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Marine samples from the Indian Ocean were used to isolate and characterize the organisms with respect to their fatty acid profiles. Six mesophilic isolates (MBRI 6, MBRI 8, MBRI 9, MBRI 10, MBRI 12 and MBRI 13) were obtained from three different water samples. They were i) Gram-negative, ii) catalase positive, iii) produced acid from glucose and maltose, iv) tolerated 5 to 15% NaCl v) except MBRI 9, showed pH tolerance in the range of 5.0 to 9.0 with optimum pH 7.0 to 8.0 v) grew well at 30°C and were able to grow in the range of 15 to 45°C. EPA, an essential omega-3 fatty acid, was produced by these isolates in the range of 12 to 60% at 30°C. MBRI 12 was found to be a potential source as it produced 60% EPA. This isolate was further identified by partial 16S rDNA sequencing and phylogenetic analysis revealed that the strain belonged to Gammaproteobacteria and was closely related to Halomonas bolviensis (96% sequence similarity, 570 bp). Thus a new genus of Halomonas may be included in earlier reported EPA- producing prokaryotic genera affiliated to the Gammaproteobacteria.
The effect of fructose, glucose, maltose and sucrose at various concentrations on Brassica napus embryos was studied. The morphogenetic reaction depended on the type and concentration of sugar in the medium. The frequency of developing embryos was highest on sucrose, followed by maltose and glucose. Fructose did not stimulate embryo growth. Spectrophotometry of autoclaved fructose showed an absorbance rise between 260-320 nm that could correspond to the formation of furfural derivatives. Autoclaving-induced toxicity probably inhibited embryo growth; heart-shaped stage embryos developed on filter-sterilized fructose. The frequency of developing embryos increased with sugar concentration, but normal embryogenesis occurred only on 1% sucrose and maltose; at higher concentrations callus and/or shoots were formed. On media with 6% sucrose and 12% maltose, shoots and somatic embryos were produced.
To show the role of MalT protein in the regulation of mal genes, encoding proteins involved in transport and metabolism of maltose/ maltodextrins in Yersinia enterocolitica, we constructed a malT mutant which was characterized by a strong reduction in maltose transport and a loss of MBP protein. We also studied the influence of MalT activity on the production of Yop proteins in Y. enterocolitica and found that the level of these virulence factors is not changed in the malT mutant. Subsequently, transcriptional fusion malT::lacZYA was applied to study the activity of malT promoter. Monitoring of β-galactosidase activity suggests the influence of catabolic repression on malT transcription, since the activity of ma/Tpromoter was decreased twofold in the presence of glucose. Furthermore, Mlc protein was identified in Y. enterocolitica as a factor regulating the transcription of malT. We observed a two-fold increase in the level of malT transcription in the mlc mutant background. Moreover, overproduction of Mlc protein strongly inhibited the activity of malT promoter. Thus, the data presented in this study suggest that the level of mal gene expression in Y enterocolitica may be regulated by two proteins: MalT, the activator of mal transcription and Mlc, the repressor of malT expression.
Optimizing production of α-amylase production by Thermoactinomyces vulgaris isolated from Egyptian soil was studied. The optimum incubation period, temperature and initial pH of medium for organism growth and enzyme yield were around 24 h, 55°C and 7.0, respectively. Maximum α-amylase activity was observed in a medium containing starch as carbon source. The other tested carbohydrates (cellulose, glucose, galactose, xylose, arabinose, lactose and maltose) inhibited the enzyme production. Adding tryptone as a nitrogen source exhibited a maximum activity of α-amylase. Bactopeptone and yeast extract gave also high activity comparing to the other nitrogen sources (NH₄Cl, NH₄NO₃, NaNO₃, KNO₃, CH₃CO2 NH₄). Electrophoresis profile of the produced two α-amylase isozymes indicated that the same pattern at about 135145 kDa under different conditions. The optimum pH and temperature of the enzyme activity were 8.0 and 60°C, respectively and enzyme was stable at 50°C over 6 hours. The enzyme was significantly inhibited by the addition of metal ions (Na⁺, Co²⁺ and Ca²⁺) whereas Cl⁻ seemed to act as activator. The enzyme was not affected by 0.1 mM EDTA while higher concentration (10 mM EDTA) totally inactivated the enzyme.
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