bluuebunny/crossref_metadata_2025 huggingface dataset:
HPLC analyses of cultures of Phoma spp.: Differentiation among groups and species through secondary metabolite profiles
Authors: Pedras MS C , Biesenthal Corinne J
Published: April 2011

The metabolite profiles of 26 isolates of the blackleg fungus (Leptosphaeria maculans (Desm.) Ces. et de Not., asexual stage Phoma lingam (Tode ex Fr.) Desm.), obtained from diverse parts of the world (part of the International Blackleg Crucifer Network collection), were studied utilizing specific culture conditions, HPLC analysis, and a set of chemical markers. This fungus is the causative agent of blackleg disease of brassica oilseeds; a virulent strain of the pathogen has caused significant rapeseed (Brassica napus L., and B. rapa L.) and canola (B. napus L., and B. rapa L.) losses in Canada, and is also considered a serious agricultural problem worldwide. Effective surveys of blackleg epidemics require simple and reliable analytical methodology to differentiate among the diverse groups of isolates. The chemical analysis of phytotoxins and related secondary metabolites is perhaps one of the most discriminating and the least ambiguous methods for differentiation of Phoma blackleg isolates. Following HPLC analyses, the 26 isolates could be placed in three main groups, irrespective of country of origin: isolates producing phomamide and sirodesmins, isolates producing indolyl dioxopiperazines, and isolates producing polyketides. Discussion of the implications of our findings and suggestions for species reclassification are provided.
Clay minerals protect bacteriophage PBS1 ofBacillussubtilisagainst inactivation and loss of transducing ability by UV radiation
Authors: Vettori C , Gallori E , Stotzky G
Published: April 2011

The effect of UV radiation on the survival of and transduction by phage PBS1 of Bacillus subtilis, free or adsorbed on the clay minerals montmorillonite (M) and kaolinite (K), was studied. After free or clay-associated phage (~107PFU·mL-1) was irradiated with UV light (254 nm) for 0, 1, 2, 5, 10, and 30 min and then allowed to infect B. subtilis FB300 (thiB4 metA29 argF4 Rfmr), the phage was titered, and Met+transductants were enumerated on selective media. After 1 min of irradiation, the titer of free and clay-associated phage decreased significantly (~1.6 times for free phage, and ~ 4.9 and 6.8 times for M and K, respectively), whereas the transduction frequency increased significantly (~3 times for free phage and ~ 1.4 and 2.2 times for M and K, respectively). The titer and transduction frequency of clay-associated phage remain essentially constant between 1 and 10 min of irradiation, whereas the titer of free phage decreased by ~1 order of magnitude after 5 min of irradiation. When free phage was irradiated for 10 min, the titer and transduction frequency decreased by ~ 2 and 0.5 orders of magnitude, respectively, whereas 30 min of irradiation was necessary to obtain comparable decreases with clay-associated phage. These results indicated that phages are protected to some extent from UV radiation when adsorbed on clay minerals.Key words: UV, transduction, phage PBS1 of B. subtilis, clay.
Effect of delivery method and population size of Trichoderma harzianum on growth response of unrooted chrysanthemum cuttings
Authors: MacKenzie Amy J , Ownley Bonnie H , Starman Terri W , Windham Mark T
Published: April 2011

In a previous study, addition of Trichoderma harzianum Rifai isolate T-12 to a propagative medium resulted in improved performance of chrysanthemum cuttings. However, root and shoot growth of one cultivar, 'Dark Bronze Charm', were more responsive to a lower (5 g T-12/kg medium) than higher (25 g T-12/kg medium) rate of fungal propagules, suggesting potential phytotoxicity at higher concentrations. The objectives of this study were to investigate higher rates of T-12 medium amendment for phytotoxicity, and to examine an alternative method of delivering the fungus to the propagative medium in order to obtain a more uniform response from cuttings. Isolate T-12 was added to the propagative medium as either a powdered peat-bran amendment (0, 5, or 50 g T-12 /kg medium) or as alginate prills (80 or 800 g T-12/kg medium). There were no differences among treatments on day seven, but by day 21, shoot fresh weight and heights were significantly greater for plants treated with prills at 800 g T-12/kg medium. Both prill treatments resulted in greater shoot height on day 14 and 21 than all other treatments, which were similar to controls. Amendment with T-12 powder at 50 g/kg increased root length, but 80 g/kg medium added as prills decreased root dry weight compared to the control. The highest rate of T-12 (800 g prills/kg medium) had no effect on root growth. This suggests that moderate, rather than high rates of T-12 are more effective in promoting rooting of unrooted chrysanthemum, and that there is a potential for phytotoxic effects on root growth with higher rates.Key words: Dendranthema X grandiflorum, plant growth promotion, plant propagation.
Development of formulations of biological agents for management of root rot of lettuce and cucumber
Authors: Amer G A , Utkhede R S
Published: April 2011

