Heat-stability of peroxidase in mycelia of some toxigenic and nontoxigenic Aspergilli and Penicillia

Seven-day-old mycelia from 19 cultures of Aspergillus and 12 cultures of Penicillium were heated to 50, 60, 65, 70, 75, 80, 85, 90 or 95 C for no more than min, and tested for residual peroxidase. The peroxidase from all aspergilli survived heating at 50 through 80 C. Peroxidase from toxigenic strains of Aspergillus flavus, Aspergillus parasiticus and Aspergillus ochraceus survived heating at 85 C and often at 90 C, whereas peroxidase from nontoxigenic strains of A. flavus was inactivated at 90 C and markedly reduced in activity at 85 C. Peroxidase from all penicillia survived heating at all temperatures through 80 C, although the activity of several cultures was reduced at 80 C. Peroxidase activity in mycelia of two strains of Penicillium cyclopium and one of Penicillium puberulum failed to survive heating at 85 C. One strain each of Penicillium roqueforti and Penicillium viridicatum exhibited some peroxidase activity after heating at 90 C, whereas the peroxidase of all other penicillia was inactivated at this temperature.     

Aflatoxin is degraded by heated and unheated mycelia,filtrates of homogenized mycelia and filtrates of broth cultures of Aspergillus parasiticus

Steaming one-half of a lot of 9-day-old mycelia of Aspergillus parasiticus NRRL 2999 for 6 min resulted in little or no subsequent degradation of aflatoxin B₁ or G₁ by these mycelia. The other half of these mycelia was not heat-treated and degraded aflatoxins B₁ and G₁ Filtrates of the growth substrate which remained after the mycelium was removed from 8- to 15-day old cultures of A. parasiticus NRRL 2999 did not degrade substantial amounts of aflatoxin B₁ or G₁, whereas mycelia originally produced on these filtrates degraded substantial amounts of both aflatoxins. The supernatant fluid from homogenates of 9-day-old mycelia of A. parasiticus NRRL 2999 degraded aflatoxins B₁ and G₁ when 0.1 M or 1.0 M phosphate buffer, pH 6.5, was used to suspend the homogenate. These data support the hypothesis that the aflatoxin degrading factor(s) present in the mycelium of A. purasiticus is/are enzyme(s) or at least influenced by enzyme(s).     

Invasive properties of toxigenic and nontoxigenic Vibrio cholerae of different serogroups

Experimental data on the comparative study of the invasive properties of vct+ Hly- and vct- Hly+ V. cholerae of serogroups 01 and 0139 are presented. Both vct- Hly+ and vct+ Hly- V. cholerae of serogroups 01 and 0139 have been shown to be capable of dissemination into internal organs. No differences in the dissemination of V. cholerae of different serogroups in both immunologically immature and mature experimental animals have been detected.     

Aflatoxin is degraded at different temperatures and pH values by mycella of Aspergillus parasiticus

Summary Blended 9-day-old mycelia of Aspergillus parasiticus NRRL 2999 were tested for their ability to degrade aflatoxins B₁ and G₁ at 7,19,28,36, and 45°C. Rates for degradation of aflatoxin B₁ and G₁ were maximum at 28°C. Intermediate rates of aflatoxin degradation were observed at 19 and 36°C while little aflatoxin was degraded at 7 and 45°C. Five different pH values (2.0, 3.0, 4.0, 5.0, and 6.5) were also tested to determine the effect of pH on ability of blended 9-day-old mycelia of A. parasiticus NRRL 2999 to degrade aflatoxins. The ability of mycelia to degrade aflatoxin was pH-dependent. Of the pH values tested, greatest rates of aflatoxin B₁ and G₁ degradation occurred when pH was in the range of 5 to 6.5. Little aflatoxin was degraded at pH 4.0 and essentially no aflatoxin was degraded by mycelia at pH 2.0 or 3.0 although some aflatoxin was degraded by acid conditions only at pH values of 4 or less.     

