bluuebunny/crossref_metadata_2025 huggingface dataset:
A CBR-based hybrid model for predicting a construction duration and cost based on project characteristics in multi-family housing projects
Authors: Koo ChoongWan , Hong TaeHoon , Hyun ChangTaek , Koo KyoJin
Published: May 2010

Decision-making in the early stage of a project has a significant impact on the project. However, limited and uncertain information on the project and a complex correlation among various factors that affect the project’s construction duration and cost, make it difficult to predict and manage the project. Therefore, this study developed a case-based reasoning (CBR)-based hybrid model with which to predict the construction duration and cost of a project in its early stage. One hundred and one cases among multi-family housing projects that were completed between 2000 and 2005 were used. The CBR-based hybrid model developed in this study is the result of integrating the advantages of (i) prediction methodologies, such as case-based reasoning, multiple regression analysis, and artificial neural networks, (ii) the optimization process using a genetic algorithm, and (iii) the probability distribution and the analysis process of outlier using Monte-Carlo simulation. The results of this study are expected to support the owners and managers who are in charge of estimating budget and construction duration in both public and private sectors, in predicting accurately the construction duration and cost at the business planning or early stage of a project.
Three-dimensional numerical study of flow structure in channel confluences
Authors: Shakibainia Ahmad , Tabatabai Mohammad Reza Majdzadeh , Zarrati Amir Reza
Published: May 2010

Channel confluence is one of the important features of each river system and some hydraulic structures. The features that can dominantly control flow characteristics in a confluence are confluence angle, discharge, width ratios, and Froude number of flow. Several research studies have been conducted however a comprehensive three-dimensional (3-D) numerical study of flow characteristics in a confluence has not yet been reported. In the present study, SSIIM2.0, a 3-D numerical model, is validated and applied to investigate secondary currents, velocity distribution, flow separation, and water surface elevation in different conditions. The results of the present study illustrate that flow structure and water surface variations in a confluence are highly influenced by confluence angle, discharge, and width ratios as well as Froude number because of their effect on flow deflection, separation, and secondary currents. The graphs from the present study can be used to analyze water surface variation, velocity field, and flow separation dimensions in difference conditions for engineering designs.
Ultrastructural analysis of the effect of netropsin on sporulation of Bacillus subtilis
Authors: Beaman Blaine L. , Burtis Kenneth C. , Doi Roy H. , Yeggy James P. , Stahly Donald P.
Published: May 2010

An electron microscopic analysis of Bacillus subtilis cells revealed that netropsin blocked sporulation ultrastructurally at stages 0–I. These observations are consistent with previous results which indicated that cells were not committed to sporulation in the presence of the drug. Further, the addition of netropsin up to stage III of sporulation prevented the normal sharp increase in dihydrodipicolinate synthase activity which results in dipicolinic acid accumulation at stage IV. The addition of netropsin after stage III had much less effect on the synthesis of dihydrodipicolinate synthase and on sporulation. Thus, morphological events in sporulation are blocked early whereas a sporulation-associated enzyme may be affected at later stages. These data indicate that netropsin affects the expression of sporulation-associated genes in a differential manner.
The effect of NaCl on the upper temperature limit for growth of and enterotoxin synthesis by Staphylococcus aureus
Authors: Hughes A. , Hurst A.
Published: May 2010

The upper temperature limit for growth of an enterotoxin A producing strain (MF 31) and of an enterotoxin B producing strain (S6) was about 44–45 °C in either a peptone-based medium or heart infusion broth. In the presence of NaCl, growth and production of enterotoxin, coagulase, and thermostable nuclease occurred up to 2 °C higher. The optimal concentration of NaCl for the temperature elevation effect was 1 M.
Enteric viruses in renovated water in Manitoba
Authors: Sekla L. , Stackiw W. , Kay C. , VanBuckenhout L.
Published: May 2010

Using various concentration procedures (including the gauze pad method, ultrafiltration, and adsorption–elution), enteric viruses, mainly vaccine strains of polioviruses, were isolated from 61.8% of sewage, 20.5% of effluents, 3.0% of river water, and 6.7% of drinking water samples collected from a waterway system in Manitoba. The presence of polioviruses in the drinking water of the town utilizing this waterway was not correlated with an increase in the number of infectious diseases reported.
The atypical cell wall composition of Thermomicrobium roseum
Authors: Merkel G. J. , Durham D. R. , Perry J. J.
Published: May 2010

The cell wall of Thermomicrobium roseum, a Gram-negative, obligately thermophilic bacterium, has a composition unlike other Gram-negative thermophilic organisms. The purified cell wall was composed predominantly of a protein with a monomeric molecular weight of 75 000. The amino acid composition of this protein revealed high concentrations of proline, glutamic acid, glycine, and alanine.
Dynamics of Rhizobium competition for nodulation of Pisum sativum cv. Afghanistan
Authors: Broughton W. J. , Egeraat A. W. S. M. van , Lie T. A.
Published: May 2010

Nodulation of Pisum sativum cv. Afghanistan by Rhizobium leguminosarum strain Tom can be blocked by the nonnodulating R. leguminosarum strain PF2. This system was used to study the dynamics of rhizobial binding to seedling root surfaces. Appreciable numbers of 35S-labeled rhizobia bound to the root surface within 2 h after inoculation. PF2 colonized the root surfaces earlier and in greater numbers that did Tom. Radioactive extracellular polysaccharides and lipopolysaccharides from either organism failed to bind to the seedling roots in measurable quantities.
Unique aspects of the cell surface polysaccharide of Pseudomonas phaseolicola as demonstrated by bacteriophage specificity
Authors: Anderson Anne J.
Published: May 2010