The effect of various carrier formulations of Bacillus subtilis and Pseudomonas putida were tested on germination, growth, and yield of lettuce and cucumber crops in the presence of Pythium aphanidermatum and Fusarium oxysporum f.sp. cucurbitacearum, respectively. Survival of B. subtilis and P. putida in various carriers under refrigeration (about 0°C) and at room temperature (about 22°C) was also studied. In all carrier formulations, B. subtilis strain BACT-0 survived up to 45 days. After 45 days of storage at room temperature (about 22°C), populations B. subtilis strain BACT-0 were significantly higher in vermiculite, kaolin, and bacterial broth carriers compared with other carriers. Populations of P. putida were significantly higher in vermiculite, peat moss, wheat bran, and bacterial broth than in other carriers when stored either under refrigeration (about 0°C) or at room temperature (about 22°C) for 15 or 45 days. Germination of lettuce seed was not affected in vermiculite, talc, kaolin, and peat moss carriers, but germination was significantly reduced in alginate and bacterial broth carriers of B. subtilis compared to the non-treated control. Germination of cucumber seed was not affected by any of the carriers. Significantly higher fresh lettuce and root weights were observed in vermiculite and kaolin carriers of B. subtilis compared with P. aphanidermatum-inoculated control plants. Lettuce treated with vermiculite, and kaolin carriers of B. subtilis, or non-inoculated control lettuce plants had significantly lower root rot ratings than talc, peat moss, bacterial broth, and P. aphanidermatum-inoculated control plants. Growth and yield of cucumber plants were significantly higher in vermiculite-based carrier of P. putida than the other carriers and Fusarium oxysporum f.sp. cucurbitacearum-inoculated plants.Key words: Bacillus subtilis, Pseudomonas putida, Fusarium oxysporum f.sp. cucurbitacearum, Pythium aphanidermatum, talc, vermiculite, alginate, kaolin, peat moss, wheat bran, oat bran.
Molecular analysis of mutatedLactobacillus acidophiluspromoter-like sequence P15
Authors: Arsenijevic Slavica , Topisirovic Ljubisa
Published: April 2011

The promoter-like sequence P15 that was previously cloned from the chromosome of Lactobacillus acidophilus ATCC 4356 is active in Lactobacillus reuteri, Lactobacillus plantarum, Lactobacillus acidophilus, and Escherichia coli, but not in Lactococcus lactis. N-methyl-N-nitroso-N-guanidine (MNNG) mutagenesis of P15 was used to select for a promoter active in L. lactis MG1363. Molecular analysis of the mutated promoter (designated P16) revealed a 90 bp deletion and a T[Formula: see text]A transversion. This deletion, in combination with the addition to the transversion, created a promoter with putative -35 and -10 hexamers identical to the consensus promoter sequence found in E. coli and Bacillus subtilis vegetative promoters. The activity of P16 was measured by its ability to promote chloramphenicol resistance in different bacteria when inserted in the promoter-probe plasmid pBV5030 (designated pLA16). The MIC of chloramphenicol in L. lactis, L. reuteri, L. plantarum, E. coli, and L. acidophilus harbouring pLA16 were 30, 170, 180, >500, and 3 µg/mL, respectively. This represents an increase in promoter activity compared to P15 in L. reuteri of 3-fold, in L. plantarum of 9-fold, and in E. coli of at least 2.5-fold, but a decrease in L. acidophilus of 7-fold.Key words: Lactobacillus acidophilus, promoter-like sequence, mutagenesis.
The use of anonymous DNA markers in assessing worldwide relatedness in the yeast speciesPichia kluyveriBedford and Kudrjavzev
Authors: Ganter Philip F , Lopes Miguel de Barros
Published: April 2011

Pichia kluyveri, a sexual ascomycetous yeast from cactus necroses and acidic fruit, is divided into three varieties. We used physiological, RAPD, and AFLP data to compare 46 P. kluyveri strains collected worldwide to investigate relationships among varieties. Physiology did not place all strains into described varieties. Although the combined AFLP and RAPD data produced a single most parsimonious tree, separate analysis of AFLP and RAPD data resulted in significantly different trees (by the partition homogeneity test). We then compared the distribution of strains per band to an expected distribution. This suggested we could separate both the AFLP and RAPD datasets into bands from rapidly and slowly changing DNA regions. When only bands from slowly changing regions (from each dataset) were included in the analysis, both the RAPD and AFLP datasets supported a single tree. This second tree did not differ significantly from the cladogram based on all of the DNA data, which we accepted as the best estimate of the phylogeny of these yeast strains. Based on this phylogeny, we were able to demonstrate the strong influence of geography on the population structure of this yeast, confirm the monophyly of one variety, question the utility of maintaining another variety, and demonstrate that the physiological differences used to separate the varieties did not do so in all cases.Key words: RAPD, AFLP, yeast, data homogeneity, Pichia kluyveri.
Production and monomer composition of exopolysaccharides by yogurt starter cultures
Authors: Frengova Ginka I , Simova Emilina D , Beshkova Dora M , Simov Zhelyasko I
Published: April 2011

As components of starter cultures for Bulgarian yogurt, Streptococcus salivarius subsp. thermophilus and Lactobacillus delbrueckii subsp. bulgaricus revealed extensive exopolysaccharide (EPS) production activity when cultivated in whole cow's milk. The polymer-forming activity of thermophilic streptococci was lower (230-270 mg EPS/L) than that of the lactobacilli (400-540 mg EPS/L). Mixed cultures stimulated EPS production in yogurt manufacture, and a maximum concentration of 720-860 mg EPS/L was recorded after full coagulation of milk. The monomer structure of the exopolysaccharides formed by the yogurt starter cultures principally consists of galactose and glucose (1:1), with small amounts of xylose, arabinose, and/or mannose.Key words: Streptococcus thermophilus, Lactobacillus bulgaricus, starter cultures, yogurt, exopolysaccharides.
Rapid differentiation of the closely related Kluyveromyces lactis var. lactis and K. marxianus strains isolated from dairy products using selective media and PCR/RFLP of the rDNA non transcribed spacer 2
Authors: Nguyen Huu-Vang , Pulvirenti Andrea , Gaillardin Claude
Published: April 2011

