The Pseudomonas stutzeri strain A1501 (formerly known as Alcaligenes faecalis) fixes nitrogen under microaerobic conditions in the free-living state and colonizes rice endophytically. The authors characterized a region in strain A1501, corresponding to most of the nif genes and the rnf genes, involved in electron transport to nitrogenase in Rhodobacter capsulatus. The region contained three groups of genes arranged in the same order as in Azotobacter vinelandii: (1) nifB fdx ORF3 nifQ ORF5 ORF6; (2) nifLA-rnfABCDGEF-nifY2/nafY; (3) ORF13 ORF12-nifHDKnifTY ORF1 ORF2-nifEN. Unlike in A. vinelandii, where these genes are not contiguous on the chromosome, but broken into two regions of the genome, the genes characterized here in P. stutzeri are contiguous and present on a 30 kb region in the genome of this organism. Insertion mutagenesis confirmed that most of the nif and the rnf genes in A1501 were essential for nitrogen fixation. Using lacZ fusions it was found that nif and rnf gene expression was under the control of ntrBC, nifLA and rpoN and that the rnf gene products were involved in the regulation of the nitrogen fixation process.

Disruption of ipdC, a gene involved in indole-3-acetic acid (IAA) production by the indole pyruvate pathway in Azospirillum brasilense Sp7, resulted in a mutant strain that was not impaired in IAA production with lactate or pyruvate as the carbon source. A tryptophan auxotroph that is unable to convert indole to tryptophan produced IAA if tryptophan was present but did not synthesise IAA from indole. Similar results were obtained for a mutant strain with additional mutations in the genes ipdC and trpD. This suggests the existence of an alternative Trp-dependent route for IAA synthesis. On gluconate as a carbon source, IAA production by the ipdC mutant was inhibited, suggesting that the alternative route is regulated by catabolite repression. Using permeabilised cells we observed the enzymatic conversion of tryptamine and indole-3-acetonitrile to IAA, both in the wild-type and in the ipdC mutant. IAA production from tryptamine was strongly decreased when gluconate was the carbon source.

BackgroundAberrant glycosylation is a characteristic of tumour cells. The expression of certain glycan structures has been associated with poor prognosis. In cervical carcinoma, changes in the expression levels of some glycogenes have been associated with lymph invasion. Human papillomavirus (HPV) infection is one of the most important factors underlying the development of cervical cancer. The HPV oncoproteins E6 and E7 have been implicated in cervical carcinogenesis and can modify the host gene expression profile. The roles of these oncoproteins in glycosylation changes have not been previously reported.MethodsTo determine the effect of the E6 and E7 oncoproteins on glycogene expression we partially silenced the E6 and E7 oncogenes in HeLa cells, we performed a microarray expression assay to identify altered glycogenes and quantified the mRNA levels of glycogenes by RT-qPCR. A protein-protein interaction network was constructed to identify potentially altered glycosylation pathways.ResultsThe microarray analysis showed 9 glycogenes that were upregulated and 7 glycogenes that were downregulated in HeLa shE6/E7 cells. Some of these genes participate in glycosylation related to Notch proteins and O-glycans antigens.ConclusionsOur results support that E6 and E7 oncoproteins could modify glycogene expression the products of which participate in the synthesis of structures implicated in proliferation, adhesion and apoptosis.