bluuebunny/crossref_metadata_2025 huggingface dataset:
Fluorescence study of lectinlike receptors involved in the flocculation of the yeast Saccharomyces cerevisiae
Authors: Masy C. L. , Henquinet A. , Mestdagh M. M.
Published: May 2010

Flocculation of some yeasts involves lectinlike receptors with two different patterns of inhibition by sugars: mannose sensitive (MS) and glucose-mannose sensitive (GMS). The visualization and quantification of these receptors were performed using neoglycoproteins fluorescent probes. Fluorescence microscopy showed a homogeneous distribution of surface receptors for the strain belonging to the MS group and a polar distribution for cells belonging to the GMS group. Affinity constants, estimated by fluorimetry, were shown to have different values (MS, 2.6 ± 0.7 × 105 M−1; GMS, 2 ± 1 × 106 M−1), but the number of sites was estimated to be smaller for strain NCYC 1195 which belongs to the GMS group than for strain NCYC 869 from the MS group (MS, 2.4 ± 0.2 × 107 sites/cell; GMS, 3.9 ± 0.8 × 106 sites/cell). Key words: flocculation, neoglycoproteins, Saccharomyces, lectinlike.
Enzyme-labeled oligonucleotide probes for detection of the genes for theromostable direct hemolysin (TDH) and TDH-related hemolysin (TRH) of Vibrio parahaemolyticus
Authors: Yamamoto Koichiro , Honda Takeshi , Miwatani Toshio , Tamatsukuri Shigeru , Shibata Shuji
Published: May 2010

Alkaline phosphatase conjugated oligonucleotide probes were developed to detect the genes (tdh and trh) coding for the thermostable direct hemolysin (TDH) and TDH-related hemolysin (TRH) of Vibrio parahaemolyticus. Using dot blot hybridization, probes were tested with 94 clinical isolates of V. parahaemolyticus. Results agreed well with those obtained using radio-labeled recombinant DNA probes for the genes tdh and trh. Specificity and sensitivity of enzyme tdh probes for detection of the trh gene were 100 and 93%, respectively, and those of the trh probes for trh gene detection were 93 and 86%, respectively. The tdh probes also hybridized with tdh-like genes processed by all strains of V. hollisae, and some strains of V. mimicus and V. cholerae non-O1, but neither tdh nor trh probes reacted with other bacterial species isolated from diarrheal stools. However, some V. parahaemolyticus strains that were negative with the enzyme trh probe hybridized weakly with a radio-labeled trh DNA fragment probe at medium stringency, and a few strains that were negative in high stringency conditions with a radio-labeled trh DNA fragment probe hybridized with the enzyme trh probe. This suggests that some strains of V. parahaemolyticus may carry another gene resembling trh. Key words: oligonucleotide DNA, enzyme, Vibrio parahaemolyticus, hemolysin.
Pichia stipitisL-rhamnose dehydrogenase and a catabolite-resistant mutant able to utilize 2-deoxy-D-glucose
Authors: Pardo E. H. , Funayama S. , Pedrosa F. O. , Rigo L. U.
Published: May 2010

The yeast Pichia stipitis, strain NRC 5568, when grown on L-rhamnose as sole carbon source produced an NAD+-dependent L-rhamnose dehydrogenase enzyme, which is repressed by D-glucose. Mutants defective in carbon catabolite repression were isolated, using a selective medium containing 2-deoxy-D-glucose. Six of eight mutants resistant to 2-deoxy-D-glucose showed L-rhamnose dehydrogenase synthesis insensitive to D-glucose repression. All eight mutants, named PR mutants, as well as the parent strain, were found to grow on D-glucose, L-rhamnose, and glycerol. In addition, they were all capable of growing on 2-deoxy-D-glucose as sole carbon source, D-Glucose and 2-deoxy-D-glucose caused almost complete inhibition of L-rhamnose dehydrogenase synthesis in the wild-type strain but only a slight decrease in the enzyme synthesis in the mutant strain PR1. The wild-type and mutant strains showed the same pattern of inhibition by cycloheximide, 8-hydroxyquinoline, and benomyl. Key words: Pichia stipitis, L-rhamnose dehydrogenase, catabolite-resistant mutant, 2-deoxy-D-glucose.
Inactivation of coliphage MS-2 and poliovirus by copper, silver, and chlorine
Authors: Yahya Moyasar T. , Straub Timothy M. , Gerba Charles P.
Published: May 2010

The efficacy of electrolytically generated copper and silver ions (400 and 40 μg/L, respectively) was evaluated separately and in combination with free chlorine (0.2 and 0.3 mg/L) for the inactivation of coliphage MS-2 and poliovirus type 1 in water at pH 7.3. The inactivation rate was calculated as log10 reduction/min: k = −(log10Ct/C0)/t. The inactivation of both viruses was at least 100 times slower in water containing 400 and 40 μg/L copper and silver, respectively (k = 0.023 and 0.0006 for MS-2 and poliovirus, respectively), compared with water containing 0.3 mg/L free chlorine (k = 4.88 and 0.036). Significant increases in the inactivation rates of both viruses were observed in test systems containing 400 and 40 μg/L copper and silver, respectively, with 0.3 mg/L free chlorine when compared with the water systems containing either metals or free chlorine alone. Poliovirus was approximately 10 times more resistant to the disinfectants than coliphage MS-2. This observation suggests either a synergistic or an additive effect between the metals and chlorine for inactivation of enteric viruses. Use of copper and silver ions in water systems currently used in swimming pools and spas may provide an alternative to high levels of chlorination. Key words: enteric viruses, poliovirus, coliphage MS-2, bacteriophage, disinfection, inactivation, copper, silver, chlorine.
Morphological and biochemical changes in peanut nodules during photosynthate stress
Authors: Siddique A. B. M. , Bal A. K.
Published: May 2010