Bacteriophage 12P caused lysis of Pseudomonas phaseolicola but not other plant pathogenic or saprophytic pseudomonads. Specificity of the bacteriophage may depend on recognition of some unique feature of the P. phaseolicola cell surface polysaccharides. Exopolysaccharide (EPS) and lipopolysaccharide (LPS) from P. phaseolicola were more efficient at inhibiting bacteriophage attachment than were identically prepared extracts from five other pseudomonad species. Mutants of P. phaseolicola with bacteriophage resistance produced EPS and LPS different in amount and composition from those of the parental strain. Thus, in some manner the EPS and LPS structures of P. phaseolicola are distinct from those of other plant pathogenic and saprophytic species. The difference may prevent recognition and initiation of resistance events when P. phaseolicola challenges its susceptible host plant, bean.
The role of delayed hypersensitivity in the enhancement of host resistance to infection
Authors: Hsu H. S. , Miller Kathy B. , Nakoneczna Irene
Published: May 2010

Swiss-Webster mice were vaccinated by the intraperitoneal route (i.p.) with Mycobacterium tuberculosis BCG and challenged i.p. 4–10 weeks later with 104 virulent Salmonella typhimurium in the presence or absence of purified protein derivative (PPD) of tuberculin. Normal control mice were similarly challenged. Such an infection was fatal to the normal mice within 12 days. BCG vaccination prolonged the survival time and protected about 36% of the salmonella-infected mice from death. In contrast, tuberculin sensitivity, elicited in the BCG-vaccinated mice, significantly increased the survival time and protected about 70% of the mice against an otherwise fatal challenge. When these experiments were repeated using an infective dose of 106 organisms, the protective effect of the tuberculin reaction became substantially reduced, but there remained a statistically significant improvement in the survival distribution of the challenged mice as compared with that among the BCG-vaccinated mice. The examination of peritoneal washings obtained from BCG-vaccinated mice stimulated with PPD showed that the enhanced resistance to salmonella infection was directly associated with a quantitatively increased influx of phagocytic leukocytes accumulating at the site of infection as a result of the elicitation of tuberculin sensitivity.
Aeromonas hydrophila in rainbow trout: relation between virulence and surface characteristics
Authors: Mittal K. R. , Lalonde G. , Leblanc D. , Olivier G. , Lallier R.
Published: May 2010

Motile Aeromonas isolated from fish were studied for their virulence in fish in relation to some surface characteristics. The results showed that only the most virulent strains of A. hydrophila used in this study shared a common O antigen, did not agglutinate in acriflavine, settled down after boiling, and were resistant to the bactericidal action of fresh normal mammalian serum. The least virulent strains could not be grouped into this O antigenic group, they did not settle after boiling, and were sensitive to the bactericidal effect of serum. It is suggested that agglutination in acriflavine, stability after boiling, and sensitivity to normal fresh serum could be used for screening the Aeromonas isolates for virulence in fish.
Sclerotia of the Gasteromycete Pisolithus tinctorius
Authors: Dennis John J.
Published: May 2010

Hyphal masses, morphologically identified as the sclerotia of Pisolithus tinctorius, were found associated with root systems of containerized pine seedlings inoculated with this mycorrhizal fungus. The sclerotia are described and the results and method used for isolation are reported.
A single medium for the isolation of acetylene-reducing (dinitrogen-fixing) bacteria from soils
Authors: Rennie R. J.
Published: May 2010

A single medium, containing standard basal salts and three common carbon sources (sucrose, mannitol, and sodium lactate) is proposed to replace nitrogen-free media in common use for isolating dinitrogen-fixing bacteria. Eight commonly isolated genera of dinitrogen-fixing bacteria exhibited growth on this combined carbon medium that equalled or bettered growth on other carbon-containing media. Combined carbon medium also yielded the highest counts of putative dinitrogen-fixing bacteria from three southern Alberta soils. A survey of the bacteria isolated aerobically from the Burdett soil on combined carbon agar indicated that, at higher dilutions, 75% of the isolates exhibited acetylene reduction. These bacteria were identified as Azospirillum spp., Bacillus polymyxa, B. macerans, Klebsiella pneumoniae, Erwinia herbicola, and Enterobacter cloacae. The inclusion of yeast extract in combined carbon medium is considered essential to supply organic growth factors and may supply "starter" nitrogen that promotes growth without inhibiting acetylene reduction.
Hyperbaric oxygen toxicity and ribosome destruction in Escherichia coli K12
Authors: Harley John B. , Flaks Joel G. , Goldfine Howard , Bayer Manfred E. , Rasmussen Howard
Published: May 2010

The viability of resting suspensions of Escherichia coli K12 Ymel exposed to air plus 300 psi (1 psi = 6.895 kPa) oxygen (hyperbaric oxygen) decreased as an apparent first-order process after an initial period of constant viability. Control suspensions exposed to air plus 300 psi nitrogen (hyperbaric nitrogen) did not lose viability over the 96 h of the experiment. It was observed that a decrease in the refractive index of the cells preceded the loss of viability in hyperbaric oxygen. This finding together with electron micrographs, which showed extensive loss of ribosomal particles in bacteria incubated in hyperbaric oxygen, led us to suspect that ribosome injury or disassociation might be important in hyperbaric oxygen toxicity. In support of this we found that cellular RNA, labeled with [5-3H]uridine, was much more rapidly and more completely degraded in hyperbaric oxygen than in hyperbaric nitrogen. Furthermore, a far greater proportion of RNA was degraded than was DNA or protein. A direct assay for ribosome particles by sucrose gradient centrifugation showed that only 34% of the 70S ribosome particles was lost during the first 24 h in hyperbaric nitrogen whereas in hyperbaric oxygen 99.6% of the 70S particles was degraded during the same period. In hyperbaric oxygen the rate of viability loss between 24 and 72 h was equal to the rate of 70S ribosome degradation during the first 24 h. If 70S ribosome disassociation in hyperbaric oxygen continues at the same rate after the first 24 h, then cumulative 70S ribosome disassociation or injury may lead to and provide an explanation for irreversible bacterial cell injury and the loss of viability.
Type I nitroreductases of Escherichia coli
Authors: Bryant D. W. , McCalla D. R. , Leeksma M. , Laneuville P.
Published: May 2010

