Showing papers in "Journal of Basic Microbiology in 2002"

Extracellular β-D-glucosidase from Chaetomium thermophilum var. coprophilum: production, purification and some biochemical properties

Abstract: The thermophilic fungus Chaetomium thermophilum var. coprophilum produced large amounts of extracellular and intracellular beta-glucosidase activity when grown on cellulose or cellobiose as carbon sources. The presence of glucose in the culture medium drastically decreased the level of beta-glucosidase activity, while cycloheximide prevented the induction of the extracellular enzyme activity by cellobiose. An extracellular beta-glucosidase induced by avicel was purified by a procedure involving acetone precipitation and chromatography on two DEAE-cellulose columns. The purified enzyme was a basic protein, with a carbohydrate content of 73%. The deglycosylated enzyme exhibited a molecular mass of 43 kDa, with pH and temperature optima of 5.5 and 65 degrees C respectively. The beta-glucosidase hydrolysed only cellobiose and p-nitrophenyl-beta-D-glucopyranoside, exhibiting apparent Km values of 3.13 mM and 0.76 mM, respectively. The native purified enzyme was stable up to 2 hours at 60 degrees C, and its thermal stability was directly dependent on glycosylation.

Candida dubliniensis, a new fungal pathogen.

Abstract: There is a high interest in Candida species other than Candida albicans because of the rise and the epidemiological shifts in candidiasis. These emerging Candida species are favored by the increase of immunocompromised patients and the use of new medical practices, and m. Most oropharyngeal candidiasis can be foundare observed in those HIV-infected patients infected with human immunodeficiency virus (HIV). Candida dubliniensis is a recently described opportunistic pathogen that is closely related to C. albicans but differs from it with respect to epidemiology, certain virulence characteristics, and the ability to develop fluconazole resistance in vitro. C. dubliniensis has been linked to oral candidiasis in AIDS patients, although it has recently been associated to invasive disease. C. dubliniensis shares diagnostic characteristics with C. albicans, as germ tube- and chlamydospore-production, and it is generally misclassified as C. albicans by standard diagnostic procedures. Several recent studies have attempted to elucidate useful phenotypic and genotypic characteristics for separating both species. A large variety of methods have been developed with the aim of facilitating rapid and, accurate identification of this species. These have included differential chromogenic isolation platesculture media, direct immunological tests, and enhanced manual and automated biochemical and enzymatic panels. Chromogenic isolation media, as CHROMagar Candida, demonstrate better detection rates than traditional media, and allow the presumptive identification of C. dubliniensis by means of colony color (dark-green colonies). API 20 C AUX system is considered a reference method, but ID 32 C strip, the VITEK Yeast Biochemical Card and the VITEK 2 ID-YST system correctly identify most C. dubliniensis isolates, being the latter the most accurate. Spectroscopic methods, such as Fourier transformed-infrared spectroscopy, offer potential advantages. However, many authors consider that standard methods for differentiation of Candida species are time-consuming, often insensitive and can fail to distinguish C. dubliniensis. To overcome these low sensitivity, poor specificity and intolerable delay,drawbacks, molecular tools have been developed to discriminate C. dubliniensis, and particularly those based on the polymerase chain reaction. But, molecular tools prove difficult and too complex for routine use in the clinical laboratory setting and new developments are necessary. Moreover, an increased resistance to antifungal drugs has been described. Although preliminary studies indicate that most strains of C. dubliniensis are susceptible to antifungal agents, fluconazole-resistant strains have been detected. Furthermore, fluconazole-resistant strains are easily derived in vitro, showing an increased expression of multidrug resistance transporters, as MDR1.

Emulsifier from a tropical marine yeast, Yarrowia lipolytica NCIM 3589

Abstract: A tropical marine strain of Yarrowia lipolytica, NCIM 3589 produced emulsifier in the presence of alkanes or crude oil. The mode of alkane uptake in this organism was by attachment to large droplets. An emulsifier (lipid-carbohydrate-protein) complex was associated with the cell wall. This emulsifier increased the hydrophobicity of the cells during the growth phase. In the stationary phase, the organism produced the emulsifier extracellularly under conditions of carbon excess and nitrogen limitation. Other requirements for extracellular emulsifier production included an initial pH of 8.0 and the presence of sodium chloride at a concentration of 2 to 3% (342 to 513 mM). The cell-associated and extracellular emulsifier was shown to have similar properties.

