bluuebunny/crossref_metadata_2025 huggingface dataset:
Physicochemical properties of a novel α-L-arabinofuranosidase fromRhizomucor pusillusHHT-1
Authors: Shofiqur Rahman A KM , Kawamura Shinya , Hatsu Masahiro , Hoq M M , Takamizawa Kazuhiro
Published: April 2011

The zygomycete fungus Rhizomucor pusillus HHT-1, cultured on L(+)arabinose as a sole carbon source, produced extracellular α-L-arabinofuranosidase. The enzyme was purified by (NH4)2SO4fractionation, gel filtration, and ion exchange chromatography. The molecular mass of this monomeric enzyme was 88 kDa. The native enzyme had a pI of 4.2 and displayed a pH optimum and stability of 4.0 and 7.010.0, respectively. The temperature optimum was 65°C, and it was stable up to 70°C. The Kmand Vmaxfor p-nitrophenyl α-L-arabinofuranoside were 0.59 mM and 387 µmol·min1·mg1protein, respectively. Activity was not stimulated by metal cofactors. The N-terminal amino acid sequence did not show any similarity to other arabinofuranosidases. Higher hydrolytic activity was recorded with p-nitrophenyl α-L-arabinofuranoside, arabinotriose, and sugar beet arabinan; lower hydrolytic activity was recorded with oatspelt xylan and arabinogalactan, indicating specificity for the low molecular mass L(+)-arabinose containing oligosaccharides with furanoside configuration.Key words: α-L-arabinofuranosidase, enzyme purification, amino acid sequence, Rhizomucor pusillus.
Isolation and characterization of a chromosomally encoded disulphide oxidoreductase from Salmonella enterica serovar Typhimurium
Authors: Turcot I , Ponnampalam T V , Bouwman C W , Martin N L
Published: April 2011

In this study, the chromosomally encoded disulphide oxidoreductase dsbA from Salmonella typhimurium was cloned and characterized. A survey of a number of serovars of Salmonella subspecies I showed that dsbA is highly conserved in most, but not all members of this subclass of Salmonella species. Using motility, β-galactosidase, and alkaline phosphatase assays as indirect indicators of disulphide oxidoreductase activity, we demonstrated that DsbA from S. typhimurium LT2 can only partially complement an Escherichia coli dsbA-null strain. This is surprising considering the high degree of conservation between these two DsbA proteins (87% amino acid identity). To determine the contribution of DsbA to the proper folding and assembly of proteins of S. typhimurium, deletion mutants were created in the avirulent strain LT2 and in the virulent strain SL1344. These null alleles were constructed by partial deletion of the dsbA-coding region and then insertion of an antibiotic resistance marker in the gene. Mutants no longer expressing a functional disulphide oxidoreductase exhibit pleitropic effects, including an increase in colony mucoidy, a dramatic decrease in motility, and an increased susceptibility to the cationic peptide protamine sulphate. The disruption of disulphide bond formation was also shown to specifically affect the stability of several proteins secreted into the extracellular environment.Key words: disulphide oxidoreductase, protein folding, Salmonella typhimurium, DsbA.
Phylogeny of mitosporic entomopathogenic fungi: Is the genus Paecilomyces polyphyletic?
Authors: Oborník Miroslav , Jirku Milan , Dolezel David
Published: April 2011

We analyzed sequences of the divergent domain at the 5' end of the large subunit rRNA gene from the mitosporic entomopathogenic fungi Paecilomyces sp., Paecilomyces fumosoroseus, Paecilomyces farinosus, Paecilomyces lilacinus, Verticillium lecanii, Verticillium psalliotae, Beauveria bassiana, Aschersonia sp., Aschersonia placenta, ascomycetous Cordyceps sp., and Cordyceps militaris. Phylogenetic analysis showed P. fumosorseus as the best characterized out of the analyzed species with the B. bassiana clade as its sister group. Two of the P. farinosus isolates were invariably placed within the Verticillium cluster, which also contained C. militaris. The only analyzed P. lilacinus isolate appeared on the root of the hyphomycetous fungi and was characterized as the most distinct from all the hyphomycetous fungi tested. Polyphyly of the genus Paecilomyces was well supported by the Kishino-Hasegawa test. In all trees based on the small subunit rRNA gene sequences obtained from the GenBank(tm), V. lecanii, V. psalliotae, P. fumosoroseus, P. tenuipes and B. bassiana form, together with that of C. militaris, the best supported cluster in the tree. The rest of Cordyceps spp. constitute a distinct clade. Phylogenetic relationships derived from both tested DNA regions show polyphyly of the genus Paecilomyces and close relationships among entomopathogenic species of the genera Verticillium, Paecilomyces, and Beauveria.Key words: Paecilomyces, Verticillium, Beauveria, Aschersonia, entomopathogenic fungi, molecular phylogeny, ribosomal RNA genes.
Molecular analysis of thePseudomonas aeruginosaregulatory genesptxRandptxS
Authors: Colmer Jane A , Hamood Abdul N
Published: April 2011