Nitrogen fixation in legume root nodules is believed to be supported by the supply of photosynthate of the current photoperiod. However, in peanut nodules, prolonged periods of darkness or detopping do not disrupt nitrogen fixation for at least 48 h. During this period, nodule oleosomes (lipid bodies) have been shown to decrease in number within the infected cells, and it has been suggested that lipids from oleosomes are mobilized to maintain the energy and carbon requirements of the nitrogen-fixing nodules. We present morphological evidence, at the ultrastructural level, for the utilization of oleosomes during photosynthate stress. The biochemical status of the nodule has also been assessed and correlated with ultrastructure. For comparison cowpea nodules were used that totally lacked oleosomes. In peanut nodules leghemoglobin and total protein remained unchanged along with integrated ultrastructure on nodule cells for 48 h, whereas in cowpea a decline in proteins with ultrastructural damage became apparent within a very short period of photosynthate stress. In peanut nodules empty or partially empty oleosomes were taken as evidence for their utilization during the stress period. Key words: N2 fixation, photosynthate stress, lipid bodies, catalase, malate synthase, peanut nodule, β-oxidation.
Overexpression of the dctA gene in Rhizobium meliloti: effect on transport of C4 dicarboxylates and symbiotic nitrogen fixation
Authors: Rastogi Vipin , Labes Monika , Finan Turlough , Watson Robert
Published: May 2010

Symbiotic nitrogen fixation may be limited by the transport of C4 dicarboxylates into bacteroids in the nodule for use as a carbon and energy source. In an attempt to increase dicarboxylate transport, a plasmid was constructed in which the Rhizobium meliloti structural transport gene dctA was fused to a tryptophan operon promoter from Salmonella typhimurium, trpPO. This resulted in a functional dctA gene that was no longer under the control of the dctBD regulatory genes, but the recombinant plasmid was found to be unstable in R. meliloti. To stably integrate the trpPO-dctA fusion, it was recloned into pBR325 and recombined into the R. meliloti exo megaplasmid in the dctABD region. The resultant strain showed constitutive dctA-specific mRNA synthesis which was about 5-fold higher than that found in fully induced wild-type cells. Uptake assays showed that [14C]succinate transport by the trpPO-dctA fusion strain was constitutive, and the transport rate was the same as that of induced control cells. Acetylene reduction assays indicated a significantly higher rate of nitrogen fixation in plants inoculated with the trpPO-dctA fusion strain compared with the control. Despite this apparent increase, the plants had the same top dry weights as those inoculated with control cells. Key words: acetylene reduction, genetic engineering, nodule, plasmid stability, promoter.
A cryptic plasmid of indigenous Rhizobium meliloti possesses reiterated nodC and nifE genes and undergoes DNA rearrangement
Authors: Rastogi V. K. , Bromfield E. S. P. , Whitwill S. T. , Barran L. R.
Published: May 2010

Indigenous Rhizobium meliloti were previously characterized on the basis of plasmid profiles and phage sensitivity patterns (phage types). Rhizobium meliloti 1076, which contained two cryptic plasmids, was one of four isolates comprising phage type 23. In this study, the large cryptic plasmid pVS1(size >500 b) was transferred from isolate 1076 into the plasmid-free strain of Agrobacterium tumefaciens UBAPF1. This plasmid contained nucleotide sequences homologous to genes for nodulation (nodB, nodC) and nitrogen fixation (nifH, nifD, nifK, nifE). Cosmid clones possessing the nod and nif homologous sequences, which had been selected from a genomic bank of A. tumefaciens UBAPF1 containing pVS1, complemented R. meliloti nodC and nifE mutants, respectively. These results demonstrate that the nodC and nifE homologous sequences are functionally expressed. Three of four isolates comprising phage type 23 possessed a megaplasmid band in agarose gels characteristic of R. meliloti, as well as two cryptic plasmids. The fourth isolate (No. 323) lacked the large cryptic plasmid corresponding to pVS1, but instead showed a band of lesser mobility than that of the megaplasmids. Nevertheless, its restricted genomic DNA retained the nodC and nifE hybridizing fragments characteristic of pVS1, indicating that the cryptic plasmid has undergone DNA rearrangement. Key words: Rhizobium, plasmid, reiteration, genes, rearrangement.
Cultivation of Bradyrhizobium CB756 on sucrose prefermented by yeast
Authors: Lie T. A. , Muilenburg Martin , Hiep Nguyen Huu , Ayhan Kamuran
Published: May 2010

Saccharomyces cerevisiae, grown with sucrose as a substrate, converts the sucrose to glycerol and produces yeast cells. The yield of glycerol was doubled by adding CaCO3. The fermented medium, containing glycerol and yeast cells, was an excellent medium for the cultivation of Bradyrhizobium CB756. Best results were obtained after dilution of the fermented medium to 10% (v/v) with a basal salts solution, but even with dilutions of 5 and 2.5%, high numbers of Bradyrhizobium CB756 cells were obtained. Key words: Bradyrhizobium, glycerol, nitrogen fixation, inoculants.
Soil biomass of Bradyrhizobium japonicum inoculated via irrigation water
Authors: Clafardini G. , Marinelli G. , Missich R.
Published: May 2010