Analysis of partially purified crude extract of Escherichia coli K12 by chromatography and gel electrophoresis has resulted in the separation of three distinct activities which catalyse the reduction of nitrofurazone (semicarbazone of 5-nitro-2-furaldehyde) in the presence of oxygen (type I nitroreductases). The major enzymatic activity (type IA), which was dependent solely on NADPH as a cofactor, was absent from nitrofurazone-resistant strains NFR 402 and NFR 502, but present in SIL 41, a strain which is only marginally resistant to the nitrofuran. The remaining nitroreductase activities (IB1 and IB2) utilize either NADH or NADPH as a cofactor. These activities coelute from DEAE-cellulose at pH 7.2, but may be differentiated by their behaviour on CM-cellulose at pH 5.8. The reductase activity missing in SIL 41 was observed in extracts of strain NFR 402 but not NFR 502. This enzyme (IB1) though retained by DEAE-cellulose had no affinity for CM-cellulose. The only reductase present in extracts of NFR 502 (a nitrofuran-resistant strain selected after two mutational events) was type IB2. This activity, also detectable in SIL 41 and NFR 402, has not been mapped genetically. An interesting feature of the type IB2 enzyme is its apparent inactivation by MnCl2 which has been routinely used as a partial purification step in the past.
Influence of methylheptenone and related phytoplankton norcarotenoids on heterotrophic aquatic bacteria
Authors: Reichardt W.
Published: May 2010

Certain norcarotenoids, which have recently been found as excretion products of freshwater cyanobacteria and algae, are potent inhibitors of different metabolic functions in heterotrophic bacteria. 6-Methylhept-5-en-2-one showed the strongest effects and acted as a noncompetitive inhibitor of both glucose uptake and respiration by aquatic isolates of Chromobacterium lividum and Arthrobacter sp. Inhibition of the heterotrophic potential of glucose uptake by 6-methylhept-5-en-2-one was characterized by considerably lower inhibitor constants for bacterial cultures (Ki = 0.4 and 1.6 μM) than for a river water sample (Ki = 186.0 μM).
Ethanol production by Zymomonas mobilis and Saccharomyces uvarum on aflatoxin-contaminated and ammonia-detoxified corn
Authors: Nofsinger G. W. , Bothast R. J.
Published: May 2010

Zymomonas mobilis demonstrated greater fermentative activity than Saccharomyces uvarum during the 1st day in the fermentation of two lots of aflatoxin-contaminated corn and two corresponding lots of ammonia-detoxified corn. Final ethanol yields and conversion efficiencies were generally highest in Zymomonas fermentations of ammonia-detoxified corn. Aflatoxin levels in postfermentation solids from ammonia-detoxified corn all ranged below the Food and Drug Administration feedstuff guideline of <20 parts per billion, whereas the amount of aflatoxin in postfermentation solids from aflatoxin-contaminated corn was greater than in the initial corn.
Immunochemical reactivity of simian sarcoma virus polypeptides isolated by preparative sodium dodecyl sulfate polyacrylamide gel electrophoresis
Authors: Johnson James C. , Higuchi Tomoko , Geissler Edwin
Published: May 2010

The polypeptides associated with a zonal centrifugation purified simian sarcoma virus propagated in lymphoblastoid NC-37 cells were isolated by preparative polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate (SDS) using a procedure designed to minimize the loss of immunochemical reactivity. The proteins p10, p15, p28, p36, p44, p75, and p86 were obtained in large yield and high degree of homogeneity. The electrophoretically purified p28 was analyzed by competition radioimmunoassay using antiserum to a pore exclusion and ion exchange purified simian sarcoma virus p28. Complete competition was observed with extracts of simian sarcoma virus infected cells. No competition was observed with uninfected or unrelated, infected cell extracts. The antigen–antibody affinity as measured by the slope of the competition curve using antiserum to p28 and 125I-labeled and electrophoretically purified p28 was the same as that for the p28 released from sonication-disrupted simian sarcoma virus. The data indicates that preparative purifications by polyacrylamide gel electrophoresis in the presence of SDS may be generally applicable for the isolation of proteins with essentially the same immuno-specificities and affinity for a specific antiserum as proteins isolated by procedures that avoid the use of SDS and electrophoresis.
Plasmid composition of Staphylococcus species
Authors: Kloos Wesley E. , Orban Barbara S. , Walker Diane D.
Published: May 2010

