Microbios最新文献

A Mycobacterium bovis gene coding for a putative MalE maltose binding protein was cloned and its full-length sequence determined. Database searches revealed 99.9% identity with IpqY, encoding a putative sugar uptake protein from Mycobacterium tuberculosis strain H37Rv. The deduced protein product showed high sequence similarity to MalE-like proteins from a variety of bacterial species, including Mycobacterium leprae. Analysis of flanking database sequences from M. tuberculosis and M. leprae revealed the presence of malF-, malG- and malK-like genes. Comparison of these mycobacterial sequences with other maltose operons has allowed us to deduce a unique genomic arrangement of the genes involved in the uptake of maltose in members of the Mycobacterium tuberculosis complex and M. leprae.

The ability of casamino acids and vitamin-assay casamino acids to support gellan production by Sphingomonas paucimobilis ATCC 31461 was examined in a medium containing glucose or corn syrup as the carbon source relative to yeast extract supplementation. When glucose or corn syrup served as the carbon source, the presence of yeast extract in the growth medium stimulated gellan production by strain ATCC 31461 on casamino acids. Using vitamin-assay casamino acids as the nitrogen source, the addition of vitamins lowered gellan synthesis by glucose-grown cells regardless of yeast extract supplementation while gellan elaboration by corn syrup-grown strain ATCC 31461 cells could only be increased by supplementing vitamins into medium lacking yeast extract. Independent of carbon source, the absence of yeast extract in the medium reduced biomass production. Biomass production by the strain grown on either carbon source was increased by supplementing vitamins in the medium containing yeast extract.

The adhE gene, encoding the fermentative alcohol dehydrogenase, from Salmonella typhimurium (Genbank accession number U68173) was cloned and sequenced. The Salmonella AdhE protein has 619/878 (70%) amino acid residues identical to the AdhE protein of Escherichia coli. Salmonella AdhE was synthesized only anaerobically. It was present in higher amounts when cells were grown on reduced substrates such as sorbitol, instead of glucose. Growth on glucuronate, which generated no net nicotinamide-adenine dinucleotide reduced (NADH) during metabolism, showed the lowest AdhE levels. Analysis of fermentation products by in vivo nuclear magenetic resonance showed that the proportion of ethanol was highest with sorbitol, intermediate with glucose and negligible with glucuronate. The Salmonella enzyme had a lower Michaelis-Menten constant (Km) for alcohol substrates than AdhE of E. coli although both enzymes displayed a similar Km for nicotinamide-adenine dinucleotide (NAD+). Although AdhE of E. coli was inactive with alcohols longer than four carbons, the Salmonella enzyme was still active with alcohols up to eight carbons.

A mycelial mat of Lentinus edodes was treated with 0.01% (w/v) colchicine solution for 240 h at 26 degrees C and autopolyploidization occurred. The mycelia were treated subsequently with the haploidizing reagent, benomyl, and fanshaped sectors were produced from colonies. Among such sectors, cellulase hyperproducers could be selected. The cellulase productivity of the hyperproducer, L1, did not decrease through five generations.

A new lysis solution designated TZ, consisting of 2.0% Triton X-100 plus 2.5 mg sodium azide/ml in 0.1 M Tris-HCl buffer at pH 8.0, yielded higher levels of genomic DNA from Escherichia coli O157:H7 cells compared with a number of other commonly used cell lysis methods. Ethidium bromide stained DNA bands resulting from PCR amplification of target DNA from 100 CFU of E. coli O157:H7 were readily detected following electrophoresis of agarose gels. In contrast, conventional cell lysis methods failed to detect target DNA from 100 CFU after PCR amplification. The new solution was highly effective for lysing cell suspensions of Salmonella enteritidis, Pseudomonas putida, Lysteria monocytogenes and Psychrobacter immobilis.

A new microbial isolate, Pseudomonas 2HS, produced trace amounts of a greenish-yellow pigment when grown aerobically in a 1% yeast extract medium at 30 degrees C and shaken at 250 rpm for 5 days. In contrast, cells produced more greenish-yellow pigment (2.16 mg/15 ml culture) when grown in the presence of 0.5% 12-hydroxyoctadecanoic acid (w/v). The greenish-yellow pigment was identified as phenazine-1-carboxylic acid (tubermycin B), and the Pseudomonas 2HS was identified as P. aeruginosa 2HS. This is the first report that 12-hydroxyoctadecanoic, ricinoleic and other fatty acids can enhance the production of phenazine-1-carboxylic acid by a Pseudomonas species.

The potentiality of 25 fungal species, belonging to fourteen genera isolated from Egyptian soils, to produce mevinolin, a hypocholesterolaemic agent, when grown on selected substrates was tested. Samples of culture filtrates were tested by thin layer chromatography and the positive results were further assessed by high pressure liquid chromatography analysis. It was found that nearly one-third of the fungi showed positive results for production of mevinolin. Aspergillus terreus was distinguished by its capacity to produce mevinolin when cultivated on selected media. Some factors influencing mevinolin production and the growth of A. terreus were also studied. The maximal mevinolin yields were achieved after 8 days incubation at 30 degrees C. An initial pH value of 5-6 was the optimum for growth of A. terreus and mevinolin production.

Mutants of Anabaena sp. PCC 7120 resistant to chlorate were isolated using transposon mutagenesis. The Anabaena population of 5 x 10(7) cells ml(-1) and log phase Escherichia coli cultures in undisturbed conditions produced maximum exconjugants. Nitrate-promoted growth and cellular constituents observed in the parent were absent in the mutants. Nitrate repressed heterocyst formation and N2-fixation in the parent, but had little or no effect on the mutants.

The current investigation was carried out in order to compare directly the multiple tube fermentation method (MTF), using standard procedures (lactose broth, LB) and the Colilert reagent, with the membrane filter method (MF) using Les Endo agar (LEA), m-faecal coliform agar (mFCA) and chromogenic coliform agar (CCA), for recovery of coliforms and Escherichia coli in 80 surface water samples. Total coliforms were isolated from 100% of samples by all methodologies. Faecal coliforms/E. coli were detected in 100% of samples by MTF methods, but only in 75.5% by MF-mFCA and in 86.2% by MF-CCA. Even if MTF-LB counts were consistently higher, the Colilert reagent accurately determined total coliforms and E. coli levels within 24 h with no additional confirmatory tests. Therefore, it could be a powerful tool for rapidly assessing possible faecal contamination and a suitable alternative to the traditional MTF and MF techniques utilized for coliform detection.

The ability of the ectomycorrhizal fungus Suillus grevillei (Klotzsch) Singer to grow in agitated submerged culture was investigated by employing the Marx-Melin-Norkrans (MMN) medium. The operating conditions suitable for improving the biomass production were determined. Batch experimental tests were carried out in either shake flasks or a stirred tank reactor. The results showed that at least two factors strongly affected the fungal growth, namely the pH and the ammonia-nitrogen concentration in the medium. By controlling the acidity in the pH range 4-5 with a Na-citrate buffer solution and introducing the ammonia-nitrogen in a step-feed way (without exceeding a concentration of approximately 0.07 kg N/m3), the exponential growth phase continued for longer than that of the control culture (no stationary phase seemed to be reached after 17 days) and an approximately 2-fold increase of the biomass/substrate growth yield was obtained compared with the control culture.