2 but survived this treatment after exposure to lower (0.3 mM), nonlethal doses of H2O2. The ability to adapt to H2O2 may be related to the behaviour of J-1 on roots where active oxygen species are produced by root surface enzymes. J-1 colonized root surfaces at wild-type levels and produced catalases A and B after exposure to root surfaces for 12 h. Key words: Pseudomonas putida, catalase, root colonization.
Transferable drug resistance in bacteria from fish-farm sediments
Authors: Sandaa Ruth-Anne , Torsvik Vigdis Lid , Goksøyr Jostein
Published: May 2010

Antibiotic-resistant bacteria were isolated from sediment samples collected beneath two fish farms west of Bergen (Norway). The samples were collected just after the fish had been treated with oxytetracycline. Eighty-four bacterial isolates were tested for susceptibility to antibacterial agents. Most of the isolates were resistant to oxytetracycline, kanamycin, and sulfamethoxazole. Transferable plasmid-related resistance was shown by direct cell transfer and agarose gel electrophoresis. Among 34 multiple-resistant isolates, 7 isolates were able to transfer resistance to Escherichia coli HB101. Phenotypical characterization indicated that these seven isolates belonged to the genera Vibrio and Pseudomonas. The results indicate that sediments beneath fish farms may serve as a reservoir for transferable antimicrobial resistance genes. Key words: drug resistance, gene transfer, marine sediment bacteria.
Antimicrobial activity of 2-aminophenoxazin-3-one under anaerobic conditions
Authors: Atwal A. S. , Teather R. M. , Liss S. N. , Collins F. W.
Published: May 2010

Potential toxicity of 2-aminophenoxazin-3-one to 20 bacterial species and two fungi and its inactivation under anaerobic conditions were investigated. Minimum inhibitory concentration for cellulolytic bacteria was in the range of 50–100 μg∙mL−1, but at 100 μg∙mL−1 of 2-aminophenoxazin-3-one, there was no effect on the growth of any of the noncellulolytic bacteria. Four noncellulolytic bacterial strains showed no inhibition of growth, even at 200 μg∙mL−1 of this compound. Under anaerobic conditions and in the presence of cysteine, the long wavelength absorption band of this compound slowly shifted from about 434 to 320 nm, and its inhibitory effect on RNA synthesis was relieved after one-half of a generation time in cultures of cellulolytic ruminai bacteria. A similar shift of absorption band was observed in rumen fluid filtered through a 0.22-μm Millipore filter. It was concluded that protonation of 2-aminophenoxazin-3-one under anaerobic conditions present in the rumen would considerably reduce its potential toxicity to cellulolytic bacteria. Key words: questomycin A, cellulolytic bacteria, cysteine, 2-aminophenoxazin-3-one, RNA synthesis.
Toxicity of free riboflavin and methionine–riboflavin solutions to Phytophthora infestans and the reduction of potato late blight disease
Authors: Jordan C. M. , Wakeman R. J. , DeVay J. E.
Published: May 2010

Treatments of sporangia and zoospores of Phytophthora infestans race 1.2.3.4 with methionine or riboflavin for durations of up to 8 h under fluorescent light did not affect its colonization of rye-seed agar. In contrast, exposure of sporangia and zoospores to methionine-riboflavin mixture for 2 h or more resulted in the failure of race 1.2.3.4 to grow when transferred to rye-seed agar medium. Hyphal growth of races 1.2.3.4 and 0, when incubated in liquid synthetic medium, was inhibited by free riboflavin. Potato plants, Solanum tuberosum cv. Kennebec, when pretreated with a methionine–riboflavin mixture and then spray inoculated with race 1.2.3.4 developed fewer diseased leaves per plant than plants pretreated with water, methionine, or riboflavin. Key words: Solanum tuberosum, hydroxyl radical, superoxide anion.
The thermostable direct hemolysin of Vibrio parahaemolyticus is a pore-forming toxin
Authors: Honda Takeshi , Ni Yuxin , Miwatani Toshio , Adachi Toshiyuki , Kim Jeman
Published: May 2010