A total of 342 staphylococci representing 13 different recognized species were screened for plasmid composition using agarose gel electrophoresis techniques. Plasmids of molecular weight (MW) 30 × 106 or larger in size were uncommon in staphylococci. Moderately large plasmids of MW 15 × 106 to 29 × 106 were not or only occasionally found in the species Staphylococcus sciuri, S. intermedius, S. hyicus, or S. simulans, but were common in S. aureus (55%) and members of the S. epidermidis (79%) and S. saprophyticus (86%) species groups. Small plasmids were common in most of the species. They produced more complex profiles in simian subspecies or biotypes than in human subspecies or biotypes, e.g., in the species S. warneri, S. haemolyticus, S. cohnii, S. xylosus, and S. aureus. Although some of the species appeared to have rather unique plasmid patterns, we would currently hesitate to use this feature as a taxonomic character, considering the occurrence of exceptional strains and possible plasmid transfer between species.
Effect of sludge type on poliovirus association with and recovery from sludge solids
Authors: Pancorbo Oscar C. , Scheuerman Phillip R. , Farrah Samuel R. , Bitton Gabriel
Published: May 2010

Sludge type was found to affect the degree of association between seeded poliovirus type 1 (LSc) and sludge solids. The mean percent of solids-associated viruses for activated sludge mixed liquors, anaerobically digested sludges, and aerobically digested sludges was 57.2, 70.4, and 94.7, respectively. The degree of association between poliovirus and sludge solids was significantly greater for aerobically digested sludges than for the other two sludge types. Sludge solids associated viruses were eluted using 0.05 M glycine buffer, pH 10.5–11.0, and subsequently concentrated by organic flocculation. The effectiveness of the glycine method in the recovery of solids-associated viruses was also found to be affected by sludge type. Significantly lower mean poliovirus recovery was found for aerobically digested sludges (14.5%) than for mixed liquors or anaerobically digested sludges (72.3 and 60.2%, respectively). The eluent used in the method was not as effective in dissociating the virus from aerobic sludge solids as it was for the other two sludge types. All other virus adsorption–elution steps of the method (i.e., virus concentration steps) were equally effective in poliovirus recovery for all three sludge types. It is suggested that future methods developed for the recovery of viruses from sludges be evaluated for the various sludge types likely to be tested.
Cellulolytic enzyme system of Acetivibrio cellulolyticus
Authors: Saddler J. N. , Khan A. W.
Published: May 2010

Polyacrylamide gel electrophoresis of the cellulolytic system from culture supernates of Acetivibrio cellulolyticus showed the presence of four major enzymes: a β-glucosidase, an exoglucanase, and two endoglucanases. The relative proportions of these enzymes in the culture supernate were affected by the nature of the cellulosic substrate and by the length of the incubation period. The molecular weights of the cellulolytic enzymes were β-glucosidase, 81 000; exoglucanase, 38 000; endoglucanase C2, 33 000; and endoglucanase C3, 10 400, as estimated by their electrophoretic mobilities relative to proteins of known molecular weight. Treatment of the high molecular weight endoglucanase with SDS–mercaptoethanol led to reversible dissociation of the enzyme into polypeptide subunits similar to the low molecular weight endoglucanase. Endoglucanase activity could be assayed for directly using a novel method of incorporating carboxymethyl cellulose in the polyacrylamide gels. The molecular weights and functions of these enzymes are compared with those detected in culture filtrates of various fungi.
Isozyme differentiation among three pathotypes of the entomogenous fungus Nomuraea rileyi
Authors: Joslyn D. J. , Boucias D. G.
Published: May 2010

The zymogram technique has been applied to three pathotypes of the entomopathogenic fungus Nomuraea rileyi. Isozyme profiles of isolates from Heliothis zea, Pseudoplusia includens, and Anticarsia gemmatalis were compared for 17 enzymes of known metabolic function. Electrophoretic data supported the taxonomic differences inferred for the three pathotypes based on host specificity. The isolate from A. gemmatalis was found consistently to be the most distinct.This study demonstrates that isozyme analysis may be used to distinguish closely related fungal isolates of N. rileyi.
A scanning electron microscopy study of the invasion of leaflets of a bloat-safe and a bloat-causing legume by rumen microorganisms
Authors: Fay J. P. , Cheng K. -J. , Hanna M. R. , Howarth R. E. , Costerton J. W.
Published: May 2010

A newly developed technique using ruthenium red to detect foci of bacterial digestion in mounts of whole leaflets that had been incubated with rumen bacteria was used to compare the digestion of alfalfa, a bloat-causing legume, and sainfoin, a bloat-safe legume. When whole leaflets were suspended in an artificial rumen medium and inoculated with rumen bacteria, massive bacterial adhesion and proliferation were noted at the stomata of alfalfa leaflets after 6 h of incubation, whereas only a few isolated bacteria adhered near the stomata of sainfoin leaflets. After 22 h of incubation, the epidermal layers of alfalfa leaflets had peeled away in many areas, revealing an extensive bacterial invasion of the underlying mesophyll tissue in which large bacterial microcolonies had formed in intercellular spaces, and in intracellular spaces in several areas where plant cell walls had broken down. After 22 h of incubation, the surface of sainfoin leaflets resembled that of alfalfa leaflets at 6 h, with bacterial microcolonies adhering to the area surrounding the stomata, but without sloughing of the epidermis. Uninoculated control leaflets of both species showed no surface alterations but part of their normal bacterial flora had proliferated to form microcolonies on the surface after 22 h of incubation.Dry matter loss due to leaching or bacterial digestion when whole leaflets of legumes were suspended in an artificial rumen medium, alone or with rumen bacteria, was significantly higher in the bloat-causing group. Values of leaching and of bacterial digestion were positively correlated.We conclude that reported differences in plant anatomy, and in cell wall chemistry, produce distinct rates of organic nutrient release from legume leaflets, and that these same differences produce an equally distinct susceptibility of leaflets to bacterial invasion, plant cell rupture, and the consequent release of intracellular plant components. The rate of release of organic nutrients from legume leaflets may be important in the etiology of foamy pasture bloat.This technique of in vitro digestion of whole leaflets followed by ruthenium red staining shows some promise of providing a rapid and qualitative test to distinguish, within a species, cultivars that may differ in their bloat-related characteristics.
Alteration by heat activation of enzymes localized in spore coats of Bacillus cereus
Authors: Srivastava Om P. , Fitz-James Philip C.
Published: May 2010

