Thermal stability of beta-xylanases produced by different Thermomyces lanuginosus strains

The thermostability of beta-xylanases produced by nine thermophilic Thermomyces lanuginosus strains in a coarse corn cob medium was assessed. The xylanase produced by T. lanuginosus strain SSBP retained 100% of its activity after 6 h at temperatures up to 65 degrees C. In comparison seven ATCC strains and the DSM 5826 strain of T. lanuginosus only retained 100% xylanase activity at temperatures up to 60 degrees C. Culture filtrates of T. lanuginosus strain SSBP grown on coarse corn cobs, oatspelts xylan, birchwood xylan, wheatbran, locust beangum, and sugar cane bagasse, retained 100% xylanase activity at temperatures up to 60 degrees C. The xylanase produced on corn cobs was the most thermostable and showed an increase of approximately 6% from 70 degrees C to 80 degrees C. The T(1/2) of all strains at 70 degrees C at pH 6.5 varied greatly from 63 min for strain ATCC 28083 to 340 min for strain SSBP. The xylanase of strain SSBP was much less thermostable at pH 5.0 and pH 12.0 with T(1/2) values of 11.5 min and 15 min, respectively at 70 degrees C. At 50 degrees C, the enzyme of T. lanuginosus strain SSBP produced on coarse corn cobs was stable within the pH range of 5.5-10.0. Furthermore, the enzyme retained total activity at 60 degrees C for over 14 days and at 65 degrees C for over 48 h. The xylanase of T. lanuginosus strain SSBP possesses thermo- and pH stability properties that may be attractive to industrial application.     

Structural studies on exopolysaccharides produced by three different propionibacteria strains

The exopolysaccharides produced by three propionibacteria strains, Propionibacterium freudenreichii 109, Propionibacterium freudenreichii 111, and Propionibacterium thoenii 126, grown on whey-based media, were found to be charged heteropolymers, composed of D-glucose, D-mannose, and D-glucuronic acid in molar ratios of 2:2:1. By means of methylation analysis, mass spectrometry, partial acid hydrolysis, and 1D/2D NMR (1H and 13C) studies, it was determined that all three exopolysaccharides contain the same branched, pentasaccharide repeating unit: [Formula: see text].     

不同品系萼花臂尾轮虫休眠卵的形态特征

对采自青岛和芜湖两地的萼花臂尾轮虫在3种温度(20 ℃、25 ℃和30 ℃)和2种藻类食物浓度(1.0×10⁶和5.0×10⁶ cells·ml^-1)下所产休眠卵的长径、短径和体积等形态特征进行了显微测量、计算和分析.结果表明,2种食物浓度下,培养温度以及培养温度和品系间的交互作用均对轮虫休眠卵的长径、短径和体积具有显著影响.当食物浓度分别为1.0×10⁶和5.0×10⁶ cells·ml^-1时,轮虫在20 ℃下所产休眠卵的长径、短径和体积均最大;在25 ℃和30 ℃下所产休眠卵的短径和体积均最小.品系对轮虫休眠卵长径、短径和体积的影响也取决于食物浓度.当食物浓度为1.0×10⁶ cells·ml^-1时,芜湖品系轮虫的休眠卵长径、短径和体积(156.00 μm、99.95 μm和12 269.11 μm³)均显著大于青岛品系轮虫的休眠卵(145.13 μm、91.97 μm和10 498.19 μm³);而当食物浓度为5.0×10⁶ cells·ml^-1时,芜湖品系轮虫的休眠卵长径、短径和体积(155.68 μm、100.85 μm和12 348.59 μm³)均与青岛品系轮虫的休眠卵(156.63 μm、98.04 μm和12 054.20 μm³)之间无显著差异.两品系中,仅芜湖品系轮虫休眠卵的长径、短径和体积分别与温度呈曲线相关.同一温度下,两品系轮虫的休眠卵体积均随着食物浓度升高而增大;但30 ℃下芜湖品系轮虫所产休眠卵体积却随着食物浓度的升高而减小.     

