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1.
K. R. N. Reddy Ch. Surendhar Reddy P. Nataraj Kumar C. S. Reddy K. Muralidharan 《World journal of microbiology & biotechnology》2009,25(1):33-39
Twenty-two aflatoxin B1 (AFB1) producing Aspergillus flavus strains were isolated from 1,200 discolored rice grain samples collected from 20 states across India and tested their potential
to produce AFB1 on different agar media. Further these isolates were characterized through randomly amplified polymorphic
DNA method. All the strains of A. flavus were produced AFB1 on yeast extract sucrose agar media and none of the strains on A. flavus and A. parasiticus agar. Among the 22 strains, two strains from Tamil Nadu (DRAf 009) and Maharashtra (DRAf 015) produced high amount of AFB1
in all the media tested. To assess the genetic variability in A. flavus, the isolates were analyzed by using random amplified polymorphic DNA markers. Isolates showed 17–80% similarity with standard
culture of A. flavus (MTCC 2799). 相似文献
2.
Yokochi T Nakahara T Higashihara T Yamaoka M Kurane R 《Marine biotechnology (New York, N.Y.)》2001,3(1):68-73
A new isolation method for labyrinthulids, marine microbes with spindle-shaped vegetative cells and gliding movement, is
presented. The method for isolating labyrinthulids has been found to be more difficult and less reproducible than that for
thraustochytrids, classified in the same order. So far serum seawater agar fortified with antibiotics has been proposed to
be the best for isolation of labyrinthulids. The method presented here involves placing plant samples on an agar medium on
which a marine bacterium, Psychrobacter phenylpyruvicus, has been grown. The new method, which utilizes fallen mangrove leaves as source material, was more than twice as effective
as isolation agar medium without the bacterium. The increased effectiveness appears to derive partly from the bacterial colonies'
delaying extension of fungal mycelium. The bacterium was more effective for the isolation of labyrinthulids than either the
bacterium Shewanella sp. or the yeast Rhodotorula rubra. 相似文献
3.
In the present study, Escherichia coli cells exhibited antibiotic resistance after transformation with exogenous plasmid DNA adsorbed onto chrysotile particles during agar-exposure. We previously demonstrated penetration of E. coli by chrysotile particles during agar-exposure. To further investigate the mechanism by which transformation of E. coli is achieved through the use of chrysotile fibers, the interaction between E. coli cells and chrysotile was examined during agar-exposure. Dispersion of chrysotile particles within the chrysotile solution was analyzed by flow cytometry. A suspension containing E. coli cells expressing blue fluorescence protein and chrysotile particles was exposed to agar using stirring apparatus, which allowed a constant vertical reaction force to be applied to the surface of the gel. Fluorescence microscopy was then used to illustrate the adsorption of fluorescein isothiocyanate-conjugated DNA oligomers to chrysotile. Larger aggregates were observed when increasing concentrations of chrysotile were added to the solution. With prolonged exposure, during which surface moisture diffused into the agar gel, greater concentrations of chrysotile were observed on the agar surface. In addition, chrysotile aggregates exceeding 50 m developed on the agar surface. They were shaped like a chestnut bur. The chrysotile aggregates penetrated the cell membranes of adherent E. coli cells during agar-exposure due to sliding friction forces generated at the interface of the agar and the stirring stick. E. coli cells thus acquired plasmid DNA and antibiotic resistance, since the plasmid DNA had been adsorbed onto the chrysotile particles. The inoculation of plasmid DNA into E. coli cells demonstrates the usefulness of chrysotile for E. coli transformation. 相似文献
4.
Carla Fontana Teresa Jezzi Gian Piero Testore Benedetto Dainelli 《Microbiology and immunology》1995,39(4):231-235
A simple, rapid and reliable outline for identification of clostridia isolates from human infections was developed. It consists of a combination of API ZYM and API LRA Oxidase tests. The enzymatic activities were performed with strains sub-cultured onto carbohydrate-free medium (Columbia blood agar). Fifty-five strains of Clostridium difficile, C. bifermentans, C. sordellii, and C. perfringens from clinical specimens and eight reference standard strains representing different species of the same genus were analyzed. The accuracy of the new method was evaluated by comparison with the results obtained by DNA/DNA analysis. 相似文献
5.