We have previously described two Pseudomonas aeruginosa genes, ptxR, which enhances toxA and pvc ( the pyoverdine chromophore operon) expression, and ptxS, the first gene of the kgu operon for the utilization of 2-ketogluconate by P. aeruginosa. ptxS interferes with the effect of ptxR on toxA expression. In this study, we have utilized DNA hybridization experiments to determine the presence of ptxR and ptxS homologous sequences in several gram-negative bacteria. ptxR homologous sequences were detected in P. aeruginosa strains only, while ptxS homologous sequences were detected in P. aeruginosa, Pseudomonas putida, and Pseudomonas fluorescens. Using Northern blot hybridization experiments and a ptxSlacZ fusion plasmid, we have shown that P. aeruginosa ptxR and ptxS are expressed in P. putida and P. fluorescens. Additional Northern blot hybridization experiments confirmed that ptxS is transcribed in P. putida and P. fluorescens strains that carried no plasmid. The presence of a PtxS homologue in these strains was examined by DNA-gel shift experiments. Specific gel shift bands were detected when the lysates of P. aeruginosa, P. putida, and P. fluorescens were incubated with the ptxS operator site as probe. kgu-hybridizing sequences were detected in P. putida and P. fluorescens. These results suggest that (i) ptxR is present in P. aeruginosa, while ptxS is present in P. aeruginosa, P. putida, and P. fluorescens; (ii) both ptxR and ptxS are expressed in P. putida and P. fluorescens; and (iii) a PtxS homologue may exist in P. putida and P. fluorescens.Key words: Pseudomonas aeruginosa, ptxR, ptxS, DNA hybridization, kgu operon.
Interspecies biofilms ofPseudomonas aeruginosaandBurkholderia cepacia
Authors: Tomlin Kerry L , Coll Oisin P , Ceri Howard
Published: April 2011

The leading cause of morbidity and mortality in cystic fibrosis (CF) continues to be lung infections with Pseudomonas aeruginosa biofilms. Co-colonization of the lungs with P. aeruginosa and Burkholderia cepacia can result in more severe pulmonary disease than P. aeruginosa alone. The interactions between P. aeruginosa biofilms and B. cepacia are not yet understood; one possible association being that mixed species biofilm formation may be part of the interspecies relationship. Using the Calgary Biofilm Device (CBD), members of all genomovars of the B. cepacia complex were shown to form biofilms, including those isolated from CF lungs. Mixed species biofilm formation between CF isolates of P. aeruginosa and B. cepacia was readily achieved using the CBD. Oxidationfermentation lactose agar was adapted as a differential agar to monitor mixed biofilm composition. Scanning electron micrographs of the biofilms demonstrated that both species readily integrated in close association in the biofilm structure. Pseudomonas aeruginosa laboratory strain PAO1, however, inhibited mixed biofilm formation of both CF isolates and environmental strains of the B. cepacia complex. Characterization of the soluble inhibitor suggested pyocyanin as the active compound.Key words: Burkholderia cepacia, Pseudomonas aeruginosa, mixed biofilms, cystic fibrosis, pyocyanin.
Physical, chemical, and microbiological characteristics of microbial mats (KOPARA) in the South Pacific atolls of French Polynesia
Authors: Che L Mao , Andréfouët S , Bothorel V , Guezennec M , Rougeaux H , Guezennec J , Deslandes E , Trichet J , Matheron R , Campion T Le , Payri C , Caumette P
Published: April 2011

Microbial mats that develop in shallow brackish and hyposaline ponds in the rims of two French polynesian atolls (Rangiroa and Tetiaroa) were intensively investigated during the past three years. Comparative assessment of these mats (called kopara in polynesian language) showed remarkable similarities in their composition and structure. Due to the lack of iron, the color of the cyanobacterial pigments produced remained visible through the entire depth of the mats (2040 cm depth), with alternate green, purple, and pink layers. Profiles of oxygen, sulfide, pH, and redox showed the anoxia of all mats from a depth of 23 mm. Analyses of bacterial pigments and bacterial lipids showed that all mats consisted of stratified layers of cyanobacteria (mainly Phormidium, Schizothrix, Scytonema) and purple and green phototrophic bacteria. The purple and green phototrophic bacteria cohabit with sulfate reducers (Desulfovibrio and Desulfobacter) and other heterotrophic bacteria. The microscopic bacterial determination emphasized the influence of salinity on the bacterial diversity, with higher diversity at low salinity, mainly for purple nonsulfur bacteria. Analyses of organic material and of exopolymers were also undertaken. Difference and similarities between mats from geomorphological, microbiological, and chemical points of view are discussed to provide multicriteria of classification of mats.Key words: microbial mats, cyanobacteria, bacterial pigments, French Polynesia atolls, exopolymers.
Co-inoculation withBacillussp. CECT 450 improves nodulation inPhaseolus vulgarisL.
Authors: Camacho M , Santamaría C , Temprano F , Rodriguez-Navarro D N , Daza A
Published: April 2011

The strain Bacillus sp. CECT 450 increased nodulation on bean (Phaseolus vulgaris L.) when co-inoculated with Rhizobium tropici CIAT 899. This positive effect occured under controlled conditions on perlitevermiculite, sand, or in a mixture of soil and sand. This increase was also observed in a field assay. Nodulation kinetic studies suggested that the synergistic effect is pronounced during the latter stages of cultivation. In contrast, the same bacteria co-inoculated with Bradyrhizobium japonicum USDA 110 reduced nodulation on soybean (Glycine max (L.) Merr.). Inoculation with Bacillus sp. CECT 450 alone had no effect on bean plants, but reduced root growth in soybean. The survival of Bacillus sp. CECT 450 on inoculated seeds was high, even when inoculated seeds were maintained for several months at room temperature.Key words: Rhizobium spp., Bacillus sp., Phaseolus vulgaris, nodulation, co-inoculation.
Enteric bifidobacteria: isolation from human infants and challenge studies in mice
Authors: Locascio M , de Ruiz Holgado A Pesce , Perdigón G , Oliver G
Published: April 2011

