bluuebunny/crossref_metadata_2025 huggingface dataset:
A method for measuring the response of sediment microbial communities to environmental perturbations
Authors: Furutani Akira , Rudd John W. M. , Kelly C. A.
Published: May 2010

A method has been developed for studying direct and indirect responses of microbial processes in lake sediments to environmental perturbations. Responses of the entire microbial community as well as specific members of the community were studied using in vitro sediment systems for periods of weeks or months under control and experimentally perturbed conditions. Effects of perturbations at the community level were determined by comparing rates of organic matter decomposition (CO2 + CH4 production) in the control and test (acidified) systems. At the same time and under the same conditions, rates of specific processes such as mercury methylation and sulfate and nitrate reduction were assayed to see if these processes responded in the same manner as did the activity of the entire community. Acidification (lowering from pH 6.3 to 4.2) did not affect either community activity or nitrate reduction. However, decreases were observed in sulfate reduction and mercury methylation which were independent of community activity, suggesting that acidification may affect these two specific processes directly. Use of this method provides comprehensive information about the interaction of sediment microbial processes as they respond to environmental perturbations.
Adaptational changes in Staphylococcus aureus MF 31 grown above its maximum growth temperature when protected by sodium chloride: lipid studies
Authors: Hurst A. , Ofori Esther , Vishnubhatla Indira , Kates M.
Published: May 2010

Staphylococcus aureus MF31 was grown to stationary phase in a complex medium at 30, 37, and 43 °C in the absence of salt and at 37 and 46 °C in the same medium supplemented with 1 M NaCl. The principal phospholipids were cardiolipin, phos-phatidylglycerol, aminoacylphosphatidyl glycerol, mono- and di-glycosyldiglyceride, and traces of phosphoglycolipid. The proportion of cardiolipin decreased with increasing growth temperature, but only slightly in the presence of 1 M NaCl, while that of aminoacylphosphatidyl glycerol was unaffected by growth temperature in absence of salt, but was about halved in the presence of 1 M NaCl. The net negative charge per mole phospholipid was greatly increased in the presence of 1 M NaCl. In the absence of salt, temperature had no effect on the total lipid content, but cells from the 46 °C culture in 1 M NaCl contained 25% less total lipid. The proportion of phospholipid in the total lipids, both in the absence and presence of salt, declined with increasing growth temperature. The proportion of glycolipids, however, increased with temperature both in the absence and presence of salt. It is suggested that the increase in glycolipid content and in negative charge/mole phospholipid is a part of the adaptation of S. aureus to the combination of high temperature and 1 M NaCl giving its membrane increased stability and possibly helping to exclude Cl− anion from the cell interior.
Role of antibiosis in antagonism of Streptomyces hygroscopicus var. geldanus to Rhizoctonia solani in soil
Authors: Rothrock Craig S. , Gottlieb David
Published: May 2010

Streptomyces hygroscopicus var. geldanus controlled rhizoctonia root rot of pea in previously sterilized soil if incubated for 2 or more days prior to infesting soil with Rhizoctonia solani and planting. Streptomyces hygroscopicus also reduced saprophytic growth and the population of R. solani in soil. Growth of R. solani was inhibited by geldanamycin, an antibiotic produced by S. hygroscopicus, on nutrient media. Methanol extracts of soils in which the antagonist was incubated for 2 or more days inhibited growth of R. solani. Geldanamycin concentration was 88 μg per gram of soil after 7 days of incubation. Bioautography of soil extracts indicated that the inhibitory compounds were geldanamycin and two other compounds, also found in the geldanamycin standard. The period of incubation necessary for antibiotic production and disease control was similar, with no disease control occurring where no antibiotic was detected. Amending soil with geldanamycin, in amounts equivalent to that produced after 2 or 7 days of incubation, controlled disease and reduced saprophytic growth of the pathogen. Lesser amounts of the antibiotic did neither. No evidence for antagonism owing to competition (nitrogen, carbon) or parasitism was found. Streptomyces hygroscopicus and geldanamycin also affected plant growth.
Sulphur acquisition by Neisseria meningitidis
Authors: Port J. L. , DeVoe I. W. , Archibald F. S.
Published: May 2010

Group B Neisseria meningitidis (SD1C) was grown on defined medium supplemented with each of a variety of sulphur compounds as the sole source of sulphur. The organism grew on sulphate, sulphite, bisulphite, thiosulphate, dithionite, hydrosulphide, thiocyanate, L-cysteine, L-cystine, reduced glutathione, methionine, mercaptosuccinate, and lanthionine, but not on dithionate unless previously sulphur starved. Good growth was seen on concentrations of sulphate or thiosulphate as low as 10 μM. When pregrown on and subsequently starved for sulphate, the meningococcus showed enhanced transport capacity for this ion. Optimal conditions for assessing sulphur transport by active sulphur-limited cells were determined. The maximal sulphate uptake velocity was 9.3 nmol sulphate∙mg protein−1∙min−1, and the apparent Km was 1.4 μM, far below human nasopharyngeal or serum sulphate levels.
Oxygen toxicity in Treponema pallidum: deoxyribonucleic acid single-stranded breakage induced by low doses of hydrogen peroxide
Authors: Steiner Bret M. , Wong Grace H.W. , Sutrave Pramod , Graves Stephen
Published: May 2010

