|
|
|
|
|
|
Multiple Formate Dehydrogenase Enzymes in the Facultative Methylotroph Methylobacterium extorquens AM1 Are Dispensable for Growth on Methanol. Ludmila Chistoserdova, 2004.Formate dehydrogenase has traditionally been assumed to play an essential role in energy generation during growth on C1 compounds . However, this assumption has not yet been experimentally tested in methylotrophic bacteria . In this study, a whole-genome analysis approach was used to identify three different formate dehydrogenase systems in the facultative methylotroph Methylobacterium extorquens AM1 whose expression is affected by either molybdenum or tungsten . A complete set of single, double, and triple mutants was generated, and their phenotypes were analyzed . The growth phenotypes of the mutants suggest that any one of the three formate dehydrogenases is sufficient to sustain growth of M . extorquens AM1 on formate, while surprisingly, none is required for growth on methanol or methylamine . Nuclear magnetic resonance analysis of the fate of [13C]methanol revealed that while cells of wild-type M . extorquens AM1 as well as cells of all the single and the double mutants continuously produced [13C]bicarbonate and 13CO2, cells of the triple mutant accumulated [13C]formate instead . Further studies of the triple mutant showed that formate was not produced quantitatively and was consumed later in growth . These results demonstrated that all three formate dehydrogenase systems must be inactivated in order to disrupt the formate-oxidizing capacity of the organism but that an alternative formate-consuming capacity exists in the triple mutant . Whole-Genome Analysis of Genes Regulated by the Bacillus subtilis Competence Transcription Factor ComK. Mitsuo Ogura, 2002.The Bacillus subtilis competence transcription factor ComK is required for establishment of competence for genetic transformation . In an attempt to study the ComK factor further, we explored the genes regulated by ComK using the DNA microarray technique . In addition to the genes known to be dependent on ComK for expression, we found many genes or operons whose ComK dependence was not known previously . Among these genes, we confirmed the ComK dependence of 16 genes by using lacZ fusions, and three genes were partially dependent on ComK . Transformation efficiency was significantly reduced in an smf disruption mutant, although disruption of the other ComK-dependent genes did not result in significant decreases in transformation efficiency . Nucleotide sequences similar to that of the ComK box were found for most of the newly discovered genes regulated by ComK . PCR Detection of a Newly Emerged Pandemic Vibrio parahaemolyticus O3:K6 Pathogen in Pure Cultures and Seeded Waters from the Gulf of Mexico. Michael L. Myers, 2003.This study describes the optimization of PCR parameters and testing of a wide number of microbial species to establish a highly specific and sensitive PCR-based method of detection of a newly emerged pandemic Vibrio parahaemolyticus O3:K6 strain in pure cultures and seeded waters from the Gulf of Mexico (gulf water) . The selected open reading frame 8 (ORF8) DNA-specific oligonucleotide primers tested were found to specifically amplify all 35 pathogenic V . parahaemolyticus O3:K6 pandemic isolates, whereas these primers were not found to detectably amplify two strains of V . parahaemolyticus O3:K6 that were isolated prior to the 1996 outbreaks, 122 non-O3:K6 strains of V . parahaemolyticus, 198 non-V. parahaemolyticus spp., or 16 non-Vibrio bacterial spp . The minimum level of detection by the PCR method was 1 pg of purified genomic DNA or 102 ORF8-positive V . parahaemolyticus O3:K6 cells in 100 ml of water . The effectiveness of this method for the detection of ORF8-positive isolates in environmental samples was tested in gulf water seeded with 10-fold serial dilutions of this pathogen . A detection level of 103 cells per 100 ml of gulf water was achieved . Also, the applicability of this methodology was tested by the detection of this pathogen in gulf water incubated at various temperatures for 28 days . This PCR approach can potentially be used to monitor with high specificity and well within the required range of sensitivity the occurrence and distribution of this newly emerged pathogenic V . parahaemolyticus O3:K6 strain in coastal, marine, and ship ballast waters . Early detection of V . parahaemolyticus O3:K6 will help increase seafood safety and decrease the risk of infectious outbreaks caused by this pathogen .
|
© 2005
Transgalactic Ltd (manufacturer of Bioscreen C software) |
Privacy Statement | P.O. Box
1393, 00101 Helsinki, Finland,
Last modified: May 25, 2005
| ||||||