Heat activation (70 °C for 20 min) resulted in alteration in structural proteins and enzymes found in Bacillus cereus spore coats. The three notable changes were increased glycosylation of coat proteins, alteration in polypeptide pattern on sodium dodecyl sulfate – polyacrylamide gels, and an increase in free SH groups of proteins. About three polypeptides leaked out in small quantities from the spore coats during heat activation.The extraction of five spore coat associated enzyme activities was followed during the coat stripping procedures, which left the cortex and core intact. Two of these activities, L-alanine dehydrogenase and purine nucleoside hydrolase, were solubilized when the undercoat was extracted by 1,4-dithioerythritol (DTE) at pH 9.8. Three other activities, a protease, a corticolytic enzyme, and purine nucleoside phosphorylase, were solubilized by both DTE alone and DTE plus urea at pH 9.8. The DTE plus urea extraction removed the two more insoluble coat layers, the outer cross-patch, and the inner pitted layers. Mutants deficient in the cross-patch layer contained normal amounts of the protease, corticolytic, and purine nucleoside phosphorylase activities suggesting their association with the pitted layer.In intact spores all five enzymes were found to be stable to the heat activation treatment. However, extracted and partially purified preparations of protease, purine nucleoside phosphorylase, and L-alanine dehydrogenase were heat sensitive. Similar preparations of corticolytic enzyme and purine nucleoside hydrolase were stable to the heat activation conditions.
Improved method for the use of proportioning injectors to condition large volumes of water for virological analysis
Authors: Payment Pierre , Trudel Michel
Published: May 2010

A bypass system with a valve permits the use of low flow rate injecting proportioners, which are much less sensitive to back pressure buildup. The system can be used to condition water at flow rates of 1–15 L/min during sampling procedures for virological monitoring by the Wallis–Melnick method.
Comparison of Marion's anaerobic culture/set-A and the Baltimore Biological Laboratory GasPak anaerobic system in the cultivation and recovery of bacteria from human dental plaque
Authors: Syed S. A. , Stoll J. , Harper S.
Published: May 2010

Marion's anerobic culture/set-A (Bio-Bag A) and the Baltimore Biological Laboratory (BBL) Gaspak anaerobic system were evaluated for their efficiency in the cultivation and recovery of anaerobes and capnophilic organisms from human dental plaque samples. Both culture systems were relatively efficient in supporting the growth of pure cultures of various bacterial species recently isolated from the human dental plaques. When the dental plaque samples were cultured the organisms commonly found were cultivatable in both culture systems. However, the counts and proportions of Fusobacterium nucleatum from the samples were significantly higher in Marion's culture system, whereas the proportions of black-pigmented Bacteroides sp. were significantly higher in the BBL anaerobic system.
The genetic and physical basis of variability in Escherichia coli strains carrying a reference Inc N group plasmid
Authors: Konarska-Kozlowska M. , Iyer V. N.
Published: May 2010

The nature and basis of variability in the conjugational behaviour of RM98+ (RM98-carrying) strains of Escherichia coli K-12 that are otherwise similar in phenotype was studied. An explanation for such variability is provided.Some RM98+ strains of E. coli have a plasmid aggregate, which upon conjugation yields two different conjugative plasmids. The first (pCU1) is an N conjugative group plasmid by all available criteria. The second (pCU2) could not be placed in any conjugative group known among the Enterobacteriaceae. Reciprocal DNA hybridization experiments and the gel patterns displayed by the two plasmid DNAs upon digestion with different restriction endonucleases indicate no extensive sequence homology between pCU1 and pCU2. pCU2 DNA is much longer than pCU1 DNA.Despite the absence of extensive homology, the DNA of pCU1 and pCU2 can interact. Derivatives can be selected that have all the antibiotic markers of the aggregate plasmid but that neither contain nor segregate pCU2. It is shown that in such strains a DNA fragment of molecular weight 7.9 × 106 has been added to pCU1 concurrently with a tetracycline resistance marker originally present in pCU2 and absent in pCU1. These observations suggest that tetracycline resistance in pCU2 may be part of a large translocatable element.RM98 has been used to designate a reference Inc N group plasmid. The results presented indicate that this can lead to ambiguity. pCU1 would now be the appropriate reference plasmid.
Identification of rumen bacteria that anaerobically degrade aliphatic nitrotoxins
Authors: Majak W. , Cheng K.-J.
Published: May 2010

Of 33 pure strains of rumen bacteria from the Lethbridge laboratory collection, 5 degraded both 3-nitropropanol (NPOH) and 3-nitropropionic acid (NPA) under anaerobic conditions, and another 5 strains degraded only NPA. The nitroacid was metabolized at a faster rate than the nitroalcohol by both pure cultures of rumen bacteria and mixed rumen microorganisms.Nitrite was detected during incubation of NPOH and of NPA with resting cells but not with growing cultures of active strains of rumen bacteria. Nitrite was metabolized much faster than the nitrotoxins by both pure cultures of rumen bacteria and mixed rumen microorganisms. The results suggest that the nitro moiety of NPA or NPOH is metabolized to inorganic nitrite and nitrite is reduced to ammonia by rumen microorganisms, thereby resulting in its detoxification.
Comparison of highly basic cyanogen bromide peptides from strains of southern bean mosaic virus
Authors: Tremaine J. H. , Ronald W. P. , Kelly E. M.
Published: May 2010

