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The Pyrimidine Nucleotide Reductase Step in Riboflavin and F420 Biosynthesis in Archaea Proceeds by the Eukaryotic Route to Riboflavin. Marion Graupner, 2002.The Methanococcus jannaschii gene MJ0671 was cloned and overexpressed in Escherichia coli, and its gene product was tested for its ability to catalyze the pyridine nucleotide-dependent reduction of either 2,5-diamino-6-ribosylamino-4(3H)-pyrimidinone 5'-phosphate (compound 3) to 2,5-diamino-6-ribitylamino-4(3H)-pyrimidinone 5'-phosphate (compound 4) or 5-amino-6-ribosylamino-2,4(1H,3H)-pyrimidinedione 5'-phosphate (compound 7) to 5-amino-6-ribitylamino-2,4(1H,3H)-pyrimidinedione 5'-phosphate (compound 5) . Only compound 3 was found to serve as a substrate for the enzyme . NADPH and NADH functioned equally well as the reductants . This specificity for the reduction of compound 3 was also confirmed by using cell extracts of M . jannaschii and Methanosarcina thermophila . Thus, this step in riboflavin biosynthesis in these archaea is the same as that found in yeasts . The absence of the other genes in the biosynthesis of riboflavin in Archaea is discussed . Comparative Genomics of Salmonella enterica Serovar Typhi Strains Ty2 and CT18. Wen Deng, 2003.We present the 4.8-Mb complete genome sequence of Salmonella enterica serovar Typhi strain Ty2, a human-specific pathogen causing typhoid fever . A comparison with the genome sequence of recently isolated S . enterica serovar Typhi strain CT18 showed that 29 of the 4,646 predicted genes in Ty2 are unique to this strain, while 84 genes are unique to CT18 . Both genomes contain more than 200 pseudogenes; 9 of these genes in CT18 are intact in Ty2, while 11 intact CT18 genes are pseudogenes in Ty2 . A half-genome interreplichore inversion in Ty2 relative to CT18 was confirmed . The two strains exhibit differences in prophages, insertion sequences, and island structures . While CT18 carries two plasmids, one conferring multiple drug resistance, Ty2 has no plasmids and is sensitive to antibiotics . Effect of Incubation Temperature on Isolation of Campylobacter jejuni Genotypes from Foodstuffs Enriched in Preston Broth. Pam Scates, 2003.Preston broth and agar incubated at either 37 or 42°C have been widely used to isolate campylobacters from foodstuffs . The consequences of using either incubation temperature were investigated . Retail packs of raw chicken (n = 24) and raw lamb liver (n = 30) were purchased . Samples were incubated in Preston broth at 37 and 42°C and then streaked onto Preston agar and incubated as before . Two Campylobacter isolates per treatment were characterized . Poultry isolates were genotyped by random amplification of polymorphic DNA (RAPD), pulsed-field gel electrophoresis (PFGE), and flagellin PCR-restriction fragment length polymorphism, and lamb isolates were genotyped by RAPD only . In total, 96% of the poultry and 73% of the lamb samples yielded campylobacters . The lamb isolates were all Campylobacter jejuni, as were 96% of the poultry isolates, with the remainder being Campylobacter lari . The incubation temperature had no significant effect on the number of positive samples or on the species isolated . However, genotyping of the C . jejuni isolates revealed profound differences in the types obtained . Overall (from poultry and lamb), the use of a single incubation temperature, 37°C, gave 56% of the total number of RAPD C . jejuni genotypes, and hence, 44% remained undetected . The effect was especially marked in the poultry samples, where incubation at 37°C gave 47% of the PFGE genotypes but 53% were exclusively recovered after incubation at 42°C . Thus, the incubation temperature of Preston media selects for certain genotypes of C . jejuni, and to detect the widest range, samples should be incubated at both 37 and 42°C . Conversely, genotyping results arising from the use of a single incubation temperature should be interpreted with caution .
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