Bifidobacteria from breast-fed infants, formula-fed infants, or premature babies fed by parenteral methods were isolated and identified. The persistence of these microorganisms in the gastrointestinal tract of mice, after oral administration, was studied to determine the optimal dose and frequency of translocation to the liver and spleen. The rate of isolation among infants varied between 19 and 82% depending on the origin of the samples, with the highest values seen in breast-fed babies. The predominant species found in all cases was Bifidobacterium adolescentis. The optimal dose for oral administration of bifidobacteria to mice was 107 cells per day per animal for up to 2, 5, or 7 days. These bacteria remained up to 5 days postfeeding, even if feeding was interrupted. The results of bacterial translocation assays showed differences for the different strains and doses tested.Key words: Bifidobacterium, intestinal ecology, breast-fed, probiotics.
Structural analyses of the deduced amino acid sequences of a novel type hemecopper terminal oxidase, cytochromeaco3, from alkalophilicBacillusYN-2000
Authors: Denda Kimitoshi , Oshima Akira , Fukumori Yoshihiro
Published: April 2011

Cytochrome aco3from a facultatively alkalophilic bacterium, Bacillus YN-2000, was found to be alkaline- and heat-tolerant. To better understand the structural features of Bacillus YN-2000 cytochrome aco3, the gene encoding this enzyme was cloned and sequenced. Nucleotide sequence analyses of the region neighboring the acoI (subunit I) gene revealed that the acoII (subunit II) and acoIII (subunit III) genes were concomitantly clustered upstream and downstream of the acoI gene, respectively, forming an operon with transcriptional polarity. The deduced amino acid sequence of subunit I was highly similar to that of cytochrome caa3from thermophilic bacterium Bacillus PS3 in which the heme a3could be replaced with heme o. Furthermore, a marked paucity of basic amino acid residues was found in the cytochrome c-binding subunit II, which might be a result of the adaptation to a highly alkaline external milieu.Key words: cytochrome c oxidase, alkalophile, thermostability, heme o, Bacilli.
Isolation and in vitro cultivation of the aphid pathogenic fungusEntomophthora planchoniana
Authors: Freimoser Florian M , Jensen Annette B , Tuor Urs , Aebi Markus , Eilenberg Jørgen
Published: April 2011

Entomophthora planchoniana is an important fungal pathogen of aphids. Although Entomophthora chromaphidis has been considered a synonym for E. planchoniana, the two species are now separated, and E. planchoniana is reported not to grow in vitro. In this paper, we describe for the first time the isolation and cultivation of this species. Entomophthora planchoniana was isolated from a population of Ovatus crataegarius (Homoptera, Aphididae), which was infected by E. planchoniana only. The isolates did not sporulate, but the sequence of the small subunit rDNA and the restriction fragment length polymorphism patterns of the first part of the large subunit rDNA and the ITS II region confirm that the isolates were E. planchoniana. The isolated fungus grew in a medium consisting of Grace's insect cell culture medium supplemented with lactalbumin hydrolysate, yeastolate, and 10% fetal bovine serum or in GLEN medium with 10% fetal bovine serum. Vegetative cells of E. planchoniana were long and club-shaped and did not stain with Calcofluor, thus suggesting that they were protoplasts.Key words: biological control, entomopathogen, Entomophthorales, protoplast, Zygomycetes.
Developmentally regulated protein synthesis during intraperiplasmic growth ofBdellovibrio bacteriovorus109J
Authors: McCann M P , Solimeo H T , Cusick, Jr. F , Panunti B , McCullen C
Published: April 2011

Bdellovibrio bacteriovorus 109J is an obligate intraperiplasmic predator of other Gram-negative bacteria. Collision with a suitable prey cell initiates a developmental sequence ultimately resulting in the destruction of the prey cell and the production of progeny bdellovibrios. Two-dimensional gel analysis of patterns of protein synthesis at various times in a synchronously growing culture of Bdellovibrio bacteriovorus 109J revealed over 30 polypeptides whose syntheses are developmentally regulated. The majority of these polypeptides fall into nine categories: attack phase specific or one of eight different kinetic groups expressed during the intraperiplasmic growth phase. The results indicate that Bdellovibrio bacteriovorus 109J has a complex system for regulating gene expression during its developmental cycle.Key words: gene regulation, development, two-dimensional gels, Bdellovibrio bacteriovorus.
A hydrogen peroxide resistant mutant ofSpirillum volutanshas NADH peroxidase activity but no increased oxygen tolerance
Authors: Alban Patrick S , Krieg Noel R
Published: April 2011

The catalase-negative microaerophile Spirillum volutans is killed rapidly by levels of H2O2greater than 10 μM. A mutant isolated by single step mutagenesis with diethyl sulfate was able to survive and grow after exposure to 40 μM H2O2and was effective in eliminating H2O2added to the medium. Nevertheless, the mutant was no more colerant to O2than the wild type. The only apparent phenotypic difference between the wild type and the mutant was that the mutant had high NADH peroxidase activity (0.072 IU.mg-1) whereas the wild type had no detectable activity (<0.0002 IU.mg-1). NADH peroxidase has not previously been reported in gram-negative bacteria or in bacteria having a strictly respiratory type of metabolism.Key words: microaerophile, Spirillum volutans, peroxidase, oxygen tolerance, hydrogen peroxide.
Fructose 2,6-bisphosphate biosynthesis and regulation of carbohydrate metabolism inAspergillus oryzae
Authors: Rádis-Baptista Gandhi , Valdivia David N. Urquizo , Abrahão-Neto José
Published: April 2011

