bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of oxygen supply during growth on the production of cytochromes, enzymes, and acid end products by Haemophilus parasuis
Authors: Martin P. G. , Niven D. F.
Published: May 2010

Haemophilus parasuis, grown under conditions of high aeration, was found to lack a tricarboxylic acid cycle but to possess phosphoenolpyruvate carboxylase and a reductive pathway leading to the production of succinate. Such organisms contained approximately equal quantities of b-, c-, and d-type cytochromes and excreted acetate. When the oxygen supply for growth was either reduced or eliminated, the specific activities of phosphoenolpyruvate carboxylase, malate dehydrogenase, fumarase, fumarate reductase, and NADH:fumarate oxidoreductase were increased substantially, and the acid products were succinate, acetate, and formate. Organisms grown under the latter conditions also contained increased quantities of b- and c-type cytochromes, some of which were low-potential cytochromes. These low-potential cytochromes were reduced by NADH and oxidized by fumarate, and hence, appeared to be components of NADH:fumarate oxidoreductase. Our results indicate that in H. parasuis, growing aerobically in medium containing glucose, the sole function of the reductive pathway is to provide intermediates for biosynthetic processes, and oxygen is the preferred electron acceptor. As the supply of oxygen is reduced or eliminated, the reductive pathway becomes more involved in NAD+ recycling and fumarate becomes the acceptor. In effect, irrespective of the oxygen supply, the growth of H. parasuis is absolutely dependent upon the presence of an electron transport system. Key words: Haemophilus parasuis, cytochromes, enzymes, acids.
Interaction between flocculent and nonflocculent cells of Saccharomyces cerevisiae
Authors: Soares Eduardo V. , Teixeira José A. , Mota Manuel
Published: May 2010

Interaction between nonflocculent and flocculent cells of Saccharomyces cerevisiae was studied. Adhesion experiments were done using three types of nonflocculent cells and a flocculent one. Two types of nonflocculent cells were obtained from the flocculent strain by changing environmental growth conditions. The integration of nonflocculent cells in the flocs was observed by two different methods: measurement of the sedimentation capacity of mixtures and microscopic observation of stained nonflocculent cells blended with flocculent cells. It was possible to verify that cell–cell interaction corresponds to a true stable binding and not to a simple entrapment inside the floe matrix. Key words: yeast, Saccharomyces cerevisiae, flocculation, adhesion.
Ergosterol content of living and submerged, decaying leaves and twigs of red mangrove
Authors: Newell S. Y. , Fell J. W.
Published: May 2010

Ergosterol was measured in red-mangrove (Rhizophora mangle) materials as an index of eumycotic fungal mass. Living green and senescent leaves and living twigs contained no detectable ergosterol (< 1μg∙g organic mass −1). After falling into the water and reaching the red–brown stage of decomposition (mass loss of about 30%), leaves exhibited ergosterol contents ranging from undetectable to 19 μg∙g−1. At the black submerged stage (mass loss of about 40–60%), ergosterol contents of leaves ranged from undetectable to 85 μg∙g−1. Submerged, decaying twigs and dead twigs on the tree had similar ranges of ergosterol content (9–79 μg∙g−1). The maximum value for standing crop of eumycotic fungal mass in submerged, decaying mangrove materials, calculated on the basis of the present ergosterol analyses, was 1.7% organic fungal mass of organic leaf mass. It may be that marine oomycotes (species of Halophytophthora), which do not contain ergosterol, are more important than ergosterol-containing fungi in decay of submerged mangrove leaves. Key words: ergosterol, mangrove, decomposition, fungi, oomycotes.
Inhibition of microbial adherence by sphinganine
Authors: Bibel Debra Jan , Aly Raza , Shinefield Henry R.
Published: May 2010

Sphingosines (precursors and degeneration products of complex sphingolipids) are mediators in membrane second-messenger cascades and in a wide variety of functions in eukaryotic cells. Sphingosines are also lethal for gram-positive microorganisms. In addition to its direct effect, sphinganine is here reported to affect the adherence of Streptococcus mitis to buccal epithelial cells and of Staphylococcus aureus to nasal mucosal cells after incubation for 90 min at 37 °C. When the bacteria were pretreated with 8.1, 16.2, 32.5, or (for Strep. mitis) 65 μM sphinganine for 60 min at 37 °C, adherence counts were reduced for Staph. aureus by 27, 37, and 60% and for Strep. mitis by 19, 44, 54, and 73%, respectively (p < 0.001). In contrast, pretreatment of buccal cells with 81.2 μM lipid increased adherence by 14% (p < 0.01), but no change occurred at either 16.2 or 325 μM lipid. These results further demonstrate the double-edged ability of sphingosines to regulate cellular activities and their potential as multifunctional therapeutic agents for infectious diseases. Key words: adherence, sphingosine, Staphylococcus aureus, Streptococcus mitis.
Use of phage JHJ-1 to assess restriction in the genus Saccharopolyspora
Authors: Gaudreau Luc R. , Boucher Dominique , Lavoie Jean M. , Brzezinski Ryszard , Déry Claude V.
Published: May 2010

Restriction of phage growth occurred when phage JHJ-1 propagated in one member of the genus Saccharopolyspora (S. hirsuta, S. taberi, S. rectivirgula, or the erythromycin-producing S. erythraea) was used to infect a different member. Of several S. erythraea strains tested, S. erythraea NRRL 2359 exhibited the weakest restriction. Phage SE-3 did not appear to be strongly restricted in Saccharopolyspora strains, whereas restriction of phages FRb-P and FRa-C was confined mainly to S. hirsuta NRRL B-5792. There was no correlation between the restriction of phage growth and the presence of exocytoplasmic DNAse. Key words: Saccharopolyspora, restriction, host range, bacteriophage JHJ-1, bacteriophage SE-3, bacteriophage FRa-C, bacteriophage FRb-P.
Plasmids from Xylella fastidiosa strains
Authors: Chen J. , Chang C. J. , Jarret R. L.
Published: May 2010

