bluuebunny/crossref_metadata_2025 huggingface dataset:
Ultrastructure of Saccharomyces cerevisiae strain AG1-7 and its responses to changes in environment
Authors: Willison J. H. M. , Johnston G. C.
Published: May 2010

Asynchronous populations of the budding yeast Saccharomyces cerevisiae strain AG1-7 were examined by freeze-fracture electron microscopy for ultrastructural changes occurring in response to changes in the environment, specifically the following: temperature (23 or 37 °C); cell density (exponential, early stationary, and stationary phases); various periods of nitrogen starvation at low cell density, and return of nitrogen-starved cells to nitrogen-replete medium. This information has been gathered in preparation for ultrastructural examination of comparable responses of temperature-sensitive cell-cycle mutants. The plasma membrane was found to be particularly responsive to changes in environment. A high proportion (75%) of cells in exponential phase populations at 37 °C displayed paracrystalline arrays of plasma membrane particles, whereas this proportion was much lower (20%) at 23 °C in the same medium; plasma membrane grooves were longer at 37 than at 23 °C. In budded cells, the mother cell displayed paracrystalline arrays more frequently than the bud. Entry of cells into stationary phase, either through permitting population growth or by limiting nitrogen supply, resulted in increases in numbers of paracrystalline arrays and grooves. Groove depth also increased. The paracrystalline-array and groove-density responses were independent, both during entry into stationary phase and during the subsequent lag phase. Unusual groove forms appeared during stationary phase in high cell density populations, but not in low cell density nitrogen-starved populations. "Aggregate" and "geometric" tonoplast forms, previously described in strain A364A when grown under some of the conditions used here, were not found in AG1-7 under any of the conditions used here. It was demonstrated that particle-free patches can arise rapidly on the tonoplast of AG1-7 in response to temperature change from 37 to 23 °C. During stationary phase, spherosomes (lipid droplets) increased in size, particularly in response to nitrogen depletion. After 72 h of nitrogen starvation, about 10% of cell volume consisted of spherosomes. Changes in vacuolar content and mitochondrial form were also noted during entry into stationary phase.
Long-term survival of human rotavirus in raw and treated river water
Authors: Raphael Roderick A. , Sattar Syed A. , Springthorpe V. Susan
Published: May 2010

This study was aimed at assessing the role of water as a vehicle for rotavirus spread by determining how well these viruses survive in the water environment. A cell culture adapted strain of human rotavirus subgroup 2, grown in MA-104 cells, was used as a model. Virus survival was tested in the following types of water samples, derived from the Ottawa River, at two different times of the year: (i) raw water (RW), (ii) municipally treated tap water (TW), and (iii) raw water that had been filtered (FW) through a membrane (0.22 μm). The water samples, with approximately 5.0 × 104 plaque-forming units (PFU) of the virus, were held at either 4 or 20 °C and tested for infectious virus over a period of 64 days. The TW samples had a total and free chlorine content of 0.05 and <0.05 mg/L, respectively. The chlorine in these samples was not neutralized before virus contamination. Irrespective of the holding temperature, the virus titre in FW remained essentially unaltered throughout the test period. In TW held at 4 °C, there was no significant drop in the virus titre even after 64 days, whereas at 20 °C the titre in TW was reduced by about 2 log10 over the same period. Even though the loss of virus infectivity was most rapid in RW held at 20 °C, it took about 10 days for a 99.0% reduction in the plaque titre of the virus. These findings, therefore, indicate that rotaviruses can survive for several days in raw and treated river water thus making recreational and potable waters potential vehicles for the transmission of rotavirus infections.
Purification and some properties of the extracellular α-amylase from Aspergillus awamori
Authors: Bhella Resham S. , Altosaar Illimar
Published: May 2010

Alpha-amylase was purified from the extracellular culture medium of Aspergillus awamori by means of ethanol precipitation. Sephacryl-200 gel filtration and anion-exchange chromatography on Dowex (AG1-X4) resin. The enzyme preparation was found to be homogeneous by means of sodium dodecyl sulfate–polyacrylamide gel electrophoresis. The purified enzyme had a molecular weight of 54 000 ± 2 500 and its isoelectric point was pH 4.2. The enzyme was found to be most active between pH 4.8 and 5.0 and was stable between pH 3.5 and 6.5. The optimal temperature for the enzyme activity was around 50 °C and the enzyme was stable for at least 1 h up to 45 °C retaining more than 80% of its original activity. The Km (37 °C, pH 5.3) for starch hydrolysis was 1.0 g∙L−1 and maltose inhibited the enzyme activity uncompetitively with a K1 value of 20.05 g∙L−1
Airborne microorganisms in a municipal solid waste recovery system
Authors: Lembke Linda L. , Kniseley Richard N.
Published: May 2010

The types of bacteria and fungi present in the air of a municipal solid waste recovery system have been characterized and the population densities estimated. Conventional methods were successful in enumerating coagulase-positive staphylococci, Klebsiella spp., gram-negative bacteria, fungi, and common indicator organisms. Selective and enrichment media, however, did not yield Salmonella isolates. Salmonella and Shigella were recovered at a frequency of 3% or less on trypticase soy agar. A broad spectrum of bacteria and fungi were isolated. No evidence has been found that indicates that these organisms have produced adverse health effects.
Influence of nitrogen source and growth status on glutamine synthetase and glutamate synthase activity in Mycobacterium avium
Authors: McCarthy Charlotte M. , Alvarez Maria E.
Published: May 2010