Soybean (Glycine max (L.) Merr.), when grown in soil poor in Bradyrhizobium japonicum, shows low nitrogen-fixation activity as a result of the small number of nodules produced. In an attempt to increase the biomass of the symbiont in the soil and nodulation in soybean cv. Hodgson, a study was performed using B. japonicum USDA 122 cover inoculated with the irrigation water at the time of sowing or at the three-node (V3 phenophase) stage. The B. japonicum cover inoculation performed alone or in combination with traditional seed inoculation with peat bacteria inoculum (control) resulted in an 8-fold average increase of symbiont biomass in the soil. Cover inoculation at the V3 stage combined with seed inoculation with peat inoculum tripled the number of nodules per plant, increasing nitrogen fixation in the plant during pod filling (R6 phenophase). The ureide concentration in the soybean decreased with plant age. Cover inoculation at the V3 stage combined with seed inoculation with peat inoculum significantly increased the ureide concentration in leaves and stalks of plants in the R6 stage. The total nitrogen concentration in leaves and stalks was also always greater in the plants that were both seed and cover inoculated. Cover inoculation is a new agricultural technique that can increase nitrogen fixation and bean yield per hectare of soybean without recourse to chemical nitrogen fertilizers. Key words: Bradyrhizobium japonicum, inoculation, soil biomass.
Extension programs to promote rhizobial inoculants for soybean and groundnut in Thailand
Authors: Chanaseni C. , Kongngoen S.
Published: May 2010

The promotion of rhizobial inoculants for soybean (Glycine max) and groundnut (Arachis hypogaea) in Thailand has been conducted by the Thai Department of Agricultural Extension (DOAE). The inoculant is produced by the Thai Department of Agriculture (DOA), which has a production capacity of 200 metric tons per year. The DOAE has emphasized inoculant use since 1982 through the Soybean Marketing and Production Development Project and the Groundnut Extension and Development Project. These projects are aimed at increasing the average yield and total production of the legumes, especially soybean. Both projects have been promoted through training, on-farm activities, local mobile units, and field day activities. There has been approximately a 35-fold increase in yearly legume inoculant use between 1977 and 1990. In 1990, the DOA produced a total of 126.35 metric tons of inoculants for soybean, groundnut, mung bean, and other minor legumes. Of this total, 117.67 metric tons were sold. This figure represents in 200-g bag quantities (i) 477 333 bags of soybean inoculant; (ii) 72 746 bags groundnut inoculant; (iii) 35 461 bags mung-bean inoculant; and (iv) 2 810 bags inoculant for minor legumes. In addition, the private sector under the Soybean Joint Venture Project has produced and distributed approximately 100 000 bags inoculant (also 200 g each) per year in 1989 and 1990. Key words: rhizobial inoculants, Thai Agricultural Extension, agricultural extension, legume inoculation.
Sealed-tube combustion for natural 15N abundance estimation of N2 fixation and application to supernodulating soybean mutants
Authors: Eskew D. L. , Gresshoff P. M. , Doty M. , Mora C.
Published: May 2010

Measurement of biological N2 fixation by the natural 15N abundance technique is based on the fact that soil N is usually enriched in 15N compared with atmospheric N2. The technique has been limited by the care required to prevent isotope fractionation in the Kjeldahl method. We describe a sealed-tube combustion technique that reduces isotope fractionation problems. Plant samples were combusted at 850 °C in Vycor tubes with Cu, CuO, CaO, and Ag foil, and N2 gas was admitted directly into the mass spectrometer. A δ15N value of 5.43 ± 0.01 (SE, n = 11) was obtained for a nonnodulating soybean seed sample. This method was used to estimate N2 fixation by soybean cv. Bragg and three supernodulating mutants, nts246, nts382, and nts1007, in the field. Average percent N derived from the atmosphere was 70 ± 4% in vegetative parts at physiological maturity and 72 ± 2% in the grain at harvest. No significant differences were found. The N harvest index averaged 77%; thus, despite the high percent N derived from the atmosphere, these soybean crops would have been net exporters of soil N. The natural 15N abundance method consistently gave estimates of N2 fixation that were 60–90 kg N ha−1 higher than the N difference method. Key words: sealed-tube combustion, natural 15N abundance, supernodulating soybean mutants, biological N2 fixation.
Binding of mutagenic pyrolyzates to fractions of intestinal bacterial cells
Authors: Zhang Xue Bin , Ohta Yoshiyuki
Published: May 2010

The binding of mutagenic pyrolyzates to cell fractions from some gram-negative intestinal bacteria and to thermally treated bacterial cells was investigated. 3-Amino-1,4-dimethyl-5H-pyrido[4,3-b]indole (Trp-P-1) and 3-amino-1-methyl-5H-pyrido[4,3-b]indole (Trp-P-2) were effectively bound by several of the bacterial cells. The cell wall skeletons of all bacteria effectively bound Trp-P-1 and Trp-P-2. Their cytoplasmic fractions retained Trp-P-1 and Trp-P-2, but to a lesser extent than the cell wall skeletons. 2-Amino-3-methylimidazo [4,5-f]quinoline (IQ) was not found in their cytoplasmic fractions. These cell wall skeletons also bound 2-amino-6-methyldipyrido[1,2-a:3′2′-d] imidazole (Glu-P-1), 2-amino-5-phenylpyridine (Phe-P-1), IQ, 2-amino-3,4-dimethylimidazo[4,5-f]quinoline (MeIQ), and 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQX). The amount of each mutagen bound differed with the type of mutagen and the bacterial strain used. The outer membrane of Escherichia coli IFO 14249 showed binding of about 123.7 μg/mg of Trp-P-2, and its cytoplasmic membrane bound 57.14 μg/mg. Trp-P-2 bound to the bacterial cells was extracted with ammonia (5%), methanol, and ethanol but not with water. Key words: cell wall skeletons, outer membrane, cytoplasmic membrane, binding of mutagenic pyrolyzates.
Relationship of low lysine and high arginine concentrations to efficient ethanolic fermentation of wheat mash
Authors: Thomas Kolothumannil C. , Ingledew W. M.
Published: May 2010