Kellie Byrne Giuseppe C. Zuccarello John West Ming-Long Liao Gerald T. Kraft 《Phycological Research》2002,50(4):295-311
Select species of the agarophyte Gracilaria were studied from southeastern Australia. The morphology and anatomy of species is described and molecular relations are inferred based on plastid and mitochon‐drial DNA sequence data. Agar yields and qualities are determined for each species. Gracilaria chilensis, found in Tasmania and Victoria, is morphologically and molecularly similar to G. chilensis from New Zealand and Chile and has low agar yields of 11–16%. Gracilaria cliftonii from Victoria, has high crude agar yield (52%) and is molecularly uniform. Gracilaria perplexa sp. nov., known only from Botany Bay, New South Wales, has an agar yield of 39%. The agar of G. perplexa is unusual in requiring the addition of 0.1 mol L?1 NaCl for alcohol precipitation and is cold‐water (25°C) soluble because of the very high sulfate ester content. Molecular phylogeny shows that G. perplexa is closely related to Gracilaria preissiana from western Australia, but differs from the latter in its reduced branching and narrower more terete axes. 相似文献
6.
Losses due to postharvest decay may occur at any time during postharvest handling, from harvest to consumption affecting the produce quality and quantity. Accurate identification of the pathogen causing postharvest disease is essential to the selection of an appropriate disease control approach. Nine isolates of Fusarium recovered from orange fruit were identified as Fusarium solani. The fungus is involved with fruit decay. The obtained cultures were purified and grown on potato-dextrose agar (PDA), malt yeast agar (MYA), and Czapek's nutrient media (CNM) under light for identification. A pathogenicity test was carried out to fulfil Koch's postulates. The pathogen could only enter ripe orange fruit through wounds and cracks causing the rot disease. The identification of the fungal isolates was confirmed to be F. solani by DNA sequencing, which was 99 to 100% homologous to those deposited in the Gen- Bank. The identity of nine fungal isolates was confirmed to be F. solani by DNA sequencing of the internal transcribed spacer (ITS) rDNA region (GenBank Accession Nos. DQ486874 to DQ486881 and KC758879). To our knowledge, this is the first morphogenetic identification of F. solani isolated from orange fruit in Egypt. 相似文献
7.
A simple method developed for genomic DNA isolation from fungus was tested on the red alga, Gelidium sesquipedale (Clem.) Born et Thur., which is commercially exploited for its high sulfated polysaccharide (agar) content. This method is faster, cheaper, and less toxic than conventional phenol/chloroform methods. Random amplified polymorphic DNA (RAPD) amplifications were performed successfully without the necessity of purifying the DNA. RAPD markers were used to investigate the genetic similarity among three natural populations of G. sesquipedale from southern Portugal. Bulked-genomic DNA samples of 15 different individuals were made in each population. These can be conceived of as a sample of the population DNA. Of the 62 primers screened, 41 produced bands and 22 revealed polymorphisms. Genetic similarities among populations were high. Populations that are further away from each other have the lowest similarity coefficients, whereas the intermediate Ingrina population, located on the south coast, showed higher genetic similarity with the Odeceixe population located on the southwest coast, than with the São Rafael southern population. This suggests a higher genetic flow between Odeceixe and Ingrina or the result may be a founder effect in the sense that the species has propagated from the east coast to the south coast of Portugal. We conclude that the use of this isolation method with RAPD analysis is appropriate to characterize the genetic variability of this commercial species along its geographical distribution. Large sample sizes can be screened at a relatively low cost. Finding genetic markers for commercial populations of G. sesquipedale may be of industrial interest. 相似文献
8.
Summary
Penicillium commune and Aspergillus flavus were grown on a microporous membrane (pore diameter 2.4 nm) overlaying an agar medium. The mycelium was easily separated from the membrane disc and assayed for dry weight, protein and DNA content, while the concentrations of total aflatoxins and cyclopiazonic acid were determined in the mycelium and in the underlying agar. Mycotoxin production commenced during the exponential phase of growth and concentrations of both toxins were still increasing after 7 days incubation. Toxins were detected in the mycelium 1–2 days before they could be detected in the agar. 相似文献
9.