The biosynthesis and role of fructose 2,6-bisphosphate (Fru-2,6-P2) in carbohydrate metabolism during induction of an amylolytic system in Aspergillus oryzae was studied. Fluctuations in Fru-2,6-P2were not dependent on the external glucose concentration during induction, whereas the level of Fru-2,6-P2increased significantly when the oxygen concentration was diminished. Phosphofructokinase II (PFK II) of A. oryzae was sensitive to phosphorylation in vitro by the catalytic subunit of cyclic AMP dependent protein kinase, which increased the Vmax(twofold), although the Km(0.7 mM) remained unchanged. Phosphofructokinase I was neither activated by micromolar Fru-2,6-P2nor inhibited by high ATP concentrations. The activity of fructose-1,6-bisphosphatase (FBPase) was subject to strong inhibition by Fru-2,6-P2. Addition of glucose to cultures under gluconeogenic conditions caused a decrease of approximately 40% in the FBPase activity within 4 min. These results indicate that the effect of Fru-2,6-P2in A. oryzae could preferentially control gluconeogenesis. The addition of 0.1 M glucose under gluconeogenic culture conditions also showed that Fru-2,6-P2fluctuations appeared to be, at least in short term, more closely related to temporal changes in the hexose-6-phosphate concentration.Key words: Aspergillus oryzae; fructose-2,6-bisphosphate; phosphofructokinase II (PFK II); cyclic AMP; gluconeogenesis control.
Binding of heterocyclic amines by lactic acid bacteria from miso, a fermented Japanese food
Authors: Rajendran Rajam , Ohta Yoshiyuki
Published: April 2011

Miso, a widely used Japanese fermented food was analysed for its lactic acid bacterial count on bromocresol purple agar. The binding of eight different foodborne carcinogenic heterocyclic amines to 25 bacterial isolates from miso were investigated. The heterocyclic amines used were 3-amino-1,4-dimethyl[5H]pyrido(4,3-b)indole (Trp-P-1), 3-amino-1-methyl[5H]pyrido(4,3-b)indole (Trp-P-2), 2-amino-6-methyldipyrido(1,2-a:3'2'-d)imidazole (Glu-P-1), 2-amino-1-methyl-6-phenylimidazo(4,5-b)pyridine (PhIP), 2-amino-dimethylimidazo(4,5f)quinoline (IQ), 2-amino-3,4-dimethylimidazo(4,5-f) quinoline (MeIQ), 2-amino-3,8-dimethylimidazo(4,5-f)quinoxaline (MeIQx), and 2-amino-3-methyl-9H-pyrido(2,3)indole (MeAαC). The lyophilized cells of all of the isolates exhibited high binding activity towards Trp-P-1, Trp-P-2, MeAαC, and PhIP, while Glu-P-1 and IQ were not effectively bound. Of the isolates tested, the strongest and weakest binders were identified as Pediococcus acidilactici 1 and 2, respectively. Lyophilized cell wall fractions, heat-treated cells, and the cytoplasmic contents of P. acidilactici 1 and 2 were analysed for their ability to bind to different mutagens. Pure cell wall and peptidoglycan showed greater binding activity than the bacterial cells. Cytoplasmic content also showed some binding, but it was much less effective. The impact of enzymes (amylase, protease, cellulase, chitinase, muraminase, and peptidase) and acetylation of Trp-P-1 and IQ on the binding action of bacteria and cell wall material were also analysed to understand the possible processes involved in the binding of lactic acid bacteria to carcinogenic heterocyclic amines.Key words: mutagen, heterocyclic amines, lactic acid bacteria, binding, miso.
Chemically emulsified crude oil as substrate for bacterial oxidation: differences in species response
Authors: Bruheim Per , Eimhjellen Kjell
Published: April 2011

Four bacterial species were tested for their abilities to oxidize alkanes in crude oil in water emulsions. The emulsions were prepared by nonionic sorbitan ester and polyoxyethylene ether surfactants. The oxidation rates were measured as initial attack on the emulsions by resting cells pregrown in crude oil media. The bacteria responded differently and both positive and negative effects of surfactant amendment were observed. The same surfactant affected various bacteria differently and the response to the surfactant amendment depended on the physiological state of the bacteria, i.e., exponential versus stationary growth phase. The surfactants caused a marked decrease in cell adhesion to the oil phase for all the bacteria, irrespective of the growth phase and any positive effect on the oil oxidation rates. The response of Deleya salina 128 to polyoxyethylene surfactant emulsified crude oil depended on the length and structure of the hydrophobic tail, the number of hydrophilic ethoxy groups, and the relative proportion of the hydrophobic and hydrophilic constituents in the individual surfactant.Key words: biodegradation, bacteria, nonionic surfactants, crude oil.
Protease activity ofClostridium difficilestrains
Authors: Poilane Isabelle , Karjalainen Tuomo , Barc Marie-Claude , Bourlioux Pierre , Collignon Anne
Published: April 2011

The production of proteolytic enzymes by 10 Clostridium difficile isolates of varying toxigenicity and clinical origin was studied to determine if all isolates secreted proteases. Different protease substrates were studied: gelatin, collagen, phenylazobenzyloxycarbonyl-leucyl-glycyl-L-prolyl-D-arginine (Pz-peptide), casein, azocasein, and azocoll. All isolates degraded gelatin, collagen, and azocoll. The supernatants of all isolates contained an enzyme capable of attacking gelatin incorporated in a polyacrylamide gel (zymograms) and forming two closely spaced lytic bands with an estimated molecular mass of 35→40 kDa. Polyclonal antibodies, produced against the C. difficile gelatinase, revealed in Western blots a 35-kDa protein in the culture supernatants of all C. difficile isolates. In the same manner, Clostridium perfringens collagenase polyclonal antibodies detected a 120-kDa protein in the culture supernatants of all isolates; this suggests that at least two proteases may exist in C. difficile. The protease activities of the 10 strains examined did not seem strikingly different quantitatively but were in general weak and their role in pathogenicity is suspect.Key words: Clostridium difficile, proteolytic enzymes.
Associations of bacterial endophyte populations from red clover and potato crops with potential for beneficial allelopathy
Authors: Sturz A V , Christie B R , Matheson B G
Published: April 2011