PCR/RFLP of the NTS2 (IGS2) of rDNA was applied to differentiate two closely related yeast species, Kluyveromyces lactis var. lactis (referred to as K. lactis) and K. marxianus. Using specific primers, the NTS2 region was amplified from DNA of both K. lactis and K. marxianus type and collection strains. AluI restriction of amplified fragments generated patterns characteristic for each species. The NTS2 region from K. lactis var. drosophilarum and related species K. aestuarii, K. africanus, K. dobzhanskii, and K. wickerhamii could also be amplified with the same primers, but AluI patterns generated were clearly different. PCR/RFLP of the NTS2 appears thus to be a convenient method for rapid identification of K. lactis and K. marxianus, frequently found in dairy products. This test was validated therefore on K. lactis and K. marxianus from natural habitats. We showed that all yeast strains collected from whey samples and scoring blue on X-gal glucose plates were either K. lactis or K. marxianus. For application purposes, we propose here an approach for quickly screening for K. lactis/marxianus and Saccharomyces cerevisiae in dairy products using X-gal coloured and lysine growth media.Key words: yeast, Kluyveromyces, ribosomal DNA, karyotype, taxonomy.
Genetic diversity of rhizobia nodulating Trifolium ambiguum in North America
Authors: Seguin P , Graham P H , Sheaffer C C , Ehlke N J , Russelle M P
Published: April 2011

Kura clover (Trifolium ambiguum M.B.) is a persistent rhizomatous forage legume, whose use in the U.S.A. is limited by establishment difficulties in part attributable to nodulation problems. In this study, soil was collected from established stands of Kura clover growing in 9 diverse North American environments. Rhizobia were plant-trapped using Kura clover cv. Endura as host, then rhizobia from nodules fingerprinted using BOX-PCR. The diversity of isolates from North America was then contrasted to that of rhizobia from a single Caucasian environment (Russia), the center of origin for this species. Populations were characterized using clustering methods, and genetic diversity estimated using the Shannon-Weaver diversity index. The genetic diversity of the North American populations was extremely limited, all isolates being closely related to two of the strains found in a locally available commercial inoculant. In contrast, Russian isolates formed a distinct cluster with significant internal genetic diversity. Genetic diversity indices for the North American and Russian populations were 3.5 and 10.76, respectively. The implication of this and other studies is that Kura clover is highly specific in Rhizobium requirement. If the performance of this legume in the U.S.A. is to be improved, either by modifying current establishment practices or plant breeding, it is essential that these studies be paralleled by more collections and evaluation of rhizobia from its center of origin, given the extremely limited diversity of rhizobia found in North America.Key words: genetic diversity, rhizobia, Kura clover, BOX-PCR.
Metschnikowia lochheadii and Metschnikowia drosophilae, two new yeast species isolated from insects associated with flowers
Authors: Lachance Marc-André , Bowles Jane M , Kwon Sabrina , Marinoni Gaëlle , Starmer William T , Janzen Daniel H
Published: April 2011

Two new haplontic heterothallic species of Metschnikowia were isolated from floricolous insects and flowers. Metschnikowia lochheadii was recovered from insects found in various flowers on the Hawaiian Islands of Kauai and Maui, and from Conotelus sp. (Coleoptera: Nitidulidae) in northwestern Guanacaste Province, Costa Rica. The morphology, physiology, and sexual cycle are typical of the large-spored Metschnikowia species, and the partial ribosomal DNA large subunit (D1D2) sequences suggest that the new species is most closely related to Candida ipomoeae. Metschnikowia lochheadii is nearly indistinguishable from its ascogenous relatives and conjugates freely with Metschnikowia continentalis, forming sterile asci. It also exhibits asymmetric mating with Metschnikowia hawaiiensis. Metschnikowia drosophilae was found in morning glory (Ipomoea sp.) flowers and associated Drosophila bromeliae on Grand Cayman Island. Its nutritional profile is atypical of the genus, being the only species that does not utilize sucrose or maltose as carbon sources, and one of the few that does not utilize melezitose. D1D2 sequences show that Metschnikowia drosophilae is a sister species to Candida torresii, to which it bears considerable similarity in nutritional profile. The type cultures are: Metschnikowia lochheadii, strains UWO(PS)00-133.2 = CBS 8807 (h+, holotype) UWO(PS)99-661.1 = CBS 8808 (h, isotype); and Metschnikowia drosophilae, strains UWO(PS)83-1135.3 = CBS 8809 (h+, holotype) and UWO(PS)83-1143.1 = CBS 8810 (h, isotype).Key words: Metschnikowia lochheadii, Metschnikowia drosophilae, new yeast species, insects, flowers.
Comparison of the PR mutant with the wild-type strain ofProteus mirabilisbrings insight into peroxide resistance factors and regulation of catalase expression
Authors: Andreoletti Pierre , Franzetti Bruno , Nussaume Laurent , Andrieu Jean-Pierre , Gagnon Jean , Luche Sylvie , Rabilloud Thierry , Jouve Helene
Published: April 2011

The peroxide resistant mutant (PR) of Proteus mirabilis was characterized by an increased constitutive catalase activity concomitant with a large production of specific mRNA. Survival toward hydrogen peroxide during exponential phase was increased by H2O2pretreatment in the wild type but not in the mutant, although the catalase of both strains was not inducible under these conditions. In the mutant, besides catalase, over-produced proteins comprised two different alkyl hydroperoxide reductase subunit C (AhpC) proteins and a protein homologous to the stationary phase transcription factor SspA of Escherichia coli. Conversely, the flagellin A (FlaA) of P. mirabilis was repressed in the PR mutant. Genomic DNA fragments of 2.9 kb carrying the catalase gene (katA) together with the 5' and 3' flanking regions were isolated from both strains and found to be identical. Upstream of katA, a Fur box-like sequence was found, but surprisingly, restricting iron in the culture medium caused a decrease in catalase production. The PR mutant presents similarities with other peroxide resistant mutants, but the regulation of catalase biosynthesis in P. mirabilis seems somewhat different from other close species such as E. coli.Key words: Proteus mirabilis, hydrogen peroxide, peroxide resistant mutant, catalase.
Regulation of nitrogenase in the photosynthetic bacteriumRhodobacter sphaeroidescontainingdraTGandnifHDKgenes fromRhodobacter capsulatus
Authors: Yakunin Alexander F , Fedorov Alexander S , Laurinavichene Tatyana V , Glaser Vadim M , Egorov Nikolay S , Tsygankov Anatoly A , Zinchenko Vladislav V , Hallenbeck Patrick C
Published: April 2011