The effect of hydrogen peroxide on Treponema pallidum was investigated. The in vitro loss of virulence (as measured by rabbit inoculation) of T. pallidum was accelerated by as low as 100 μM hydrogen peroxide in the complex maintenance medium used. Higher doses led to rapidly accelerated death with 500 μM hydrogen peroxide causing sterilization of the medium within 3 to 4 h. Since hydrogen peroxide is known to cause single-stranded breaks in DNA, the effect of hydrogen peroxide on the treponemal genome was examined. Extensive breakage was caused by 100 μM hydrogen peroxide as determined on alkaline sucrose gradients. A limit was reached at 250 μM and above. Single-stranded breaks could be demonstrated as early as 5 – 10 min after exposure to hydrogen peroxide when the treponemes were exposed to 250 μM hydrogen peroxide; accelerated death was evident by 2 h past exposure demonstrating that DNA breakage was preceding death. Treponemal death caused by penicillin did not result in DNA breakage. The repair-proficient bacterium Escherichia coli K-12 was compared with T. pallidum. It required 10 – 100 times more hydrogen peroxide to cause various levels of breakage. Escherichia coli K-12 rapidly repaired DNA breakage once hydrogen peroxide was removed by addition of catalase. Treponema pallidum, in comparison, showed little or no repair in vitro. Addition of catalase or dithiothreitol to the medium protected against all but a low level of breakage; this may reflect on the ability of catalase and reducing agents to protect T. pallidum against oxygen toxicity in vitro.
Purification and properties of the proteinase produced in vitro by Verticillium dahliae
Authors: Lambert François , Pujarniscle Serge
Published: May 2010

Verticillium dahliae, a vascular parasite of sunflower, was grown in a medium supplemented with sunflower cell walls as a sole nitrogen source. The culture filtrate contained three proteinases. The largest amounts were associated with the proteinase PIII fraction, while proteinases PI and PII fractions were in very small quantities. The properties of the purified proteinases were similar and it seemed likely that PI and PII fractions resulted from autolysis of the PIII fraction. The PIII proteinase showed a molecular weight of 12 750 and optimal action at pH in the 7.5–9.5 range. Activity was that of an endopeptidase which hydrolyzed casein, haemoglobin, gelatin, and N-benzoyl-DL-arginine-p-nitroanilide and was much less active on N-tosyl-L-arginine methyl ester and did not hydrolyze N-benzoyl-L-tyrosine ethyl ester. Ethylenediaminetetraacetate and calcium had no effect on the PIII proteinase which was inhibited by HgCl2, phenyl-methyl-sulfonyl fluoride, N-p-tosyl-L-lysine-chloromethyl ketone and L-1-tosyl-amide-2-phenyl-ethyl-chloromethyl ketone. This indicated that the active site in the PIII proteinase probably contained free sulfhydryl groups.
Virulence differences of Fusarium roseum isolates in red clover roots not explained by phytotoxins activity
Authors: Stutz J. C. , Leath K. T. , Lukezic F. L.
Published: May 2010

The relationship of toxic fungal metabolites to the virulence of Fusarium roseum 'Acuminatum' and 'Avenaceum' isolates that cause root rot of red clover was investigated. The biological activity of filtrates of root solution cultures was tested, using seed germination, rust spore germination, and root electrolyte and potassium-ion leakage as assays. Although activity was detected for all pathogenic isolates in all assays except the rust spore germination assay, it was not positively correlated with the virulence of the isolates. Histological examinations of infected roots showed a close relationship between hyphal development and visible symptoms. Differences in virulence between isolates of F. roseum could not be obviously related to differential production of phytotoxins.
Composition chimique et ultrastructure des parois des corps hyphaux et des azygospores de Conidiobolus obscurus
Authors: Latgé J. P. , Fournet B. , Cole G. , Dubourdieu D. , Tong N.
Published: May 2010

The mycelial wall of Conidiobolus obscurus is essentially composed of β(1 → 3)-glucan (soluble in cold NaOH) associated with small amounts of protein and chitin. It is also characterized by the absence of galactose, uronic acids, and chitosan. The wall of the azygospore is different from that of the mycelium and is almost exclusively composed of a chitin–protein complex associated with a very small amount of hexoses. The mycelial wall is easily fractionated by cold or hot NaOH and hot acetic acid, whereas the spore wall is very resistant to both acid and alkali treatments. The composition of the various fractions is outlined. Chitin is present as short microfibrils while protein occurs in an amorphous form; β(1 → 3)-glucans are present in both amorphous and fibrillar forms. An architectural scheme of the mycelial and spore walls is proposed.
Detection of cellulase and xylanase activity in isoelectric-focused gels using agar substrate gels supported on plastic film
Authors: MacKenzie C. R. , Williams R. E.
Published: May 2010

A simple, rapid, and highly sensitive technique is described for the detection of endoglucanase and endoxylanase in isoelectric-focused gels. Agar substrate gels containing 0.1% carboxymethyl cellulose or xylan are prepared on GelBond® plastic film and placed in contact with an electrofocused gel containing the enzymes under study. Hydrolysis zones in substrate gels are visualized by staining with Congo red. As little as 1 ng of enzyme is detected in 5 min using this technique.
Hydrolysis of linamarin by intestinal bacteria
Authors: Fomunyam R. T. , Adegbola A. A. , Oke O. L.
Published: May 2010

Linamarin, a cyanogenic glucoside, was hydrolyzed by Escherichia coli and Streptococcus faecalis but not by Clostridium perfringens when these organisms were grown on a glucose or lactose medium.
Bacterial and fungal activity in sulphur dioxide polluted soils
Authors: Bewley R. J. F. , Parkinson D.
Published: May 2010