Very high gravity wheat mashes containing 20 or more grams of carbohydrates per 100 mL were fermented completely by Saccharomyces cerevisiae, even though these mashes contained low amounts of assimilable nitrogen. Supplementation of wheat mashes with various amino acids or with yeast extract, urea, or ammonium sulfate reduced the fermentation time. However, lysine or glycine added as single supplements, inhibited yeast growth and fermentation. With lysine, yeast growth was severely inhibited, and a loss of cell viability as high as 80% was seen. Partial or complete reversal of lysine-induced inhibition was achieved by the addition of a number of nitrogen sources. All nitrogen sources that relieved lysine-induced inhibition of yeast growth also promoted uptake of lysine and restored cell viability to the level observed in the control. They also increased the rate of fermentation. Experiments with minimal media showed that for lysine to be inhibitory to yeast growth, assimilable nitrogen in the medium must be in growth-limiting concentrations or totally absent. In the presence of excess nitrogen, lysine stimulated yeast growth and fermentation. Results indicate that supplementing wheat mash with other nitrogen sources increases the rate of fermentation not only by providing extra nitrogen but also by reducing or eliminating the inhibitory effect of lysine on yeast growth. Key words: very high gravity, lysine inhibition, fuel alcohol, free amino nitrogen.
Alcoholic glucose and xylose fermentations by the coculture process: compatibility and typing of associated strains
Authors: Laplace J. M. , Delgenes J. P. , Moletta R. , Navarro J. M.
Published: May 2010

As part of the simultaneous fermentation of both glucose and xylose to ethanol by a coculture process, compatibilities between xylose-fermenting yeasts and glucose-fermenting species were investigated. Among the Saccharomyces species tested, none inhibited growth of the xylose-fermenting yeasts. By contrast, many xylose-fermenting yeasts, among the 11 tested, exerted an inhibitory effect on growth of the selected Saccharomyces species. Killer character was demonstrated in three strains of Pichia stipitis. Such strains, despite their high fermentative performances, cannot be used to ferment D-xylose in association with the selected Saccharomyces species. From compatibility tests between xylose-fermenting yeasts and Saccharomyces species, pairs of microorganisms suitable for simultaneous xylose and glucose fermentations by coculture are proposed. Strains associated in the coculture process are distinguished by their resistance to mitochondrial inhibitors. The xylose-fermenting yeasts are able to grow on media containing erythromycin (1 g/L) or diuron (50 mg/L), whereas the Saccharomyces species are inhibited by these mitochondrial inhibitors. Key words: killer character, erythromycin resistance, diuron resistance, Pichia stipitis.
Construction of the physical maps of Mycoplasma hyopneumoniae and Mycoplasma flocculare and the location of rRNA genes on these maps
Authors: Huang Y. , Stemke G. W.
Published: May 2010

The genomes of Mycoplasma flocculare and Mycoplasma hyopneumoniae, two mycoplasmas of the porcine respiratory system, were studied. Based upon antigenic cross-reactivity and DNA–DNA hybridization, these species have given indication of a close genetic relationship. By using field-inversion gel electrophoresis and employing the restriction digest fragments obtained from the gels as the probes, physical maps of the genomes of the two species were constructed. Mycoplasma hyopneumoniae is similar to M. flocculare in having a single set of rRNA genes and the 5S-rRNA gene is separated from the 16S and 23S rRNA genes. Based upon the location of the rRNA genes on the physical maps in both species, the distance between the 5S and the 16S and 23S rRNA genes is at least 150 kbp. Thus, there is further evidence for the close relationship between these organisms. Key words: Mycoplasma, Mollicutes, physical maps, rRNA.
Chromosome mobilization of Legionella pneumophila with RK2::Mu and Tn5-Mob
Authors: Mintz Clifford S. , Zou Chang Hua
Published: May 2010

RK2::Mu plasmids and transposon Tn5-Mob were used to mobilize the Legionella pneumophila chromosome. Plate matings between L. pneumophila donors that contained RK2::Mu plasmids and auxotrophic recipients yielded recombinants at fequencies ranging from 10−6 to 10−7 per recipient for the markers tested. The presence of a Mu insertion in the chromosome of donors that harbored RK2::Mu plasmids increased the frequency of chromosome transfer of certain selected markers as compared with strains that contained RK2::Mu alone. Cotransfer experiments with Mu-containing donors and a thymidine and tryptophan auxotroph failed to reveal any linkage between the thy and trp loci in L. pneumophila. A strain that contained a chromosomal Tn5-Mob insertion and helper plasmid pRK24.4 transferred chromosomal markers at frequencies of 10−7 per recipient. These findings suggest that RK2::Mu plasmids and Tn5-Mob may be useful for genetic mapping experiments with L. pneumophila. Key words: Legionella pneumophila, chromosome transfer, Tn5-Mob, RK2::Mu.
Évaluation du pouvoir adhérant du Lactobacillus helveticus au polystyrène expansé
Authors: Dion Nathalie , Goulet Jacques , Boyaval Patrick
Published: May 2010