An investigation was made of the activity of glutamine synthetase and glutamate synthase from batch-cultured cells of Mycobacterium avium. The bacteria were grown in medium with ammonium chloride concentrations of 0, 0.1, 0.25, 1, 5, or 25 μmol/mL or with glutamine at 0.1 or 1 μmol/mL. The specific activity of the two enzymes was determined at 0, 22, 45, and 70 h of incubation. Regardless of the ammonia concentration in the medium, glutamate synthase specific activity was two to five times higher in extracts from elongating cells, incubated 22 h, than in those from shortened cells, incubated 45 or 70 h. In contrast, there was no apparent difference in glutamine synthetase specific activity with regard to culture age; however, glutamine synthetase specific activity varied inversely with the concentration of ammonium chloride in the medium. Cells grown in glutamine had high activity of glutamine synthetase.
Purification and characterization of C28–55 fatty acids from Mycobacterium smegmatis
Authors: Sathyamoorthy Neeraja , Qureshi Nilofer , Takayama Kuni
Published: May 2010

The nonmycolic C16 to C55 fatty acids obtained from Mycobacterium smegmatis ATCC 356 by saponification were enriched with respect to the C28 to C55 acids by successive chromatography on silicic acid and Sephadex LH-20 columns. These partially purified fatty acids were then derivatized to the p-bromophenacyl ester and further fractionated by argentation thin-layer chromatography and reverse-phase high-performance liquid chromatography into their individual components.The esters were characterized by electron impact mass spectrometry. Two structural series of C28:1 to C42:1 and C45:2 to C55:2 fatty acids were identified as possible precursors of the monoenyl and dienyl mycolic acids, respectively. These acids were structurally related to the α-alkylhydroxyl group of the corresponding mycolic acid. The results suggest that these C28 to C55 fatty acids (meromycolic acids) of M. smegmatis might be precursors of mycolic acids.
Characteristics of the outer membrane of selected oral Bacteroides species
Authors: Williams G. D. , Holt S. C.
Published: May 2010

The outer membranes from selected oral Bacteroides species were isolated and characterized morphologically, chemically, and physically. Both sucrose density gradient centrifugation and sodium dodecyl sulfate – polyacrylamide gel electrophoresis (SDS–PAGE) revealed outer membranes which varied slightly with the species, as well as showing complex polypeptide patterns after SDS–PAGE. The polypeptide distribution revealed a species-specific pattern; however, there was often a variation within a given species in many minor polypeptide bands, with heat-modifiable minor peptides occurring in nearly all species. Protein-associated carbohydrates occurred in several species. Outer membrane fragments (blebs) recovered by ultracentrifugation of the growth supernatants were either nearly identical to the outer membrane polypeptide patterns, or contained reduced amounts of specific polypeptides, again varying with the species. l25I-labelling of whole cells indicated possible surface exposure for several of the major polypeptides.
Benomyl-marked populations of Chaetomium globosum: survival on apple leaves with and without benomyl and antagonism to the apple scab pathogen, Venturia inaequalis
Authors: Cullen Daniel , Andrews John H.
Published: May 2010

Resistance to the fungicide benomyl (BenR) was induced with N-methyl-N′-nitro-N-nitrosoguanidine in Chaetomium globosum isolated from apple leaves. The population densities of a resistant strain reintroduced to leaves on apple trees in an orchard were determined at 3 h, and 1 and 3 weeks following inoculation. Relative to wild-type parents, BenR populations declined more rapidly on orchard trees, but the rate of decline was reduced by amending initial inoculum with 18.5 ppm benomyl. Survival of BenRC. globosum increased 40–58% relative to BenRC. globosum applied without benomyl. In growth chamber experiments with potted apple seedlings, the BenR strain was as antagonistic as were the wild-type parents to the scab pathogen, Venturia inaequalis. The marked strain alone did not significantly reduce scab infection on saplings in the field; however, when it was applied with benomyl, scab severity was significantly (P = 0.01) less than with benomyl alone.
An ultrastructural investigation of Leishmania donovani infection in genetically resistant and susceptible mouse strains
Authors: Weldon Peter R. , Kongshavn Patricia A. L.
Published: May 2010

Natural resistance to the growth of Leishmania donovani in mice is controlled by a gene (Lsh) which is expressed, in an unknown fashion, in macrophages. Early net growth rate of the parasite is much higher in mice strains bearing the susceptible allele (Lshs) than in resistant (Lshr) mice. Intracellular events occurring in the Kupffer cells during this period have been studied at the ultrastructural level. It was found that the number of dividing amastigotes per thin section of infected cell was approximately 10-fold greater in susceptible (B10.A SgSn) than in resistant (A/J) strains of mice, both 7 and 14 days following infection. These findings support the hypothesis that high natural resistance to leishmaniasis (Lshr) is expressed as a microbistatic effect, exerted within the parasitized macrophage of the host.
Immunochemical examination of the Pseudomonas aeruginosa glycocalyx: a monoclonal antibody which recognizes L-guluronic acid residues of alginic acid
Authors: Irvin Randall T. , Ceri Howard
Published: May 2010