Trypanosoma cruzi: protection of mice with epimastigote antigens from immunologically different parasite strains

Antigens, prepared by the aid of pressure, from epimastigotes of strains of T. cruzi belonging to the different immunological groups described, conferred equal protection in mice against lethal infections of T. cruzi trypomastigotes of the T strain, which belongs to one of those immunological groups. Humoral antibodies were detected by the direct agglutination and immune fluorescent tests in all the immunized groups. The B and T strains produced earlier antibody responses than G and L strains. The weakest antibody response was induced by antigens obtained from the L strain. All the immunized mice sacrificed 21 days after challenge infection showed prominent inflammatory reactions at the tissue level, as well as free amastigote-like bodies. Four months after challenge injection, myocardium, liver, and spleen appeared histologically normal when compared to uninfected control mice. However, histological alterations were detected usually in striated muscle. The latter tissue seemed to be the best to check residual infections.     

Genotype-dependent mice behavior in cognitive tasks. Effect of noopept

The interstrain differences in performance of C57BL/6J, BALB/c and DBA/2J male mice in two cognitive tasks were found. Mice C57BL/6J showed good learning ability and preservation of memory traces tested 10 days after performance in a simplified version of Morris water maze. Mice BALB/c learned the task but, virtually, no long-term memory traces were revealed, whereas DBA/2J demonstrated poor learning. The effect of nootropic drug Noopept (GVS-111, N-phenil-acetyl-L-prolylglycin ethyl ether) was shown to be genotype-dependent. Its administration (0.5 mg/kg i.p., 15 min before learning) improved the long-term memory in Morris test in BALB/c mice but failed to produce any improvement in C57BL/6J. The ability of mice for extrapolation of the direction of stimulus movement differently changed after Noopept injections: the proportion of correct task solutions increased in C57BL/6J and BALB/c mice, whereas the performance of DBA/2J did not change.     

Major secondary metabolites produced by two commercial Trichoderma strains active against different phytopathogens

AIMS: Trichoderma harzianum strains T22 and T39 are two micro-organisms used as active agents in a variety of commercial biopesticides and biofertilizers and widely applied amongst field and greenhouse crops. The production, isolation, biological and chemical characterization of the main secondary metabolites produced by these strains are investigated. METHODS AND RESULTS: Of the three major compounds produced by strain T22, one is a new azaphilone that shows marked in vitro inhibition of Rhizoctonia solani, Pythium ultimum and Gaeumannomyces graminis var. tritici. In turn, filtrates from strain T39 were demonstrated to contain two compounds previously isolated from other T. harzianum strains and a new butenolide. The production of the isolated metabolites was also monitored by liquid chromatography/mass spectrometry during in vitro interaction with R. solani. CONCLUSIONS: This paper reports the isolation and characterization of the main secondary metabolites obtained from culture filtrates of two T. harzianum strains and their production during antagonistic interaction with the pathogen R. solani. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first work on secondary metabolites produced by the commercially applied strains T22 and T39. Our results provide a better understanding of the metabolism of these fungi, which are both widely used as biopesticides and/or biofertilizers in biocontrol.     

Action of antimicrobial substances produced by different oil reservoir Bacillus strains against biofilm formation

Microbial colonization of petroleum industry systems takes place through the formation of biofilms, and can result in biodeterioration of the metal surfaces. In a previous study, two oil reservoir Bacillus strains (Bacillus licheniformis T6-5 and Bacillus firmus H₂O-1) were shown to produce antimicrobial substances (AMS) active against different Bacillus strains and a consortium of sulfate-reducing bacteria (SRB) on solid medium. However, neither their ability to form biofilms nor the effect of the AMS on biofilm formation was adequately addressed. Therefore, here, we report that three Bacillus strains (Bacillus pumilus LF4—used as an indicator strain, B. licheniformis T6-5, and B. firmus H₂O-1), and an oil reservoir SRB consortium (T6lab) were grown as biofilms on glass surfaces. The AMS produced by strains T6-5 and H₂O-1 prevented the formation of B. pumilus LF4 biofilm and also eliminated pre-established LF4 biofilm. In addition, the presence of AMS produced by H₂O-1 reduced the viability and attachment of the SRB consortium biofilm by an order of magnitude. Our results suggest that the AMS produced by Bacillus strains T6-5 and H₂O-1 may have a potential for pipeline-cleaning technologies to inhibit biofilm formation and consequently reduce biocorrosion.     