A selective inhibitor technique was used to determine the relative contributions of bacteria and fungi to total microbial respiration in pine forest soils from three "ecologically analagous" sites at intervals of 2.8 km (site 1), 6.0 km (site 2), and 9.6 km (site 3) from a "sour gas" plant emitting sulphur dioxide, SO2. The ratios of bacterial to fungal respiration given as percentages of total activity were 5:95, 14:83, and 18:82 in the F/H horizon and 31:70, 36:62, and 38:62 in the mineral soil (to 5 cm depth) at sites 1, 2, and 3, respectively. An unexplained stimulation of respiration sometimes occurred, however, in the organic soil of site 1, when streptomycin was added. There was a reduction in total microbial biomass in the organic soil of site 1 compared with sites 2 and 3, but no such differences between sites in the mineral soil. The predominant fungi isolated at all three sites were Aureobasidium pullulans from intact, washed pine needles and Trichoderma viride from washed fragments of the F/H horizon.
Improved recovery of fecal coliforms from the Ottawa River by membrane filters in the presence of food debris
Authors: Farber Jeffrey M. , Sharpe Anthony N. , Kalab Miloslav
Published: May 2010

In the absence of food debris, Sartorius and Millipore HA filters recovered substantially fewer fecal coliforms from Ottawa River water than did Millipore HC. On addition of a small quantity of sterile blended carrot to water samples, recovery by the poorer filters equalled that on Millipore HC. Scanning electron microscopy revealed bacteria sheltered in crevices formed by carrot fibres and thus protected from the normal stresses of exposure. Addition of carrot debris (e.g., 0.03 g carrot to 100 mL of sample) thus provides a convenient and inexpensive means of reducing variations in fecal coliform recovery between brands of membrane filters.
Association of Candida guilliermondii with amylolytic filamentous fungi on preharvest corn
Authors: Horn Bruce W.
Published: May 2010

Candida guilliermondii var. guilliermondii was the dominant yeast isolated from preharvest Georgia corn and comprised 3.6–47.0% of the total fungi as measured by dilution plating. The yeast was confined mainly to kernels visibly molded by filamentous fungi, primarily Fusarium moniliforme and Aspergillus flavus. When grown in liquid shake culture, Cand. guilliermondii was unable to utilize starch. Growth of the yeast increased considerably when associated with amylolytic F. moniliforme or Asp. flavus. Utilization of starch hydrolyzates by Cand. guilliermondii in mixed cultures was reflected by a decrease in reducing sugar concentrations and a reduction in growth of F. moniliforme and Asp. flavus. When glucose replaced starch as a carbon source, F. moniliforme and Asp. flavus did not affect the maximum growth of Cand. guilliermondii. The association between Cand. guilliermondii and amylolytic filamentous fungi on preharvest corn is probably commensalistic.
Seasonal distribution of enteroviruses and adenoviruses in domestic sewage
Authors: Krikelis Vassilis , Spyrou Niki , Markoulatos Panayotis , Serie Charles
Published: May 2010

A seasonal distribution of enteroviruses and adenoviruses in raw sewage effluents of Athens, Greece, was observed over a 15-month surveillance period. All 36 samples tested were positive for both virus groups. Adenovirus concentration levels ranged from 70 to 3200 cytopathic units per litre of sample, whereas the corresponding values for enteroviruses were 90–900 cytopathic units per litre. Peak values for adenoviruses were recorded during the months of April and June 1983, whereas for enteroviruses the peak was recorded in September 1983. All three types of poliovirus were present. Coxsackievirus types B-1, B-2, B-4, and B-5 and echovirus type 7 were also isolated. Adenovirus types 1, 2, 3, 5, 7, and 15 were detected as well.
Evaluation of differential media for the identification of Corynebacterium genitalium and Corynebacterium pseudogenitalium (group JK corynebacteria)
Authors: Coppola Karen M. , Furness Geoffrey
Published: May 2010

Tween purple agar containing 1% fructose (TFP agar) differentiated Corynebacterium genitalium from C. pseudogenitalium, which respectively formed colorless and yellow colonies after 72 h incubation at 37 °C aerobically or in 5–10% CO2 in air. Thus TFP agar is a differential medium. Corynebacteria-like colonies grown on nonspecific urethritis (NSU) chocolate agar from urogenital material were identified as C. genitalium, C. pseudogenitalium, or commensals when subcultured on TPF agar. TFP agar was unsuitable for their primary isolation since the commensals turned the medium yellow with 24 h incubation. Gentamicin cannot be employed as a selective agent in medium for the isolation of these corynebacteria. TFP agar containing 10 μg/mL gentamicin inhibited most strains of C. pseudogenitalium and C. genitalium isolated from urogenital infections. It did not inhibit isolates of these corynebacteria from cancer patients or suppress the normal bacterial flora of the urogenital tract. Evidence that gentamicin-resistant strains are characteristic of nosocomial infections is presented.
Evaluation of difference imagery for visualizing and quantitating microbial growth
Authors: Caldwell Douglas E. , Germida James J.
Published: May 2010