Mice immunized with Formalin-fixed mucoid Pseudomonas aeruginosa cells developed an immune response directed, in part, towards the P. aeruginosa glycocalyx. The polyclonal mouse sera produced good immunofluorescent staining of the P. aeruginosa glycocalyx and cell surface. A library of 250 hybridoma cell lines which produced monoclonal antibodies directed against P. aeruginosa was established. Twelve clones (4.8%) produced antibody which reacted with alginate in an enzyme-linked immunosorbent assay (ELISA). Clone Ps 53 was chosen for further study, cloned, and an ascites tumor established. Clone Ps 53 was chosen for further study because the antibody produced demonstrated a specificity similar to that of a recently isolated heparin – rat-lung lectin which recognizes alginates of the Homma nontypable P. aeruginosa strains. The Ps 53 clone produced an immunoglobulin M which reacted with P. aeruginosa alginate and produced good immunofluorescent staining of the P. aeruginosa glycocalyx. The Ps 53 monoclonal antibody has an apparent specificity for L-guluronic residues in ELISA. Competitive binding studies with various alginates and monosaccharides suggest that the C6 carboxyl group of uronic acids are recognized by the antibody and that the antigen-binding site is fairly large and may recognize a particular sequence or epitope of alginic acid which is rich in L-guluronic acid. The Ps 53 monoclonal antibody did not react uniformily with all P. aeruginosa alginates but did react with all of the alginates of the Homma nontypable strains tested, suggesting that acetylation or various modifications found in P. aeruginosa alginates may interfere with antibody binding and define specific epitopes. The Ps 53 antibody also reacted with purified outer membrane, indicating that some alginate or L-guluronic acid is intimately associated with outer membrane.
Nutrient effects on anthracycline production by Streptomyces peucetius in a defined medium
Authors: Dekleva Michael L. , Titus Jeffrey A. , Strohl William R.
Published: May 2010

A defined medium was developed for Streptomyces peucetius that optimally contained 0.5 mM magnesium, 1 mM phosphate, 75–125 mM glucose, 10 mM nitrate, and microelements. Poorer results were obtained with nitrite, aspartate, or ammonia as sole nitrogen sources. Other carbon sources which supported best growth and highest anthracycline titers were fructose, maltose, and soluble starch. In each case, substantial residual carbon remained at the end of 6 days, suggesting a lack of catabolite repression by the carbohydrate carbon sources on anthracycline biosynthesis. Studies involving limiting and nonlimiting concentrations of glucose supplemented with arabinose, a poorly utilizable carbon source, indicated that high carbon concentrations were not necessary for osmotic stabilization. Inorganic phosphate was found to have an inhibitory effect on anthracycline production. Furthermore, when cultures at early stages of anthracycline production were spiked with inorganic phosphate, a delay in further anthracycline production resulted until the added phosphate was depleted. A 10% inoculum of stationary phase cells yielded the best growth and most consistent anthracycline production. Spectrophotometric analyses at 495 nm of chloroform–methanol-extracted material were also found to be useful for the determination of total anthracyclines in culture extracts.
A thiol-activated hemolysin in Gram-negative bacteria
Authors: Albesa Inés , Barberis Lucila Isabel , Pajaro María Cristina , Farnochi María Cecilia , Eraso Alberto Jorge
Published: May 2010

An investigation of Klebsiella pneumoniae hemolytic activity was carried out. Strains isolated from different infected specimens were hemolytic in tryptic soy agar with rabbit blood; incubation at 4 °C enhanced the hemolysis. There was no evident red blood cell lysis in plates with human, sheep, mouse, and chicken erythrocytes. The culture in tryptic soy broth, its supernatant and bacterial lysate did produce evident hemolysis of rabbit red blood cells when they were preincubated with 2-mercaptoethanol. Klebsiella pneumoniae hemolysin showed the Arrhenius effect, while temperatures over 60 °C for 10 min reduced the activity of crude hemolysin to zero; purified hemolysin, however, was heat stable. Two hemolysins active on rabbit red blood cells were purified and both shared several properties. This work represents the initial description of a thiol-activated hemolysin in Gram-negative bacteria.
Interaction between killer strains of Hansenula anomala var. anomala and Saccharomyces cerevisiae yeast species
Authors: Rosini Gianfranco
Published: May 2010

The cross-reaction between 6 killer strains of Saccharomyces cerevisiae and 41 killer strains of Hansenula anomala var. anomala was examined. Fifteen strains of Hansenula killed one or more cultures of S. cerevisiae. None of the killer strains of H. anomala var. anomala was killed by S. cerevisiae killer strains or by killer strains of the same species. In S. cerevisiae different killer toxin and immunity systems were represented. Intraspecific killing activity was not found among the 41 strains of H. anomala var. anomala.
Ultrastructural changes observed in Rickettsia rickettsii incubated at different temperatures in cell-free medium
Authors: Pontefract R. D. , Ng C. W. , Bergeron G.
Published: May 2010

When cells of Rickettsia rickettsii were suspended at different temperatures in growth medium free of host cells, ultrastructural changes were observed in some of these organisms. Depending upon the temperature and length of incubation, loosely organized cells developed into compact, intensely stained, rod-shaped organisms. These compact cells closely resembled the morphology of the original culture of Rickettsia used for inoculation. Morphological changes were primarily noted in cells maintained at 21 °C. The viability of the cells was also affected by the temperature of incubation.
Genetic linkage but independent expression of functional HSV-1 tk and mammalian aprt genes after cotransfer to L cells
Authors: Block Timothy , Brzykcy John , Hastie Nicholas , Hughes Jr. Robert G.
Published: May 2010