Electrophoresis patterns of cyanogen bromide (CNBr) peptides from the proteins of the cowpea (SBc), bean (SBb), Mexican (SBm), and Ghana (SBg) strains of southern bean mosaic virus showed a marked similarity between SBc and SBg and between SBb and SBm. A highly basic CNBr peptide from SBc, cCB-1, was isolated by Sephadex and ion-exchange chromatography. The size and amino acid composition of cCB-1 was similar but differed from that of the N-terminal CNBr peptide bCB-1 from SBb described previously.Antisera to cCB-1 or bCB-1 conjugated to tomato bushy stunt virus (TBSV) were used in gel diffusion tests with virus particles of the four SB strains. With the bCB-1–TBSV conjugate antiserum, SBb gave a reaction of identity with SBm and reactions of partial identity with SBc and SBg. With the cCB-1–TBSV conjugate antiserum, SBc gave a reaction of identity with SBg and reactions of partial identity with SBb and SBm. Cross absorption of bCB-1–TBSV conjugate antiserum with TBSV yielded an antiserum that reacted with SBb but not with TBSV. Cross absorption with bCB-1 yielded an antiserum that reacted with TBSV but not with SBb.Limited tryptic proteolysis of SBc in 0.01 M sodium phosphate buffer containing 0.01 M ethylenediaminetetraacetic acid, pH 8.0, resulted in the formation of viruslike particles and smaller spherical particles. Sixteen peptides were isolated from these digests and the compositions of most of them were similar to but not identical to peptides isolated from limited tryptic proteolysis of SBb.
Use of fluorescence microscopy for monitoring periodontal disease state
Authors: Chan E. C. S. , Vries J. de , Harvey R. F. , Tam Y.-C.
Published: May 2010

Samples of subgingival plaque from patients with periodontal disease and control subjects were stained with the Fluoretec fluorescent test kits (Pfizer Inc., New York) developed for the rapid detection of members of the Bacteroides fragilis and B. melanino genicus groups of anaerobes. The same fluorescent fields were also examined by dark-field microscopy for the total count of bacteria. Bacteroides fragilis and B. melaninogenicus were found in plaque samples of healthy subjects and periodontally diseased patients with no significant difference in percent of total flora. Oral spirochetes also fluoresced with the antisera used. Samples from healthy sites showed virtually no spirochetes; spirochetes were present in diseased sites. Tests with other antisera also showed that fluorescein-labelled antibodies can be absorbed nonspecifically to the surface of spirochetes. Such a phenomenon can be used to monitor an individual's periodontal disease state.
The influence of nutrition and temperature on the growth of colonies of Escherichia coli K12
Authors: Lewis Mary W. A. , Wimpenny Julian W. T.
Published: May 2010

Growth of Escherichia coli was faster in liquid cultures than on the same medium solidified with agar. Colony profiles indicated a common basic structure with a size variation due to nutritional conditions. Radial growth rates were linear and height also increased approximately linearly, especially in the early part of the growth period. The ratio of rate of height increase to diameter increase depended on nutrition. Conditions favouring rapid growth led to faster radial growth relative to height increase. A rise in incubation temperature led to increases in height and in diameter; however, diameter increased relatively more than height. These results are discussed in terms of the structure of the colony.
The transmembrane electrical potential and intracellular pH in methanogenic bacteria
Authors: Jarrell Ken F. , Sprott G. Dennis
Published: May 2010

The magnitudes of the electrical potential and proton gradient in Methanospirillum hungatei GP1 and Methanobacterium thermoautotrophicum were determined. No ΔpH (inside alkaline) could be demonstrated in either organism suspended in growth media at normal growth pH values by the distribution of 5,5-dimethyl-2,4-oxazolidinedione (DMO), butyrate, propionate, or methylamine. The internal pH, estimated to be approximately 6.7 under our growth conditions, was not constant, but varied as the external pH was adjusted. However, the internal pH was always more neutral than the external pH (except at pH 6.7 where the two were equal). The distribution of triphenylmethylphosphonium cation, in the presence of tetraphenylboron anion, gave estimates of 119 and 79 mV (interior negative) for the electrical potentials of the thermophile and mesophile, respectively, for cells suspended in a phosphate buffer (pH 7.0). The uptake of 86Rb+, in the presence of valinomycin, gave similar results for M. thermoautotrophicum, ranging from 143 mV (at pH 5.8) to 120 mV (at pH 8.0). Electrical potentials compared to the size of the respective K+ gradients, maintained between the cytoplasm and growth medium. The results are interpreted in terms of proton efflux and monovalent cation antiport activities at the cytoplasmic membrane, with possible proton pumping at the site of internal vesicles.
Differences in virulence for mice between disease and carrier strains of Neisseria meningitidis
Authors: Holbein Bruce E.
Published: May 2010

The virulences of 11 prototype strains of Neisseria meningitidis, which had been used in the development of the serotyping scheme for serogroup B meningococci, were examined in mice treated with iron dextran. These strains, together with those previously examined, allowed for a good assessment of the virulence differences between carrier and disease strains. All of a total of 17 disease strains displayed virulence for mice (60% with high virulence), whereas only approximately 50% of 13 carrier strains possessed virulence (only 15% with high virulence).Because the ability to initiate infection in mice is independent of exogenous iron, this model system for infection appears particularly suited to studies of the physiological bases for virulence in N. meningitidis.
The reduction of trimethylarsine oxide by Candida humicola
Authors: Pickett A. W. , McBride Barry C. , Cullen W. R. , Manji H.
Published: May 2010