Isolation and characterization of bacteria from crude petroleum oil contaminated soil and their potential to degrade diesel fuel.

Abstract: Potential hydrocarbon degrader bacteria were isolated from soil samples that have been exposed to crude petroleum oil spills. Bacterial population of these polluted soils showed counts ranging between 9.5 x 10(5) and 237.5 x 10(5) CFU/g soil with 2 different colony types of bacterial strains which have been recovered on the agar plates. Results indicated that longer aged contamination exhibited a greater number of microorganisms. Phenotypic examination of the recovered bacteria revealed that they belong mainly to the genus Pseudomonas, Enterobacter and Acinetobacter. Turbidity, dry weight and physical appearance were used as an indication for the ability of these bacteria to grow on diesel. Action of three different Pseudomonas species, Acinetobacter lowffi, Enterobacter cloacae and Rhodococcus erythropolis on 0.1 % (v/v) diesel was followed at 1, 2, 6 and 12 h. Pseudomonas putida and P. mallei and Enterobacter cloacae indicated a positive reaction; however, Pseudomonas maltophilia and Acinetobacter lowffi showed no effect.

Occurrence of crude oil degrading bacteria in gasoline and diesel station soils.

Abstract: Microbial enumeration and identification were carried out on several oil contaminated soil samples collected from gasoline and diesel stations. Bacteria were the most dominant microbiota and were therefore classified to generic level. Eleven main genera were detected and Corynebacterium was the predominant genus in all the samples. Biochemical characterisation and substrate utilisation showed high percentage of lipolytic ability combined with high inorganic nitrogen utilisers. The ability of these cultures to degrade crude oil was tested individually and in mixed bacterial consortium at different temperatures and pH values. Maximum crude oil biodegradation of 78% was achieved using a bacterial consortium containing five cultures (Micrococcus sp. GS2-22, Corynebacterium sp. GS5-66, Flavobacterium sp. DS5-73, Bacillus sp. DS6-86 and Pseudomonas sp. DS10-129) with 1% crude oil at 30 degrees C and pH 7.5. Such a consortium may be useful for bioaugmentation of oil contaminated environments.

Comparison of long-chain alcohols and other volatile compounds emitted from food-borne and related Gram positive and Gram negative bacteria.

Abstract: Numerous reports have been published on the antimicrobial activity of synthetic volatile long chain alcohols, such as 1-decanol and 1-dodecanol, against bacteria and fungi. The objective of the present study was to survey microorganisms for emission patterns of naturally occurring long chain alcohols and other volatile components to determine if these compounds are associated with certain groups of bacteria. Cultures were grown in trypticase soy broth overnight and volatile compounds were trapped on a porous polymer and identified by mass spectrometry. Subsequently, volatile compounds were collected from 26 strains of food associated bacteria using solid-phase microextraction and analyzed by gas chromatography. Alcohols comprising 1-octanol, 1-decanol, and 1-dodecanol occurred as products from enteric Gram negative bacteria, which included Citrobacter, Enterobacter, Klebsiella, Salmonella, and Shigella. However, the long chain alcohols were not detected as products from the nonenteric Gram negative species studied which included Acinetobacter, Pseudomonas, and Shewanella. Among Gram positive bacteria, including Bacillus, Enterococcus, Lactococcus, Leuconostoc, Listeria, Staphylococcus, and Streptococcus, the only long chain alcohol detected was 1-decanol and, if present, it occurred in relatively small amounts. Other classes of compounds emitted by bacteria included methylketones and sulfides. The methylketones were found as products from Gram positive and Gram negative bacteria, whereas the sulfides were closely associated with Gram positive bacteria. In summary, the emission patterns of volatile compounds from bacteria showed many trends including the association of long chain alcohols with enteric Gram negative bacteria. The results provide a basis for future in vivo studies to determine if volatile compounds such as natural long chain alcohols function in the ecology of food-borne Gram negative bacterial pathogens.

Antibacterial activity of Australian plant extracts against methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant enterococci (VRE).