Plasmids were observed from three strains of Xylella fastidiosa. A restriction map of a plasmid, pXFPW1 of 1.3 kb, isolated from Xyl. fastidiosa strain PWT-22, causing periwinkle wilt disease, was constructed using EcoRI, HaeIII, HinfI, MspI, StyI, and TaqI fragments. No restriction site for BamHI, BglI, DraI, EcoRV, HindIII, PstI, SalI, NcoI, or XbaI was evident. Studies based on the intensity of ethidium bromide staining indicated that there are at least 60 copies of pXFPW1 per genome. pXFPW1 shares a high degree homology with two other plasmids from strains PD82-21 and mul1, the pathogens of Pierce's disease of grapevine and mulberry leaf scorch disease, respectively. Key words: Xylella fastidiosa, plasmids.
Rotavirus electropherotypes in Malaysian children
Authors: Yap K. L. , Wong Y. H. , Khor C. M. , Ooi Y. E.
Published: May 2010

A 12-month study was carried out on the molecular epidemiology of rotavirus in urban and suburban Malaysian children. Analysis of faecal samples from 973 hospitalized diarrhoeic children by polyacrylamide gel electrophoresis detected 268 rotaviruses (28%). All isolates were group A rotaviruses, which produced 22 electropherotypes: 16 (91.5%) with long RNA migration patterns and 6 (8.5%) with short patterns. One of the long-pattern electropherotypes was the predominant strain (71.1% of the total electropherotypes) isolated during this study. Although 3 other strains were detected sporadically over the study period, 16 others were present only during the first 7 months and 2 others were confined to the last 5 months. Long- and short-pattern electropherotypes were found to co-circulate extensively. There was a significant association of short-pattern electropherotypes with infection in older children. In addition, the prevalence of vomiting and mean duration of diarrhoea were significantly associated with different electropherotypes. Key words: rotavirus electropherotypes.
Characterisation of Rhizobium isolates by amplification of DNA polymorphisms using random primers
Authors: Harrison Stephen P. , Mytton Lance R. , Skøt Leif , Dye Malcolm , Cresswell Ann
Published: May 2010

The use of single random primers, selected in the absence of target sequence information, has been shown to be effective in producing DNA amplifications that provide fingerprints which are unique to individual organisms. DNA amplification by random priming was applied to the DNA from isolates of Rhizobium leguminosarum biovar trifolii. Amplification products were produced using a number of primers, and the resulting fingerprints allowed strain differentiation. However, the effectiveness of primers was dependent upon length and GC content. It was also possible to amplify DNA directly from cells in culture and in nodule tissue. Lysis of these cells was achieved simply through heat applied in the initial DNA denaturation stage of the thermal reaction. The ability to produce varied amplification patterns from different Rhizobium isolates, especially directly from nodules, gives this method potential for use in examining genetic structures and relationships in Rhizobium populations. Key words: Rhizobium, DNA amplification, random primers.
Possible ecological implications of the high cell surface hydrophobicity of the fish pathogen Aeromonas salmonicida
Authors: Enger Øivind , Thorsen Berit K.
Published: May 2010

The abundance of the fish pathogenic bacterium Aeromonas salmonicida in different parts of the marine environment was determined in a fish farm stocked with Atlantic salmon (Salmo salar) suffering from furunculosis. By application of highly specific monoclonal antibodies and immunofluorescence techniques, the bacterium was found in high abundances (4.3 × 103 cells/mL) at the air-water interface. Aeromonas salmonicida was also registered in high numbers in the sediments beneath the farm, and in moderate to low numbers in the water column. When samples were collected in the environment outside the fish farm, the number of A. salmonicida was below the detection limit in surface samples, but the bacterium could be detected in the water column in samples collected downstream to the farm. The high number of A. salmonicida found in the lipid-rich air-water interface is discussed, taking into consideration the high hydrophobicity of the cell surface of the bacterium and the physical and ecological conditions in this specific habitat. Key words: immunofluorescence, total bacterial counts, surface microlayer, furunculosis.
Development and comparison of methods for measuring growth of filamentous fungi on wood
Authors: Boyle C. David , Kropp Bradley R.
Published: May 2010

Measures of fungal growth with potential for use on wood-chip media were developed. These included (i) visual inspection, (ii) substrate dry weight loss, (iii) rate of fluorescein diacetate hydrolysis, (iv) extractable protein content, and (v) chitin content of the colonized substrate. The responses of the various assays to different growing conditions were assessed by using them on measured weights of mycelium, collected at intervals from liquid media with various composition. Growth of various species on either nutrient supplemented or unsupplemented wood chips was then measured. Each assay measured a different aspect of growth. The relationship between these changed in a distinctive way for each species during growth. Chitin gave the best measure of biomass, whereas fluorescein diacetate hydrolysis was a measure of growth-related metabolic activity. The protein and substrate dry weight loss data gave information about fungal protein and carbohydrate metabolism of the species, respectively. Addition of nutrient supplement to the wood increased both biomass and growth-related metabolic activity. It also increased the amount of wood used to produce a given amount of biomass by about 500% with some species. Some species showed a strong capacity to lower their cellular protein concentration during growth, which is probably of advantage for growth on a low-N substrate such as wood. Used together, the assays gave insight into different strategies fungi use to grow on wood. Key words: fungi, growth, chitin, fluorescein diacetate.
Distribution quantitative et qualitative des actinomycètes dans les horizons de sol de surface et profonds d'une palmeraie algérienne
Authors: Sabaou Nasserdine , Hacène Hocine , Bennadji Achour , Bennadji Hayet , Bounaga Nicole
Published: May 2010