Trimethylarsine oxide, a probable intermediate in the biological transformation of arsenate, was reduced to volatile trimethylarsine by Candida humicola. A simple assay for the rate of trimethylarsine production from trimethylarsine oxide by the fungus was developed. The optimum pH for the reduction was determined as 5.1–5.2, and the optimum temperature was 40 °C. The rate of reduction was directly proportional to cell concentration and followed Michaelis–Menten type kinetics. There was almost no trimethylarsine produced by heated or broken cells. The reaction was inhibited by a number of electron transport inhibitors and uncouplers of oxidative phosphorylation including cyanide, azide, and 2,4-dinitrophenol. The rate of reduction was modified by arsenate, methylarsonate, dimethylarsinate, selenate, and tellurate. Preincubation of cells with trimethylarsine oxide increased the rate of reduction 69-fold; this increase in activity was blocked if the cells were incubated with the protein synthesis inhibitor cycloheximide.
Purification by affinity chromatography of a membrane dicarboxylate binding protein from Bacillus subtilis
Authors: Kay William W.
Published: May 2010

Membrane vesicles of Bacillus subtilis W23 actively transport the C4 and C5 dicarboxylates of the tricarboxylate cycle by system(s) of relatively high affinity for their requisite substrates (Km 4–53 μM). Glutamate and succinate binding activities were readily solubilized from membrane vesicles by nonionic detergents, particularly by Lubrol WX. From this extract, glutamate binding activity was highly enriched by affinity chromatography on phloroglucinol-expanded Sepharose-6B to which L-aspartate was coupled via divinylsulfone. Another protein (41 000 molecular weight), which bound both L-glutamate and L-malate, was purified from affinity columns to which either L-glutamate or L-malate had been coupled via bisdiglycidyl ether. This protein bound labelled L-malate as well as L-glutamate with affinities similar to those seen with membrane vesicles (Kd's 8 μML-malate and 52 μML-glutamate).
2-Phosphoglycerate phosphatase and serine biosynthesis in Veillonella alcalescens
Authors: Pestka J. J. , Delwiche E. A.
Published: May 2010

The constituent enzymes for the phosphorylated and nonphosphorylated serine biosynthetic pathways in Veillonella alcalescens were identified and included phosphoserine phosphatase, 3-phosphoglycerate dehydrogenase, glycerate dehydrogenase, phosphoserine aminotransferase, and serine–pyruvate aminotransferase. Cell extracts of the organism were also found to cause the specific dephosphorylation of 2-phosphoglycerate. The phosphatase was purified 39-fold by manganese chloride precipitation, ammonium sulfate precipitation, and DEAE-cellulose chromatography. Sephadex G-200 gel filtration data established an apparent molecular weight of 50 000 for the enzyme. The 2-phosphoglycerate phosphatase had a pH optimum of 5.5 and was distinct from phosphoglyceromutase. Assays conducted with the purified enzyme on a number of other phosphorylated intermediates indicated that the phosphatase was most specific for 2-phosphoglycerate. Glucerate, hydroxypyruvate, and serine inhibited the enzyme, whereas succinate stimulated activity. Veillonella 2-phosphoglycerate phosphatase is the first such enzyme to be described in a prokaryote and is probably involved in glycerate generation for the nonphosphorylated serine biosynthetic pathway.
The effect of temperature and other growth conditions on the fatty acid composition of Escherichia coli
Authors: McGarrity James T. , Armstrong John B.
Published: May 2010

During exponential growth, strain AW405 of Escherichia coli K-12 did not regulate the fatty acid composition of its lipids in response either to temperature or to the addition of NaCl, KCl, or MgCl2 to the medium. Growth was severely restricted at temperatures below 21 °C. Differential scanning calorimetry (DSC) of the isolated lipids from a culture with a typical exponential-phase composition yielded a broad transition, extending from approximately 0 to 33 °C, with a midpoint at 19 °C.During late stages of growth, the fatty acid composition changed. The percentage of palmitic acid increased and cyclopropane fatty acids replaced some of the equivalent unsaturated fatty acids. The increase in palmitate seemed largely independent of growth conditions, whereas the increase in the cyclopropane fatty acids was stimulated by the addition of salts or sucrose. Cultures grown in the presence of sucrose also had higher cyclopropane fatty acid levels during exponential growth. DSC of lipids from a sucrose culture, in which the compositional changes were most pronounced, yielded a much narrower transition with a midpoint at 27 °C.
Observations of fouling biofilm formation
Authors: McCoy W. F. , Bryers J. D. , Robbins J. , Costerton J. W.
Published: May 2010

Fouling biofilm development was monitored in a completely mixed tubular recycle reactor. A unique sampling system allowed direct (brightfield, epifluorescence, and scanning electron photomicroscopy) and indirect (increased fluid frictional resistance) observations of biofilms. Low fluid velocity (138.5 cm/s) experiments had shorter induction times and biofilm matrixes which included firmly adherent filamentous bacteria. High fluid velocity (265.4 cm/s) experiments had longer induction times with firmly adherent filamentous bacteria present only after the accumulation of extracellular materials. In both cases the fluid frictional resistance increased after filamentous bacteria became a permanent part of the biofilm.
Hydroxyproline-rich protein in the capsule of a strain of Staphylococcus aureus
Authors: Usui Yukio , Yoshida Kosaku , Clemente C. L. San
Published: May 2010