We measured the surface tension of a three-phase (solid–solid–liquid) system consisting of the bacterium Lactobacillus helveticus in a culture medium containing an expanded polystyrene support, to determine the adherence capacity of the bacteria to the support. The surface tension of the expanded polystyrene and the L. helveticus cells was evaluated by measuring contact angles. The Wilhelmy's microslide method was used to measure the surface tension of the liquid phase. The values obtained showed that the adherence capacity of the L. helveticus cells to expanded polystyrene pellets was not facilitated under the experimental thermodynamic conditions. The pellet surfaces and adhering bacterial cells were examined with a scanning electron microscope. The pellets exhibited several grooves in which microbial cells preferentially accumulated. Key words: Lactobacillus helveticus, adherence, surface tension, expanded polystyrene. [Translated by the journal]
Specificity of bacterial attachment sites on the filamentous diatom Navicula confervacea (Bacillariophyceae)
Authors: Rosowski James R.
Published: May 2010

The association in soil–water cultures of bacteria with the siliceous wall (frustule) of Navicula confervacea was examined with scanning electron microscopy. This diatom is filamentous through serial valve–face unions. Thus, the valve mantle and girdle bands are exposed to the aqueous environment and its bacterial flora, whereas the internally isolated adhering valve–face surfaces are not. Secretion of diatom mucilage strands occurred largely from parallel slits in the valve mantle and from valve–band and band–band sutures. These strands appeared to create a surface environment that discouraged bacterial adhesion. However, as the diatoms divided, their newly exposed mucilage-free bands provided a substratum for bacterial attachment. Dense aggregates of bacteria sometimes occurred at frustule apices, where filaments most easily bend and where recently formed adjacent hypovalves emerge. Along mucilage-free segments of the diatom filament, bacterial development occasionally engulfed the frustules; more commonly, bacteria were sparse but in specific locations. Bacterial attachment structures were mostly straight fibers, even on cocci, whereas strands from diatoms were contorted. Attachment by rods and spirilla was most often by their apices, with or without obvious lateral anchoring fibers. Scanning electron microscopy of cocci, rods, vibrio, and spirilla suggests that these bacteria initially prefer mucilage-free attachment sites near openings likely to leak cellular nutrients, i.e., slits of the mantle and band sutures rather than on the substratum between them, where presumably, other nutrients would have been available through their adsorption from the medium. Key words: bacterial adhesion, diatom girdle, mucilage, trail fibers.
Serotyping of Bacillus thuringiensis environmental isolates by extracellular heat-stable somatic antigens
Authors: Ohba Michio , Ueda Kousuke , Aizawa Keio
Published: May 2010

A total of 525 Bacillus thuringiensis environmental isolates, belonging to the five flagellar (H) serovars (alesti, sotto, kenyae, aizawai, and morrisoni), were serotyped by extracellular heat-stable somatic antigens (HSSAs). The isolates belonging to a given H serovar were assigned to a single HSSA serogroup at a high frequency, 87–100%. This indicates that the extent of HSSA variation within a single H serovar is small in the field populations of these B. thuringiensis serovars. Key words: Bacillus thuringiensis, serotyping, extracellular heat-stable somatic antigen.
Escherichia coli serotyping and disease in man and animals
Authors: Ørskov Frits , Ørskov Ida
Published: May 2010

Serotyping of Escherichia coli is useful, but complex, with 173 O antigens, 80 K antigens, and 56 H antigens, which can all be subdivided into partial antigens. The O, K, and H antigens can be found in nature in many of the possible combinations. The final number of E. coli serotypes is very high, 50 000 – 100 000 or more. The number of frequent pathogenic serotypes is, however, limited. Two main groups of such frequent serotypes are (i) serotypes from diarrhoeal disease and (ii) serotypes from extraintestinal disease. Serotypes from diarrhoeal diseases are mostly species specific, and could at present be used as epidemiological markers for bacterial clones equipped with special virulence markers, such as toxins and adhesins. Their O-antigen lipopolysaccharides may be regarded as virulence factors. These strains are not inhabitants of the normal intestine. Serotypes from extraintestinal diseases constitute a different set of clones, which are good colonizers of the intestinal tract, that under certain conditions succeed in invading host tissues. They are characterized by virulence factors different from those found in strains from diarrhoeal disease. Thus, the two groups of pathogenic E. coli are both composed of a limited number of clones for which the O:K:H serotypes are excellent, although not faultless, markers. Key words: Escherichia coli, serotype, extraintestinal, diarrhoea, disease.
Virulence determinants of Escherichia coli: present knowledge and questions
Authors: Smith Harry
Published: May 2010

This paper describes the present state of research on the pathogenicity of Escherichia coli and points out the gaps in knowledge that should be filled in the future. First, the great versatility of E. coli in producing disease is noted, as well as the invaluable contributions that studies of it have made to the development of general knowledge on bacterial pathogenicity. Then, the biological requirements for pathogenicity: infection of mucous surfaces; penetration of those surfaces; multiplication in vivo; interference with host defence mechanisms; and damage to the host, are taken in turn, and an enquiry is made on how far studies have progressed toward identifying their molecular determinants and relating structure to biological action. Only for mucous surface adhesins and protein toxins are studies at the structure–function level. Some progress has been made on interference with host defence, but little is known about competition with commensals on mucous surfaces, invasion into the tissues, and growth in vivo. Key words: virulence determinants, Escherichia coli.
Some nutritional requirements of a mixed culture transforming Reichstein's compound S into prednisolone
Authors: Ghanem K. M. , Yusef H. H.
Published: May 2010