Online computer image enhancement and analysis were used to visualize and quantitate microbial growth in slide cultures. Images of a single field were collected, enhanced, and stored in random access memory at 15-min time intervals. The image obtained at time 0 was subtracted from each of the subsequent images. This produced a series of difference images showing microbial growth as a black object on a grey background and eliminating debris. Data obtained using difference imaging were compared to data obtained by computer analysis of the original images. The initial rate of growth (2.8 μm3∙field−1∙h−1) was determined within an error of 2% and continuously increased during the first 2 h of incubation. The images of seven soil fractions and of stationary phase cells were superimposed on both the initial and final images before subtraction to evaluate difference imaging as an aid in visually discriminating growing microorganisms from simulated artifacts. The coarse clay fraction (0.2–2.0 μm) was the most difficult to visually distinguish from microbial cells, but was easily eliminated in difference images. The potential for application of difference imaging in the direct measurement of in situ metabolic activity is also discussed.
Histopathological evidence for protective immunity induced by sonicated Salmonella vaccine
Authors: Hsu H. S. , Nakoneczna I. , Guo Yan-nie
Published: May 2010

The highly susceptible inbred C3H/HeNMTV mice were vaccinated with fragments derived from sonicated Salmonella typhimurium and then infected with the pathogen. All of the vaccinated mice survived an otherwise rapidly fatal challenge of 105 organisms, i.e., >103 × mean lethal dose (LD50). The vaccine also protected two-thirds of the mice infected with 106 bacteria and extended the survival time of the remainder in their fatal disease. Histopathological findings showed that, like the control mice, the vaccinated and infected mice developed abscesses with infiltration of polymorphonuclear leukocytes in the organs of the reticuloendothelial system during the early stage of the infection. However, unlike the primary lesions in the control mice, the lesions of the vaccinated mice tended to be discrete and self-limiting. They began to transform into granulomas after the first week of infection. Recovery and regeneration of tissues were evident 3 weeks after the infection.
Octopine, nopaline, and octopinic acid utilization in Pseudomonas
Authors: Rossignol G. , Dion P.
Published: May 2010

Culture media selective for Agrobacterium were inoculated with dilutions of soil and crown gall tumor suspensions. Colonies on the selective media were replica plated on a medium with octopine or nopaline. More than 500 isolates were recovered, about 10% of which were confirmed as octopine-utilizing, fluorescent pseudomonads. These strains, together with four other strains of Pseudomonas that had been isolated in a previous study, were characterized for species identity, for utilization of various carbon sources, and for capacity to grow with various opines and amino acids as the sole carbon and nitrogen source. The capacities for octopine and nopaline utilization were generally dissociated, which is similar to the situation found in Agrobacterium. However, most of the octopine-utilizing strains of Pseudomonas showed markedly different growth kinetics in octopine and octopinic acid, two compounds that, in the Agrobacterium system, have been classified into the same opine family. Generally, poor octopinic acid utilization was not correlated with poor ornithine utilization.
The toxicity of copper to the marine bacterium Vibrio alginolyticus
Authors: Schreiber Donald R. , Gordon Andrew S. , Millero Frank, J.
Published: May 2010

The toxicity of copper to the marine bacterium Vibrio alginolyticus was examined. Experiments were conducted with both aerobic and anaerobic cultures. Calorimetric and radiochemical techniques were used to examine the effect of copper on heat production, respiration, and carbon assimilation by the cultures. Plate counts were used to determine the number of viable cells present. Copper was more toxic to the bacterium in anaerobic culture (mean toxic concentration (TC50) = 2.1 μM)) than in aerobic culture (TC50 = 6.4 μM). Both cytotoxic and cytostatic effects were observed. The cytotoxic effect was not significantly different under aerobic and anaerobic conditions. The cytostatic effect, observed only in anaerobic culture, resulted in a decrease in the rate of metabolism of the surviving cells. The magnitude of the cytostatic and cytotoxic effects were dependent on the copper concentration, exhibiting saturation at higher concentrations. Organic chelators EDTA and nitrilotriacetic acid protected the anaerobic cultures from the copper, indicating that Cu–organic complexes are not toxic to the organism.
Lignin degradation by Phanerochaete chrysosporium in agitated cultures
Authors: Reid Ian D. , Chao Ema E. , Dawson Peter S. S.
Published: May 2010

Contrary to previous reports, cultures of Phanerochaete chrysosporium agitated on a gyrotory shaker degraded synthetic lignin to CO2 approximately as rapidly and extensively as static cultures. Agitated cultures also degraded the lignin in aspen wood to CO2 and water-soluble products as well as static cultures, if the wood particles became enmeshed in the mycelium. An atmosphere of oxygen stimulated lignin degradation, compared with air, in both agitated and static cultures. The mycelia in agitated cultures with ligninolytic activity formed single, large pellets.
Detection of collagenase activity in oral bacteria
Authors: Mayrand D. , Grenier D.
Published: May 2010

Collagenolytic activity of 12 species of oral bacteria was assessed using two methods of detection. Except for two species, all bacterial strains tested were capable of degrading at least one general protein substrate. Results of collagenolytic activity in a growth assay indicate that Bacteroides gingivalis is the only bacterium capable of degrading collagen when the substrate is sterilized using ethylene oxide. However, if the substrate is sterilized by autoclaving, in the presence or absence of the growth medium, other bacterial species could be shown to be collagenolytic. Collagenolytic activity was also demonstrated when whole or broken cells were used in a [14C]collagen assay. Results from this assay and from inhibition studies indicate that collagenolytic activity can either be the result of the combined activities of both a specific collagenase and nonspecific proteases (B. gingivalis) or nonspecific proteases only (other strains in this study), although in the latter case, the time taken to hydrolyze collagen can be 10 times longer than with a specific collagenase.
Location of cellulolytic enzyme activity in the marine fungus Trichocladium achrasporum
Authors: MacDonald Malcolm J. , Hartley Donna L. , Speedie Marilyn K.
Published: May 2010