Qualitative and quantitative distributions of actinomycetes were studied in surface and deeper soil horizons of a palm plantation in Algeria. The distributions were influenced directly by certain morphological and pedological factors of horizons, among which, the most important besides depth, were the quantity and quality of organic matter, clay abundance and calcareous content. Determination of 350 isolates showed that the genus Streptomyces was dominant in most of the horizons, with the exception of two of them, where Actinomadura and Nocardioides species were proliferating. However, whereas soil surface horizons contained very diversified species, each deeper horizon was characterized by the dominance of a particular species, often to a considerable extent. In a decreasing order of importance, the following species were found among the dominant: Streptomyces coerulescens in very deep reddish brown clay–silt sandy soils; Actinomadura cremea in light brown and sandy–silt soils; Nocardioides albus and Streptomyces aurantiogriseus in yellow nearly inorganic sandy soils. The influence of the above factors upon species distribution is discussed. Key words: actinomycetes, systematics, ecology. [Journal translation]
Expression of the 4-chlorobenzoate dehalogenase genes from Pseudomonas sp. CBS3 in Escherichia coli and identification of the gene translation products
Authors: Savard Pierre , Charest Hugues , Sylvestre Michel , Shareck François , Scholten Jeffrey D. , Mariano Debra Dunaway
Published: May 2010

The genes encoding the 4-chlorobenzoate dehalogenase of Pseudomonas sp. strain CBS3 were, in an earlier study, cloned in Escherichia coli DH1 with the cosmid vector pPSA843 and then mobilized to the 4-chlorobenzoate dehalogenase minus strain Pseudomonas putida KT2440. In this paper we report on the expression of 4-chlorobenzoate dehalogenase in these clones and on the polypeptide composition of the active enzyme. The dehalogenase activity in whole cells suspended in 3.2 mM 4-chlorobenzoate (30 °C) was determined to be approximately 27 units (micromoles 4-hydroxybenzoate produced per minute) per 100 g of E. coli - pPSA843 cells and approximately 28 units per 100 g of P. putida-pPSA843 cells. Dehalogenase activity in fresh cellular extracts (pH 7.4, 30 °C) prepared from the is. E. coli and P. putida clones was unstable and at least 20-fold lower than that observed with the whole cells. The polypeptide components of the dehalogenase were identified by selective expression of the cloned dehalogenase genes and analysis of the gene translation products. Analysis of dehalogenase activity in Ω insertion mutants and deletion mutants circumscribed the dehalogenase genes to a 4.8-kilobase (4.8 kb) stretch of the 9.5-kb DNA fragment. Selective expression of the dehalogenase genes from a cloned 4.8-kb DNA fragment in a maxicell system revealed a 30-kDa polypeptide as one of the components of the dehalogenase system. Selective expression of the dehalogenase genes using the T7 polymerase promoter system revealed the 30-kDa polypeptide and 57- and 16-kDa polypeptide products. Determination of which of the three polypeptides were translated in deletion mutants provided the relative positions of the encoding genes on a single DNA strand and the direction in which they are transcribed. Key words: peptide expression, bacteria, dehalogenation, gene product analysis.
Detection of enterotoxigenicity of Staphylococcus aureus strains: a comparative use of the modifed Ouchterlony precipitation test, reversed passive latex agglutination test, and avidin–biotin ELISA
Authors: Adesiyun A. A. , Eschbach M. , Lenz W. , Schaal K. P.
Published: May 2010

The avidin–biotin enzyme-linked immunosorbent assay (ELISA), reversed passive latex agglutination (RPLA) test, and the modified Ouchterlony precipitation test (MOPT) were compared in detecting enterotoxin production by Staphylococcus aureus strains. A total of 1015 strains isolated from human beings, animals, and foods were tested for staphylococcal enterotoxins A (SEA), B (SEB), and C (SEC). Of these, 495 (48.8%), 467 (46.0%), and 204 (20.1%) were classified as enterotoxigenic by the ELISA, RPLA test, and MOPT, respectively. The difference in the number of strains classified as enterotoxigenic by the ELISA and RPLA test was not significant (P ≥ 0.05; χ2), but both tests detected significantly (P < 0.001; χ2) more enterotoxigenic strains than the MOPT. The combined use of the three assay systems classified 258 (25.4%), 278 (27.4%), and 263 (25.9%) of 1015 strains tested as positive for SEA, SEB, and SEC, respectively. However, the three systems were all positive in only 29.1% of SEA-producing strains, 32.0% of SEB-producing strains, and 25.1% of SEC-producing strains. The MOPT was negative when the corresponding ELISA and RPLA test were positive (46.9% for SEA, 43.5% for SEB, and 40% for SEC); the RPLA test was negative when the corresponding Elisa was positive (10.5% for SEA, 15.5% for SEB, and 25.5% for SEC); and the ELISA was negative when the RPLA test was positive (13.6% for SEA, 9.0% for SEB, and 9.5% for SEC). All factors considered, the RPLA test appears most suitable for quantitatively screening large numbers of strains for staphylococcal enterotoxins. Key words: enterotoxigenicity, assay, methods, Staphylococcus aureus.
Heat shock protein synthesis and restriction fragment length polymorphism in a virulent and a weakly virulent strain of Leptosphaeria maculans
Authors: Chakraborty U. , Chakraborty B. N. , Kapoor M.
Published: May 2010