The photosynthetic bacteria Rhodobacter capsulatus and Rhodospirillum rubrum regulate their nitrogenase activity by the reversible ADP-ribosylation of nitrogenase Fe-protein in response to ammonium addition or darkness. This regulation is mediated by two enzymes, dinitrogenase reductase ADP-ribosyl transferase (DRAT) and dinitrogenase reductase activating glycohydrolase (DRAG). Recently, we demonstrated that another photosynthetic bacterium, Rhodobacter sphaeroides, appears to have no draTG genes, and no evidence of Fe-protein ADP-ribosylation was found in this bacterium under a variety of growth and incubation conditions. Here we show that four different strains of Rba. sphaeroides are incapable of modifying Fe-protein, whereas four out of five Rba. capsulatus strains possess this ability. Introduction of Rba. capsulatus draTG and nifHDK (structural genes for nitrogenase proteins) into Rba. sphaeroides had no effect on in vivo nitrogenase activity and on nitrogenase switch-off by ammonium. However, transfer of draTG from Rba. capsulatus was sufficient to confer on Rba. sphaeroides the ability to reversibly modify the nitrogenase Fe-protein in response to either ammonium addition or darkness. These data suggest that Rba. sphaeroides, which lacks DRAT and DRAG, possesses all the elements necessary for the transduction of signals generated by ammonium or darkness to these proteins.Key words: nitrogenase regulation, nitrogenase modification, photosynthetic bacteria.
Transcriptional regulation of theEnterobacter cloacaeUW4 1-aminocyclopropane-1-carboxylate (ACC) deaminase gene (acdS)
Authors: Li Jiping , Glick Bernard R
Published: April 2011

Based on DNA sequence analysis and 1-aminocyclopropane-1-carboxylate (ACC) deaminase activity, the region of DNA immediately upstream of the Enterobacter cloacae UW4 ACC deaminase gene (acdS) contains several features that appear to be involved in its transcriptional regulation. In the present study, the 5' upstream region of acdS was cloned into the promoter-probe vector, pQF70, which carries the promoterless luciferase gene (luxAB), and luciferase expression was monitored. The data obtained from studying the expression of the luciferase gene showed that (i) a leucine responsive regulatory protein (LRP)-like protein encoded within the upstream region is located on the opposite strand from acdS under the control of a promoter stronger than the one responsible for acdS transcription, (ii) luciferase gene expression required both ACC and the LRP-like protein, (iii) luciferase expression was increased three-fold under anaerobic conditions, consistent with the involvement of a fumarate-nitrate reduction (FNR)-like regulatory protein box within the upstream region, and (iv) the addition of leucine to the growth medium decreased luciferase activity in the presence of ACC and increased luciferase activity in the absence of ACC, consistent with leucine acting as a regulator of the expression of the LRP-like protein.Key words: plant growth promotion, ethylene, ACC deaminase, regulation, Enterobacter cloacae.
Separation of a phenol carboxylating organism from a two-member, strict anaerobic co-culture
Authors: Letowski Jaroslaw , Juteau Pierre , Villemur Richard , Duckett Marie-France , Beaudet Réjean , Lépine François , Bisaillon Jean-Guy
Published: April 2011

In a culture converting phenol to benzoic acid under anaerobic conditions and previously described as being constituted of only a Clostridium-like strain 6, another bacterium (strain 7) was observed. Each organism was enriched by centrifugation on a Percoll gradient. Strain 6 was purified by dilution and plating. Strain 7 did not grow on solid media, but a strain 7 culture, cleared of strain 6, was obtained by subculturing in the presence of ampicillin and by dilution. In fresh medium, phenol was transformed by the reconstituted co-culture but not by each strain alone. In a supernatant from a co-culture or from a strain 6 culture, strain 7 alone transformed phenol but not strain 6. Maintenance of an active strain 7 in fresh medium instead of co-culture supernatant became possible when phenol was replaced by 4-hydroxybenzoate (4-OHB), which is decarboxylated to phenol before being transformed to benzoate. Even with 4-OHB, the use of co-culture (or strain 6 culture) supernatant resulted in faster transformation activity and growth rate. A phylogenetic analysis placed strain 7 in a cluster of uncultivated or nonisolated bacteria (9296% homology). Strain 7 is also related to Desulfotomaculum, Desulfitobacterium, Desulfosporosinus, Moorella, and Sporotomaculum genera (8792% homology).Key words: co-culture, carboxylation, decarboxylation, anaerobic.
The effect of temperature on the fatty acids and isozymes of a psychrotrophic and two mesophilic species ofXenorhabdus, a bacterial symbiont of entomopathogenic nematodes
Authors: He Hongjun , Gordon Roger , Gow John A
Published: April 2011