The hemolytic mechanism of thermostable direct hemolysin (TDH), a possible virulence factor of Vibrio parahaemolyticus, was studied. We demonstrated that TDH acts as a "pore-forming toxin" in temperature-dependent and -independent steps. The first temperature-dependent step requires only about 1–2 min incubation at 37 °C and makes a "pore" with a functional diameter of approximately 2 nm. The pore size was deduced from the molecular diameter of the colloidal inhibitory polysaccharides. The formation of the pores on TDH-treated erythrocyte membranes was also demonstrated by electron microscopic examination. The second step, which is a temperature-independent lytic step, causes the erythrocytes to swell owing to a colloidal osmotic influx of water via the "pores" into cells, resulting in erythrocyte lysis (or rupture) owing to increased intracellular pressure. Key words: Vibrio parahaemolyticus, hemolysin, hemolysis, pore-forming toxin.
Prolonged survival of Bordetella pertussis in a simple buffer after nasopharyngeal secretion aspiration
Authors: Halperin Scott , Kasina Alicja , Swift Margaret
Published: May 2010

A simple method for recovery of Bordetella pertussis is described using phosphate-buffered saline containing a casein hydrolysate for transporting secretions collected by nasopharyngeal aspirate. Bordetella pertussis was reisolated from 92% of clinical specimens held at 4 °C for 1 week and from all specimens held at −20 °C. This method will facilitate the centralization of laboratory facilities for the diagnosis of pertussis. Key words: Bordetella pertussis, specimen transport, nasopharyngeal secretions.
A review of issues related to measuring colonization of plant roots by bacteria
Authors: Kloepper Joseph W. , Beauchamp Chantal J.
Published: May 2010

Root colonization by introduced bacteria is an important step in the interaction of beneficial bacteria with the host plant. Investigators attempting to measure root colonization by bacteria must face several issues. A clear concept or definition of root colonization should be stated in each research summary, as several different definitions have been proposed. We consider true root colonists to be those bacteria that colonize roots in competitive conditions, i.e., natural field soils. Different methods of processing root samples are required if one is measuring external root colonization alone, internal colonization alone, or both. Given that most beneficial bacterial strains currently under investigation as root colonists are members of taxa naturally found in soils, a marking system is required to differentiate the introduced strain from members of the indigenous rhizosphere community. Spontaneous antibiotic resistance, immunological approaches, and foreign DNA sequences are among the marking systems that have been used and each has some possible advantages and disadvantages. More research is needed in the development and comparison of marking systems. The design of experiments to measure root colonization should take into account several statistical issues. One must decide what constitutes the sample unit for each replication of a given treatment, e.g., whole root systems or root segments. Consideration should also be given to how best to express the estimated population of root colonists (e.g., cfu/g fresh or dry weight root, cfu/cm root, or cfu/surface area root). Statistical analysis by standard analysis of variance tests should be used whenever possible to separate treatment means of colonization levels; however, one must determine that the underlying assumptions of these tests are correct for each experiment. Finally, in quantification of populations on roots, one will almost certainly encounter replications with no bacteria, i.e., zeros. There are several options for how to calculate treatment means when one or more replications is a zero, and the implications of these options are discussed. Key words: bioluminescence, genetic markers, plant growth-promoting rhizobacteria, rhizosphere bacteria, root, colonization.
Utilization of tartaric acid and related compounds by yeasts: taxonomic implications
Authors: Fonseca Alvaro
Published: May 2010