Two strains of Leptosphaeria maculans, differing in virulence on Brassica napus and with distinct cultural characteristics, were tested for their heat shock response. Following exposure to elevated temperatures, both the strains responded by rapidly synthesizing a set of heat shock proteins (HSPs). Protein synthesis profiles, visualized by labelling with [35S]methionine and resolution on one-dimensional Laemmli gels, revealed a classical heat shock specific pattern: three major thermally induced polypeptides corresponding to the 90-, 80-, and 70-kDa HSPs were observed in both strains. At the optimum heat shock temperature of 40 °C, 11 and 5 new polypeptides appeared labelled in the virulent and weakly virulent strains, respectively. At 45 °C only the three prominent high molecular mass polypeptides were synthesized by the virulent strain, while the weakly virulent strain synthesized these and also showed sustained synthesis of several other normal cellular proteins. Protein synthesis was completely abolished on transfer to 48 °C. Qualitative and quantitative differences were detected in the overall polypeptide profiles of the two strains. Southern blots of genomic DNA of the two strains, digested with three restriction endonucleases and probed with a fragment of the Neurospora crassa hsp70 gene, revealed restriction fragment length polymorphisms with all the three enzymes. Key words: Leptosphaeria maculans, virulent–avirulent pathotypes, heat shock proteins, RFLP, hsp70.
Evidence for proliferation of Enterobacter cloacae on carbohydrates in cucumber and pea spermosphere
Authors: Roberts Daniel P. , Sheets Carol J. , Hartung John S.
Published: May 2010

Enterobacter cloacae EcCT501 grew on a variety of mono- and oligo-saccharides in vitro but did not grow on any of the polysaccharides tested. Carbohydrates found in seed exudates supported growth as did major monosaccharide constituents of seed storage carbohydrates and various seed-associated oligosaccharides. In addition, a rifampicin-resistant mutant of E. cloacae EcCT501, strain 501R3, grew on several of these mono- and oligo-saccharides in a natural gravely loamy sand soil. Glycosidase activities were detected in E. cloacae EcCT501 cultures that have the potential to degrade carbohydrate seed exudates and the oligosaccharide components of seed storage carbohydrates. Aqueous extracts from corn and pea seed induced activities of α-galactosidase 15- and 18-fold, respectively. Activities of α-glucosidase, β-glucosidase, and β-xylosidase were slightly induced by corn and pea seed extracts. Induction of these glycosidase activities by these extracts is consistent with their involvement in spermosphere proliferation. No carbohydrate depolymerase activities were detected. Strain A-11, which was isolated after mutation of strain 501R3 with transposon mini-Tn5 Km, lost the ability to grow on or had a reduced growth rate on several carbohydrates. Strain A-11 was similar to strain 501R3 in other nutritional tests. In cucumber spermosphere proliferation assays populations of strains 501R3 and A-11 were significantly different (P = 0.001) at 20 and 45 h. Strain A-11 did not proliferate in cucumber spermosphere, while strain 501R3 increased in number 21-fold after 45 h. In pea spermosphere, populations of strains A-11 and 501R3 increased 345- and 690-fold, respectively, after 45 h (significantly different at P = 0.1). These data are consistent with the hypothesis that spermosphere mono- and oligo-saccharides have roles as nutrients during spermosphere proliferation by E. cloacae. Key words: carbohydrate nutrition, spermosphere proliferation, glycosidase.
Influence of onion seed bacterization on germination and mycosphere microflora of Sclerotium cepivorum sclerotia
Authors: Reddy M. S. , Rahe J. E. , Levesque C. A.
Published: May 2010

Diallyldisulfide (DADS) and onion seedlings grown from bacterized seeds significantly enhanced the germination of Sclerotium cepivorum sclerotia in muck soil compared with germination in the absence of seedlings or in the presence of seedlings grown from surface-sterilized nonbacterized seeds. Germination was greater for sclerotia on the soil surface than for buried sclerotia. When used for seed bacterization, Bacillus subtilis strain B-2 and four other bacterial strains obtained from rhizospheres of field-grown onions differed in their abilities to enhance germination of sclerotia. Strains B-2, UI-2, and B caused significantly greater germination of sclerotia than did strains UI-1 and W. Sclerotia in soil containing onion seedlings bacterized with B-2, UI-2, and B significantly supported reduced general indigenous bacterial and fungal populations. Treatment of soil with DADS reduced general indigenous bacterial but not fungal populations associated with sclerotia. There were significant inverse correlations between the proportions of sclerotia germinating and populations of bacteria and fungi associated with sclerotia of S. cepivorum. Key words: onion white rot, sclerotia, seed bacterization, mycosphere microflora, germination.
Posttranslational modification of fimbrial protein from Ustilago violacea
Authors: Castle Alan J. , Boulianne Robert , Xu Jianhua , Day Alan W.
Published: May 2010