Reichstein's compound S was successfully converted to prednisolone in a single-step fermentation using a mixed culture of Curvularia lunata and Mycobacterium smegmatis. Introducing additional medium at the time of bacterial inoculation and increasing the M. smegmatis inoculum to 8% were necessary for maximal dehydrogenation of cortisol to prednisolone (86%). However, beef extract, corn-steep solids, and malt extract were inhibitory to the dehydrogenase activity and stimulatory to hydroxylase. Of the vitamins tested, nicotinic acid and riboflavin at 0.2 and 1.13 mg/L, respectively, resulted in maximum transformation of Reichstein's compound S (100%) and optimized prednisolone yields (92%) in the mixed culture. The trace elements present in the medium were sufficient for maximal transformation, and there was no need for an exogenous supply. Addition of ATP, sodium acetate, and NAD inhibited the dehydrogenation reaction. Key words: biotransformation of Reichstein's compound S, mixed-culture transformations, transformation of steroids.
Regulation of α-aminoadipate reductase from Penicillium chrysogenum in relation to the flux from α-aminoadipate into penicillin biosynthesis
Authors: Lu Ying , Mach Robert L. , Affenzeller Karin , Kubicek Christian P.
Published: May 2010

The activity and regulation of α-aminoadipate reductase in three Penicillium chrysogenum strains (Q176, D6/1014/A, and P2), producing different amounts of penicillin, were studied. The enzyme exhibited decreasing affinity for α-aminoadipate with increasing capacity of the respective strain to produce penicillin. The enzyme from all three strains was inhibited by L-lysine, and the enzyme from the lowest producer, Q176, was least sensitive. Between pH 7.5 and 6.5, inhibition of α-aminoadipate reductase by L-lysine was pH dependent, being more pronounced at lower pH. The highest producer strain, P2, displayed the lowest α-aminoadipate reductase activity at pH 7.0. In Q176, the addition of 0.5–1 mM of exogenous lysine stimulated penicillin formation, whereas the same concentration was ineffective or inhibitory with strains D6/1014/A and P2. The addition of higher (up to 5 mM) lysine concentrations inhibited penicillin production in all three strains. In mutants of P. chrysogenum D6/1014/A, selected for resistance to 20 mM α-aminoadipate, highest penicillin production was observed in those strains whose α-aminoadipate reductase was most strongly inhibited by L-lysine. The results support the conclusion that the in vivo activity of α-aminoadipate reductase from superior penicillin producer strains of P. chrysogenum is more strongly inhibited by lysine, and that this is related to their ability to accumulate increased amounts of α-aminoadipate, and hence penicillin. Key words: α-aminoadipate, α-aminoadipate reductase, regulation of lysine biosynthesis, penicillin biosynthesis, Penicillium chrysogenum.
Identification of degradation artifacts formed upon treatment of hydroxydiether lipids from methanogens with methanolic HCl
Authors: Ekiel Irena , Sprott G. Dennis
Published: May 2010

Treatment of purified 3-hydroxydiether lipid from Methanosarcina barkeri by standard conditions for head-group removal (2.5% methanolic HCl, 70 °C) resulted in conversion to six identifiable degradation products. The four most abundant products were identified by mass spectrometry and nuclear magnetic resonance as monophytanylglycerol, 3-methoxydiether, and cis–trans isomers of a diether unsaturated between carbons 3 and 4. The latter lipid products may be mistaken for 2,3-di-O-phytanyl-sn-glycerol (standard diether) and 2-O-sesterterpanyl-3-O-phytanyl-sn-glycerol when separated by thin-layer chromatography. Key words: hydroxydiether lipids, degradation artifacts, methanolic HCl, Methanosarcina barkeri.
Prevention of 5-fluorouracil-induced infection with indigenous Escherichia coli in tumor-bearing mice by nonspecific immunostimulation
Authors: Nomoto Koji , Yokokura Teruo , Nomoto Kikuo
Published: May 2010

We have previously reported that the lethal toxicity of 5-fluorouracil (5-FU) in specific-pathogen-free mice is due to an indigenous infection with Escherichia coli (K. Nomoto, T. Yokokura, Y. Yoshikai, et al. Can. J. Microbiol. 37: 244–247, 1991). In the present study, we demonstrate that nonspecific immunostimulation augments host resistance against the lethal toxicity of 5-FU in tumor-bearing mice. Intravenous administration of a preparation of heat-killed Lactobacillus casei (LC 9018), a nonspecific immunostimulant, at a dose of 20 mg/kg to BALB/c mice augmented their resistance against the lethal toxicity of 5-FU if the preparation was injected into the mice 10–40 days before administration of 5-FU. Injection of LC 9018 into BALB/c mice bearing Meth A fibrosarcoma also enhanced their resistance against the lethality of 5-FU. Systemic infection with E. coli was induced in all of the 5-FU-treated tumor-bearing mice 10 days or more after administration of the drug at a lethal dose of 500 mg/kg, and it was accompanied by an overgrowth of the bacteria in the intestine. Treatment of tumor-bearing mice with LC 9018 resulted in decreased rates of occurrence of systemic infection with E. coli and inhibition of overgrowth of the bacteria in the intestine after administration of 5-FU. A single administration of either LC 9018 or 5-FU significantly inhibited the growth of Meth A cells in vivo, and a combined antitumor effect was shown in the mice treated with both 5-FU and LC 9018. Key words: tumor-bearing mice, fluorouracil, nonspecific immunostimulation, indigenous infection, Escherichia coli.
The symbiotic vesicle is a major site for respiration in Frankia from Alnus incana root nodules
Authors: Vikman Per-Åke
Published: May 2010