In the first part of this study, generation times relative to temperature, together with cardinal and conceptual temperatures, were determined for four strains of Xenorhabdus bacteria that represented three geographically distinct species. The data showed that the NF strain of Xenorhabdus bovienii, like the Umeå strain of the same species, is psychrotrophic, while Xenorhabdus sp. TX strain resembles Xenorhabdus nematophila All strain in being mesophilic. In the second part, the capacity of these bacteria to adapt to changes in temperature, shown by changes in fatty acid composition, was investigated. As temperature declined, the proportions of the two major unsaturated fatty acids, palmitoleic (16:1ω7) acid and oleic (18:1ω9) acid, increased significantly in all of the strains. The proportion of the prevalent saturated fatty acid, which was palmitic acid (16:0), decreased. In the All, NF, and Umeå strains, myristic acid (14:0), margaric acid (17:0), cyclopropane (17:0c), and arachidic acid (20:0) decreased with decreasing temperature. In the third part of the study, the synthesis of isozymes in response to changing temperature was investigated. For the seven enzymes studied, the numbers for which isozyme synthesis was temperature related were as follows: five for Umeå, four for All, three for NF, and two for TX. Where the study dealt with fatty acid composition and isozyme synthesis, the results show a broad capacity for physiological temperature adaptation among strains of different climatic origin.Key words: Xenorhabdus, temperature, psychrotroph, mesophile, fatty acid, isozyme.
Iron content ofStreptococcus suisand evidence for adprhomologue
Authors: Niven Donald F , Ekins Andrew
Published: April 2011

The type strain of Streptococcus suis was investigated for features that might help the organism to tolerate the H2O2that is produced during growth. Enzyme assays, using soluble extracts, revealed that the type strain, which lacks catalase, lacks NADH peroxidase in both the mid-exponential and stationary phases of the growth cycle. Although iron could not be detected colourimetrically in dense cell suspensions, determination of the cellular iron content following growth to early stationary phase in the presence of55FeCl3demonstrated that S. suis does contain iron and hence is incapable of iron exclusion. Gene amplification, using oligonucleotide primers based on dpr of Streptococcus mutans, followed by nucleotide sequencing, revealed in S. suis, the presence of a gene that encodes a Dpr homologue. It is concluded that in S. suis, tolerance of H2O2is due to iron sequestration by Dpr and the consequent effect of this process on the extent of Fenton chemistry.Key words: Streptococcus suis, iron, NADH peroxidase, Dpr.
Do mycoplasmas cause human cancer?
Authors: Cimolai Nevio
Published: April 2011

A linkage between mycoplasmas and malignancy was mainly proposed in the 1960s when human-associated mycoplasmas were becoming of interest given the novel characterization of the human respiratory pathogen Mycoplasma pneumoniae. Associations with leukemia and other malignancies, however, were largely ascribed to tissue-culture contamination, which is now recognized as a significant potential problem in molecular biology circles. A few epidemiological studies, however, continue to raise concern over such a linkage. As well, in vitro data have demonstrated the potential for some mycoplasmas to induce karyotypic changes and malignant transformation during chronic tissue-culture infestation. As cellular and molecular mechanisms for such transformation become studied, a resurgence of interest in this area is inevitable. A role for mycoplasmas in malignancy of any sort is conjectural, but there remains a need to continue with focussed epidemiological and laboratory investigations.Key words: mycoplasma, cancer, oncogenesis, leukemia.
The effect of condensed tannins fromLotus pedunculatusandLotus corniculatuson the growth of proteolytic rumen bacteria in vitro and their possible mode of action
Authors: Molan A L , Attwood G T , Min B R , McNabb W C
Published: April 2011

Five strains of proteolytic rumen bacteria were treated with condensed tannins (CT) purified from Lotus pedunculatus and Lotus corniculatus to investigate their effect on the growth of these bacteria in vitro. Streptococcus bovis NCFB 2476, Eubacterium sp. C124b, Prevotella bryantii B14, Butyrivibrio fibrisolvens H17c, and Clostridium proteoclasticum B316Twere tested against 200, 400, and 600 µg CT·mL1extracted from L. pedunculatus and L. corniculatus. In the absence of CT, all bacterial strains showed typical growth and reached maximum optical density (OD) after 68 h of incubation in a plant protein medium. Growth of Eubacterium sp., P. bryantii, and B. fibrisolvens was inhibited (P < 0.010.001) more by the CT from L. pedunculatus than by the CT from L. corniculatus. All strains continued to grow in the presence of 200 µg·mL1of the CT from L. pedunculatus, but attained significantly (P < 0.050.01) lower maximum OD600values than (minus CT) controls, except for S. bovis. At 400 and 600 µg·mL1, the addition of CT from L. pedunculatus inhibited (P < 0.050.001) the growth of all bacterial strains tested compared with controls. The growth of Eubacterium sp. and P. bryantii was stimulated for the first 46 h of incubation (P < 0.001) by 200 µg·mL1of CT from L. corniculatus, but then declined leading to a significant difference in OD values compared with the controls. At 400 µg·mL1, the CT from L. corniculatus reduced (P < 0.050.01) the growth of all strains except S. bovis, while 600 µg·mL1inhibited (P < 0.010.001) the growth of all strains. To study the mechanism of CT action, the degradation of the large subunit (LSU) of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco; Fraction 1 Leaf protein) was followed after bacterial cells or Rubisco were preincubated with CT extracted from L. corniculatus and L. pedunculatus. Both preincubations decreased LSU degradation, but they differed in their response to polyethylene glycol (PEG) addition. Addition of PEG to CTRubisco preincubations negated the effects of CT, while PEG addition to CTbacteria preincubations did not. This implies that the CTbacterial interaction is stronger than the CTRubisco interaction or the interaction is of a different type. Also, L. pedunculatus CT reduced the degradation of the LSU to a greater extent than the CT from L. corniculatus when preincubated with bacteria.Key words: condensed tannins, growth, in vitro, proteolytic rumen bacteria, mode of action, Rubisco.
Reduction of linoleic acid inhibition in production of conjugated linoleic acid byPropionibacterium freudenreichiissp.shermanii
Authors: Rainio A , Vahvaselkä M , Suomalainen T , Laakso S
Published: April 2011