Fimbriae from the fungus Ustilago violacea were shown to consist of 74-kDa protein subunits. The 74-kDa protein was strongly recognized on immunoblots reacted with a polyclonal antiserum against U. violacea fimbrial protein. Staining of the subunits with periodic acid – Schiff reagent indicated that the proteins were glycosylated. Approximately 10% of the glycoprotein was estimated to be carbohydrate, since treatment of defimbriated cells with tunicamycin or removal of the carbohydrate portion of the subunit by trifluoromethanesulfonic acid treatment resulted in a 67-kDa polypeptide. Mannose was identified as the predominant sugar. Separation of fimbrial protein by two-dimensional gel electrophoresis resolved it into a least six isoelectric forms. All isoelectric forms were recognized on immunoblots by the antiserum. Examination of fimbrial protein samples from three independent isolates indicated that the production of these isoelectric forms and posttranslational glycosylation of fimbrial protein were not dependent on mating type or environmental conditions. Key words: fimbriae, glycoprotein, oligosaccharides, Ustilago violacea, fungus.
Yeasts associated with Drosophila in tropical forests of Rio de Janeiro, Brazil
Authors: Morais Paula B. , Hagler Allen N. , Rosa Carlos A. , Mendonca-Hagler Leda C. , Klaczko Louis B.
Published: May 2010

The distribution and diversity of yeast species vectored by and from the crop of eight species groups of Drosophila is described for two rain forest sites and an urban wooded area in Rio de Janeiro, Brazil. The typical forest Drosophila groups guarani, tripunctata, and willistoni showed a higher diversity of yeasts than the cosmopolitan melanogaster species group, suggesting different strategies of utilization of substrates. Apiculate yeasts, including Kloeckera apis, Kloeckera javanica, and Kloeckera japonica, were the prevalent species. Geotrichum spp. and Candida citrea were also frequent isolates in the forest sites. Similarities between the yeasts from the external surfaces and crops of Drosophila suggested that the feeding substrates were the main source of the yeasts vectored by these flies. Most of the yeasts were strong fermenters and assimilated few compounds, usually sucrose, cellobiose, and glycerol. This indicated a preference of the flies for food sources such as fruits. Some yeasts were primarily isolated from one group of Drosophila; for example, Kloeckera javanica from the melanogaster group, Debaryomyces vanrijiae var. yarrowii from the tripunctata group, and Kluyveromyces delphensis from the willistoni group. These associations and differences in the yeast communities among the fly groups suggested a differentiation of diets and specialization of the yeast-Drosophila association in the tropical forests. Key words: Yeast communities, Drosophila, rain forest, tropical climate.
Thiamine secretion in yeast
Authors: Haj-Ahmad Yousef , Bilinski Carl A. , Russell Inge , Stewart Graham G.
Published: May 2010

To isolate thiamine excretors and (or) overproducers, 188 cultures belonging to nine yeast and three fungal genera were screened. Nine excreted thiamine as determined by both the presence of cross-feeding zones on a thiamine-free agar medium seeded with a thiamine-requiring yeast strain and by the direct detection of excreted thiamine on agar plates. Several of these cultures produced several-fold more intracellular thiamine than the general culture population. Thiamine-requiring strains of Saccharomyces cerevisiae and S. uvarum (carlsbergensis) were identified and were tentatively assigned to 10 complementation groups. Key words: thiamine, yeast, thiamine secretion, thiamine requiring.
Mutagenesis and chromosome mobilization in Hyphomicrobium facilis B-522
Authors: Gliesche Christian G. , Hirsch Peter
Published: May 2010

Spontaneously derived antibiotic-resistant mutants of Hyphomicrobium facilis B-522, a restricted facultative methylotroph, occurred at a high frequency on agar plates with low antibiotic concentrations. Mutants specifically defective in methanol oxidation have been obtained using an allyl alcohol direct selection technique. By chemical mutagenesis with N-methyl-N′ -nitro-N-nitrosoguanidine in the presence of chloramphenicol several stable auxotrophic mutants could be isolated: three leucine auxotrophs, two threonine auxotrophs, and two leucine–methionine double auxotrophic mutants. Optimal conditions for transposon mutagenesis have been developed by comparing several transposon delivery vectors. With the suicide plasmid pRK2013 as a vector, the tetracycline resistance conferring transposon Tn5-132 was introduced into the genome of H. facilis B-522. The following insertion mutants have been obtained: leu-3::Tn5-132, ilv-1::Tn5-132, and pur-1::Tn5-132. Broad host range IncP-1 plasmids could be successfully transferred by interspecific matings. Chromosome mobilization was demonstrated with the conjugative IncP-1 plasmids RP1, R68.45, pMO60, and H. facilis 2189 (leu-2, met-1, mox-1, nfs-1, str-12) as recipient strain. Transconjugants occurred at frequencies ranging from 10−6 to 10−8 for each marker. Key words: methylotrophs, Hyphomicrobium, N-methyl-N′-nitro-N-nitrosoguanidine mutagenesis, transposon mutagenesis, promiscuous plasmids, chromosome mobilization.
Enrichment of bacteriorhodopsin with isotopically labeled amino acids by biosynthetic incorporation in Halobacterium halobium
Authors: Helgerson S. L. , Siemsen S. L. , Dratz E. A.
Published: May 2010

The growth of Halobacterium halobium was optimized in a chemically defined synthetic medium. Arginine, isoleucine, leucine, lysine, methionine, tyrosine, and valine were found to be essential for growth. Optimal growth rates and cell yields were obtained when the medium was also supplemented with the nonessential amino acids alanine, asparagine, glutamic acid, glycine, phenylalanine, proline, serine, and threonine. The complete synthetic medium supported the same maximum growth rate, cell yield, and production of the integral membrane protein bacteriorhodopsin as was obtained in a complex peptone-based growth medium. Using this defined synthetic medium, isotopically labeled bacteriorhodopsin was produced with several 13C-enriched amino acids. The yield of 13C-labeled bacteriorhodopsin was greater than 35 milligrams of purified protein per litre of cell culture. Key words: bacteriorhodopsin, biosynthetic isotopic labeling, synthetic culture medium, nuclear magnetic resonance.
Specificity of the microimmunofluorescence assay for the serodiagnosis of Chlamydia pneumoniae infections
Authors: Ozanne Gérard , Lefebvre Johanne
Published: May 2010