Abstract: Ethanolic extracts of five traditional Australian medicinal plants, previously shown to display antibacterial activity against laboratory strains of the Gram positive bacteria Staphylococcus aureus and Enterococcus faecalis, were investigated for their abilities to inhibit clinical isolates of methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant enterococci (VRE). Using plate-hole diffusion assays, the following results were obtained: (a) extract from the leaves of Eremophila alternifolia (Myoporaceae) showed activity against MRSA; (b) extract from the leaves of Acacia kempeana (Mimosaceae) showed incomplete inhibition of VRE; (c) extracts from the leaves of Amyema quandong (Loranthaceae) and Eremophila duttonii (Myoporaceae) were active against both types of bacteria; (d) extract from the stem base of Lepidosperma viscidum (Cyperaceae) was active against MRSA and exhibited incomplete inhibition of VRE. All active extracts were evaluated using time-kill assays. Most of the extracts showed bactericidal effects and reduced the number of viable cells by 4-6 logs within four hours, while the extracts from Acacia kempeana leaves and Lepidosperma viscidum stem base exhibited bacteriostatic activity against VRE. The extract from the leaves of Eremophila duttonii was the most active and reduced the number of viable cells of MRSA and VRE to undetectable levels within 1 hour.

Synthesis of alpha-amylase by Aspergillus oryzae in solid-state fermentation.

Abstract: Spent Brewing Grains (SBG) was evaluated for its efficacy to be used as sole carbon source for the synthesis of alpha-amylase in solid-state fermentation using a fungal strain of Aspergillus oryzae NRRL 6270. Enzyme production was superior when the culture grew on mesophilic temperatures and best yields were at 25 degrees C. At 30 degrees C, yields were almost comparable. Maximum production of alpha-amylase [6870 U/g dry substrate (gds)] was obtained when SSF was carried out at 30 degrees C for 96 h using SBG medium, which had initial moisture of 70% and was inoculated using a spore suspension containing 1 x 10(7) spores/ml. Supplementation of SBG with external carbon sources such as mono-, di and polysaccharides caused repression in enzyme synthesis by the fungal culture.

Production of laccase as the sole phenoloxidase by a Brazilian strain of Pleurotus pulmonarius in solid state fermentation.

Abstract: The production of laccase by a Brazilian strain of Pleurotus pulmonarius was studied in solid state fermentation using wheat bran as substrate. Among oxidative and hydrolytic enzymes tested (laccase, aryl alcohol oxidase, lignin peroxidase, Mn peroxidase, xylanase and cellulase), laccase was the main enzyme produced by P. pulmonarius. The most suitable condition for maximum production of laccase (8,600 U/g substrate) was initial moisture content of 75% and 5 days of cultivation at 30 degrees C. The optimum pH and temperature for laccase activity were found to be 6.5 and 50 degrees C, respectively. P. pulmonarius laccase was stable at 50 degrees C for more than 6 hours, and it retained about 73% and 18% of its activity when heated for 1 h at 55 and 60 degrees C, respectively. The enzyme was greatly stable at alkaline pH, but not at acidic pH. The laccase activity appear to be correlated with the ability of crude extract to decolourize several industrial dyes.

Alcohol production from starch by mixed cultures of Aspergillus awamori and immobilized Saccharomyces cerevisiae at different agitation speeds.

Abstract: The influence of different agitation speeds on alcoholic fermentation by free and immobilized cells of Saccharomyces cerevisiae in a co-culture with free cells of Aspergillus awamori was investigated. Starch hydrolysis and glucose, glucoamylase and alpha-amylase accumulation in the fermentation medium was affected by agitation speed. Maximum amounts of the enzymes were obtained at 150-200 rpm after 72 h where, maximum growth and glucose accumulations were noticed at 200-300 rpm. Alcohol production was stimulated by low agitation speed (50 rpm) and decreased at higher speeds. The results also showed that the amount of produced alcohol was affected by the time of yeast inoculation. When the inoculation of yeast was carried out after the growth of fungi for 72 h, the amounts of produced alcohol increased by 84, 75, 89 and 68% at 50, 100, 150 and 200 rpm, respectively than that produced when the two organisms were inoculated together at the beginning of the fermentation process. A batch culture of the two organisms produced about 2% (v/v) alcohol from 12% (w/v) corn starch in 72 h at 50 rpm. On the other hand, the immobilized yeast and suspended A. awamori produced more alcohol reaching 3.7% (v/v) at 200 rpm under the same cultivation conditions. The fermentation process was less affected by alginate and cell concentrations of the immobilized yeast. Repeated batch fermentation by co-culture of A. awamori and immobilized yeast cells were successfully used for 12 times without a significant loss in alcohol production.