Clover and potatoes, in a crop rotation, were found to share specific associations of bacterial endophytes. Twenty-five bacterial species from 18 genera were common to both clover and potatoes and represented 73% of all the bacteria recovered from clover root tissues and 73% of all the bacteria recovered from potato tubers. Endophytic bacteria tested in potato plant bioassays were predominantly plant growth neutral (56%). The remainder were either plant growth promoting (21%) or plant growth inhibiting (24%)(P < 0.05). Of the plant growth promoting bacteria, 63% increased shoot height, 66% increased shoot wet weight, and 55% increased root wet weight. The effects of plant growth inhibiting bacteria were restricted to reductions in plant height (86%) and shoot wet weight (36%); root weight was not affected. Of the bacteria tested, 74% showed some degree of in vitro antibiosis to the clover and potato pathogen Rhizoctonia solani. Such endophytic intercrop bacterial associations appear to be complementary in nature and support the view that there are microbial benefits to be gained from clover in crop sequences with potatoes, beyond those of the residual nitrogen left in the soil and the organic matter added.Key words: Trifolium, allelopathy, endophytic, plant growth promoting, antifungal, crop rotation, Solanum.
Expression of a Bacillus thuringiensis δ-endotoxin gene by Bacillus pumilus
Authors: Selinger L B , Khachatourians G G , Byers J R , Hynes M F
Published: April 2011

The δ -endotoxin genes from Bacillus thuringiensis were introduced into a rhizosphere-inhabiting Bacillus pumilus isolate to create a δ -endotoxin expression and delivery system for subterranean feeding insects such as the larvae of pale western cutworm (Agrotis orthogonia Morrison (Lepidoptera: Noctuidae)). Preliminary experiments indicated that Bacillus thuringiensis subsp. kurstaki cultures were toxic to pale western cutworm larvae. Three different cry genes from Bacillus thuringiensis subsp. kurstaki were cloned into high and low copy number vectors and mated into Bacillus pumilus RB8. When carried on high copy number vectors, cry genes appeared to inhibit sporulation and δ -endotoxin production in Bacillus pumilus RB8 cultures, since microscopic examination of these cultures revealed that <0.1% of the cells of late stationary phase cultures had sporulated and produced parasporal inclusions. On low copy number vectors, the cry genes did not inhibit sporulation; however, production of δ -endotoxins was undetectable. Using a heat shock regime for enrichment of sporogenous crystalliferous variants, a Bacillus pumilus isolate, carrying cryIA(c) on a high copy number plasmid, was obtained in which high level δ -endotoxin production occurred concomitant with sporulation. Synthesis of functional δ -endotoxin by this strain was confirmed by Western blot analysis and bioassay with pale western cutworm larvae. These results show that rhizosphere-inhabiting bacilli are indeed a potential route for introduction of δ -endotoxins to the root environment for biocontrol purposes.Key words: Bacillus thuringiensis, δ -endotoxin, conjugation, sporulation, expression.
Interaction between the pili of Pseudomonas aeruginosa PAK and its carbohydrate receptor β-D-GalNAc(1->4) β-D-Gal analogs
Authors: Schweizer Frank , Jiao Hailong , Hindsgaul Ole , Wong Wah Y , Irvin Randall T
Published: April 2011

Pseudomonas aeruginosa employs pili to mediate adherence to epithelial cell surface receptors. Previously, it has been shown that the pilus adhesin of P. aeruginosa PAK binds to the ganglioside asialo-GM1. In particular, it was found that the carbohydrate sequence β-D-GalNAc(1->4) β-D-Gal is the minimal carbohydrate receptor sequence of asialo-GM1. To study the binding specificity of P. aeruginosa, O-modified and N-modified sugar analogs, where each hydroxyl group was substituted either by O-methyl or O-propyl and the acetamido group was changed to a propionamido group, were synthesized. The sugar analogs were evaluated as inhibitors in a competitive solid phase binding assay. The results demonstrate that the pili of P. aeruginosa PAK accepts a variety of sugar analogs possessing the sequence β-D-GalNAc(1->4) β-D-Gal. Most sugar analogs bind with a similar order of magnitude (50% inhibitory concentration (IC50) = 60-130 μM) except for the 2-O-propyl derivative 7 (IC50 = 8 ± 4 μM) compared with an IC50 of 79 ± 18 μM for the native compound. The significant increase in binding affinity of 2-O-propyl derivative 7 suggests that improved inhibitors of adhesion may be prepared by introducing a hydrophobic side chain at the 2-position of galactose.Key words: Pseudomonas aeruginosa, pili, adhesion, carbohydrate.
Transcriptional and translational regulation of major heat shock proteins and patterns of trehalose mobilization during hyperthermic recovery in repressed and derepressedSaccharomyces cerevisiae
Authors: Gross Claudia , Watson Kenneth
Published: April 2011