A method for the production of conjugated linoleic acid (CLA) from linoleic acid (LA) using growing cultures of Propionibacterium freudenreichii ssp. shermanii JS was developed. The growth inhibitory effect of LA was eliminated by dispersing it in a sufficient concentration of polyoxyethylene sorbitan monooleate detergent. For the whey permeate medium used, the optimum LA:detergent ratio was 1:15 (w/w). As a result, the cultures tolerated at least 1000 µg·mL1LA, which was converted to CLA with 57%87% efficiency. The cis-9, trans-11 and trans-9, cis-11 isomers constituted 85%90% of the CLA produced. The feasibility of the method was demonstrated also in de Man  RogosaSharpe (MRS) broth.Key words: conjugated linoleic acid, linoleic acid, Propionibacterium freudenreichii ssp. shermanii.
Analysis of the relationship between growth, cephalosporin C production, and fragmentation in Acremonium chrysogenum
Authors: Sándor Erzsébet , Szentirmai Attila , Paul Gopal C , Thomas Colin R , Pócsi István , Karaffa Levente
Published: April 2011

Mycelial fragmentation in submerged cultures of the cephalosporin C (CPC) producing fungus Acremonium chrysogenum was characterized by image analysis. In both fed-batch and chemostat cultures, the proportion of mycelial clumps seemed to be the most sensitive morphological indicator of fragmentation. In a fed-batch fermentation culture, this declined from roughly 60% at inoculation to less than 10% after 43 h. Subsequent additions of glucose resulted in a sharp increase back to near the initial value, an increase that reversed itself a few hours after glucose exhaustion. Meanwhile CPC production continued to decline steadily. On the other hand, the addition of soybean oil enhanced CPC production, but had no significant effect on the morphology. Although it may sometimes appear that morphology and productivity are related in batch or fed-batch cultures, this study suggests that this is because both respond simultaneously to more fundamental physiological changes, dependent on the availability of carbon. In circumstances, such as supplementary carbon source addition, the relationship is lost. Chemostat cultures supported this belief, as CPC-production rates were hardly affected by the specific growth rate, but the morphology showed significant differences, i.e., lower dilution rates resulted in a lower proportion of clumps and in smaller clumps.Key words: image analysis, Acremonium chrysogenum, morphology, fragmentation, cephalosporin C.
Salicylate inhibits the translation and transcription ofompFinEscherichia coli
Authors: Ramani Nat , Boakye Kwaku
Published: April 2011

OmpF is a major outer membrane protein in Escherichia coli whose expression is regulated by a large number of factors, including the osmolarity of the growth medium and the concentration of salicylate. We have previously shown that at low osmolarity, OmpF is post-transcriptionally regulated by micF mRNA, and that at high osmolarity, regulation occurs primarily by the inhibition of transcription by OmpR (Ramani et al. 1994). In contrast, salicylate was reported to alter OmpF expression solely by blocking translation primarily through micF mRNA (Rosner et al. 1991). We examined the effect of salicylate by analyzing the levels of OmpF in wild-type and micFstrains grown with salicylate. At low concentrations of salicylate (04 mM), OmpF levels were inhibited strongly in wild-type cells, whereas no inhibition of OmpF was observed in the micFstrain. At high concentrations of salicylate (1020 mM), both the wild type and the micFstrain showed strong inhibition of OmpF. To study the effect of salicylate on transcription, ompF mRNA and micF mRNA were analyzed in wild-type cells. micF mRNA levels increased during growth with 1, 2, and 4 mM salicylate. In contrast, ompF mRNA levels were not affected by low concentrations of salicylate, but decreased strongly at 10 and 20 mM salicylate. Taken together, these results suggest that similar to osmoregulation, salicylate inhibits both the translation and transcription of ompF.Key words: salicylate, OmpF, micF, osmoregulation.
Root colonization of faba bean (Vicia fabaL.) and pea (Pisum sativumL.) byRhizobium leguminosarumbv.viciaein the presence of nitrate-nitrogen
Authors: Beauchamp Chantal J , Kloepper Joseph W , Shaw Joseph J , Chalifour François-P.
Published: April 2011

There is a lack of knowledge concerning the effect of nitratenitrogen (NO3N) at levels known to inhibit nodule formation and functioning on root colonization of dinitrogen-fixing legumes. Firstly, this study investigated potential differences between Rhizobium leguminosarum bv. viciae 175F9 and its bioluminescent-labeled strain 175F9.lux on root colonization of faba bean (Vicia faba L.) and pea (Pisum sativum L.). These two strains similarly colonized the roots of both hosts. Secondly, this study evaluated the effects of 0 and 10 mol·m3NO3N on root colonization of faba bean and pea by strain 175F9.lux, over time. Averaged over both hosts and harvest dates, the presence of NO3N increased the rhizobial population and the root length colonized. In addition, our results showed that bioluminescence activity increased from 7 to 14 days after sowing and was not correlated to rhizobial population. Finally, to demonstrate that an increase in bioluminescence activity was not an indirect effect of nitrate on R. leguminosarum bv. viciae 175F9.lux, this study investigated the effects of increasing carbon (mannitol) and nitrogen (NO3N) concentrations on the rhizobial population and bioluminescence activity. The carbon source was more important than the nitrogen source to increase the rhizobial population and bioluminescence activity, which increased with increasing mannitol concentration, but not with increasing nitrate concentration. Results from this study demonstrated that NO3N increased rhizobial population, especially for faba bean, and the length of root colonized.Key words: nitrate, nitrogen, rhizosphere, rhizobacteria, luminescence
Peptidases affecting recombinant protein production by Streptomyces lividans
Authors: Yun Soon-Il , Yahya Ahmad RM , Malten Marco , Cossar Doug , Anderson William A , Scharer Jeno M , Moo-Young Murray
Published: April 2011