Cellulase activity in Trichocladium achrasporum was demonstrated by its ability to produce cell-associated and extracellular cellulolytic enzymes when grown on a crystalline cellulose substrate. In addition, azure dye was solubilized from dyed crystalline cellulose, appearing in the growth medium during the phase of cell lysis. Exoglucanase activity was highest in the culture filtrate, with slight activity in the cell fractions, while endoglucanase was associated only with the mycelium. No desorbable exoglucanase nor endoglucanase activity could be released by sonication of residual cellulose particles removed from actively growing cultures. β-Glucosidase activity was located only in the cell-associated fractions during active growth. All enzymes had optimal activity at 50 °C; in the particulate fraction β-glucosidase exhibited a second optimum at 30 °C. In the filtrate, soluble intracellular and particulate fractions optimal exoglucanase activity occurred at pH 6.4, 7.0, and 5.8, respectively. Endoglucanase activity was optimal at pH 5.8 in the soluble cell fraction, and at pH 5.4 in the particulate fraction.
Effects of peptidoglycans from periodontal pathogens on selected biological activities of CD-1 murine peritoneal macrophages
Authors: Barnard M. , Holt S. C.
Published: May 2010

Resident CD-1 murine peritoneal macrophages were exposed to various concentrations of purified peptidoglycan isolated from members of the genera Bacteroides, Eikenella, and Actinomyces. Macrophage viability, the release of lysozyme, acid phosphatase, and prostaglandins E, and E2 were assayed as a function of peptidoglycan concentration and time. Macrophages responded as a function of peptidoglycan concentration with increased release of acid phosphatase and prostaglandins; all cells remained > 90% viable during the course of the experiments. However, concentrations of peptidoglycan > 50 μg/mL were toxic to the macrophages, while the peptidoglycan from B. capillus strain 925.08 and Actinomyces viscosus strain T14AV consumed complement by both the classical and the alternate pathways. Cellular lysozyme activity and phagocytosis of Saccharomyces cerevisiae were significantly reduced in the presence of peptidoglycan. When viewed by scanning electron microscopy, the activated macrophages were rounded, lacked distinct pseudopod extensions, and possessed an increased number of microvilli and plasma membrane associated vesicles. These morphological alterations occurred as early as 3 h. Transmission electron microscopy revealed the purified peptidoglycan to have been taken up into numerous phagosomes; however, even after 24 h incubation, it was only partially degraded.
Effect of homogenization procedures on Escherichia coli counts in naturally contaminated cheese
Authors: Peterkin Pearl I. , Sharpe Anthony N. , Warburton Donald W.
Published: May 2010

A comparison was made between blending in 2% sodium citrate and stomaching in 0.1% peptone or 0.1% peptone – 1% Tween 80 for the enumeration of Escherichia coli in naturally contaminated cheeses. Statistical analysis of the results from 25 samples of cheese showed that there were no significant differences in recovery by the three methods at the 95% confidence level.
Characterization of a substance produced by Azospirillum which causes branching of wheat root hairs
Authors: Jain Devender K. , Patriquin David G.
Published: May 2010

Previous studies have shown that Azospirillum or its culture filtrates induce root hairs in wheat seedlings to branch; this phenomenon is influenced by the bacterial genome at the strain level and by the plant genome at the cultivar level. Strain Sp245 caused most branching of root hairs; between wheat cultivars frequency of branching increased in the following order: cv. Tobari, cv. Tonari, cv. BH1146, cv. Lagoa. Similarly, plant growth response to inoculation with Azospirillum, measured in mature plants, increased in the same order, suggesting that both phenomena (root hair branching and plant growth response) have a similar basis. In this study, the "branching substance" present in Azospirillum culture filtrate was found to be thermostable at 100 °C, removed by dialysis, present in the acidic nonpolar fraction of the cell-free extract, and co-chromatographed with authentic indole acetic acid on thin-layer chromatograms. Purified indole acetic acid caused branching of root hairs similar to that caused by the Azospirillum culture filtrates. Susceptibility of wheat cultivars to indole acetic acid induced branching increased in the order: cv. Tobari, cv. Tonari, cv. BH1146, cv. Lagoa. Of five strains examined, strain Sp245 produced the most indole acetic acid in culture in the presence of tryptophan. The presence of indole acetic acid was confirmed by gas chromatography – mass spectrometry.
Competition studies with fast-growing Rhizobium japonicum strains
Authors: McLoughlin Thomas J. , Owens P. Ann , Alt Scott G.
Published: May 2010

The ability of eight fast-growing strains of Rhizobium japonicum to compete for nodule sites against two slow-growing strains of R. japonicum was measured using different input ratios (1:1, 1:10, and 10:1) on Glycine max cv. Peking and cv. Jacques 130 in growth pouches. The slow growers formed >60% of the nodules on cv. Peking even when the fast growers were added at a 10:1 ratio in their favor. We also measured the competitive ability of 10 fast-growing strains of R. japonicum, including these 8 strains, and ANU240 (a fast-growing broad host range strain) at two inoculum levels, 106 and 109 cells/seed on cv. Peking and cv. Jacques 130 in pots containing two midwestern soils which contained high numbers of indigenous rhizobia. In one soil, 3 of the 10 fast-growing strains occupied >60% of the nodules on cv. Peking at 109 inoculum level. No nodules were formed by the fast-growing strains on cv. Jacques 130 in any of the experiments.
An unsaturated fatty acid mutant of Aspergillus niger with partially defective Δ9-desaturase
Authors: Chattopadhyay Panchanon , Banerjee Santu Kumar , Sen Kalyani , Chakrabarti Parul
Published: May 2010