DNA-mediated gene transformation of mouse Ltk−aprt−hprt− cells was used to obtain stable, doubly selected transformants simultaneously expressing herpes virus thymidine kinase (TK) and mammalian adenine phosphoribosyltransferase (APRT). Cotransformants occurred at a frequency of 5 × 10−6, a similar frequency for the transfer of the aprt marker has been previously observed. Isozyme and Southern blot analysis show that the TK and APRT expressed in these transformants resulted from gene transfer. For one stable cotransformant, [3H]thymidine ([3H]TdR) selection against TK activity resulted in the loss of APRT activity as well, suggesting that these genes had become genetically linked together. Similarly selection against APRT expression resulted in the loss of a subset of the transferred herpes simplex virus tk genes. 5-Bromodeoxyuridine (BUdR) selected TK− variants differed from [3H]TdR selected TK− variants, in that they retained tk genes. However, BUdR-selected variants expressed full levels of APRT. Therefore, even though the transferred tk and aprt genes had become genetically linked together, they were, in this case, independently expressed since these cells were phenotypically TK− and APRT+.
Comparison of fluorescent antibody, bacitracin susceptibility, latex agglutination, coagglutination, and API 20S for identifying group A streptococci
Authors: Lesher R. J. , Casiano-Colon A. E.
Published: May 2010

A total of 200 beta-hemolytic streptococci, isolated from clinical specimens submitted to our laboratory, were identified as group A versus non-A using the fluorescent antibody technique (FA), bacitracin susceptibility (BBL, Difco, and Raven disks), SeroSTAT, Streptex, Phadebact, and the API 20S system. Of the 122 group A isolates, all methods except SeroSTAT and Phadebact yielded 92–99% agreement when compared with the Lancefield precipitin test. Phadebact yielded an 84% agreement and SeroSTAT changed from 83 to 98% after trypsinization. Numerous false positives were obtained and only FA (91%) and API 20S (96%) yielded better than 90% agreement on non-A identification when compared with the Lancefield test. The most false positives were obtained (45%) using the SeroSTAT reagents. Considering accuracy, our data suggests the FA technique to be the method of choice for identifying group A streptococci.
Isolation and characterization of antibiotic-resistance plasmids in thermophilic bacilli
Authors: Hoshino Takayuki , Ikeda Takayuki , Narushima Hiroyuki , Tomizuka Noboru
Published: May 2010

Four antibiotic-resistance plasmids isolated from thermophilic bacilli were characterized in detail. Three tetracycline-resistance (Tcr) plasmids were designated as pTHT9 (7.7 kilobases (kb)), pTHT15 (4.5 kb) and pTHT22 (8.4 kb). From the results of restriction endonuclease analysis and the subsequent Southern hybridization, these were found to possess extensive genetic homology in the regions that include the replication origin and the Tcr gene. Detailed restriction maps of the smallest Tcr plasmid pTHT15 and a kanamycin-resistance (Kmr) plasmid pTHN1 (4.8 kb) were constructed. The positions of antibiotic-resistance loci and regions essential for plasmid replication were determined by cloning plasmid fragments in Bacillus subtilis. These four plasmids were found to replicate and express the resistance genes stably in both B. subtilis and B. stearothermophilus.
The effect of ions on the adhesion and internalization of Chlamydia trachomatis by HeLa cells
Authors: Sneddon John M. , Wenman Wanda M.
Published: May 2010

The adhesion and internalization of Chlamydia trachomatis by HeLa cells was unaffected by removal of K+, Mg2+, or glucose from the incubation medium, slightly reduced by removal of Na+, and significantly reduced by omission of Ca2+. Sr2+, Mg2+, and Mn2+ could replace Ca2+ in the adhesion but only Sr2+ supported internalization, and La3+, Co2+, Fe3+, Ba2+, and Zn2+ all reduced internalization more than adhesion. During initial infection there was no measurable difference in the uptake or release of 45Ca2+ or 86Rb+ between infected and noninfected HeLa monolayers. Infection was not prevented by pretreatment of the monolayers with the calcium channel blockers, verapamil, D600, and nitrendipine, or the calmodulin inhibitors, TMB-8 or trifluperazine. The results suggest that divalent cations are not essential for chlamydial infection but that the process of internalization is facilitated by the presence of cations, particularly Na+ and Ca2+.
Characterization of two surface-localized antigenic sites on porin protein F of Pseudomonas aeruginosa
Authors: Mutharia Lucy M. , Hancock Robert E. W.
Published: May 2010

A rapid colony immunoblot screening procedure was used to demonstrate the surface localization of porin protein F on bacterial colonies of Pseudomonas aeruginosa. By this method, we demonstrated that protein F was accessible to four different specific monoclonal antibodies in a wide variety of both mucoid and nonmucoid P. aeruginosa strains. Controls were performed to demonstrate that, using this procedure, only surface-exposed epitopes bound monoclonal antibodies and that nonspecific binding of monoclonal antibodies either to cells lacking protein F or to mucoid exopolysaccharide did not occur. Monoclonal antibodies MA4-4, MA2-10, and MA4-10, specific for protein F, also interacted with colonies of Pseudomonas putida and Pseudomonas syringae, whereas the protein F specific monoclonal antibody MA5-8 interacted only with P. aeruginosa strains. Using the above-named monoclonal antibodies, we investigated the antigenic structure of protein F. Monoclonal antibodies MA4-4, MA2-10, and MA4-10 bound to 29–31 kilodalton proteolytic fragments produced after papain or trypsin digestion of purified protein F or of protein F in outer membranes or intact cells. Antibody MA5-8 did not interact with proteolytically digested protein F but did interact with two of the six fragments produced after partial cyanogen bromide cleavage of protein F. Antibodies MA4-4, MA2-10, and MA4-10 did not interact with protein F after reduction of its internal disulphide bonds with 2-mercaptoethanol; in contrast, the reactivity of MA5-8 was unaffected. This data suggests that there are at least two distinct highly conserved surface epitopes on porin protein F.
The regulation of sexual development in Dictyostelium discoideum: cannibalistic behaviour of the giant cell
Authors: Lewis Keith E. , O'Day Danton H.
Published: May 2010