Arthur Hanson Cameron Michelle Joubert Elizabeth Witthuhn R. Corli 《World journal of microbiology & biotechnology》2011,27(2):443-447
The consumption of herbal teas is an increasing phenomenon among tea consumers globally. Some of these herbal teas are not
pre-treated to reduce their microbial load before consumption, and thus constitute a health risk to consumers. In this study,
the effect of steam pasteurization, at >99 °C for 2.5 min, on the microbial load of Lippia multiflora herbal tea leaves was evaluated. Microbial enumeration was conducted on potato dextrose agar, plate count agar, violet red
bile agar, yeast peptone dextrose agar, and DeMan-Rogosa-Sharpe agar. Morphologically distinct colonies were isolated, sub-cultured
and their Gram reaction recorded. These bacteria were identified to the species level using 16S ribosomal DNA sequence data.
Most of the bacteria identified belonged to the genus Bacillus. One species each from the genera Pantoea and Kocuria was also identified, but only the Bacillus species survived the steam pasteurization treatment. Coliform bacteria detected prior to pasteurization were not detected
after the steam treatment. Steam pasteurization reduced the microbial load from 104 to 102 c.f.u.g−1and it is potentially an effective method to treat L. multiflora herbal teas prior to consumption. It is important to note that the steam treatment should complement good agricultural and
hygienic practices rather than replace them, as some bacteria can survive this treatment. 相似文献
10.
Summary Methods for countingAzotobacter species in soil have been examined. The highest counts were obtained from soil suspensions shaken in sterile distilled water containing 10-g glass beads and plated on to glucose agar. Mannitol has been rejected as a suitable substrate in agar media because it gives lower counts of Azotobacter than glucose, an effect which is further enhanced by drying the agar plates. A clear medium free from precipitated phosphate and CaCO3 is recommended for the agar-plate method; the Azotobacter count is affected by the phosphate concentration.The agar-plate and dilution-tube methods were compared; the latter is less accurate but more convenient when many soil samples have to be examined. 相似文献
11.
Summary Nuclease halo (nuh) mutants of the ascomycete Neurospora crassa have been isolated which are characterized reduced release of deoxyribonuclease (DNase) activities from colonies grown on sorbose-containing agar media. To identify nuh mutants, mutagenized isolates were transferred to commercial DNase test agar, or grown on minimal medium and then overlayed with agar that contained heat-denatured DNA. DNase activity was visualized by acid precipitation which produced clear rings of digestion (haloes) around the colonies.To identify the number of genes in which mutations lead to reduced release of nuclease activity, eleven nuh mutants were checked for close linkage and linked pairs were tested for complementation. These mutants were assigned to eight genes, and all except one were mapped in six small regions of the Neurospora linkage maps. In addition, among a large number of existing mutants which were tested for nuclease haloes, two mutants were found that showed the Nuh phenotype, namely uvs-3 and uvs-6. One of the isolated nuh mutants was also found to be sensitive to UV and was mapped close to uvs-3; it may represent a new allele of this gene.As a first step towards identification of genuine nuclease mutants, extensively backcrossed strains of mutants from different genes have been assayed for nuclease activity with denatured DNA in extracts. A pronounced reduction, compared to wild type at the same stage of growth, was found in uvs-3 and also in nuh-3, a mutant that is not UV-sensitive. 相似文献
12.