The wild-type Aspergillus niger (V35) does not require fatty acids for growth. Four unsaturated fatty acid auxotrophs designated as UFA1, UFA2, UFA3, and UFA4 have been produced from this organism by treating the conidia of the wild-type strain with a mutagen, N-methyl-N′-nitro-N-nitrosoguanidine, followed by isolation on media containing monounsaturated fatty acids and the nonionic detergent, Brij 58. Optimal growth of the mutants comparable with that of the wild type was achieved with medium supplemented with C16 or C18 unsaturated fatty acids containing at least one cis double bond at the Δ9 position. Some other fatty acids (18:1 Δ11cis and 16:1 Δ9trans) support growth to some extent. The mutants do not grow at all in the presence of saturated fatty acids. Fatty acid analyses of the mutant, UFA2, grown in the presence of different fatty acid supplements reveal that it may be defective in a desaturase system. Experiments with unlabeled and [1-14C]palmitoyl-CoA have shown that the microsomes of the mutant (UFA2) contain a partially defective Δ9-desaturase system.
Bacteristatic activity of phenanthrolines against Escherichia coli and Bacillus subtilis
Authors: Sharrock Patrick
Published: May 2010

Using optical turbidimetry to measure the growth of Escherichia coli and Bacillus subtilis, we determined the mean lethal dose (LD50) values for various phenanthrolines. The dimethyl-substituted compounds are found to be more toxic to bacteria, with doses near 5 μg/mL reducing the number of viable cells by 50% over a 24-h period. 2,9-Dimethyl phenanthroline is the most potent compound against B. subtilis, being six times more effective than against E. coli. Bipyridine is the least toxic substance and is twice as effective against E. coli as it is against B. subtilis. Evidence is presented to show copper ions enhance the antibacterial action of phenanthrolines and may be required for activity.
Virulence of Pseudomonas aeruginosa strains with mechanisms of microbial persistence for β-lactam and aminoglycoside antibiotics in a mouse infection model
Authors: Bryan L. E. , Godfrey A. J. , Schollardt T.
Published: May 2010

A series of mutations and transductants producing low-level aminoglycoside and β-lactam antibiotic resistance of Pseudomonas aeruginosa have been constructed in an isogenic background. The phenotypes of these mutations are identical to or closely resemble those of clinical isolates of P. aeruginosa associated with therapeutic failure or microbial persistence in the presence of members of one or both groups of drugs. Virulence of the mutants was examined in an infection model using iron–dextran treated mice and bacteria grown in low-iron medium. All β-lactam resistant mutants affecting affinity of penicillin-binding proteins for β-lactams, constitutive β-lactamase, or permeability of β-lactams retained parental levels of virulence. Aminoglycoside-resistant mutants with defective energy generation or transductants with modified lipopolysaccharide showed reduced virulence. Strains with the preceding forms of resistance are likely to account for therapeutic failure or microbial persistence with antibiotic treatment. We propose that mechanisms of low or unstable forms of resistance should be designated mechanisms of persistence to differentiate them from more classical mechanisms of resistance.
The contribution of exoproducts to virulence of Pseudomonas aeruginosa
Authors: Nicas Thalia I. , Iglewski Barbara H.
Published: May 2010

Pseudomonas aeruginosa produces a large number of extracellular products which may contribute to its virulence. We have employed a genetic approach to determine the contribution of toxin A, exoenzyme S, elastase and alkaline protease to the pathogenesis of P. aeruginosa. Mutations have been introduced with chemicals or transposons. Mutants have been identified using immunological, chemical, or toxicity assays. Mutants were extensively characterized in vitro to ascertain that they were identical to their parent strain except for the production of the desired product. Appropriate mutants were compared with their parent strains in several animal models: the burned mouse model, the mouse corneal infection model, and a rat model of chronic lung infection. The data indicate that virulence of P. aeruginosa is multifactorial. Further, the relative contribution of a given P. aeruginosa product may vary with the type of infection.
Isolation and characterization of a Saccharomycopsis lipolytica mutant showing increased production of citric acid from canola oil
Authors: Good David W. , Droniuk Randal , Lawford G. Ross , Fein Jared E.
Published: May 2010

A process for the production of citric acid from canola (rapeseed) oil using the yeast Saccharomycopsis lipolytica was examined. A citrate nonutilizing strain, designated NTG9, which had an improved citric to isocitric acid ratio, was isolated after mutagenesis of S. lipolytica ATCC 20228 with nitrosoguanidine. Although the mutant grew well on canola oil, unlike the parent strain or a spontaneous revertant (JF2), it did not grow on glycolytic intermediates below glycerate-3-phosphate, amino acids, hexadecane, or yellow kerosene. The mutant was shown to be impaired in the gluconeogenic pathway because of a loss of phosphoenolpyruvate carboxykinase activity. A preliminary study of the effect of micronutrients on citric acid production by S. lipolytica NTG9 showed that manganese had a stimulatory effect on the process whereas zinc and iron were inhibitory. A revised growth medium was tested and found to increase citric acid production while decreasing that of isocitric acid.
Role of substrate mycelium in colony development in Streptomyces
Authors: Méndez Carmen , Brana Alfredo F. , Manzanal Manuel B. , Hardisson Carlos
Published: May 2010