产毒和非产毒霍乱弧菌在甘露醇 和Luria-Bertani培养液中的基因表达差异

摘要：【目的】分析霍乱弧菌产毒株和非产毒株在甘露醇发酵液和LB (Luria-Bertani) 培养液中生长的基因表达谱和代谢差异特征。【方法】提取甘露醇发酵液和LB培养液中霍乱弧菌甘露醇慢发酵株（产毒株）N16961和快发酵株（非产毒株）93097生长第一小时的总RNA,应用霍乱弧菌N16961基因组芯片分析各菌株在不同培养液中的表达差异基因。【结果】 筛选出产毒株N16961在甘露醇发酵液和LB中表达差异基因142个,非产毒株93097有418个,这些表达差异基因主要分属于6个不同的功能类群,主要是转运结合、能量代谢以及蛋白质合成代谢功能。【结论】甘露醇发酵液和LB中产毒株和非产毒株的许多功能基因的转录水平有显著差异,这些表达差异基因可能与霍乱弧菌在甘露醇发酵液中代谢产酸有关,这为进一步分析霍乱弧菌代谢甘露醇的机制、以及分析产毒株与非产毒株的甘露醇发酵快慢机制提供了基础。     

Effect of light intensity on the relative dominance of toxigenic and nontoxigenic strains of Microcystis aeruginosa

In aquatic ecosystems, the factors that regulate the dominance of toxin-producing cyanobacteria over non-toxin-producing strains of the same species are largely unknown. One possible hypothesis is that limiting resources lead to the dominance of the latter because of the metabolic costs associated with toxin production. In this study, we tested the effect of light intensity on the performance of a microcystin-producing strain of Microcystis aeruginosa (UTCC 300) when grown in mixed cultures with non-microcystin-producing strains with similar intrinsic growth rates (UTCC 632 and UTCC 633). The endpoints measured included culture growth rates, microcystin concentrations and composition, and mcyD gene copy numbers determined using quantitative PCR (Q-PCR). In contrast to the predicted results, under conditions of low light intensity (20 μmol·m(-2)·s(-1)), the toxigenic strain became dominant in both of the mixed cultures based on gene copy numbers and microcystin concentrations. When grown under conditions of high light intensity (80 μmol·m(-2)·s(-1)), the toxigenic strain still appeared to dominate over nontoxigenic strain UTCC 632 but less so over strain UTCC 633. Microcystins may not be so costly to produce that toxigenic cyanobacteria are at a disadvantage in competition for limiting resources.     

Hemolytic activity of Vibrio cholerae eltor and V. cholerae O139 toxigenic and nontoxigenic strains

A total of 20 ctx- and 16 ctx+ V. cholerae eltor strains, 20 ctx- and 22 ctx+ V. cholerae O139 strains were under study. Hemolytic activity was tested in modified Greig test with sheep, guinea pig and rabbit red blood cells. The comparative study of the hemolytic properties of V. cholerae O1 and O139 under different conditions of cultivation demonstrated their capacity of lysing sheep red blood cells (SRBC) irrespective of the presence of toxigenic properties. A wider spectrum of lytic activity of ctx- strains in Greig test with respect to red blood cells of different animals and the capacity of lysing SRBC, most resistant to the action of toxin, may be due to a considerably greater content of Hly+ clones in their population.     

产毒和非产毒霍乱弧菌在甘露醇发酵液和Luria-Bertani培养液中的基因表达差异

[目的]分析霍乱弧菌产毒株和非产毒株在甘露醇发酵液和LB(Luria-Bertani)培养液中生长的基因表达谱和代谢差异特征.[方法]提取甘露醇发酵液和LB培养液中霍乱弧菌甘露醇慢发酵株(产毒株)N16961和快发酵株(非产毒株)93097生长第一小时的总RNA,应用霍乱弧菌N16961基因组芯片分析各菌株在不同培养液中的表达差异基因.[结果]筛选出产毒株N16961在甘露醇发酵液和LB中表达差异基因142个,非产毒株93097有418个,这些表达差异基因主要分属于6个不同的功能类群,主要是转运结合、能量代谢以及蛋白质合成代谢功能.[结论]甘露醇发酵液和LB中产毒株和非产毒株的许多功能基因的转录水平有显著差异,这些表达差异基因可能与霍乱弧菌在甘露醇发酵液中代谢产酸有关,这为进一步分析霍乱弧菌代谢甘露醇的机制、以及分析产毒株与非产毒株的甘露醇发酵快慢机制提供了基础.     