Patterns of heat shock gene transcription and translation, as well as trehalose content, were investigated in both glucose (repressed) and acetate (derepressed) grown cells of Saccharomyces cerevisiae during heat shock and subsequent return of cells to 25°C. Heat-shocked cells (37°C for 30 min), grown in either glucose- or acetate-supplemented media, initially acquired high thermotolerance to a 50°C heat stress, which was progressively lost when cultures were allowed to recover at 25°C and subsequently exposed to a second heat stress. In all cases, with the notable exception of repressed cells of a relatively thermosensitive strain, inhibition of protein synthesis and coincident decrease in trehalose accumulation during the heat shock had little effect on the kinetics of loss of thermotolerance. Heat shock at 37°C elicited a marked increase in transcription and translation of genes encoding major heat shock proteins (hsps). During recovery at 25°C, both metabolic activities were suppressed followed by a gradual increase in hsp mRNA transcription to levels observed prior to heat shock. De novo translation of hsp mRNAs, however, was no longer observed during the recovery phase, although immuno- detection analyses demonstrated persistence of high levels of hsps 104, 90, 70, and 60 in cells throughout the 240-min recovery period. In addition, while heat shock induced trehalose was rapidly degraded during recovery in repressed cells, levels remained high in derepressed cells. Results therefore indicated that the progressive loss of induced thermotolerance exhibited by glucose- and acetate-grown cells was not closely correlated with levels of hsp or trehalose. It was concluded that both constitutive and de novo synthesized hsps require heat shock associated activation to confer thermotolerance and this modification is progressively reversed upon release from the heat-shocked state.Key words: thermotolerance, hyperthermic recovery, hsp transcription, hsp translation, trehalose.
Overproduction of theBacillus subtilisglutamyl-tRNA synthetase in its host and its toxicity toEscherichia coli
Authors: Pelchat Martin , Lacoste Lucille , Yang Fu , Lapointe Jacques
Published: April 2011

The Bacillus subtilis glutamyl-tRNA synthetase (GluRS), encoded by the gltX gene, aminoacylates its homologous tRNAGluand tRNAGlnwith glutamate. This gene was cloned with its sigmaApromoter and a downstream region including a rho-independent terminator in the shuttle vector pRB394 for Escherichia coli and B. subtilis. Transformation of B. subtilis with this recombinant plasmid (pMP411) led to a 30-fold increase of glutamyl-tRNA synthetase specific activity in crude extracts. Transformation of E. coli with this plasmid gave no recombinants, but transformation with plasmids bearing an altered gltX was successful. These results indicate that the presence of B. subtilis glutamyl-tRNA synthetase is lethal for E. coli, probably because this enzyme glutamylates tRNA1Glnin vivo as it does in vitro.Key words: glutamyl-tRNA synthetase overproduction, Bacillus subtilis, toxicity, Escherichia coli.
Saline stress affects the attachment ofAzospirillum brasilenseCd to maize and wheat roots
Authors: Jofré Edgardo , Fischer Sonia , Rivarola Viviana , Balegno Héctor , Mori Gladys
Published: April 2011

The present work was designed to study the effect of saline stress on the attachment of Azospirillum brasilense to maize and wheat roots. We demonstrate that both attachment steps (adsorption and anchoring) are altered. A 100-kDa protein disappeared under these experimental conditions. Coincidently, a 100-kDa flagellum protein has been identified as the agent responsible for adsorption. However, the adhesive properties of bacteria appear to involve other factors, such as the ionic strength of the medium. The impairment of anchoring ability was correlated with alterations in exopolysaccharide, glucan, and lipopolysaccharide contents.Key words: Azospirillum brasilense, saline stress, Azospirillum-root interaction.
Microbial utilization of the neurotoxin domoic acid: blue mussels (Mytilus edulis) and soft shell clams (Mya arenaria) as sources of the microorganisms
Authors: Stewart James E , Marks L J , Gilgan M W , Pfeiffer E , Zwicker B M
Published: April 2011

The neurotoxin domoic acid is produced in quantity by the diatom Pseudo-nitzschia multiseries and is released to the environment directly and indirectly via food chains. Presumably there is a mechanism for the biodegradation and disposal of domoic acid and as bacteria are logical candidates for such an activity, a search for bacteria competent to carry out biodegradation of domoic acid was initiated. Extensive trials with a wide variety of bacteria isolated mainly from muds and waters taken from the marine environment showed that the ability to grow on or degrade domoic acid was rare; in fact, domoic acid was inhibitory to resting cells or growing cultures of most of these bacteria. In contrast, using enrichment techniques, it was possible to isolate from molluscan species that eliminate domoic acid readily, i.e., blue mussels (Mytilus edulis) and soft-shell clams (Mya arenaria), bacteria that exhibited growth with and biodegradation of domoic acid when supplemented with low concentrations of growth factors. The species that retain domoic acid for lengthy periods, such as sea scallops (Placopecten magellanicus) and red mussels(Modiolus modiolus), only occasionally yielded bacteria with this capability. The differences may be a result of the mechanisms used by the different shellfish in dealing with domoic acid, i.e., freely available in the blue mussels and soft shell clams but likely sequestered in the digestive glands of sea scallops and red mussels and thus, largely unavailable for bacterial utilization. The results show that Mytilus edulis and Mya arenaria, almost uniquely, are prime and reliable sources of domoic acid utilizing bacteria. These findings suggest a strong possibility that autochthonous bacteria may be significant factors in the elimination of the neurotoxin in these two species of shellfish.Key words: bacteria, neurotoxin, domoic acid, elimination, bivalve molluscs.
Toxicity of hydrogen peroxide produced by electroplated coatings to pathogenic bacteria
Authors: Zhao Zhi-Hong , Sakagami Yoshikazu , Osaka Tetsuya
Published: April 2011