A technique was developed for preparation of Frankia symbiotic vesicles, free of hyphae. The symbiotic vesicles were isolated by isopycnic centrifugation of disrupted Frankia vesicle clusters prepared from root nodules of Alnus incana (L.) Moench. Activities in symbiotic vesicles were compared with activities in intact symbiotic vesicle clusters on a total protein basis. Respiratory capacity was tested with 6-phosphogluconate, malate + glutamate, and NADH as added substrates. With all three substrates, specific respiration was doubled after symbiotic vesicle isolation. Nitrogenase was used as a symbiotic vesicle specific marker and its specific activity increased similarly to respiration. Activities of four respiratory enzymes were assayed on crude cell-free extracts obtained after sonication of symbiotic vesicle preparations. According to the increased specific rates after symbiotic vesicle isolation, NAD+:6-phosphogluconate dehydrogenase (EC 1.1.1.44) and glucose-6-phosphate dehydrogenase (EC 1.1.1.49) were mainly localized in symbiotic vesicles. NAD+:malate dehydrogenase (EC 1.1.1.37) and glutamate-oxaloacetate transaminase (EC 2.6.1.1) were also present in symbiotic vesicles, but their specific activities were not increased compared with the symbiotic vesicle clusters. The magnitude of increased activities suggested that the symbiotic vesicle is a major site for hexose respiration in symbiotic Frankia. An apparent Km for O2 between 20 and 30 μM indicated that symbiotic vesicles in symbiotic vesicle clusters have a restricted oxygen diffusion rate. Key words: Frankia, symbiotic vesicles, respiration, nitrogenase, oxygen diffusion.
Nonspecificity of the Anda A60-tb ELISA test for serodiagnosis of mycobacterial disease
Authors: Qadri S. M. Hussain , Smith Kevin K.
Published: May 2010

The conventional methods for the laboratory diagnosis of tuberculosis and other mycobacterial diseases are time consuming and beyond the scope of most of the small and medium-sized hospital facilities. Therefore, there has been considerable interest in the development of a serological method for the detection of antibodies against mycobacteria. We recently evaluated a commercially available ELISA test (Anda Biologicals, Strasbourg, France) that measures antibody levels to A60 antigen, a membrane glycoprotein that is found in most mycobacteria. Of the 123 patients with positive pulmonary cultures for Mycobacterium tuberculosis, 82% had detectable antibodies against the kit antigen. Of the 68 patients with extrapulmonary tuberculosis, 59% yielded positive results. Specimens from 2 of the 12 patients that grew Mycobacterium avium–intracellulare complex, and one each with Mycobacterium fortuitum and Mycobacterium chelonei, were considered significant on the basis of medical history and repeated isolation of the bacterium from clinical specimens, and these patients yielded positive serology. Of the healthy, normal PPD positive and PPD negative controls, 24% gave false positive results. Key words: Anda A60-tb ELISA, serodiagnosis of mycobacteria, mycobacterium.
Candida fennica: enhancement of protoplast formation and fusion
Authors: Andrade Carolina M. M. , Oliveira Flavia M. , Linardi Valter R.
Published: May 2010

Auxotrophic mutants were obtained by exposing Candida fennica FTPT/CCT-8903 to ultraviolet light and treating the cells with nystatin in an enrichment procedure. The mutants were used for protoplast fusion. The highest protoplast regeneration frequency was obtained when cells were treated with 10 mg NovoZym 234/mL in the presence of 0.8 M KCl for 60 min. Fusion frequency was in the range 5.84 × 10−5 to 7.2 × 10−5. Five prototrophic hybrid colonies, designated S9, S15, S17, S18, and S25, were isolated, and their DNA contents were measured. These measurements indicated that the S17 hybrid is haploid, S9 and S18 are polyploid, and S15 and S25 are both aneuploid. Key words: Candida fennica, nystatin, auxotrophic mutants, protoplast fusion.
Effect of incubation of Escherichia coli cells with halophyte extracts on their subsequent survival in seawater
Authors: Flatau G. N. , Clement R. L. , Gauthier M. J. , Puel D. C.
Published: May 2010

Organic osmolytes are utilized by enteric bacteria for their survival when entering a high-osmolarity medium such as seawater. As these are commonly synthetized by marine organisms (fauna and flora), the purpose of this work was to investigate the effects of aqueous extracts from some marine phytoplanktonic species, alga, and phanerogam on the survival of Escherichia coli cells in seawater. Some of the tested halophyte extracts greatly enhanced survival, whereas others were inhibitory. The efficiency of the extracts could not be correlated to the taxonomic position of the halophyte or to the presence of Dragendorff-positive compounds known to be osmoprotective. Key words: Escherichia coli, survival, seawater, halophytes, osmoprotection.
A filamentous-like mutant of Listeria monocytogenes with reduced expression of a 60-kilodalton extracellular protein invades and grows in 3T6 and Caco-2 cells
Authors: Gutekunst Karen A. , Pine Leo , White Elizabeth , Kathariou Sophia , Carlone George M.
Published: May 2010

We describe a spontaneous rough mutant of Listeria monocytogenes that produces reduced amounts of a 60-kilodalton major extracellular polypeptide (p60) as shown by sodium dodecyl sulfate – polyacrylamide gel electrophoresis and Western blot analysis. The cells of this mutant are filamentous, do not give rise to smooth wild-type colonies, and produce listeriolysin O in amounts equal to that of the wild-type cells, but they show a reduced virulence in the mouse LD50 model and in the Caco-2 tissue culture virulence assay. Light and electron microscopic studies show that this mutant invades and remains filamentous during in vivo growth in both Caco-2 and 3T6 tissue culture monolayers. The reduced virulence of the rough mutant is not due to the inability of its filamentous forms to invade or to grow in nonprofessional phagocytes since invasion and growth of the smooth wild-type and the rough mutants are comparable in both Caco-2 and 3T6 monolayers. Key words: Listeria monocytogenes, invasion, nonprofessional phagocytic cells, electron microscopy.
Survival of wood-inhabiting fungi stored for 10 years in water and under oil
Authors: Johnson Gary C. , Martin Andrew K.
Published: May 2010