Chlamydia pneumoniae infections are mostly confirmed using an indirect microimmunofluorescence test for which potential cross-reactions between antigens from different chlamydial species are not well documented. Using this assay, 928 sera (507 subjects) submitted for Chlamydia pneumoniae serology were tested for specific IgM and IgG to this bacteria using the TW-183 antigen. IgM and IgG reactivities to Chlamydia trachomatis serotypes C, D, E, and L2 and Chlamydia psittaci strain 6BC antigens were also tested. A sample was interpreted as positive only when evenly fluorescent elementary bodies were observed. Twenty-five subjects (4.9%) showed serological evidence of recent Chlamydia pneumoniae infection (IgM positive and (or) IgG seroconversion); 11 of them also showed serological evidence of recent infection with at least one other chlamydial species. Specificity was 50 and 63% for IgM and IgG detection, respectively. These results suggest that mixed or temporally related infections might occur, or, more likely, that some Chlamydia pneumoniae IgM or IgG reactivities might be due to heterotypic antibodies. Key words: TWAR serology, TWAR infections, TWAR cross-reactions.
Further evidence for a possible role of trypsin-like activity in the adherence of Porphyromonas gingivalis
Authors: Grenier Daniel
Published: May 2010

The present study was undertaken to evaluate a possible correlation between the level of trypsin-like activity and the adherence properties of Porphyromonas gingivalis. It was demonstrated that strains with high cell-associated trypsin-like activity attach in higher numbers to human epithelial cells than strains with low levels of trypsin-like activity. To a lesser extent, the same tendency was also noted for the agglutination of human erythrocytes. The ability of P. gingivalis to attach to erythrocytes and epithelial cells was found to be affected by the presence of arginine and thiol protease inhibitors (leupeptin, p-chloromercuriphenylsulfonic acid). The inhibition profile was partially dependent on the age of the bacterial cells used in the adherence assay. It is suggested that adherence of mid-log P. gingivalis cells involves primarily trypsin-like proteases, whereas 2-day-old cells possess additional specific attachment mechanism(s). Key words: Porphyromonas gingivalis, adherence, proteases, periodontal disease.
The N-linked oligosaccharides of human lactoferrin are not required for binding to bacterial lactoferrin receptors
Authors: Alcantara J. , Padda J. S. , Schryvers A. B.
Published: May 2010

The oligosaccharides of human lactoferrin were enzymatically removed with glycopeptidase F, resulting in a preparation containing partial and fully deglycosylated human lactoferrin. The derivatives were separated by Concanavalin A affinity chromatography and compared with native human lactoferrin with respect to their ability to bind to bacterial receptors. Competitive binding experiments demonstrated that the lactoferrin derivatives were equally capable as native lactoferrin in binding to receptors of Neisseria meningitidis, Neisseria gonorrhoeae, and Moraxella catarrhalis. This result indicates that the oligosaccharides on human lactoferrin are not essential for binding to the bacterial receptors. Key words: lactoferrin, oligosaccharides, deglycosylation, receptor, Neisseria.
Yeasts isolated from artificial lake waters
Authors: Sláviková Elena , Vadkertiová Renáta , Kocková-Kratochvílová Anna
Published: May 2010

Fourteen genera and 29 species of yeasts were found in the water of three artificial fresh lakes. The lakes, used for recreational purposes and located in the area of the Lowland Záhorie (Slovakia), were sampled in summer and autumn. Aureobasidium, Hansenula, Candida, and Rhodotorula species occurred the most frequently. The composition of yeast species was more heterogeneous in summer than in autumn. Relatively high population levels of fermentative and pellicle-forming yeasts were found, especially of Candida krusei and Hansenula anomala. The "black yeast" Aureobasidium pullulans was frequently isolated in autumn in high counts in contrast with the numbers of other species. Key words: ecology, yeasts, quantitative and qualitative study, freshwater lakes.
Disparate efficacy of tobramycin on Ca2+-, Mg2+-, and HEPES-treated Pseudomonas aeruginosa biofilms
Authors: Hoyle Brian D. , Wong Clarence K. W. , Costerton J. William
Published: May 2010

Mucoid exopolysaccharide (MEP) obtained from Pseudomonas aeruginosa 579 was suspended in 10 mM N-2-hydroxyethylpiperazine-N′-2-ethanesulfonic acid (HEPES) pH 7.2 containing 0.1-10.0 mM of CaCl2∙2H2O or MgCl2∙4H2O. MEP treated with HEPES or <5.0 mM of the Ca2+ or Mg2+ salts remained soluble and bound tobramycin in an equilibrium dialysis bioassay. MEP treated with 5.0 or 10.0 mM of the Ca2+ or Mg2+ salts did not bind tobramycin. Five and 10 mM Ca2+-treated MEP precipitated but Mg2+-treated MEP did not. Pseudomonas aeruginosa 579 biofilms formed using a defined growth medium having <1 mM Ca2+ or Mg2+ were treated for 1 h with 10 mM HEPES ± 5.0 mM CaCl2∙2H2O or MgCl2∙4H2O, prior to an 8-h exposure to HEPES, or the defined growth medium, ± 125 μg/mL of tobramycin. The tobramycin kill kinetics for the HEPES-, Mg2+-, and Ca2+-treated biofilms were similar and gradual from T = 0–6 h. The viability of the HEPES- and Mg2+-treated populations declined sharply (from 6 to 8 h). Bacteria dispersed from the MEP in control biofilms at 0 and 8 h did not grow in the presence of 7.81 μg/mL of tobramycin. Thus, binding of tobramycin of P. aeruginosa 579 MEP may not be as influential to the impediment of tobramycin diffusion as is the steric hindrance imposed by the Ca2+ condensation of the polymer. Key words: Pseudomonas aeruginosa, mucoid exopolysaccharide, tobramycin, biofilm.
Segregation of altered parental properties in fusions between Saccharomyces cerevisiae and the D-xylose fermenting yeasts Candida shehatae and Pichia stipitis
Authors: Gupthar Abindra S.
Published: May 2010