Heterotrophic and autotrophic culture in agar and in polyurethane foam, the latter used as an alternative tissue support to agar, resulted in potato microplants with different in vitro morphologies. The microplants were visually characterised in terms of their relative developmental maturity, by comparing the respective leaf shapes in vitro with ontogenetic differences in leaf shape in glasshouse-grown potato plants. Cytosine methylation in the DNA of microplants of the different morphologies was determined using a method based on the AFLP technique but employing methylation-sensitive restriction enzymes (MSAP analysis) to test the hypothesis that DNA methylation could be used to characterise differences in microplant development in vitro. In three of the four treatments there was a good correlation between the visual assessment of relative morphological maturity and DNA base methylation levels. In these microplants there was increased DNA methylation in the leaves with mature leaf morphology represented by a decreased number of restriction fragments. The fourth in vitro morphology had the most juvenile leaf shape but did not have the predicted level of DNA methylation, having a relatively low number of restriction fragments. Subtraction analysis was used to discriminate the fragments that were unique to the juvenile and mature in vivo leaf morphologies. Comparison of the fragment patterns from the microplants with the latter reference profiles, confirmed the relationship with the total DNA methylation as detected by MSAP analysis, that is, the number of common fragments with the juvenile or mature in vivo leaf profiles, respectively. However, none of the fragment profiles, while sharing some common bands at random, was identical to any other; or to that of either the juvenile or mature in vivo leaf. The anomalous relationship of the microplants with most juvenile leaf shape and highest DNA methylation was confirmed. The measurement of DNA methylation in in vitro plants is discussed in the context of the development of a method to assess the quality of microplants produced by different in vitro protocols. 相似文献
13.
Daaka Yehia Yamamoto Yoshimasa Klein Thomas W. Newton Catherine Friedman Herman 《Current microbiology》1994,28(4):217-223
Legionella pneumophila is the causative agent of Legionellosis in man and considered an opportunistic intracellular Gram-negative bacterium that preferentially infects macrophages. The presence of a plasmid in these organisms was determined in cultures of the bacteria grown in vitro. A correlation was observed between the growth of virulent strains of theLegionella in murine macrophages and growth on standard buffered charcoal yeast extract agar supplemented with 0.1% -ketoglutarate (BCYE) agar medium rich in cysteine and widely used for growth of the bacteria in vitro. In contrast, the avirulent isolates of these strains grew well on supplemented Mueller-Hinton (SMH) agar utilized for differentiating virulent from avirulentLegionella. However, one virulent strain ofLegionella (the Iowa strain) was found to grow moderately well on the SMH agar. In addition, test strains ofLegionella that infect in vitro human monocytes were found to grow moderately well on the BCYE- agar, but did not grow on the SMH agar. Examination of these strains for plasmid DNA expression showed that extra chromosomal DNA-containing molecules were present in theL. pneumophila strains characterized as virulent for in vitro growth in macrophages. However, the avirulent strains that replicated in the human monocytes readily but only poorly in the permissive murine macrophages did not show evidence of similar plasmid DNA expression. 相似文献
14.
Donald F. Kapraun Juan Lopez-Bautista Gavino Trono Kimon T. Bird 《Journal of applied phycology》1996,8(2):125-130
Eight species of Gracilariaceae from the Philippines, representing the generaGracilaria, Gracilariopsis andHydropuntia, were investigated to quantify and characterize their nuclear genomes. DNA reassociation kinetics were used to determine nuclear genome organization and complexity in six of these species. Results indicate the presence of three second order components corresponding to fast, intermediate and slow fractions. Repetitive sequences varied from 13–74% and unique DNA ranged from 26–84%. Microspectrophotometry with the DNA-localizing fluorochrome DAPI was used to quantify nuclear DNA contents. Comparisons of mean nuclear DNA (I
f
) values to chicken erythrocytes (RBC) resulted in an estimate of 0.38–0.43 pg/2 C genomes for seven of the species investigated. Preliminary analyses of agar content and quality confirm the economic potential ofGracilaria firma, Gracilaria sp. 2 from Sorsogon andGracilariopsis bailinae. Nuclear genome profiles developed from data for genome size, organization and complexity are compared with data for agar quantity and quality. Gel quality and quantity do not appear to be correlated with either large repetitive fraction DNA or a high degree of genome complexity.Author for correspondence 相似文献
15.