Role of iron ions in the production of hemolysin by toxigenic and nontoxigenic Vibrio cholerae of different serogroups

The hemolytic activity of ctx- and ctx+ V. cholerae, serogroups eltor and O39, in a medium free of FeCl3 was studied. During the cultivation in this medium, the strains of both V. cholerae serogroups proved to be capable of lysing sheep red blood cells in the Graig test, irrespective of the presence of ctx genes. The cultivation of V. cholerae ctx+ strains of both serogroups under such conditions facilitated the production of hemolysin with the same spectrum of lytic activity as hemolysin produced by ctx- strains.     

Cellulase and protein production by Chaetomium cellulolyticum strains grown on cellulosic substrates

Summary Fermentation with Chaetomium cellulolyticum was carried out on media containing either Avicel cellulose or newspaper. Production of free cellulolytic enzymes, cellulose degradation and the formation of cell protein were studied with the original strain and a mutant strain.     

Characteristics of the immune response of inoculated and intact animals to the administration of toxigenic and nontoxigenic strains of Clostridium tetani

In experiments on guinea pigs the immune reactions of the animals immunized and not immunized against tetanus in response to the injection of C. tetani spores were studied. In the immunized animals an increase in the production of tetanus antitoxin, the development of delayed hypersensitivity and the activation of the mechanisms of cell-mediated immunity were observed. The nonimmunized animals showed specific changes in the T-system of immunity without the appearance of the clinical symptoms of tetanus, which is, probably, one of the mechanisms of natural immunity.     

Proteins involved in difference of sorbitol fermentation rates of the toxigenic and nontoxigenic Vibrio cholerae El Tor strains revealed by comparative proteome analysis

Background  

The nontoxigenic V. cholerae El Tor strains ferment sorbitol faster than the toxigenic strains, hence fast-fermenting and slow-fermenting strains are defined by sorbitol fermentation test. This test has been used for more than 40 years in cholera surveillance and strain analysis in China. Understanding of the mechanisms of sorbitol metabolism of the toxigenic and nontoxigenic strains may help to explore the genome and metabolism divergence in these strains. Here we used comparative proteomic analysis to find the proteins which may be involved in such metabolic difference.     

Antitumor activities of heteropolysaccharides of Poria cocos mycelia from different strains and culture media

Ten water-soluble heteropolysaccharide fractions were isolated from Poria cocos mycelia cultured from one wild and one cultivated strain in two identical culture media differing only in one component: either corn steep liquor or bran extract. The chemical compositions, including monosaccharide profile, protein content, and molecular mass M(w) of the mycelial polysaccharides were determined. Both the in vitro and in vivo antitumor activities of the heteropolysaccharides were evaluated and compared. The heteropolysaccharides from Poria cocos mycelia cultured with the wild strain in a medium containing corn steep liquor exhibited the highest antitumor activities against Sarcoma 180 in vivo.     

纤维素酶制备过程中不同底物、菌种的研究

比较用两个菌（黑氏木霉Ｔrichoderma reesei RutC-30及其改良菌种）和不同的纤维底物备纤维素酶解效果与酶系构成,研究表明,以玉米秸秆米为底物,发言奶菌种产酶时间比里氏木霉早２天,且改良菌种滤纸酶活要比里氏木霉高,分别为２．３９ＦＰＩＵ／mL和１．８５ＦＰＩＵ／mL,里木氏霉已实际运用到生产工艺中,如把改良菌种运用至生产工艺必将产生可观的经济效益。     

Incorporation of32P-orthophosphate into phospholipids by a toxigenic and a nontoxigenic strain of Aspergillus flavus

The incorporation of³²P-orthophosphate into phospholipids by a toxigenic and a nontoxigenic strain ofAspergillus flavus was compared on a glucose-salts medium (AM medium) and a sucrose-yeast extract medium (YES medium). AM medium gave higher incorporation of³²P than YES medium. In AM medium the highest specific activities were found in phosphatidyl choline and phosphatidyl ethanolamine but in YES medium phosphatidyl inositol and phosphatidyl serine also had specific activities of the same order as phosphatidyl choline and phosphatidyl ethanolamine. Mycelia of the toxigenic strain grown and resuspended in AM medium yielded 1.4 times specific activities given by nontoxigenic strain. The two strains did not differ very much in the incorporation obtained in the other media combination tried. These results are in contrast to the large differences obtained in the incorporation of¹⁴C-acetate in earlier studies. The significance of these findings are discussed.These results were presented at the Symposium on the Chemistry and Metabolism of Lipids and Related Subjects held at Vallabhbhai Patel Chest Institute, Delhi on October 3–5, 1969.     