Chromate sensitivity in fission yeast is caused by increased glutathione reductase activity and peroxide overproduction

Abstract: The Cr(VI)-sensitive mutant chr-51S of the Schizosaccharomyces pombe accumulated chromate (CrO(4) (2-)) and reduced Cr(V) to much greater extent, than did its parental strain 6 chr(+). Sublethal doses of K(2)Cr(2)O(7) did not induce any adaptive stress response, while H(2)O(2) or menadione pretreatment proved protective against the cell injuries caused by Cr(VI). The intracellular GSH concentration in chr-51S cells was approximately half of that for the 6 chr(+). Moreover, the glutathione disulfide reducing capacity of chr-51S was characterized by significantly increased glutathione reductase (GR) and glucose-6-phosphate dehydrogenase activities. These data strongly suggested that, instead of GSH, the NADPH/GR system was the major one-electron Cr(VI) reductant in vivo. The increased Cr(V) reduction in chr-51S mutant was accompanied by high intracellular superoxide and peroxide concentrations, required for formation of the hydroxyl radical ((*)OH). The decreased intracellular GSH levels and the Cr(VI)-sensitive phenotype of the chr-51S cells indicates that GSH might act effectively against chromate by scavenging (*)OH.

Laccase production by some Phlebia species.

Abstract: The present study was carried out to examine the ability of four species of the genus Phlebia, viz. P. floridensis, P. brevispora, P. radiata and P. fascicularia, to produce the ligninolytic enzyme laccase in liquid culture. P. floridensis was the most active species that even surpassed laccase production by Trametes versicolor, and was chosen for further study. Among several carbon sources tested, malt extract turned out to be the best medium for subsequent laccase concentration by ammonium sulfate precipitation. Specific enzyme activity increased 12-fold during this procedure and a K(m) value of 0.33 mM was calculated for the resulting laccase preparation using guaiacol as the substrate. Concentrated laccase from P. floridensis was relatively thermostable and retained 70% and 15% of its activity after 1 h preincubation at 50 degrees C and 60 degrees C, respectively.

Diversity of microfungi in the phylloplane of plants growing in a Mediterranean ecosystem.

Abstract: Mediterranean ecosystems have not been investigated as natural habitats for microorganisms in general, and microfungi in particular. Plants harvested in "Serra da Arrabida" (38 degrees 27' N, 9 degrees 02' W), a Mediterranean ecosystem in Portugal, were analyzed for the filamentous microfungi inhabiting their surface. Two field locations with distinct climatic characteristics were studied: 'Fonte do Veado' (38 degrees 28'50" N, 9 degrees 0'17" W; 300 m elevation) located on the northern slope, and 'Mata do Solitario' (38 degrees 27'55" N, 8 degrees 59'35" W; 50 m elevation), on the southern slope. From Veado zone, leaf samples yielded a total of 3,049 isolates, ranging from 317 to 1,328/sample (mean = 762). The number of species/sample ranged from 12 to 24. From Solitario zone, leaf samples yielded a total of 1,337 isolates, ranging from 189 to 528/sample (mean = 334). The number of species/sample, in this case, ranged from 10 to 17. Veado zone showed a wider range of species. The fungal species more frequently isolated from both zones (Aureobasidium pullulans (De Bary) Arnaud, Cladosporium cladosporioides (Fresen.) De Vries, C. sphaerospermum Penzig and Alternaria alternata (Fr.) Keissler) were found in all plant samples and represents 80% (Veado) and 85% (Solitario) of the total isolates.

Effect of chlorine, biodegradable dissolved organic carbon and suspended bacteria on biofilm development in drinking water systems.