The influence of peptidases on human interleukin-3 (rhIL-3) production by a recombinant Streptomyces lividans strain was investigated. The bacterium produced several general peptidases and tripeptidyl peptidases compromising the authenticity of rhIL-3. The level of peptidases depended on growth morphology. Growing S. lividans as compact pellets successfully reduced peptidase activity. Maximum general peptidase activity in pellet culture was delayed after maximum rhIL-3 concentration was achieved. The activity of the tripeptidyl peptidase was product (rhIL-3) associated.Key words: fermentation, interleukin-3, Streptomyces, tripeptidyl peptidase, proteases.
Functional characterization of theHaemophilus influenzae4.5S RNA
Authors: Jenkins G Scott , Chandler Mark S , Fink Pamela S
Published: April 2011

The putative 4.5S RNA of Haemophilus influenzae was identified in the genome by computer analysis, amplified by the polymerase chain reaction, and cloned. We have determined that this putative 4.5S RNA will complement an Escherichia coli strain conditionally defective in 4.5S RNA production. The predicted secondary structures of the molecules were quite similar, but Northern analysis showed that the H. influenzae RNA was slightly larger than the E. coli RNA. The H. influenzae gene encoding this RNA is the functional homolog of the ffs gene in E. coli. Key words: ffs gene, complementation studies, small RNA, prokaryotic genetics.
The adaptability of the methylotrophic yeastCandida boidiniion media containing pectic substances
Authors: Stratilová Eva , Breierová Emília , Vadkertiová Renáta , Machová Eva , Malovíková Anna , Sláviková Elena
Published: April 2011

The methylotrophic yeast Candida boidinii is able to utilize pectic substances as the only carbon source. The primary utilization of methanol released from pectin is followed by adaptation to pectate medium. The duration of activation of a secondary pathway was critical for survival of yeast in the absence of other carbon sources. The utilization of pectin-containing media is associated with the production of pectic enzymes. The main polygalacturonase activities were found within the upper layer of the cell wall as shown by the method of gradual ultrasonication.Key words: pectic substances, pectic enzymes, pectin utilization, Candida boidinii, ultrasound.
Differences in chemical composition between nonflocculated and flocculated Azospirillum brasilense Cd
Authors: Olubayi Olubayi , Caudales Rodulio , Atkinson Amy , Neyra Carlos A
Published: April 2011

A two-step broth replacement method was used to induce Azospirillum brasilense Cd bacteria to flocculate in vitro. Nonflocculated and flocculated cells were compared with regard to total cellular lipid composition, fatty acid profiles, and poly-beta-hydroxybutyrate (PHB), protein, and carbohydrate contents. The fatty acid profiles of nonflocculated and flocculated cells were qualitatively identical. Two unsaturated fatty acids, octadecanoate (18:1 cis-9) and hexadecanoate (16:1 cis-9), accounted for approximately 80% of the total fatty acid content in both phenotypes. The major lipids in nonflocculated and flocculated A. brasilense Cd cells were phosphatidylethanolamine, phosphatidylglycerol, and phosphatidylcholine. The process of flocculation also resulted in the synthesis de novo of a glycolipid and cardiolipin. Flocculation also resulted in a decrease in total cellular protein and lipid content and a proportional increase in total cellular PHB and carbohydrate content. Results indicated that the two-step broth replacement procedure was an effective means for the in vitro production of the stress-tolerant A. brasilense Cd cells with high PHB contents, which are desirable in commercial agricultural inocula. The PHB content of flocculated cells reached 60-65% of cell dry weight.Key words: Azospirillum, flocculation, poly-beta-hydroxybutyrate, PHB, lipid, protein, carbohydrate, fatty acid.
Analysis of upstream activation of thevnfHpromoter ofAzotobacter vinelandii
Authors: Bageshwar Umesh K , Raina Ramesh , Choudhury Nirupam Roy , Das H K
Published: April 2011

BAL-31 deletion products of the DNA fragment containing the vnfH promoter and upstream region, when cloned in a transcriptional fusion vector and analyzed for vnfH expression in Azotobacter vinelandii, revealed that the upstream activator sequence of the vnfH promoter lies about 140 nucleotides upstream of the promoter. Subsequent substitution and deletion analysis by oligonucleotide-directed mutagenesis in the upstream region of the vnfH promoter showed that sequences 5'-GTACCATGCGGAAC-3' and 5'-GTACCTGCGGGTAC-3', located 170 and 140 nucleotides upstream of the vnfH promoter, respectively, are both required for vnfH expression. Addition of four nucleotides in the intervening sequence between the vnfH promoter and the putative VnfA (analog of NifA of the conventional molybdenum-dependent nitrogen-fixation pathway) binding site resulted in a drastic reduction of expression from the vnfH promoter in Azotobacter vinelandii, where as addition of 10 nucleotides in the intervening sequence did not affect the expression. Therefore, the face of the helix-dependent contact appeared to be important. DNA bending seemed to play a crucial role in expression from vnfH promoter. The intervening sequence exhibited characteristics of sequence-dependent intrinsically curved DNA, as shown by anomalous low gel mobility with polyacrylamide gel electrophoresis, electron microscopy, and computer simulated curvature analysis. Distamycin at very low concentrations significantly reduced the anomaly in electrophoretic mobility of the intervening DNA sequence.Key words: Azotobacter vinelandii, vnfA, vnfH, promoter-lacZ fusion, DNA bending.
Molecular characterization of multiresistant strains ofSalmonella typhifrom South Asia isolated in Ontario, Canada
Authors: Harnett N , McLeod S , AuYong Y , Wan J , Alexander S , Khakhria R , Krishnan C
Published: April 2011

