Biomedical subjects

E Tamburini

Publications and source records attributed to E Tamburini.

At least 19 recordsLinked to original sources

PubMed2001

Clostridium felsineum and Clostridium acetobutylicum are two distinct species that are phylogenetically closely related.

The gene sequences encoding the 16S rRNA of Clostridium felsineum DSM 794T and NCIMB 10690T were determined. Both sequences exhibited a relatively very low degree of similarity to the previously determined 16S rRNA gene sequence from C. felsineum DSM 794T. C. felsineum is a member of the major Clostridium cluster, cluster I, and is phylogenetically closely related to Clostridium acetobutylicum. DNA-DNA hybridization results clearly indicated that C. felsineum and C. acetobutylicum belong to distinct species.

Clostridium↗

PubMed2000

Do bacterial cryptic genes really exist?

Cryptic genes have been defined as phenotypically silent DNA sequences, usually not expressed during the life cycle of a microorganism, but capable of expression in a few members of a large population by mutation, recombination, insertion processes, or other genetic mechanisms. Recently, the crypticity of several genetic systems has been questioned. It appears that in many cases cryptic genes are silent only under the experimental conditions analysed and that their expression can be induced in the natural environment. Therefore, we propose that cryptic genes might not be a peculiar class of uniquely regulated genes, but rather genes encoding unusual functions.

Acetolactate Synthase↗

PubMed1999

A putative sigma factor from Streptomyces sp. strain A21 can activate the expression of the cryptic operon bgl in Escherichia coli K-12.

Streptomyces sp A21 is a cellulolytic strain isolated from soil which was assigned to the genus Streptomyces on the basis of distinctive morphological features. A genomic library of A21 DNA has been constructed and transformed into Escherichia coli K-12 using a high-copy-number vector. One of the recombinant plasmids activates the cryptic bgl operon when inserted into appropriate strains. The complete sequence of the 1629-bp A21 DNA fragment has been determined. The analysis revealed the presence of an ORF whose putative product shows a high degree of similarity to RNA polymerase sigma factors; we therefore designated the gene psfS (Putative sigma factor, Streptomyces). Mapping of the 5' terminus of transcript by primer extension indicated that PsfS induces transcription initiation within the bgl promoter-silencer region.

Amino Acid Sequence↗

PubMed1998

Heterologous gene expression in an Escherichia coli population under starvation stress conditions.

A novel system to study the evolution of transcription signals in heterologous systems under selective starvation conditions is described. It is based on the plasmid-mediated transfer of his biosynthetic genes from Azospirillum brasilense into a heterologous Escherichia coli mutant population lacking histidine biosynthetic ability. We show that under highly selective stressful conditions, genetic changes in the donor plasmid lead to mutated sequences that are efficiently recognized as promoters by the E. coli RNA polymerase.

Adaptation, Physiological↗

PubMed1998

Evolution of the structure and chromosomal distribution of histidine biosynthetic genes.

A database of more than 100 histidine biosynthetic genes from different organisms belonging to the three primary domains has been analyzed, including those found in the now completely sequenced genomes of Haemophilus influenzae, Mycoplasma genitalium, Synechocystis sp., Methanococcus jannaschii, and Saccharomyces cerevisiae. The ubiquity of his genes suggests that it is a highly conserved pathway that was probably already present in the last common ancestor of all extant life. The chromosomal distribution of the his genes shows that the enterobacterial histidine operon structure is not the only possible organization, and that there is a diversity of gene arrays for the his pathway. Analysis of the available sequences shows that gene fusions (like those involved in the origin of the Escherichia coli and Salmonella typhimurium hisIE and hisB gene structures) are not universal. In contrast, the elongation event that led to the extant hisA gene from two homologous ancestral modules, as well as the subsequent paralogous duplication that originated hisF, appear to be irreversible and are conserved in all known organisms. The available evidence supports the hypothesis that histidine biosynthesis was assembled by a gene recruitment process.

Archaea↗

PubMed1997

Paralogous histidine biosynthetic genes: evolutionary analysis of the Saccharomyces cerevisiae HIS6 and HIS7 genes.

The HIS6 gene from Saccharomyces cerevisiae strain YNN282 is able to complement both the S. cerevisiae his6 and the Escherichia coli hisA mutations. The cloning and the nucleotide sequence indicated that this gene encodes a putative phosphoribosyl-5-amino-1-phosphoribosyl-4-imidazolecarboxiamide isomerase (5' Pro-FAR isomerase, EC 5.3.1.16) of 261 amino acids, with a molecular weight of 29,554. The HIS6 gene product shares a significant degree of sequence similarity with the prokaryotic HisA proteins and HisF proteins, and with the C-terminal domain of the S. cerevisiae HIS7 protein (homologous to HisF), indicating that the yeast HIS6 and HIS7 genes are paralogous. Moreover, the HIS6 gene is organized into two homologous modules half the size of the entire gene, typical of all the known prokaryotic hisA and hisF genes. The structure of the yeast HIS6 gene supports the two-step evolutionary model suggested by Fani et al. (J. Mol. Evol. 1994; 38: 489-495) to explain the present-day hisA and hisF genes. According to this idea, the hisF gene originated from the duplication of an ancestral hisA gene which, in turn, was the result of an earlier gene elongation event involving an ancestral module half the size of the extant gene. Results reported in this paper also suggest that these two successive paralogous gene duplications took probably place in the early steps of molecular evolution of the histidine pathway, well before the diversification of the three domains, and that this pathway was one of the metabolic activities of the last common ancestor. The molecular evolution of the yeast HIS6 and HIS7 genes is also discussed.

Aldose-Ketose Isomerases↗

PubMed1986