A prototrophic strain of Saccharomyces cerevisiae CSIR Y190 MATa xyl−, resistant to high levels of ethanol, was hybridized with xylose-fermenting, auxotrophic mutants of Candida shehatae and Pichia stipitis through polyethylene glycol-induced protoplast fusion in an attempt to produce ethanol-tolerant, xylose-fermenting hybrids. Mononucleate fusants were obtained, but these dissociated into a mixture of parental-type segregants. Purified Candida- and Pichia-resembling segregants failed to acquire improved ethanol tolerance but expressed other novel properties of S. cerevisiae, suggesting that karyogamy was impaired after internuclear gene transfer. Key words: Pichia, Candida, Saccharomyces protoplast fusion.
Temperature sensitivity of nitrogen fixation in Azospirillum spp.
Authors: Tripathi Anil K. , Klingmüller Walter
Published: May 2010

Azospirillum brasilense and Azospirillum lipoferum showed optimum acetylene-reducing activity at 25 and 30 °C, respectively, although both the bacteria grew optimally at 35 °C. Azospirillum halopraeferens displayed optimum growth and acetylene-reducing activity at 40–41 °C. Our experiments indicated that expression of nif genes was generally more sensitive to temperature than was nitrogenase activity. The NifA-dependent activation of a heterologous nifH–lacZ fusion was used to assess the impact of temperature on native NifA activity of A. brasilense and A. lipoferum. Maximum NifA activity was observed at 25 °C in A. brasilense and at 30 °C in A. lipoferum. Key words: temperature, nitrogen fixation, nifH–lacZ fusion, NifA activity, Azospirillum.
Cold shock proteins and cold acclimation proteins in a psychrotrophic bacterium
Authors: Whyte Lyle G. , Inniss William E.
Published: May 2010

The synthesis of proteins in the psychrotrophic bacterium Bacillus psychrophilus in response to both cold shock and continuous growth at low temperatures was examined. Cold shocks of 20 to 0, 5, or 10 °C resulted in the induction of nine, seven, and five cold shock proteins, respectively, as determined by 2-dimensional gel electrophoresis and computing scanning laser densitometry. Two cold shock proteins, with molecular masses of 61 and 34 kDa, which were induced in B. psychrophilus by cold shocks of 20 to 0 or 5 °C, were not induced in a cold-sensitive mutant of B. psychrophilus. Analysis of protein profiles of B. psychrophilus during continuous growth at 0, 5, or 10 °C revealed the synthesis of 11, 10, and 4 cold acclimation proteins, respectively. Some of these cold acclimation proteins were similar to cold shock proteins. In addition, the relative synthesis of both cold shock proteins and cold acclimation proteins increased with decreasing temperature. Thus, both types of proteins increased both in number and relative synthesis in response to cold shock and continuous growth at low temperature. Key words: cold shock proteins, cold acclimation proteins, psychrotrophic bacterium.
Effect of benomyl and benomyl resistance on cellulase formation by Trichoderma reesei and Trichoderma harzianum
Authors: Peterbauer Clemens K. , Heidenreich Erich , Baker Ralph T. , Kubicek Christian P.
Published: May 2010

To investigate the possible relationship between resistance to benomyl and the production of cellulases by Trichoderma spp., we investigated the effect of benomyl on growth and cellulase formation in Trichoderma reesei, Trichoderma harzianum, and the benomyl-resistant mutant T. harzianum T95. While T. reesei produced the highest and T. harzianum the lowest cellulase amounts, growth of both strains was equally inhibited by 2 μg/mL benomyl. However, sublethal doses of benomyl (0.2–0.5 μg/mL) promoted growth, stimulated cellulase production, and produced a highly branched, crippled morphology. The same phenomenon was observed with T. harzianum T-95, albeit at higher (5–10 μg/mL) benomyl concentrations. Introduction of the Neurospora crassa ben gene, coding for a benomyl-resistant β-tubulin, into a T. reesei by transformation yielded a series of transformants, which exhibited increased growth, increased cellulase formation, and highly branched, crippled morphology. Key words: Trichoderma harzianum, Trichoderma reesei, benomyl, rhizosphere competence, cellulase.
Effects of oxytetracycline, oxolinic acid, and flumequine on bacteria in an artificial marine fish farm sediment
Authors: Hansen Pia K. , Lunestad Bjørn T. , Samuelsen Ole B.
Published: May 2010