Two hundred and fourteen isolates of Salmonella typhi submitted to our laboratory between 1992 and 1996 were tested for susceptibility to 20 antimicrobial agents. Forty-eight of the 214 isolates (22.4%), recovered from individuals who had travelled in South Asia, were multiresistant. Forty-four of the 48 isolates were resistant to ampicillin, chloramphenicol, tetracycline, streptomycin, sulfamethoxazole, trimethoprim, cotrimoxazole, ticarcillin, and piperacillin; the other four isolates were resistant to four to six agents. Forty-two of the multiresistant isolates belonged to Vi phage type E1, two isolates from the Punjab State belonged to phage type A, another from the Punjab State belonged to phage type E3, one isolate from Pakistan belonged to type M1, and one isolate from India belonged to type J1. Plasmids from 45 of 48 isolates showed a temperature-sensitive mechanism of transfer to Escherichia coli K-12 strains, characteristic of HI incompatibility group plasmids. The majority of plasmids had an estimated molecular weight of 120 MDa and encoded both citrate utilization and mercury resistance. Plasmids from three isolates had an estimated molecular weight of 112-115 MDa; one of these isolates encoded citrate utilization but not mercury resistance. Analysis of isolates by pulsed-field gel electrophoresis after digestion with XbaI and SpeI indicated that the majority of multiresistant isolates shared a common restriction profile, while four isolates had unique patterns.Key words: typing, multiresistant, Salmonella typhi.
Production of the host-selective phytotoxin phomalide by isolates of Leptosphaeria maculans and its correlation with sirodesmin PL production
Authors: Pedras M Soledade C. , Biesenthal Corinne J
Published: April 2011

The production of the phytotoxins phomalide and sirodesmin PL by virulent isolates of Leptosphaeria maculans (Desm.) Ces. et de Not. (asexual stage Phoma lingam (Tode ex Fr.) Desm.), the causative agent of blackleg or stem canker disease, was investigated. The effects of temperature, light, age of spores, and calcium ions on the production of phomalide, as well as a correlation between phomalide and sirodesmin PL production, were determined. Finally, the effect of phomalide on fungal spore germination of virulent isolates and isolation of phomalide from blackleg-infected foliar tissue are reported for the first time.Key words: Leptosphaeria maculans, Phoma lingam, phomalide, sirodesmin PL, HPLC analysis.
Isolation ofDesulfovibrio intestinalissp. nov. from the hindgut of the lower termiteMastotermes darwiniensis
Authors: Fröhlich Jürgen , Sass Henrik , Babenzien Hans-Dietrich , Kuhnigk Thomas , Varma Ajit , Saxena Shailendra , Nalepa Christine , Pfeiffer Peter , König Helmut
Published: April 2011

A Gram-negative, anaerobic sulfate-reducing bacterium was isolated from hindgut contents of the lower termite Mastotermes darwiniensis Froggatt (strain KMS2). Strain KMS2 is motile by a single polar flagellum. The isolate possesses desulfoviridin and catalase activity. The G+C content of its DNA is in the range of 54.5-55.5 mol% (strain KMS2). It respires hydrogen and different low molecular weight organic compounds in the presence of sulfate, thiosulfate, and sulfite, and also oxygen. The isolated strain ferments pyruvate. Fastest growth with a doubling time of 12.5 h was obtained at 37°C and not at 28°C, the temperature at which the termites were grown. The isolate showed a 16S rDNA sequence homology of 95.9% to Desulfovibrio desulfuricans ATCC 27774 and a DNA-DNA homology of 44.6% to D. desulfuricans Essex 6 (type strain). Based on its biochemical properties and 16S rDNA sequence, the isolate was assigned to a new species named Desulfovibrio intestinalis.Key words: Desulfovibrio, termite, intestinal flora.
Isolation and partial characterisation of extracellular keratinase from a wool degrading thermophilic actinomycete strainThermoactinomyces candidus
Authors: Ignatova Z , Gousterova A , Spassov G , Nedkov P
Published: April 2011

The keratinase production by the thermophilic actinomycete strain Thermoactinomyces candidus was induced by sheep wool as the sole source of carbon and nitrogen in the cultivation medium. For complete digestion of wool by the above strain, both keratinolytic serine proteinase and cellular reduction of disulfide bonds were involved. Evidence was presented that substrate induction was a major regulatory mechanism and the keratinase biosynthesis was not completely repressed by addition of other carbon (glucose) and nitrogen (NH4Cl) sources. The enzyme was purified 62-fold by diethylaminoethyl - anion exchange and Sephadex G-75 gel permeation chromatographies. Sodium dodecyl sulfate - polyacrylamide gel electrophoresis indicated that the purified keratinase is a monomeric enzyme with a molecular mass of 30 kDa. The pH and temperature optima were determined to be 8.6 and 70°C, respectively. The purified thermophilic keratinase catalyses the hydrolysis of a broad range of substrates and displays higher proteolytic activity against native keratins than other proteinases. Ca2+was found to have a stabilizing effect on the enzyme activity at elevated temperatures.Key words: wool degradation, keratinolyic actinomycetes, keratinase, Thermoactinomyces candidus.