Sexual development leading to macrocyst formation in Dictyostelium discoideum involves the development of zygote giant cells which subsequently chemoattract and cannibalize local unfused amoebae of the same genotypes from which they formed. A system for assessing this process was developed wherein purified giant cells were fed amoebae under various conditions with the production of endocytes being assessed after neutral red staining of living cells. The phagocytic rate was linear during the 3-h assay period, was directly related to the concentration of amoebae, and demonstrated limited pH and temperature optima. Light which inhibits macrocyst development had no effect on sexual endocytosis. Cell-free conditioned medium from sexual cultures actively involved in phagocytosis enhanced giant cell endocytosis in the assay system. Drug studies revealed that microfilaments and microtubules are involved in the endocytic process and energy for it is supplied by both aerobic and anaerobic metabolic pathways. The data are discussed in terms of phagocytosis in D. discoideum and other organisms.
Suppressor mutations for crs mutants of Bacillus subtilis
Authors: Sun D. , Takahashi I.
Published: May 2010

Mutants of Bacillus subtilis which carried suppressor mutations for catabolite-resistance gene crsA47 were isolated from methylmethanesulfonate-treated cultures of GLU-47 (crsA47). The suppressor mutation, sca19, suppressed resistance of crsA47 mutant to glucose and other inhibitors of sporulation. Moreover, the suppressor mutation could restore the rate of growth and the level of IMP dehydrogenase and alkaline phosphatase of crsA47 mutant to the wild-type level. The sca19 mutation was also able to suppress catabolite resistance of other crs mutants. The map position of the sea19 mutation indicated that this mutation was an intergenic suppressor for the crs mutants. It was also found that an erythromycin-resistance mutation, ery1, could suppress the catabolite resistance of some of the crs mutants. Our results were discussed in relation to the importance of a proper state of metabolic activities and membrane functions during the initiation of sporulation.
Substrate diversity of an active heterotrophic nitrifier, an Alcaligenes sp.
Authors: Castignetti Domenic , Yanong Rosemarie , Gramzinski Robert
Published: May 2010

Several oximes, acetohydroxamic acid, and 3-nitropropionic acid were examined to determine if they could serve as substrates for heterotrophic nitrification by an Alcaligenes sp., previously isolated from soil and shown to actively nitrify pyruvic oxime. Neither acetohydroxamic acid, the aldoximes of acetaldehyde or butyraldehyde, or the alkyl oxime, acetone oxime, were used as nitrification substrates or as sole sources of carbon or nitrogen. α-Ketobutyric oxime, α-ketoglutaric oxime, and 3-nitropropionic acid, however, were nitrified and growth occurred when these compounds served as sole sources of carbon and nitrogen. Experiments with resting cells and cell-free extracts of the Alcaligenes sp. grown on α-ketobutyric oxime and α-ketoglutaric oxime indicate that these substrates are nitrified via an organic pathway as the rates of hydroxylamine (the nitrogen hydrolysis product) conversion are kinetically insufficient. 3-Nitropropionic acid metabolism by resting cells of the Alcaligenes sp. grown in 3-nitropropionic medium is restricted to nitrite production. The substrate specificities of the Alcaligenes sp. for heterotrophic nitrification and the relevance of the mineralization of 3-nitropropionic acid by the bacterium are discussed.
Extracellular polysaccharide production by Klebsiella pneumoniae and its relationship to virulence
Authors: Domenico Philip , Diedrich Dana L. , Straus David C.
Published: May 2010

Klebsiella pneumoniae serotype 1 and serotype 2 and their capsular variants were examined for production of cell-associated capsular polysaccharides and extracellular capsular polysaccharides. The virulence of these organisms in experimental animals was examined via intraperitoneal injection in mice and transtracheal inoculation into the lungs of rats. It was found that the production of either polysaccharide component correlated with the observed virulence. The extracellular polysaccharides were purified by ethanol precipitation, electrodialysis, extraction with quaternary ammonium salts, and gel filtration. These purification steps allowed for the separation and purification of both the extracellular lipopolysaccharide and the extracellular capsular polysaccharide. Purified extracellular capsular polysaccharide and extracellular lipopolysaccharide were co-injected with K. pneumoniae intraperitoneally into mice to determine if either of these substances would produce an effect on the natural course of infection in these animals. These studies showed that only purified extracellular lipopolysaccharide enhanced the virulence of K. pneumoniae when co-injected into mice, and this virulence enhancement correlated with the content of extracellular lipopolysaccharide, but not extracellular capsular polysaccharide in mixtures of these polysaccharides. Saponification of K. pneumoniae serotype 1 extracellular polysaccharides significantly decreased their virulence-enhancing capabilities in mice, further suggesting that extracellular lipopolysaccharide may play a role in these infections.
Stimulating effect of hydrogen on N2 fixation in association with field-grown wetland rice
Authors: Gowda T. K. S. , Watanabe I.
Published: May 2010