Oxytetracycline, oxolinic acid, and flumequine are at present the most frequently used antibacterial agents in the treatment of marine farmed fish in Norway. These substances are supplied with the food pellets and a substantial amount ends up in the sediment under the net pens. The effects of these antibacterial agents on the microbial community in a sediment were experimentally examined in tanks containing sediment to which was added either oxytetracycline, oxolinic acid, or flumequine, and supplied with a constant water flow. During the first 20 days of the experiment, approximately one-third of the antibacterial agents disappeared from the sediments. During the next 165 days another 25% vanished. There were elevated numbers of bacteria resistant to oxytetracycline and oxolinic acid a few days after the start of the experiment. The resistance that developed to oxytetracycline was higher and longer lasting than that to oxolinic acid and flumequine. Of the quinolones, flumequine seemed least disposed to induce resistance. The number of bacteria in all treated sediments decreased to 50–67% of the numbers in the control sediment 2 days after medication. Seven days after medication the sulfate reduction rates in the treated sediments were reduced to less than 10% of the rates found in the control. This effect lasted at least 29 days, but after 70 days the inhibition of the sulfate reduction in the treated sediments had disappeared. Key words: antibacterial agents, sediment, bacterial resistance, sulfate reduction.
Enzyme activities of D-glucose metabolism in the fission yeast Schizosaccharomyces pombe
Authors: Tsai C. S. , Shi J.-L. , Beehler B. W. , Beck B.
Published: May 2010

The activities of key enzymes that are members of D-glucose metabolic pathways in Schizosaccharomyces pombe undergoing respirative, respirofermentative, and fermentative metabolisms are monitored. The steady-state activities of glycolytic enzymes, except phosphofructokinase, decrease with a reduced efficiency in D-glucose utilization by yeast continuous culture. On the other hand, the enzymic activities of pentose monophosphate pathway reach the maximum when the cell mass production of the cultures is optimum. Enzymes of tricarboxylate cycle exhibit the maximum activities at approximately the washout rate. The steady-state activity of pyruvate dehydrogenase complex increases rapidly when D-glucose is efficiently utilized. By comparison, the activity of pyruvate decarboxylase begins to increase only when ethanol production occurs. Depletion of dissolved oxygen suppresses the activity of pyruvate dehydrogenase complex but facilitates that of pyruvate decarboxylase. Acetate greatly enhances the acetyl CoA synthetase activity. Similarly, ethanol stimulates alcohol dehydrogenase and aldehyde dehydrogenase activities. Evidence for the existence of alcohol dehydrogenase isozymes in the fission yeast is presented. Key words: yeast, glucose-metabolizing enzymes.
Use of bacteriophage for the selective isolation of thermophilic actinomycetes from composted eucalyptus bark
Authors: Kurtböke D. I. , Murphy N. E. , Sivasithamparam K.
Published: May 2010

A method was developed to reduce the numbers of thermophilic bacteria on isolation plates, which in turn facilitated the detection and isolation of thermophilic actinomycetes. The method involves exposing the test material to bacteriophage suspensions prior to inoculation on isolation plates. This method was applied to composted eucalyptus bark samples, which were then inoculated on R8 and 1/2 TSA + 0.2% casein hydrolysate agar plates. The phage susceptibility of thermophilic bacteria provided a selective means of reducing their numbers on isolation plates and hence increased the numbers of Thermomonospora, Saccharopolyspora rectivirgula, and thermophilic Streptomyces spp. on these media in comparison with the numbers recorded from control plates.Key words: bacteriophage, thermophilic bacteria, thermophilic actinomycetes, composted eucalyptus bark.
Sporocidal properties of peracetic acid and hydrogen peroxide, alone and in combination, in comparison with chlorine and formaldehyde for ultrafiltration membrane disinfection
Authors: Alasri Anouar , Valverde Michèle , Roques Christine , Michel Georges , Cabassud Corinne , Aptel Philippe
Published: May 2010

The sporocidal properties of peracetic acid, hydrogen peroxide, chlorine, and formaldehyde were compared in vitro using a dilution–neutralization micromethod. A combination of peracetic acid and hydrogen peroxide was also tested to assess their interactions. The activities of these agents, which are widely used as disinfectants, were evaluated against Bacillus spore isolates found on stored membranes and collection cultures. Peracetic acid and chlorine exhibited an excellent antimicrobial activity, with a destruction of 105 spores/mL after 5 min of contact. Generally the effects of the biocides tested were time dependent. The sporocidal activities of hydrogen peroxide and formaldehyde were the lowest. The combination of peracetic acid and hydrogen peroxide, tested by a checkerboard micromethod, was found to be synergistic. The minimal sporocidal concentration (MSC) was established in terms of time for each biocide. The lowest MSC values for peracetic acid, hydrogen peroxide, chlorine, and formaldehyde were 168–336 ppm (1–2 h of contact), 5625–11250 ppm (5–7 h), 168–336 ppm (2–3 h), and 1875–3750 ppm (5–30 min), respectively. The MSC of a biocide combination of peracetic acid and hydrogen peroxide showed that synergy was maintained with increasing contact time and that the MSC could be reduced by two to eight times when compared with those of the biocides alone. Optimal concentrations and contact times of those chemicals that were promising in vitro were then tested for their ability to disinfect ultrafiltration membranes. The sporocidal activities of peroxide compounds and chlorine were confirmed and the synergism between peracetic acid and hydrogen peroxide was also maintained. The biocide combination of peracetic acid and hydrogen peroxide gave successful results; 21 ppm of peracetic acid + 2813 ppm of hydrogen peroxide allowed a total disinfection of hollow fibers in 2–3 h of contact.Key words: peracetic acid, hydrogen peroxide, chlorine, combination, ultrafiltration membranes.