A survey of yeasts capable of growing on L(+)-tartaric acid as the sole source of carbon and energy showed that this organic acid is assimilated by a significant number of species of basidiomycetous affinity and is seldom utilized by ascomycetous yeasts. This conclusion was further supported by the fact that among approximately 100 isolates from various natural substrates, using selective media with L(+)-tartaric acid, only one strain of ascomycetous affinity was obtained. In a more comprehensive survey 442 yeast strains belonging to 138 species, mostly of basidiomycetous affinity, were also screened for the assimilation of different aldaric acids: D(−)-tartaric acid, meso-tartaric acid, L(−)-malic acid, D(+)-glucaric acid (saccharic acid), and galactaric acid (mucic acid). L(+)-Tartrate was the most frequently utilized tartaric acid isomer (55% of the total number of strains of basidiomycetous affinity belonging to either the Tremellales/Filobasidiales or the Ustilaginales) when compared with the D(−) and meso forms, which were assimilated by 12 and 18% of the total number of strains, respectively (mainly of tremellaceous species). Saccharic acid was utilized by about 75% of the total number of species of Tremellales affinity and by less than 20% of the ustilaginaceous species. Assimilation of mucic acid occurred in more than 50% of the tremellaceous species and only in 5% of the species related to the Ustilaginales. These tests, not used in standard yeast identification sets, appear to contribute to distinguishing taxa at or above the species level. Key words: assimilation, tartaric acid, aldaric acids, yeasts, taxonomy.
Changes in ribosomal proteins during colony development in Streptomyces
Authors: Quiros Luis M. , Parra Francisco , Salas Jose A.
Published: May 2010

The structure and functionality of the ribosomal subunits of the substrate and the aerial mycelium of Streptomyces antibioticus were compared. Using SDS-PAGE and HPLC, several differences between the ribosomal protein pattern from both stages of development were observed, including a clear decrease in the L7/L12 content of the aerial mycelium. The activity of the aerial mycelia ribosomes was also decreased when compared with that of the substrate mycelium. This effect was more pronounced in the 50S subunit. These results suggest that during cell differentiation in Streptomyces important changes occur at the ribosomal level, particularly in the transition from the substrate to the aerial mycelium. Key words: ribosomes, Streptomyces, differentiation.
Promotion of apple tree growth and fruit production by the EBW-4 strain of Bacillus subtilis in apple replant disease soil
Authors: Utkhede R. S. , Smith E. M.
Published: May 2010

A field trial was conducted near Kelowna, British Columbia, to determine the effect of biological treatments alone and in combination with formalin fumigation in apple replant disease soil. The response was measured by the increase in cross-sectional trunk area, total shoot growth, and fruit yield of McIntosh apple trees on M.26 rootstock. The postplanting drench application of strain EBW-4 of Bacillus subtilis alone was consistently effective in increasing cross-sectional trunk area for 5 years, total shoot growth for 4 years, and fruit yield for 3 years. The biological agent EBW-4 of B. subtilis in combination with formalin fumigation was also effective in promoting total shoot growth and cross-sectional trunk area. The application of formalin fumigation alone was effective in increasing shoot growth for 2 years and cross-sectional trunk area for 1 year only. This treatment did not increase fruit yield for 3 years. The consistent performance of strain EBW-4 of B. subtilis during 1986–1991 indicates that this bacterium has the potential for biological control of replant disease under orchard conditions in the Okanagan Valley of British Columbia. Key words: Enterobacter aerogenes, replant problem, growth promoting bacteria, plant growth promoting rhizobacteria.
Heat-shock response in Fonsecaea pedrosoi, a pathogenic fungus
Authors: Laurent-Winter Christine , Ibrahim-Granet Oumaima
Published: May 2010

Using two-dimensional electrophoresis we have investigated the heat-shock response in a pathogenic fungus, Fonsecaea pedrosoi. Fungal cultures were transferred from 37 to 45 °C for either 30 or 90 min and then returned back to the initial temperature. Analysis of the total proteins resolved on two-dimensional gels indicated important changes in the accumulation of several peptides according to the duration of treatment and the temperature. The 30-min incubation at 45 °C resulted in the induction of several new proteins, whereas other proteins were either increased or decreased. These inductions and repressions of proteins (called heat-shock and heat-stroke proteins, respectively) were either specific to this time period or still present after a 90-min incubation. In addition, the 90-min incubation period led to the enhancement of several proteins, which were therefore called late heat-shock proteins to distinguish them from the early ones detected after 30 min. Finally, when cultures were shifted back to 37 °C most of the heat-shock proteins decreased or disappeared; in parallel, most of the heat-stroke proteins were reinduced at this time. These results are in good agreement with previous studies on the heat-shock response and provide additional evidence that this phenomenon is highly conserved among species. Key words: heat-shock proteins, two-dimensional electrophoresis, pathogenic fungus, Fonsecaea pedrosoi.