Abstract: The influence of chlorine levels, the concentration of dissolved organic carbon and the abundance of bacteria in suspension, on the formation of biofilms on experimental glass surfaces were evaluated. Twelve reactors, packed with glass spheres, were continuously perfused with tap water. The properties of water were altered in different ways: chlorine was neutralized by the addition of thiosulfate, the levels of assimilable organic carbon were increased through the addition of acetate, and the bacterial load was modified by means of the continuous inoculation of a growing active culture of Pseudomonas aeruginosa. Continuous addition of bacteria to water containing 0.5 mg/l of free chlorine, did not result in the formation of detectable biofilms even after one month. When bacteria were added simultaneously with thiosulfate as a chlorine neutralizer, a community of attached bacteria appeared in less than 24 hours. Addition of acetate with the presence of 0.5 mg/l of chlorine did not stimulate the formation of biofilms. On the contrary, neutralization of chlorine with thiosulfate allowed the formation of biofilms with 10(6) cfu/cm(2) in about two weeks.

Temperature effect in the production of multiple xylanases by Aspergillus fumigatus.

Abstract: This work has evaluated the temperature effect in the production of multiple xylanases by a locally isolated strain of Aspergillus fumigatus Fresenius. Three isoenzymes, identified as xylanases I, II, and III with apparent molecular weight of 45.7 KDa, 39.8 KDa and 18.2 KDa, respectively, were produced in cultures developed at 30 degrees C and at 42 degrees C. The pattern of distribution of xylanase activity among the three isoenzymes was greatly affected by the growth temperature: at 30 degrees C, the total xylanase activity was distributed homogeneously among the three enzymes, while at 42 degrees C, the total xylanase activity was mainly due to the fractions with the highest MW (I and II) and the xylanase III was a minor component.

The pab1 gene of Coprinus cinereus encodes a bifunctional protein for para-aminobenzoic acid (PABA) synthesis: implications for the evolution of fused PABA synthases

Abstract: The pab1 gene of the basidiomycete Coprinus cinereus encodes PABA synthase, necessary for para-aminobenzoic acid production. The C. cinereus protein is bifunctional with an N-terminal glutamine amidotransferase domain and a C-terminal chorismate amination domain. In most bacteria, these two functions are encoded in separate genes (e.g., pabA and pabB of E. coli). Fused PABA synthases have so far been detected in actinomycetes, Plasmodium falciparum, fungi and Arabidopsis thaliana. Phylogenetic analysis shows that the fused PAB sequences form a tight group that also includes uncharacterized PabB homologues from several bacteria. Unfused bacterial PabA proteins group with the glutamine amidotransferase subunits of bacterial anthranilate synthases, independent of organismal systematics, indicating a complex and perhaps independent evolutionary origin. In contrast, unfused PabB group and fused PabA/B proteins form a monophyletic group on a branch separate from the chorismate amination subunits of anthranilate synthases, probably reflecting a need for recognition of different positions in the common substrate chorismate.

The effects of NaCl and some heavy metals on the denitrification activity of Ochrobactrum anthropi.

Abstract: Ochrobactrum anthropi is a well-known Gram-negative bacterium, with the ability to degrade atrazine, urea-formaldehyde and chlorophenols. Investigation were made of the nitrate and nitrite reduction capacities of the strain in succinate and glucose media, and the tolerance of its denitrification to NaCl and some heavy metals. Succinate proved to be a better carbon source to drive denitrification by O. anthropi. Batch fermentation studies in anaerobic succinate medium indicated reduction capacities of 85.4 +/- 9.1 and 48.6 +/- 5.2 mgh(-1)g(-1) dry cell for NO(3) (-) and NO(2) (-), respectively. The nitrite accumulation of the cells revealed that O. anthropi is a group C denitrifying bacterium. Its growth in DSM 1 broth containing NaCl up to 40 g l(-1) demonstrates that O. anthropi belongs in the group of moderately halophilic bacteria. Despite the fact that 42.5 g NaCl l(-1) caused 50% growth inhibition in DSM 1 broth, the cells in the stationary phase readily tolerated NaCl concentrations up to 100 g l(-1). Complete denitrification was achieved in test media containing 30 g NaCl l(-1) after 1 week and the nitrate reductase retained its activity up to 100 g NaCl l(-1). The cells were tolerant to Hg, Zn, Pb, Cu and Ni, and N(2) was producted at tolerated concentrations of the metal in the cases of Hg and Pb.

Vegetative incompatibility in the ascomycete Rosellinia necatrix studied by fluorescence microscopy.