Cellophane cultivation techniques have been proven to be useful for the study of colony growth in Streptomyces. Results obtained by this procedure indicate that, in S. antibioticus, substrate mycelium was a nutrient support for aerial mycelium growth. Oleandomycin synthesis starts before aerial mycelium formation and may play an important role during colony growth.
Lipid composition of an obligately anaerobic fungus Neocallimastix frontalis isolated from a bovine rumen
Authors: Body Denis R. , Bauchop Tom
Published: May 2010

The lipid composition of an obligately anaerobic bovine rumen fungus Neocallimastix frontalis, belonging to the Neo-callimasticaceae of the Chytridiomycetes, has been investigated. It consisted of 44% neutral lipids (triacylglycerol, fatty acid, and sterols) and 56% polar lipids. The fatty acid composition of this unusual fungus differed markedly from that of other members of Chytridiomycetes by the absence of long-chain polyenoic fatty acids and by the presence of a large proportion (48%) of a series of cis-monoenoic fatty acids between 14:1 and 24:1. The absence of polyunsaturated fatty acids is explained by the anaerobic life style of this organism. However, the formation of the large proportions of monoenoic fatty acids under anaerobic conditions constitutes a major difference which cannot be explained by known pathways of fatty acid biosynthesis in fungi. This result indicates that N. frontalis differs from other fungi in possessing an anaerobic pathway for monoenoic fatty acid biosynthesis.
Training of Rhizopus stolonifer and Cunninghamella blakesleeana to copper: cotolerance to cadmium, cobalt, nickel, and lead
Authors: Garcia-Toledo A. , Babich H. , Stotzky G.
Published: May 2010

Rhizopus stolonifer and Cunninghamella blakesleeana trained after five passages to tolerate elevated concentrations of copper simultaneously acquired a tolerance to elevated levels of cadmium, cobalt, nickel, and lead. The acquired tolerance to copper was not stable in the absence of the metal, as serial transfers to a copper-free medium progressively reduced the level of tolerance, and after the sixth passage on a copper-free medium, the tolerance was equivalent to that of the nontrained parentals ("untraining"). However, the untrained fungi regained the same tolerance to copper as the original copper-trained fungi after only three passages on copper-amended medium ("retraining"). The tolerance to copper was apparently the result of physiological adaptation rather than of the selection of resistant cells or the induction of mutation. The metal may have activated genes that coded for biochemical processes that conferred tolerance to copper as well as to other heavy metals. Furthermore, the tolerance to copper of the mycelia was transferred to the sporangiospores. The copper-trained fungi did not appear to produce extracellular metabolites that complexed with and, hence, excluded and detoxified the copper. However, the mycelia of the trained fungi removed approximately twice as much copper from solution than those of the nontrained parentals, suggesting that the tolerance to copper resulted from the binding of the metal to the cell wall or from an intracellular detoxification mechanism.
Quantitative determination of microbial activity and community nutritional status in estuarine sediments: evidence for a disturbance artifact
Authors: Findlay Robert H. , Pollard Peter C. , Moriarty David J. W. , White David C.
Published: May 2010

In estuarine sediments with a high degree of vertical heterogeneity in reduced substrate and terminal electron acceptor concentrations, the method of exposure of the microbiota to labeled substrates can introduce a "disturbance artifact" into measures of metabolic activity. The detection of this artifact is based on a quantitative measurement of the relative rates of incorporation of [14C]acetate into phospholipid fatty acids (PLFA) and endogenous storage lipid, poly-beta-hydroxyalkanoate (PHA). Previous studies have shown that PLFA synthesis measures cellular growth and that PHA synthesis measures carbon accumulation (unbalanced growth). The "disturbance artifact" of exposure to [14C]acetate was demonstrated by comparing injection of a core with the usual or pore-water replacement or slurry techniques. Only injection of labeled substrate allowed detection of a preassay disturbance of the sediment with a garden rake. The raking increased PLFA synthesis with little effect on PHA synthesis. The differences between injection and slurry inoculation techniques on disturbed sediments were not due to differences in concentration or distribution of [14C]acetate in the 10-min incubation. Bioturbation induced by sand dollar feeding in estuarine sediment could be detected in an increased PLFA/PHA ratio which was due to decreased PHA synthesis if the addition of labeled substrate was by the injection technique. Addition of labeled precursors to sediment by slurry or pore-water replacement induces greater disturbance artifacts than injection techniques.
Evidence for regulatory trehalase activity in Candida utilis
Authors: Arguelles J. C. , Gacto M.
Published: May 2010

Candida utilis cells constitutively contain an acetate-insensitive intracellular trehalase (α,α-trehalose glycohydrolase; EC 3.2.1.28) whose activity is maximal during exponential growth. Cells grown on glucose, sucrose, or ethanol as carbon source show decreased levels of this trehalase activity as the cultures enter the stationary phase. The enzyme activity from stationary phase cells can be restored to the levels present in growing cells by preincubation of the cell extracts with adenosine 3′,5′-cyclic monophosphate and adenosine 5′-triphosphate. In vitro activation is also accomplished by addition of the catalytic subunit of a protein kinase preparation and adenosine 5′-triphosphate. The enzyme activity is enhanced in vivo by the presence of glucose or fluoride. Treatment of the trehalase with phosphatase results in a substantial loss of trehalase activity. Both activated and nonactivated trehalases show similar properties (Km = 1.01 × 10−2 M) and seem to be due to an enzyme with a molecular weight of 280 000. The data obtained are consistent with a regulatory model involving phosphorylation and dephosphorylation of the enzyme to control trehalase activity. In addition, another trehalase is present in this yeast whose activity is markedly inhibited by acetate.
Heterotrophic potential of the green alga, Ankistrodesmus braunii (Naeg.)
Authors: Bollman R. C. , Robinson G. G. C.
Published: May 2010