The ability of various electroplated coatings (cobalt, zinc, copper, and cobalt-containing alloys of nickel, zinc, chromium, etc.) to inhibit the growth of pathogenic bacteria (Gram-positive bacteria Enterococcus faecalis and methicillin-resistant Staphylococcus aureus and Gram-negative bacteria Escherichia coli, Pseudomonas aeruginosa, andKlebsiella pneumoniae) was determined by a drop-method antibacterial experiment. The amounts of H2O2 produced and metal ions dissolved from the surfaces of various electroplated coatings were measured and it was found that the inhibitory ability of coatings corresponded to the amounts of H2O2 produced. The more significant the inhibition of the coating to bacterial growth, the greater the amount of H2O2 production. In addition, the bacterial survival rates on the surfaces of coatings were almost zero when H2O2 was produced in amounts greater than 10-6 mmol/cm2. However, the dominant concentrations of metal ions dissolved from coatings were outside of the bacterial lethal range.Key words: electroplated coatings, pathogenic bacteria, inhibitory ability, hydrogen peroxide.
Laboratory evaluation of crude oil biodegradation with commercial or natural microbial inocula
Authors: Thouand G , Bauda P , Oudot J , Kirsch G , Sutton C , Vidalie J F
Published: April 2011

Experiments have been performed to screen eight microbial commercial products that, according to the manufacturers, are able to degrade crude oil. This study compared the crude oil biodegradation activity of commercial inocula with that of natural inocula (activated sludge and tropical aquarium water). Some of the latter were previously adapted to the crude oil as the only carbon source. Nutrients and sorbents in the commercial formulations were eliminated, and each inoculum was precultured on marine yeast extract medium. Crude oil biodegradability tests were conducted with close initial substrate concentration to initial bacterial concentration ratios (S0/X0) of 0.94 g of crude oil/109CFU, which allowed a comparison of biodegradation activity. The inocula oxidized the crude oil after a short lag time of less than 3-18 days. After that time, the rate of oxidation varied between 45 and 244 mg O2/(L·day). Crude oil biodegradation after a 28-day test was effective only for 10 out of 12 inocula (from 0.1 to 25% in weight). Biodegradation mainly corresponded to the saturated fraction of the crude oil; the asphaltene fraction was never significantly biodegraded. Our results led to the conclusion that natural inocula, either adapted or not adapted to crude oil, were the most active (from 16 to 25% of loss in crude oil weight) and only one commercial inoculum was able to degrade 18% of the crude oil. Other inocula had a biodegradation activity ranging from 0.1 to 14%.Key words: biodegradability tests, microbial inoculum, crude oil, seeding.
The role of catalase in hydrogen peroxide resistance in fission yeastSchizosaccharomyces pombe
Authors: Mutoh Norihiro , Nakagawa Chiaki W , Yamada Kenichiro
Published: April 2011

The role of catalase in hydrogen peroxide resistance in Schizosaccharomyces pombe was investigated. A catalase gene disruptant completely lacking catalase activity is more sensitive to hydrogen peroxide than the parent strain. The mutant does not acquire hydrogen peroxide resistance by osmotic stress, a treatment that induces catalase activity in the wild-type cells. The growth rate of the disruptant is not different from that of the parent strain. Additionally, transformed cells that overexpress the catalase activity are more resistant to hydrogen peroxide than wild-type cells with normal catalase activity. These results indicate that the catalase of S. pombe plays an important role in resistance to high concentrations of hydrogen peroxide but offers little in the way of protection from the hydrogen peroxide generated in small amounts under normal growth conditions.Key words: catalase, gene disruption, induced hydrogen peroxide resistance, overexpression, Schizosaccharomyces pombe.
Characterization of metal-resistant soil eubacteria by polymerase chain reaction - denaturing gradient gel electrophoresis with isolation of resistant strains
Authors: Macnaughton Sarah , Stephen John R , Chang Yun-Juan , Peacock Aaron , Flemming Cecily A , Leung KamTin , White David C
Published: April 2011

Contamination of soils with heavy metal ions is a major problem on industrial and defense-related sites worldwide. The bioavailability and mobility of these contaminants is partially determined by the microbial biomass present at these sites. In this study, we have assessed the effect of the addition of a mixture of toxic metal salts on the prokaryotic community of microcosms consisting of sandy-loam soil using direct molecular analysis of the recoverable eubacterial 16S rDNA molecules by polymerase chain reaction - denaturing gradient gel electrophoresis (PCR-DGGE) and limited phospholipid fatty acid analysis (PLFA). Addition of toxic metals (nonradioactive surrogates of Sr, Co, Cs, Cd) resulted in rapid (ca. 1 week) changes in the DGGE profile of the indigenous eubacterial community when compared with pristine controls. These changes were stable over the course of the experiment (8 weeks). No changes in the eubacterial population of control microcosms were detected. The major changes in community structure in metal-contaminated microcosms consisted of the appearance of four novel bands not detected in controls. Sequence analysis of these bands suggested that two organisms related to the genus Acinetobacter and two related to the genus Burkholderia carried a selective advantage over other indigenous eubacteria under heavy metal induced stress. The Burkholderia spp. were then cultured and further characterized using lipid analysis.Key words: metals, PCR-DGGE, microbial community response.
Growth and survival of uninjured and sublethally heat-injured Escherichia coli O157:H7 on beef extract medium as influenced by package atmosphere and storage temperature
Authors: Semanchek Jeffrey J , Golden David A , Williams Robert C
Published: April 2011