Abstract: We describe our examination of the cytological characteristics of the vegetative incompatibility reaction in a filamentous ascomycetes, Rosellinia necatrix, by analyzing the fluorescence emitted by ethidium bromide and acridine orange stained nuclei. Hyphal anastomosis between incompatible strains, which were field and single ascospore isolates, were observed with cell death showing fused hyphae, and nuclei debris which were intensified by staining with ethidium bromide. In contrast, the nuclei in a living cell were not intensified by staining with ethidium bromide but were intensified by staining with acridine orange. A strain was found which did not form a barrier reaction, but which could be shown to undergo cell death and therefore showed a positive vegetative incompatibility reaction. We also examined the vegetative incompatibility among five single ascospore isolates and the putative parent strain from the same perithecium; all strains were incompatible. These results strongly suggest that vegetative incompatibility in R. necatrix is regulated by many loci.

Characterization of JP-7 jet fuel degradation by the bacterium Nocardioides luteus strain BAFB.

Abstract: In the fall of 1996, numerous bacteria capable of degrading JP-7 jet fuel were isolated from soil collected at Beale Air Force Base in northern California. The most prevalent organism, identified as Nocardioides luteus by16s rRNA sequencing (MIDI Labs, Inc.), was selected for further analysis. Analysis of JP-7 following inoculation with N. luteus demonstrated degradation of the C(11) alkane component of the fuel. Growth rates of N. luteus were determined with alkanes of various lengths as the sole carbon and energy source. The organism grew best on shorter length alkanes (C(8) and C(10)). Growth was measurably slower on C(11), and minimal on C(12), C(13), and C(14).

Extracts from seaweeds can promote fungal growth.

Abstract: Hormesis is the stimulation of a biological response at low concentrations of an inhibitor. Ethanolic extracts were made using Osmundaria serrata (Suhr) R. E. Norris and Stypopodium zonale (Lamouroux) Papenfuss from the East coast of South Africa. Two plant pathogens (Colletotrichum gloeosporioides (Penz.) Penz. and Sacc. and Rhizoctonia solani Kuhn) were used as test organisms in bioassays. Serial dilutions of macroalgal extracts were tested by the pour plate technique. Both growth inhibitory and promotory responses were observed. The hormetic response was observed in both the fungi when grown on low dilutions of ethanol and the O. serrata extract, and when R. solani was grown on the S. zonale extract. This study provides more evidence of hormesis in macroalgal products and the phenomenon is discussed in relation to its possible cause and significance in the application of seaweed extracts.

Immunocytochemical localization of the stress-induced DpsA protein in the cyanobacterium Synechococcus sp. strain PCC 7942

Abstract: Proteins of the Dps family are divergent ferritins that have been shown to bind DNA with high affinity during periods of nutrient and oxidative stress. Such binding protects the chromosome from peroxide attack. Surprisingly, we show by immunocytochemistry that the cyanobacterial Dps homolog, DpsA, localizes preferentially to the thylakoid membrane in Synechococcus sp. strain PCC7942. We propose that two DpsA pools are functioning in this species--an insoluble fraction bound to the chromosome, and a soluble fraction acting as a ferritin involved metal homeostasis of the photosynthetic apparatus. This model is presented in light of recent work on the E. coli Dps protein showing that DNA binding is regulated by the metal-binding capacity of the Dps complex (Frenkiel-Krispin et al. 2001). Additionally, the pattern of DpsA localization in cells as they progress through the growth curve suggests that the DpsA complex may be involved in metal ion transport across the cell envelope.

Thermus rehai sp. nov., isolated from Rehai of Tengchong, Yunnan Province, China.

Abstract: A yellow-pigmented strain of the genus Thermus, with optimum growth temperatures about 65 approximately 70 degrees C, was isolated from the hot springs in Rehai of Tengchong, Yunnan Province, China. Morphological, physiological and biochemical characteristics, pigment analysis of RH99-GF7504 strain and its phylogenetic analysis of 16S rDNA showed that this organism represented a new species of the genus Thermus. This strain had maximum temperatures for growth below 80 degrees C. The new isolate from Rehai of Tengchong could be distinguished from other strains of the genus Thermus by its special structure and by its inability to hydrolyze gelatin and starch. On the basis of phylogenetic analysis, morphological, physiological and biochemical characteristics, the name Thermus rehai sp nov is proposed for the species, represented by strain RH99-GF7504 (CCTCC-AB200292).

