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Azotobacter vinelandii presents a differentiation process leading to the formation of desiccation-resistant cysts. Alginate, the exopolysaccharide produced by this bacterium, has been postulated to have a role in cyst formation. Here, we report the cloning and characterization of the A. vinelandii gene coding for the enzyme GDP-mannose dehydrogenase (algD),(More)
Trypanosoma vivax is the principal etiological agent of bovine trypanosomosis, a widely disseminated disease in tropical and subtropical regions. Here, we present a simple and reproducible method for the purification of T. vivax from experimentally infected and immunosuppressed sheep, using an isopycnic Percoll gradient, followed by DEAE-cellulose(More)
A 36-kDa diheme c-type cytochrome abundant in Fe(III)-respiring Geobacter sulfurreducens, designated MacA, was more highly expressed during growth with Fe(III) as the electron acceptor than with fumarate. Although MacA has homology to proteins with in vitro peroxidase activity, deletion of macA had no impact on response to oxidative stress. However, the(More)
Several aspects of alginate and PHB synthesis in Azotobacter vinelandii at a molecular level have been elucidated in articles published during the last ten years. It is now clear that alginate and PHB synthesis are under a very complex genetic control. Genetic modification of A. vinelandii has produced a number of very interesting mutants which have(More)
BACKGROUND The role of the RNA polymerase sigma factor RpoN in regulation of gene expression in Geobacter sulfurreducens was investigated to better understand transcriptional regulatory networks as part of an effort to develop regulatory modules for genome-scale in silico models, which can predict the physiological responses of Geobacter species during(More)
The mechanism of fumarate reduction in Geobacter sulfurreducens was investigated. The genome contained genes encoding a heterotrimeric fumarate reductase, FrdCAB, with homology to the fumarate reductase of Wolinella succinogenes and the succinate dehydrogenase of Bacillus subtilis. Mutation of the putative catalytic subunit of the enzyme resulted in a(More)
Transcription of algD, encoding GDP-mannose dehydrogenase, the key enzyme in the alginate biosynthetic pathway, is highly regulated in Azotobacter vinelandii. We describe here the characterization of a Tn5 insertion mutant (AC28) which shows a higher level of expression of an algD::lacZ fusion. AC28 cells were morphologically abnormal and unable to encyst.(More)
Azotobacter vinelandii produces the exopolysaccharide alginate, which is essential for the encystment process. In Pseudomonas aeruginosa, as well as in A. vinelandii, the sigmaE factor encoded by algU is required for transcription of algD, which encodes a key enzyme of the alginate biosynthetic pathway. The P. aeruginosa response regulator AlgR activates(More)
Transcription of the Azotobacter vinelandii algD gene, which encodes GDP-mannose dehydrogenase (the rate-limiting enzyme of alginate synthesis), starts from three sites: p1, p2, and p3. The sensor kinase GacS, a member of the two-component regulatory system, is required for transcription of algD from its three sites during the stationary phase. Here we show(More)
The Escherichia coli LexA protein was used as a query sequence in TBLASTN searches to identify the lexA gene of the delta-proteobacterium Geobacter sulfurreducens from its genome sequence. The results of the search indicated that G. sulfurreducens has two independent lexA genes designated lexA1 and lexA2. A copy of a dinB gene homologue, which in E. coli(More)