Trypanosoma cruzi: Cardiac mitochondrial alterations produced by different strains in the acute phase of the infection

The parasite Trypanosoma cruzi is the causative agent of Chagas disease. T. cruzi invasion and replication in cardiomyocytes induce cellular injuries and cytotoxic reactions, with the production of inflammatory cytokines and nitric oxide, both source of reactive oxygen species. The myocyte response to oxidative stress involves the progression of cellular changes primarily targeting mitochondria. We studied the cardiac mitochondrial structure and the enzymatic activity of citrate synthase and respiratory chain CI–CIV complexes, in Albino Swiss mice infected with T. cruzi, Tulahuen strain and SGO Z12 isolate, in two periods of the acute infection. Changes in the mitochondrial structure were detected in both infected groups, reaching values of 71% for Tulahuen and 88% for SGO Z12 infected mice, 30 days post infection. The citrate synthase activity was different according to the evolution of the infection and the parasite strain, but the respiratory chain alterations were similar with either strain.     

Schistosoma mansoni: mice infected with different worm strains.

Infections with five geographical strains and substrains of Schistosoma mansoni were compared in mice. Two substrains (Lc-1 and Lt-1) were derived from the parent (L-1) St. Lucian strain on the basis of differing infectivity for various snail strains. The Puerto Rican strains (PR-1 and PR-2) were obtained with an interval of 25 years. Consistent differences among the lines were found in egg distribution and numbers of eggs in tissues and feces. One Puerto Rican strain (PR-2) and one St. Lucian substrain (Lc-1) had longer prepatent periods than the other strains. Mice infected with the PR-1 strain consistently had the highest egg accumulation in the tissues per worm pair. Relatively few eggs were passed in the feces of the Lt-1 strain. By Week 9 of infection, eggs were noted in the spleens of mice carrying each of the strains and substrains.     

Development of 1-cell embryos from different strains of mice in CZB medium

One-cell embryos from several different strains of mice have been cultured to the blastocyst stage in CZB medium. CZB medium can be used to culture CF1 x B6SJLF1/J 1-cell embryos to the blastocyst stage provided glucose is introduced into the medium on Day 3 of culture. The amount of glucose required for embryo development was titrated using a concentration range of 5.5 to 49.5 mM. With the exception of the highest concentration, all glucose levels tested supported 65-85% development to the morula and blastocyst stages. Variations of CZB medium were tested for their ability to support the development of 1-cell embryos from 4 strains of mice. For embryos from CF1 and DBA/2J (both x B6SJLF1/J) mice, which exhibit a "2-cell block" to development in vitro, CZB medium containing glutamine with the addition of glucose on Day 3 supported optimum development from the 1-cell stage to morula and blastocysts (79% and 87%). For embryos from B6D2F1/J and CD1 female mice (both x B6SJLF1/J males), which do not exhibit a "2-cell block" to in vitro development, optimum development to morula and blastocyst stages (95% and 50%) was in CZB medium containing both glutamine and glucose from the start of culture.     

Immunological aspects of infection of 6 inbred strains of mice by 3 different strains of Trypanosoma cruzi

We evaluated humoral and cellular immune responses in 6 inbred mouse strains (BALB/c, B-10, C3H, A/J, AKR and DBA) infected with 3 Trypanosoma cruzi strains (Peruvian, 21 SF and Colombian), which are the standards for the 3 strains Types of Andrade's classification. Negative delayed-type hipersensitivity reactions to parasite antigens were evidence of suppressed cell-mediated immunity. An early drop of IgG1 and rise of IgM levels were observed in almost all mouse strains infected by any T. cruzi strain. Elevation of IgG2a and/or IgG2b levels was higher in resistant mouse strains. Anti-T. cruzi antibody levels (Indirect immunofluorescence and ELISA) did not correlate with survival. Despite some differences among mouse strains there was a definition of an overall pattern of host response and the maintenance of biological standards which characterize the basic types of T. cruzi strains.