Donald F. Kapraun Edna Ganzon-Fortes Kimon T. Bird Gavino Trono Chris Breden 《Journal of applied phycology》1994,6(5-6):545-550
Microspectrophotometry with the DNA-localizing fluorochrome DAPI demonstrated ploidy level differences in tetrasporophytic and presumptive gametophytic phases ofGelidiella acerosa from the Philippines. Comparison of mean nuclear DNA (I
f
) values to chicken erythrocytes (RBC) resulted in an estimate of 0.32 pg/2 C genome. Karyological studies with aceto-orcein revealed a chromosome complement of six bivalents during diakinesis of tetrasporocytes. The agar yield ranges from 13–24% dry weight, depending on the method of extraction. Agar extraction in 1 N NaOH resulted in an increased gel strength of 189 g cm–2 at 1.5% concentration. Infrared spectroscopy indicated a relatively high sulfate content in native agar. The low (61 °) melting temperature is indicative of high sulfation and small molecular size. 相似文献
16.
Hybrid isolation by recovery of RNA-DNA hybrids from agar using S1 nuclease 总被引:2,自引:2,他引:0
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A method for recovering RNA-DNA hybrids from agar employing a single strand specific nuclease is described. The procedure is suitable for large scale isolations, and immobilization of the DNA in agar prior to hybridization allows a high yield of hybrid without interference by DNA reannealing. 相似文献
17.
18.
The dairy yeast Kluyveromyces marxianus is a promising cell factory for producing bioethanol and heterologous proteins, as well as a robust synthetic biology platform host, due to its safe status and beneficial traits, including fast growth and thermotolerance. However, the lack of high-efficiency transformation methods hampers the fundamental research and industrial application of this yeast. Protoplast transformation is one of the most commonly used fungal transformation methods, but it yet remains unexplored in K. marxianus. Here, we established the protoplast transformation method of K. marxianus for the first time. A series of parameters on the transformation efficiency were optimized: cells were collected in the late-log phase and treated with zymolyase for protoplasting; the transformation was performed at 0 °C with carrier DNA, CaCl2, and PEG; after transformation, protoplasts were recovered in a solid regeneration medium containing 3–4% agar and 0.8 m sorbitol. By using the optimized method, plasmids of 10, 24, and 58 kb were successfully transformed into K. marxianus. The highest efficiency reached 1.8 × 104 transformants per μg DNA, which is 18-fold higher than the lithium acetate method. This protoplast transformation method will promote the genetic engineering of K. marxianus that requires high-efficiency transformation or the introduction of large DNA fragments. 相似文献
19.
Mario Antonio Vergara-Rodarte Gustavo Hernández-Carmona Y. Elizabeth Rodríguez-Montesinos Dora Luz Arvizu-Higuera Rafael Riosmena-Rodríguez Jesús Iván Murillo-Álvarez 《Journal of applied phycology》2010,22(6):753-759
Gracilaria vermiculophylla, from Baja California Sur, Mexico, was studied in order to determine the seasonal variation of yield and quality of native
and alkaline agar during 2007–2008. The highest alkaline agar yield was obtained in summer (17%) and the highest gel strength
in spring (1,132 g cm−2). The highest melting temperature was 98°C (winter). The highest gelling temperature was 68°C (summer). The values obtained
are within the range of the most important Gracilaria species harvested worldwide. During the agar extraction step, the best results were obtained after 30 min of alkali treatment
with sodium hydroxide (7%), after which the quality decreased significantly. We produced Colagar from G. vermiculophylla which consists of the seaweeds treated with sodium hydroxide and dried. The yield and quality of the agar obtained from the
Colagar shows stability in both yield and quality during 1 year of storage, suggesting that alkali treatment is a good method
of avoiding agar hydrolysis during storage. 相似文献
20.
M.‐L. GUILLEMIN C. DESTOMBE S. FAUGERON J. A. CORREA M. VALERO 《Molecular ecology resources》2005,5(1):155-157
The red algae Gracilaria chilensis is extensively cultivated for agar production. In spite of its commercial significance as the first algal resource in Chile, no information is available on the pattern of genetic diversity. In this paper, we isolated six polymorphic microsatellite markers from a G. chilensis‐enriched DNA library. Genetic diversity was assessed in two natural populations revealing relatively low levels of heterozygosity ranging from 0.00 to 0.51. The six loci developed here are good candidates to assess the level of genetic resources within this species, which probably suffered from over‐exploitation in several localities along the Chilean coast. 相似文献