Hypersaline waters - a potential source of foodborne toxigenic aspergilli and penicillia

Previous studies of hypersaline environments have revealed the dominant presence of melanized yeast-like fungi and related Cladosporium spp. In this study, we focused on the genera Aspergillus and Penicillium and their teleomorphic forms. From oligotrophic and eutrophic hypersaline waters around the world, 60 different species were identified, according to their morphological characteristics and extrolite profiles. For the confirmation of five new species, additionally, sequence analysis of the internal transcribed spacer region, the partial large subunit-rDNA and the partial β-tubulin gene was performed. The species Aspergillus niger, Eurotium amstelodami and Penicillium chrysogenum were detected with the highest frequencies at all of the sampled sites; thus, they represent the pan-global stable mycobiota in hypersaline environments. Possible candidates were also Aspergillus sydowii and Eurotium herbariorum, as they were quite evenly distributed among the sampled sites, and Aspergillus candidus, which was abundant, but more locally distributed. These species and their byproducts can accumulate downstream following evaporation of brine, and they can become entrapped in the salt crystals. Consequently, marine salt used for consumption can be a potential source of food-borne fungi and their byproducts. For example, ochratoxin-A-producing species Penicillium nordicum was recovered from brine, salt and salted meat products.     

Cellulolytic activities ofTrichoderma hamatum grown on different carbon substrates

Summary The exoglucanase, endoglucanase and -glucosidase produced byTrichderma hamatum cultured on four different carbon sources, cellulose, cellobiose, carboxymethylcellulose (CMC) and starch, were monitored. Cellulose gave the best overall mycelial growth and highest endoglucanase activity. Exoglucanase activity was best on CMC and -glucosidase greatest on starch. The data suggest that a carbon source suitable for mycelial growth may not be suitable for cellulolytic activities, and that cellulose may not be the best substrate for the development of activity of the three enzyme components of cellulase of a particular fungus.

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Resumen Se estudió la producción de exoglucanasa, endoglucanasa y -glucosidase porTrichoderma hamatum en medios con cuatro fuentes distintas de carbono: celulosa, celobiosa, carboximetilcelulosa (CMC) y almidón. En celulosa se dió el mejor crecimiento de micelio y la mayor actividad endoglucanásica. La actividad exoglucanásica fue mejor en CMC y la -glucosidásica en almidón. Los datos obtenidos sugieren que una fuente de carbono adecuada para el crecimiento de micelio puede no serlo para las actividades celulolíticas y que la celulosa puede no ser el mejor sustrato para el desarrollo de las actividades de los tres enzimas componentes de la celulasa de un determinado hongo.

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Résumé Les exo-glucanase, endo-glucanase et -glucosidase produites patTrichoderma hamatum cultivé sur diverses sources de carbone (cellulose, cellobiose, carboxyméthyl-cellulose (CMC) et amidon) ont été étudiées. La cellulose procure la meilleure croissance mycélienne et l'activité endo-glucanase la plus élevée. L'activité exo-glucanase est plus élevée sur CMC et l'activité -glucosidase sur amidon. Ces résultats montrent qu'une source de carbone convenant à la croissance mycélienne peut ne pas convenir aux activités cellulolytiques et que la cellulose peut ne pas être le meilleur substat pour l'activité des trois enzymes composantes de la cellulase produite par un champignon donné.

     

Food additives and plant components control growth and aflatoxin production by toxigenic aspergilli: A review

Growth and aflatoxin production by toxigenic aspergilli are partially or completely inhibited by the undissociated form of acetic, benzoic, citric, lactic, propionic and sorbic acids. Salts such as sodium chloride, potassium chloride and sodium nitrate, at low concentrations, can enhance aflatoxin production. At higher concentrations they become inhibitory, but marked inhibition requires amounts of the salts greater than are commonly used in foods. Phenolic antioxidants, sometimes added to foods to prevent oxidative deterioration, also are inhibitory to toxigenic aspergilli. Other inhibitory agents include certain insecticides, methylxanthines (caffeine and theophyllin), and components of some herbs, spices and other plants.