The effect of atmospheric composition and storage temperature on growth and survival of uninjured and sublethally heat-injured Escherichia coli O157:H7, inoculated onto brain heart infusion agar containing 0.3% beef extract (BEM), was determined. BEM plates were packaged in barrier bags in air, 100% CO2, 100% N2, 20% CO2 : 80% N2, and vacuum and were stored at 4, 10, and 37°C for up to 20 days. Package atmosphere and inoculum status (i.e., uninjured or heat-injured) influenced (P < 0.01) growth and survival of E. coli O157:H7 stored at all test temperatures. Growth of heat-injured E. coli O157:H7 was slower (P < 0.01) than uninjured E. coli O157:H7 stored at 37°C. At 37°C, uninjured E. coli O157:H7 reached stationary phase growth earlier than heat-injured populations. Uninjured E. coli O157:H7 grew during 10 days of storage at 10°C, while heat-injured populations declined during 20 days of storage at 10°C. Uninjured E. coli O157:H7 stored at 10°C reached stationary phase growth within approximately 10 days in all packaging atmospheres except CO2. Populations of uninjured and heat-injured E. coli O157:H7 declined throughout storage for 20 days at 4°C. Survival of uninjured populations stored at 4°C, as well as heat-injured populations stored at 4 and 10°C, was enhanced in CO2 atmosphere. Survival of heat-injured E. coli O157:H7 at 4 and 10°C was not different (P > 0.05). Uninjured and heat-injured E. coli O157:H7 are able to survive at low temperatures in the modified atmospheres used in this study.Key words: E. coli O157:H7, sublethal injury, modified atmosphere packaging.
Removal of phenolic compounds from a petrochemical effluent with a methanogenic consortium
Authors: Charest A , Bisaillon J -G , Lépine F , Beaudet R
Published: April 2011

A methanogenic consortium was used to degrade phenol and ortho- (o-) cresol from a specific effluent of a petrochemical refinery. This effluent did not meet the local environmental regulations for phenolic compounds (178 mg/L), oils and greases (61 mg/L), ammoniacal nitrogen (75 mg/L) or sulfides (3.2 mg/L). The consortium, which degrades phenol via its carboxylation to benzoic acid, was progressively adapted to the effluent. Despite the very high effluent toxicity (EC50 of 2% with Microtox), the adapted consortium degraded 97% of 156 mg/L phenol in the supplemented effluent after 13 days in batch cultures (serum bottle). The addition of proteose peptone to the effluent is essential for phenol degradation. o-cresol was also transformed but not meta- or para-cresols. A continuous flow fixed-film anaerobic bioreactor was developed with the consortium. Treating the effluent with the bioreactor reduced phenol and phenolic compounds concentrations by 97 and 83%, respectively, for a hydraulic residence time of 6 h. This treatment also reduced by about half the effluent toxicity. Oils and greases and ammoniacal nitrogen were not affected. Similar microbiological forms were observed in serum bottles and in the bioreactors with or without the petrochemical effluent. These results indicate that this methanogenic consortium can treat efficiently the phenolic compounds in this specific petrochemical effluent.Key words: phenolic compounds, anaerobic consortium, petrochemical effluent, biodegradation, methanogenic conditions.
Identification of genes unique to Mo-independent nitrogenase systems in diverse diazotrophs
Authors: Loveless Telisa M , Bishop Paul E
Published: April 2011

A number of nitrogen-fixing bacteria were screened using PCR for genes (vnfG and anfG) unique to the V-containing nitrogenase (vnf) and the Fe-only nitrogenase (anf) systems. Products with sequences similar to that of vnfG were obtained from Azotobacter paspali and Azotobacter salinestris genomic DNAs, and products with sequences similar to that of anfG were obtained from Azomonas macrocytogenes, Rhodospirillum rubrum, and Azotobacter paspali DNAs. Phylogenetic analysis of the deduced amino acid sequences of anfG and vnfG genes shows that each gene product forms a distinct cluster. Furthermore, amplification of an internal 839-bp region in anfD and vnfD yielded a product similar to anfD from Heliobacterium gestii and a product similar to vnfD from Azotobacter paspali and Azotobacter salinestris. Phylogenetic analysis of NifD, VnfD, and AnfD amino acid sequences indicates that AnfD and VnfD sequences are more closely related to each other than either is to NifD. The results of this study suggest that Azotobacter salinestris possesses the potential to express the vanadium (V)-containing nitrogenase (nitrogenase 2) and that R. rubrum, Azomonas macrocytogenes, and H. gestii possess the potential to express the Fe-only nitrogenase (nitrogenase 3). Like Azotobacter vinelandii, Azotobacter paspali appears to have the potential to express both the V-containing nitrogenase and the Fe-only nitrogenase.Key words: Mo-independent nitrogenase systems, diverse diazotrophs, vnfG, anfG.
The inorganic ion content of native aquatic bacteria
Authors: Fagerbakke Kjell Magne , Norland Svein , Heldal Mikal
Published: April 2011

In this study we have quantified the ionic content and volume of native aquatic, and two cultured bacteria, by X-ray microanalysis (XRMA) in the transmission electron microscope (TEM). The cellular concentrations of magnesium (means of 630 and 710 mM) were more than an order of a magnitude higher than the outside concentrations. The internal concentrations of sodium were on average 50-180 mM, and the [K+]/[Na+] ratios were in the range of 0.1-0.5; lowest for apparently nonactive bacteria. Magnesium and chloride probably act as the major components of cell turgor, since no other inorganic ions were present in comparable amounts. Our carbon and nitrogen measurements indicated that organic solutes are not likely to be present at significant concentrations. The estimated charge of inorganic ions (Na, Mg, P, Cl, K, and Ca) gave a positive net internal charge for most cells. However, in cultures of Vibrio natriegens, the high internal chloride concentration made the net inorganic charge negative in these cells. Our results suggest that growing marine bacterioplankton have an internal environment in which magnesium is the dominating cation. These results suggest that actively growing marine bacteria are physiologically adapted to high internal concentrations of both magnesium and chloride.Key words: X-ray microanalysis, magnesium, osmolyte, marine bacteria.