Evaluation of carbazole degradation by Pseudomonas rhodesiae strain KK1 isolated from soil contaminated with coal tar.

Abstract: In this study, strain KK1 isolated from coal tar-contaminated soil was found to be able to mineralize carbazole as a sole source of carbon by radiorespirometric analysis. KK1 cells pregrown on phenanthrene were able to mineralize carbazole much more rapidly than cells pregrown on naphthalene, suggesting a possible close linkage between the pathways for carbazole and phenanthrene catabolism. Also, Rieske-type iron sulfur center sequence of dioxygenase from KK1 was analyzed to evaluate carbazole catabolism by KK1. A gene cloned out from KK1 using a universal dioxygenase primer set was found a dioxygenase for initial catabolism of carbazole based on deduced amino acid sequences. Northern hybridization using the putative carbazole dixoygenase gene fragment as a probe provided the information that catabolism of carbazole might be greatly activated in phenanthrene-grown cells. Analysis of PLFAs extracted from KK1 cells exposed to carbazole revealed that lipids 10:0 3OH, 17:0 cyclo, and 18:0 were representatives produced or significantly increased in response to carbazole. Strain KK1 was identified as Pseudomonas species with 94% confidence when BIOLOG system was applied, as Pseudomonas sp. with over 90% confidence by total cellular compositions of fatty acid, and as Pseudomonas rhodesiae with 99% confidence by 16S rRNA sequence. Accordingly, strain KK1 was identified as Pseudomonas rhodesiae based on combination of the data, and designated Pseudomonas rhodesiae KK1. The phylogenetic tree based on 16S rRNA suggested that strain KK1 was far away in the phylogenetic distance from the strains that can degrade carbazole.

Alternative method of inoculum and spawn production for the cultivation of the edible brazilian mushroom Pleurotus ostreatoroseus SING.

Abstract: Efficiency of solid and liquid inocula and their use for spawn production were compared so that improved cultivation conditions for the edible mushroom Pleurotus ostreatoroseus could be tested. Solid and liquid inocula were prepared respectively with Potato Dextrose Agar (PDA) and Liquid Potato Dextrose (LPD). Wheat grains and cotton residues were used as substrates for spawn preparation. Inoculum types did not affect the development of P. ostreatoroseus, and LPD spawns were cheaper, more homogenous, less contaminated. Decomposition activity of mushroom growth, as a percentage of organic matter loss (OML), was higher in the wheat grain spawn and was not influenced by the inoculum type. Advantages in the use of cotton residue for spawn production were longer storage time, lower contamination and reduced costs. The cotton residue substrate may be also used for the production of mushroom fruiting bodies.

Toxicity of Bacillus thuringiensis and B. sphaericus to laboratory populations of Drosophila melanogaster (Diptera: Drosophilidae).

Abstract: A total of 65 samples, consisting of 8 sample types, collected from the Jordan Valley, were examined for the presence of Bacillus thuringiensis and B. sphaericus and for their toxicity against the larvae of the fruit fly Drosophila melanogaster. The frequency of samples containing toxic aerobic spore-forming bacilli was 12%; of which 21.7% belonged to B. thuringiensis and 17.4% to B. sphaericus. The B. thuringiensis populations consisted of 5 serogroups: thuringiensis (H1), entomocidus (H6), pakistani (H13), autoagglunated, in addition to a new serotype. The B. sphaericus population consisted of 3 serogroups, and belonged to serovars H5, H9, and H13. All B. thuringiensis and B. sphaericus local isolates, in addition to the reference strains B. thuringiensis kuristaki, and B. thuringiensis israelensis, showed high toxicity towards 3(rd) instar larvae of D. melanogaster. The toxic concentrations ranged between 2.0 x 10(6) and 4.4 x 10(7) viable spores ml(-1).

ELISA test to detect Chlamydophila pneumoniae IgG.