The addition of H2 (10% by volume) stimulated acetylene reduction associated with excised roots, decapitated plants, and intact plants of rice grown in a continuously flooded field. Excised roots showed H2-uptake activitiy. Stimulation of N2 fixation by H2 in association with field-grown decapitated rice plants was confirmed by 15N2 incorporation.
Effect of 3-O-substituted analogues of D-glucose and D-allose on amino acid uptake by Penicillium sp.
Authors: Brown Robert G. , Embil John M.
Published: May 2010

3-O-Methyl-D-glucose and 3-O-ethyl-D-allose cause an increase in growth rate of two dextranase-producing Penicillium species which is concomitant with an increase in amino acid uptake. In contrast, 3-O-ethyl-D-glucose and 3-O-methyl-D-allose have no effect on growth and inhibit uptake of L-glutamic acid. These results indicate that considerable specificity is involved in the response of Penicillium sp. to O-alkylated sugars and some O-alkylated sugars may reduce production time of extracellular enzymes.
Somatic serogroups among 55 strains of Rhizobium phaseoli
Authors: Robert Francoise M. , Schmidt E. L.
Published: May 2010

The serological relationships among 55 strains of Rhizobium phaseoli of diverse geographical origin were examined by direct immunofluorescence. Five clear-cut serogroups and a minimum of 11 somatic antigenic determinants were detected among 42 strains using 11 fluorescent antibodies. At least a sixth serogroup exists to account for the remaining 13 unreactive strains. Serogroups 1 and 2 comprised a large number of strains (15 and 21, respectively), whereas serogroup 3 comprised only 4 strains and serogroups 4 and 5 a single strain each. These findings attest to a high degree of antigenic diversity as well as a high incidence of certain antigenic determinants in the collection of R. phaseoli examined. As a consequence, choice candidates for ecological studies would be strains endowed with a distinctive antigenic make-up as in serogroups 4 and 5.
Use of the enzyme-linked immunosorbent assay (ELISA) in the detection of Rhizobium both in culture and from root nodules of soybeans and cowpeas
Authors: Asanuma S. , Thottappilly G. , Ayanaba A. , Rao V. Ranga
Published: May 2010

The enzyme-linked immunosorbent assay (ELISA) was used to detect Rhizobium sp. in the "cowpea" group and R. japonicum both in culture and from nodules of glasshouse and field-grown plants. Double antibody sandwich (direct ELISA) and indirect ELISA were found to be equally sensitive in detecting rhizobia under controlled laboratory conditions. It was found that nodules preserved by freezing or drying over silica gel were equally good. No loss in sensitivity was detected when nodules were crushed directly in the microplates.
Salmonellae and pollution indicator bacteria in municipal and food processing effluents and the Cornwallis River
Authors: Menon A. S.
Published: May 2010

A study was conducted to determine the incidence of fecal coliforms, fecal streptococci, Aeromonas hydrophilia, and Salmonella spp. in the waste discharges of seven sewage treatment plants, four fruit and vegetable canneries, a meat packing plant, a poultry processing plant, and a potato processing plant located along the Cornwallis River in Nova Scotia, Canada. Surface water samples were also collected from 13 locations in the river to assess the impact of these waste discharges on the receiving water quality. The results showed that the final effluents from most of the sewage treatment and processing plants were of very poor bacteriological quality, with the number of indicator bacteria comparable with those found in raw sewage. Salmonellae were isolated from the effluents of the meat and poultry plants and five of the seven sewage treatment plants surveyed. No salmonellae were detected in the effluents of the fruit and vegetable canneries. The impact of the discharge of untreated municipal and food processing wastes on the Cornwallis River water quality was evidenced by the recovery from river water of five Salmonella serotypes, and the high fecal coliform counts which exceeded recommended limit for bathing and shellfish harvesting.
Observations préliminaires sur l'accumulation d'hydrocarbures chez Candida steatolytica: relation avec la synthèse des lipides
Authors: Guerzoni M. Elisabetta , Lambertini Paolo , Cavazza Agostino , Marchetti Rosa
Published: May 2010

Different cell lipid accumulation and composition patterns were observed in the yeasts Lipomyces starkeyi and Candida steatolytica by varying the nutritive conditions. In Lipomyces starkeyi 303 which accumulates high levels of lipids as triglycerides, the composition of the different lipid fractions was relatively unaffected by the culture medium. In contrast, the lipid composition of Candida steatolytica 20C was strongly affected by the composition of the medium under conditions of nitrogen limitation and when starch was used as the carbon source, high levels of straight and branched hydrocarbons were observed. [Traduction de l'auteur]
Formation of D-amino-acid oxidase in the yeast Trigonopsis variabilis
Authors: Kubicek-Pranz Eva M. , Röhr M.
Published: May 2010

Production of D-amino-acid oxidase by Trigonopsis variabilis has been investigated using a two-stage cultivation technique. After transfer of exponentially growing cells to fresh medium, the enzyme was induced by addition of D-amino acids to the growth medium, among which D-methionine and D-alanine were the most effective. The simultaneous presence of the L form of amino acids or [Formula: see text] did not affect this induction. The presence of trace metals, inorganic phosphate, and a high rate of agitation were necessary for formation of maximal D-amino-acid oxidase activity. The enzyme is not subject to glucose repression.
Barotolerant variant of Streptococcus faecalis with reduced sensitivity to glucose catabolite repression
Authors: Campbell III John , Bender Gary R. , Marquis Robert E.
Published: May 2010