Subcultures of 1064 isolates of 393 species of wood-inhabiting fungi were stored both under sterile mineral oil and in sterile water for 10 years. A high proportion (98%) of the Basidiomycotina isolates survived storage under oil, whereas only 26% survived in sterile water. Survival of most isolates of Ascomycotina (91% under oil, 72% in water) and Deuteromycotina (96% under oil, 92% in water) was somewhat less in water than under oil. Key words: fungal storage, long-term storage, oil storage, water storage, Basidiomycotina.
Characterization of lactococcal bacteriophages from Quebec cheese plants
Authors: Moineau Sylvain , Fortier Josée , Ackermann Hans-W. , Pandian Sithian
Published: May 2010

This is the first study on the characterization of lactococcal phages isolated in Canada. Thirty lactococcal phages were isolated from Quebec cheese plants reporting partial loss of starter activity. Phages were characterized by electron microscopy, DNA homology, protein profile, and host range. All phages belonged to the Siphoviridae family. Seventeen phages (57%) has prolate heads (60 × 40 nm) and 100 nm long, noncontractile tails (morphotype B2, species c2). They showed strong DNA homology with other prolate-headed phages isolated from other countries (Australia, United States). In addition to normal prolate phages, most lysates contained pairs of empty heads (no DNA) connected by a small bridge. Thirteen phages (43%) had small isometric heads (55 nm in diameter) and long, noncontractile tails (morphotype B1). Based on DNA homology, 11 of these phages were found related to phage species 936 despite differences in tail length (140 to 200 nm). The two other small isometric phages, UL36 and UL39, hybridized with phage P335 DNA, and therefore belong to this species. No DNA homology was observed between prolate and small isometric phages. Phages with prolate heads showed a broader host range than small isometric-headed phages. The DNA of phage UL36, which has a relatively narrow host range, has more restriction endonuclease sites than other lactococcal bacteriophages. Key words: lactococci, bacteriophage, taxonomy, cheese, whey.
Cloning of genetic loci involved in endoprotease activity in Streptomyces lividans 66: a novel neutral protease gene with an adjacent divergent putative regulatory gene
Authors: Butler M. J. , Davey C. C. , Krygsman P. , Walczyk E. , Malek L. T.
Published: May 2010

A skimmed-milk clearing assay was used to identify, in a multicopy Streptomyces lividans 66 genomic library, DNA fragments that lead to increased expression of protease activity in S. lividans 66. Three independent loci were identified. The majority class (slpA, which represented 68 of 71 clones) produced large zones of clearing. Two other classes (designated slpB and slpC) showed smaller zones than slpA. Subcloning and deletion analysis of the slpA locus delineated the relevant DNA to within a 2.5 kilobase pair fragment. DNA sequence analysis revealed a structural gene associated with the appearance of an extracellular protein in the culture medium. The derived amino acid sequence indicated the presence of a zinc-binding motif, which was previously noted to be characteristic of metalloprotease enzymes. However, the relatively small size of the protein (apparent molecular weight 20 000 – 24 000) suggests that it represents a novel class of neutral proteases distinct from the thermolysin-type enzymes. An adjacent divergent open reading frame was identified and shown to cause a significant increase in protease activity when present together with the protease structural gene on a multicopy plasmid in S. lividans 66. The derived amino acid sequence of this open reading frame showed homology with previously characterized regulatory proteins of the LysR family of transcriptional regulator proteins. Key words: Streptomyces, extracellular proteases, putative transcriptional regulator.
Receptors for toxic shock syndrome toxin-1 and staphylococcal enterotoxin A on human blood monocytes
Authors: See Raymond H. , Krystal Gerald , Chow Anthony W.
Published: May 2010

Staphylococcal toxic shock syndrome toxin-1 (TSST-1) as well as staphylococcal enterotoxin A (SEA) and B (SEB) have recently been shown to bind directly to the class II major histocompatibility antigen, HLA-DR. Whereas others have characterized TSST-1 and SEA binding to HLA-DR on transfected L cells or B lymphoma cell lines, we sought evidence for direct binding of TSST-1 and SEA to HLA-DR on purified human monocytes. A single class of high-affinity receptors was found for both TSST-1 (dissociation constant (Kd) 40 nM, 3.4 × 104 receptors per cell) and SEA (Kd 12 nM, 3.2 × 104 receptors per cell) on normal human monocytes. Affinity cross-linking of 125I-labeled toxins to monocytes revealed the presence of two membrane protein subunits with molecular masses consistent with the α and β chains of human HLA-DR (35 and 28 kDa, respectively). The anti-HLA-DR monoclonal antibody L243, but not L203 or 2.06, inhibited radiolabeled toxin binding to human monocytes and neutralized the mitogenic response of human T lymphocytes to both toxins. However, L243 was consistently more effective in blocking radiolabeled TSST-1 than SEA binding to human monocytes from the same donors, suggesting that TSST-1 and SEA may be binding to overlapping epitopes rather than to the same epitope on HLA-DR. Because TSST-1 and SEB bind to distinct epitopes on HLA-DR and because SEA cross competes with both TSST-1 and SEB on the HLA-DR receptor, we postulate that SEA occupies a binding site within HLA-DR that overlaps both TSST-1 and SEB. Future studies focused on receptor-mediated binding of these toxins to human monocytes and T lymphocytes from normal donors and toxic shock syndrome patients may reveal the underlying anomalies that predispose particular individuals to toxic shock syndrome. Key words: monocytes, staphylococcal toxic shock syndrome toxin-1, receptors, HLA-DR, staphylococcal enterotoxin A.