The green alga, Ankistrodesmus braunii (Naeg.), was found to possess a biphasic transport system for D-glucose. The high affinity component of the system had a Vmax of 1.2 × 10−7 pmol∙cell−1∙min−1 and a specific transport constant (Kt) of 7.7 nM glucose. The low-affinity component had a Vmax of 10.8 × 10−4 pmol∙cell−1∙min−1 at a Kt of 16.2 μM glucose. These kinetic values indicate that the alga could compete successfully with bacteria for glucose in natural waters. Ankistrodesmus braunii also grew heterotrophically on 0.1 mM glucose with a doubling time of 31.4 h. The growth rate was shown to correspond with the transport rate when an excretion rate of 3.5% and a respiration rate of 48% of the transported glucose were considered.
Characteristics of nitrite reductase activity in Lactobacillus lactis TS4
Authors: Dodds Karen L. , Collins-Thompson David L.
Published: May 2010

Nitrite reductase activity in Lactobacillus lactis TS4 was induced by the presence of nitrite and was active under anaerobic conditions. An electron donor was required. Glucose was the most efficient donor in whole cells, while NADH was the most efficient in cell extracts. The optimum nitrite concentration for reduction was 2.0 mM, with higher levels sharply inhibiting activity. The pH optimum for nitrite reduction by resting cell suspensions was 7.2, and the temperature optimum was 30 °C. High levels of NADH oxidase activity in cell extracts interfered with nitrite reductase activity. Fractionation of the cell extract by ultracentrifugation and ammonium sulphate precipitation decreased the specific activity of NADH oxidase by 40 and 41%, respectively. Nitrite reductase activity was detected in the supernatant fluid after centrifugation of cell extract at 226 000 × g for 1 h.
Adhesion of Pseudomonas aeruginosa to human buccal epithelial cells: evidence for two classes of receptors
Authors: McEachran David W. , Irvin Randall T.
Published: May 2010

The adhesion of Pseudomonas aeruginosa strain 492c to trypsinized and untrypsinized buccal epithelial cells (BECs) was studied. Kinetic analysis of the adhesion data, employing a Langmuir absorption isotherm, indicated the presence of two classes of binding sites on untrypsinized BECs: a high affinity – low copy number site (apparent association constant (Ka ≈ 1.57 × 10−8 mL/cell with ca. 29 binding sites/cell) and a low affinity – high copy number class of binding sites (Ka ≈ 4.78 × 10−10 mL/cell with ca. 264 binding sites/cell). The low affinity – high copy number class of sites was found to be trypsin sensitive. A single class of binding sites was found on trypsinized BECs exhibiting a high affinity – low copy number (Ka ≈ 3.70 × 10−7 mL/cell with ca. 31 binding sites/cell). Positive cooperativity in binding of P. aeruginosa strain 492c to the low affinity – high copy number class site on untrypsinized BECs was demonstrated by analysis of Hill plots of the adhesion data. Sugar inhibition data using a preincubation methodology showed an inhibition of adhesion to trypsinized BECs in the presence of N-acetylneuraminic acid and D-arabinose, while these same two sugars enhanced adhesion to untrypsinized BECs. D-Galactose and N-acetylglucosamine enhanced adhesion to both types of BECs though the latter did to different extents. D-Fucose only inhibited adhesion to untrypsinized BECs. Without preincubation the sugar inhibition data indicated that N-acetylglucosamine had no effect on adhesion while N-acetylneuraminic acid and D-fucose both enhanced adhesion to both types of BECs. D-Arabinose had a slight inhibitory effect on adhesion, while D-galactose had a slight enhancing effect to both cell types, but to different levels. This sugar data suggests a difference in the receptors on the two types of BECs, but the possibility of metabolism of these sugars by P. aeruginosa requires one to interpret this data with caution. Flagella were shown not to be involved in adhesion, while the alginic acid of the capsule was implicated. The low copy number binding site is speculated to be a pili-binding site, while the high copy number class of binding sites is proposed to involve a lectin which binds alginic acid.
Application of enzyme electrophoresis for the identification of isolates in Trichoderma harzianum
Authors: Zamir Daniel , Chet Ilan
Published: May 2010

Soluble enzymes were extracted from 23 geographically diverse isolates of Trichoderma harzianum and compared by electrophoresis. Seven enzyme systems were assayed and the isolates were grouped into five different types according to their isozymic profiles. The results indicate that enzyme electrophoresis can be used to distinguish between T. harzianum isolates. The potential of this system for T. harzianum breeding is discussed.
Response of birdsfoot-trefoil nodulating Rhizobium to lectins and trefoil chemotactin
Authors: Currier William W.
Published: May 2010

Concanavalin A causes visible agglutination of trefoil rhizobia in a direct agglutination assay at 10−6 M. Trefoil chemotactin does not cause agglutination at similar concentrations. The bacteria are attracted by chemotactin at concentrations below 10−7 M. Lectins that cause rhizobial agglutination do not serve as chemoattractants at these concentrations. A filter agglutination assay showed agglutination of the bacteria by concanavalin A at concentrations of 10−8 to 10−10 M. Chemotactin gives no agglutination in this assay at any concentration tested. Hence, the response of the bacteria to chemotactin probably is not due to agglutination.