Physiological characterization of the APR-11 variant of Streptococcus faecalis ATCC 9790 revealed that the variant has reduced sensitivity to glucose catabolite repression. This reduced sensitivity was indicated by the synthesis of enzymes for catabolism of lactose or arginine in cultures growing at 0.1, 40, or 70 MPa in media with levels of glucose highly repressive for the parent strain. Reduced catabolite repression appeared to be due to reduced activity of the glucose-specific, phosphotransferase system in APR-11 cells. Conversion of pyruvate to lactate or to acetate and ethanol did not appear to be altered in the variant. The APR-11 variant produced a greater final yield of biomass than the parent at all pressures tested, and its barotolerance was especially marked in media with low levels of glucose and high levels of lactose in which derepression of the lactose catabolic system was necessary for full growth. Overall, the greater barotolerance of the APR-11 strain appeared to be due to its enhanced capacity for catabolism related to its reduced sensitivity to catabolite repression by glucose.
Genetic transformation of molybdenum-starved Azotobacter vinelandii: increased transformation frequency and recipient range
Authors: Page William J.
Published: May 2010

Azotobacter vinelandii Nif− mutants UW3, UW45, and UW91 that did not become competent for genetic transformation after growth in Fe-limited competence induction medium did become competent when Mo starvation also was imposed. Mo starvation of other Fe-limited competent strains increased their frequency of transformation. Mo starvation also increased the frequency of transformation of strain UW1 with heterologous DNA from Azotobacter, Rhizobium, and Beijerinckia. Mo starvation did not increase the competence of the encapsulated A. vinelandii strain ATCC 12837. The substitution of mannitol or sorbitol for glucose in the Fe-limited competence induction medium, however, increased strain 12837 transformation frequency over 200-fold.
Isolation and partial chemical analysis of firmly bound exopolysaccharide from adherent cells of a freshwater sediment bacterium
Authors: Platt R. M. , Geesey G. G. , Davis J. D. , White D. C.
Published: May 2010

Cells of a freshwater sediment bacterium produced firmly bound extracellular polymers in laboratory cultures which, at the ultrastructural level, resembled those produced by natural sediment bacterial populations. Production of the exopolymers during subculture was maintained by using as a source of inoculum the population of cells which adhered to each other and to the wall of the glass culture vessel. The exopolymers were selectively released from the cells by blending and centrifugation in the presence of EDTA. Evaluation of glucose-6-phosphate dehydrogenase activity and 2-keto-3-deoxyoctonate concentration indicated that only small amounts of intracellular and cell wall components were released from the cells during exopolymer removal. Chemical analysis of the isolated crude exopolymer material indicated that it contained protein, polysaccharide, and DNA. The treatment promoted the selective isolation of firmly bound polymers from the surface of adherent cells.
Comparative study of membrane filtration and enrichment media for the isolation and enumeration of Pseudomonas aeruginosa from sewage, surface water, and swimming pools
Authors: Havelaar A. H. , During M. , Asch E. H. M. Delfgou-Van
Published: May 2010

The recovery of Pseudomonas aeruginosa on several selective culture media was tested using raw sewage and secondary sewage effluent samples as well as spiked chlorinated imitation swimming water and samples from whirlpools. mPA-medium B gave good recovery of both vital and chlorine-injured P. aeruginosa and selectivity was greater than 90% when analysing whirlpool samples. It is therefore the medium recommended for examination of chlorinated swimming pools. When analysing sewage polluted water with the mPA-B medium, reduced selectivity was noted from low verification rates and from overgrowth by competitive flora. A modified medium (mPA-D; addition of cetrimide, omission of sulphapyridine and actidione) was more selective and sufficiently recovered noninjured cells. Chlorine-injured cells were completely inhibited, however. C-390 (9-chloro-9-(4-diethylaminophenyl)-10-phenylacridan) was confirmed to be highly selective for P. aeruginosa when used in spread plates at a concentration of 30 μg/mL; P. aeruginosa was slightly inhibited. However, the medium could not be used with conventional membrane filtration techniques, because cellulose ester filters interfered with the selective action of C-390. Selectivity could be improved by using Gelman Tuffryn (polysulphone) filters and increasing the C-390 concentration to 120 μg/mL. At this concentration, however, the medium was strongly inhibitory to P. aeruginosa; resuscitation only partially improved recovery. Two other membrane filtration media were tested. Both cetrimide – nalidixic acid agar and Drake's medium No. 19 were inhibitory to chlorine-injured cells. Several types of membrane filters were tested and there was little difference between them. In the most-probable-number technique, recovery of P. aeruginosa was shown to be excellent when using asparagine broth. Malachite green broth was strongly inhibitory to chlorine-injured P. aeruginosa.
Glucose metabolism and pyruvate excretion by Streptomyces alboniger
Authors: Surowitz Kenneth G. , Pfister Robert M.
Published: May 2010

The formation of aerial mycelia and spores by Streptomyces alboniger has been observed to be inhibited by glucose supplied in the growth medium as the sole carbon source or supplied in combination with other utilizable carbon sources. Analysis of the metabolism of radiolabelled mannose and sucrose in the presence and absence of glucose demonstrated that glucose functions as the preferred carbon source, inhibiting the uptake and oxidation of the sugars within 15 min of its addition. The inhibition of aerial mycelium formation was shown to result from the excretion of an acidic metabolite, and could be overcome by the addition of a buffering system. The acid metabolite was identified as pyruvic acid by high-performance liquid chromatography and by paper chromatography. Acid was not produced in substantial quantities in dextrin broth or in glucose broth supplemented with 5 mM adenine. Analysis of the pathway of pyruvate overproduction demonstrated that growth on glucose resulted in increased glycolytic activity, relative to the activity of the tricarboxylic acid cycle on this substrate, while growth on dextrin or glucose supplemented with 5 mM adenine resulted in balanced glycolytic and tricarboxylic acid cycle activities.
Ammonium repression of cephalosporin production by Streptomyces clavuligerus
Authors: Braña Alfredo F. , Wolfe Saul , Demain Arnold L.
Published: May 2010