A protein fraction containing a high amount of hydroxyproline was found in the capsule of the Smith diffuse strain (encapsulated) when compared with that of dialysate medium. This content varied depending upon temperature, oxygen supply, sodium chloride, and carbohydrates. The hyroxyproline content of the single proteinaceous fraction, obtained by Sephadex G-200 column chromatography, was one fourth of the total amino acid composition.
Virosome preparation: differences between influenza and rubella hemagglutinin adsorption
Authors: Trudel M. , Nadon F.
Published: May 2010

Rubella and influenza virosomes were prepared from preformed liposomes or dried lipid films with or without nonionic detergent (β-D-octylglucoside. The preformed liposomes and lipid films were prepared from lecithin and dicetyl phosphate (3.5:1). Viral hemagglutinin rosettes were prepared from purified viruses after solubilization with Triton X-100 (1%), centrifugation through a continuous sucrose gradient containing 30 mM octylglucoside, and dialysis. Analysis of virosomes by sucrose density gradient centrifugation, hemagglutination assay, and electron microscopy revealed that rubella hemagglutinin did not require the presence of detergent to form virosomes, whereas influenza hemagglutinin could absorb efficiently to liposomes only in the presence of detergent.
AMP metabolism by the marine bacterium Vibrio (Beneckea) natriegens: purification and properties of adenylate kinase
Authors: Ramotar Karamchand , Pickard Michael A.
Published: May 2010

Adenylate kinase (EC 2.7.4.3) has been purified 484-fold from extracts of Vibrio natriegens to a specific activity of 1350 μmol ADP formed∙min−1∙mg protein−1. The preparation was 97% pure as judged by gel electrophoresis and exhibited molecular weight values of 29 000 by gel filtration and 32 000 by SDS–gel electrophoresis. The isoelectric point was at pH 4.7. Only ATP (Km 0.067 mM), ADP (Km 0.45 mM), and AMP (Km 0.12 mM) exhibited high activity as substrates, though dATP or dAMP could serve as cosubstrates with AMP or ATP, respectively, at reduced rates. The equilibrium constant in the direction of ATP formation was 1.09, and the pH optimum in both directions was broad, from pH 7.2 to pH 7.6. Enzyme activity was sensitive to the thiolalkylating agents iodacetamide and p-chloromercuriphenyl sulfonate.
Comparison of iron binding and uptake from FeCl3 and Fe-citrate by Neisseria meningitidis
Authors: Archibald Frederick S. , Simonson Catherine , DeVoe I. W.
Published: May 2010

Iron-starved Neisseria meningitidis SD1C took up Fe added as FeCl3 by a two-step process: a rapid phase occurring during the 1st min after Fe addition and unaffected by 0.5 mM KCN and a slower secondary phase of uptake sensitive to various metabolic inhibitors. The rate and extent of energy-dependent Fe uptake from stable dicitrate and nitrilotriacetate Fe3+ complexes were essentially identical to FeCl3, indicating the presence of a high-affinity Fe acquisition system. The sulfonated siderophore Desferal (deferrioxamine β-mesylate) effectively prevented any uptake of Fe from the citrate complex and was unable to remove that Fe already bound by either poisoned or active cells. The energy-independent system rapidly deferrated Fe3+ dicitrate and bound Fe to a finite number of cellular sites. Fe derived from FeCl3 was associated with these same sites as well as with a large number of apparently nonspecific sites. The extent of low-affinity, nonspecific binding was concentration dependent. Both energy-independent and energy-dependent systems involved in the uptake of Fe from the Fe3+ dicitrate were inactivated by 5 min at 60 °C, but not by 45 °C. The citrate carrier itself was recycled, being neither bound separately nor in concert with Fe3+ by these sites.
Extracellular virulence factors of Aeromonas hydrophila in fish infections
Authors: Allan Brenda J. , Stevenson Roselynn M. W.
Published: May 2010

Aeromonas hydrophila NRC 505 produced extracellular substances which were capable of causing pathological effects when injected into trout. Proteolytic activity and haemolytic activity of the extracellular products, and the effect on fish, were lost on heating. The extracellular substances from strain G35, a protease-deficient mutant, were significantly more toxic to both rainbow trout (Salmo gairdneri) and speckled trout (Salvelinus fontinalis) than the analogous preparation from the parental strain NRC 505. The response of speckled trout injected intraperitoneally with dilutions of the extracellular preparations implicates haemolytic activity as a significant lethality factor.
Replication and serial passage of a multicapsid nuclear polyhedrosis virus of Orgyia pseudotsugata (Lepidoptera: Lymantriidae) in continuous insect cell lines
Authors: Sohi S. S. , Percy Jean , Cunningham J. C. , Arif B. M.
Published: May 2010

A multicapsid nuclear polyhedrosis virus (MNPV) of the Douglas-fir tussock moth, Orgyia pseudotsugata, propagated in larvae of the white-marked tussock moth, O. leucostigma, was successfully grown in two continuous cell lines developed from minced neonate larvae of O. leucostigma. Polyhedral inclusion bodies (PIBs) appeared in the nuclei of cells within 24 h after inoculation. Cytopathological changes, as revealed by light and electron microscopy, were typical of an MNPV. The virus has been passaged in the cell cultures 55 times. The level of infection during passaging has varied from 15 to 98% of the cells, and the number of PIBs per cell from 10 to 40. The PIBs from the fourth passage of the virus in cell cultures were almost as pathogenic to O. leucostigma larvae as the PIBs produced in larvae.