Abstract: A new ELISA test (Chlamydophila pneumoniae IgG, Vircell, Spain) to detect Chlamydophila pneumoniae IgG was evaluated. The micro-immunofluorescence (MIF) test was used as reference method. Chlamydia trachomatis and Chlamydophila psittaci elementary bodies were also assayed. Two hundred and sixteen sera were included in the study: 66 from patients with peripheral arterial occlusive disease (Panel 1), 68 from adults with pneumonia (Panel 2), 44 from healthy adults (Panel 3) and 38 from patients with a sexuality transmitted disease by C. trachomatis (Panel 4). In Panel 1, 51 sera (77%) had antibody titres between 32 and 128; 4 out of 15 sera with IgG titres < 32 were positive by ELISA test and 2 sera with 32 IgG titres were uncertain by ELISA; the remaining 60 sera were correctly classified, giving a 91% concordance between the techniques. In Panel 2, 55 sera (81%) had IgG titres between 32 and 512; 2 out of 13 sera with IgG titres < 32 were positive by ELISA and 2 sera with 32 titres were uncertain by ELISA; the remaining 64 sera were correctly classified, giving a 97% concordance. In Panel 3, 22 sera (50%) had IgG titres between 32 and 64; only 1 out of 22 sera with IgG titres < 32 was positive by ELISA, giving a 97% concordance between the techniques. In Panel 4, there were 24 (63%) negative, 10 (26%) uncertain and 4 (10%) positive results by ELISA, giving an 86% concordance. The C. pneumoniae ELISA test demonstrated 100% sensitivity and 85% specificity. The IgG ELISA test demonstrated a good concordance with the MIF test without the drawbacks associated with the latter assay. We conclude that the ELISA test could be an alternative to the MIF test.

Estimation of growth inhibition by copper and cadmium in heavy metal tolerant actinomycetes.

Abstract: A new isothermic model of actinomycetes growth in presence of toxic concentrations of Cd(2+) and Cu(2+) is described. Microbial growth inhibition, displayed as a decrease of biomass, can be correlated with the increase of cadmium(II) or copper(II) concentration in the medium. The reciprocal dry biomass against metal concentration showed a linear correlation higher than 0.9 in tested strains. The mathematical model can be useful to predict the behavior of actinomycetes at inhibitory concentrations of copper(II) and cadmium(II) in large screening procedures.

Fine separation and characterization of Candida rugosa lipase isoenzymes.

Abstract: Commercial Candida rugosa lipase has been separated into two distinct fractions (CRLA and CRLB) by anion-exchange chromatography. As analyzed on SDS-polyacrylamide gel electrophoresis, CRLA and CRLB are homogenous. At high ionic strength, CRLA and CRLB have similar hydrophobicity and UV spectra, suggesting that the open extent of the large hydrophobic pockets of CRLA and CRLB may be similar. At low ionic strength, using "hydrophobic interfacial affinity chromatography", both CRLA and CRLB have been separated into four isofractions. They have different hydrophobicity and UV spectra, suggesting that the open extent of the large hydrophobic pocket of the four forms may be different. Further, the conversion of CRL isoenzymes in the process of organic solvent treatment and ester hydrolysis were examined. The results clearly showed not only that CRLB had been converted to CRLA, but also that CRLA sub-fractions with different open extent of large hydrophobic pocket had been converted

Fingerprinting of Nigerian Helicobacter pylori isolates by plasmid profile and PCR.

Abstract: Plasmid profiling and digestion of amplified PCR product of ureA genes were used to determine genomic variation in 56 strains of Helicobacter pylori isolated from patients with peptic ulcers and subjects with gastritis recruited in Lagos and Ife, Nigeria. Twenty-five (45%) of the strains were found to harbour plasmids ranging in size from 0.9 kb to > 10 kb. The plasmid profile was able to detect differences between the strains, and also to distinguish between different strains isolated from the same patient. The expected amplified ureA gene PCR product was detected in all strains and digestion with the restriction enzyme DdeI did not produce discrimination amongst the strains, however, digestion with MluI produced little discrimination amongst strains. In conclusion, plasmid profiling produced better discrimination amongst H. pylori strains than ureA PCR gene profiling.

Influence of pH on the xylose reductase activity of Candida guilliermondii during fed‐batch xylitol bioproduction

Abstract: The influence of pH on the xylose reductase (XR) activity was studied The fed-batch fermentation using exponential feeding rate was employed to produce xylitol The feeding started when the xylose concentration in the fermenter reached 50 g/l and the pH was adjusted to 25, 40 or 60 The best results for XR activity (0567 U/mg(protein)) and xylitol volumetric productivity (106 g/lh) were achieved with pH 60