Production of β-lactam antibiotics took place during growth of Streptomyces clavuligerus in chemically defined medium. The specific activities of isopenicillin N synthetase ("cyclase"), isopenicillin N epimerase, and deacetoxycephalosporin C synthetase ("expandase") increased during the exponential phase of growth. Specific cephalosporin productivity during fermentation followed a similar pattern, reaching a maximum near the end of the growth phase and decaying rapidly in the stationary phase. Ammonium chloride depressed cephalosporin production, presumably as a result of repression of cyclase and expandase formation, but not of epimerase. No inhibitory effects on enzyme activity by ammonium were found. Addition of tribasic magnesium phosphate [Mg3(PO4)2∙8H2O] prevented the repression of cyclase and markedly stimulated cephalosporin production. Cephamycin C and, in smaller amounts, O-carbamoyldeacetylcephalosporin C were the only cephalosporins detected. Growth with ammonium resulted in lower titers of both compounds, and did not change the relative proportion of each. The correlation found between cephalosporin productivity and cyclase specific activity in different media suggests that formation of this enzyme may be the rate-limiting step in the pathway.
Antibiotic activity of an isocyanide metabolite of Trichoderma hamatum against rumen bacteria
Authors: Liss S. N. , Brewer D. , Taylor A. , Jones G. A.
Published: May 2010

A metabolite of Trichoderma hamatum, 3-(3-isocyanocyclopent-2-enylidene)propionic acid, was tested for its effects on growth of and carbohydrate metabolism in 11 strains of functionally important rumen bacteria. To standardize the biological activity of this unstable metabolite, a rapid, aerobic disc diffusion assay was developed using Escherichia coli ATCC 11775. In an anaerobic broth dilution assay using a medium lacking rumen fluid and containing a soluble carbohydrate, the minimum inhibitory concentration of the metabolite which completely inhibited growth of the rumen bacteria for 18 h at 39 °C was generally < 10 μg∙mL−1; however, the minimum inhibitory concentrations for Megasphaera elsdenii B159 and Streptococcus bovis Pe18 were 10–25 and 25–64 μg∙mL−1, respectively. In general, the Gram-negative strains were more sensitive than the Gram positive. The minimum inhibitory concentration for Bacteroides ruminicola 23 grown with glucose was 1 μg∙mL−1; for B. ruminicola GA33 (glucose), B. succinogenes S85 (cellobiose), and Succinivibrio dextrinosolvens 24 (maltose), it was 2 μg∙mL−1. When added to a cellulose-containing rumen fluid medium, 1–4 μg∙mL−1 of the metabolite delayed cellulose hydrolysis by B. succinogenes S85, Ruminococcus albus 7, and R. flavefaciens FD1 for up to 4 days, and 6–7 μg∙mL−1 prevented hydrolysis for at least 1 month. In the presence of the metabolite, the proportion of acetate produced from soluble carbohydrate by the majority of strains increased, but with some strains net production of acetate decreased relative to production of other acidic fermentation products. If the metabolite gained entrance to the rumen, a concentration of as little as 1 μg∙mL−1 would probably cause a significant depression of the fermentation and result in nutritional deprivation of the animal.
Postfusion incompatibility in Physarum polycephalum: involvement of membranes
Authors: Schrauwen J. A. M.
Published: May 2010

Fusion of sensitive and killer plasmodia of Physarum polycephalum caused a change in membrane composition which did not occur after fusion of two sensitive plasmodia. This change, which was mainly the result of an increase in the synthesis of phosphatidylethanolamine, began 1.5 h after fusion. Heat production and oxygen consumption declined during the processes which underlie the lethal reaction which destroys the fused plasmodia of sensitive and killer strains.
Involvement of fungi in the increase of free fatty acids in stored soybeans
Authors: Lisker N. , Ben-Efraim A. , Henis Y.
Published: May 2010

Application of the fungicide Captan to whole soybean seeds stored at 85% relative humidity did not prevent either the development of the natural fungal population underneath the seed coat or the increase of free fatty acids. At 65 and 75% relative humidity the increase in free fatty acids and fungi development during storage were lower than at 85% relative humidity, but even at these lower levels no differences were observed between Captan-treated and nontreated seeds. In split soybeans, where fungi developed profusely on the unprotected damaged site of the seed, treatment with Captan or thiourea resulted in free fatty acid values significantly lower than those of the untreated controls. The fungi most frequently isolated from stored soybeans were Aspergillus candidus, A. ruber, A. versicolor, and Penicillium cyclopium, all of which showed lipolytic activity. Inoculation of intact soybean seeds with these fungi did not cause an increase in free fatty acids as compared with noninoculated controls, probably because the intact seed coat prevented the penetration of the inoculated fungus. The similar increase in free fatty acids in both the inoculated and the noninoculated controls was probably caused by the internal mycoflora in both treatments. Since fungicide treatments prevented the increase of free fatty acid levels in all cases where the fungicide could reach those sites at which fungi developed, it was concluded that fungi play an important role in the increase of free fatty acids in stored soybeans.