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Helicobacter pylori chronically colonises half of the world's human population and is the main cause of ulcers and gastric cancers. Its prevalence and the increase in antibiotic resistance observed recently reflect the high genetic adaptability of this pathogen. Together with high mutation rates and an efficient DNA recombination system, horizontal gene transfer through natural competence makes of H. pylori one of the most genetically diverse bacteria. We show here that transformation capacity is enhanced in strains defective for recN, extending previous work with other homologous recombination genes. However, inactivation of either mutY or polA has no effect on DNA transformation, suggesting that natural competence can be boosted in H. pylori by the persistence of DNA breaks but not by enhanced mutagenesis. The transformation efficiency of the different DNA repair impaired strains correlates with the number of transforming DNA foci formed on the cell surface and with the expression of comB8 and comB10 competence genes. Overexpression of the comB6-B10 operon is sufficient to increase the transformation capacity of a wild type strain, indicating that the ComB complex, present in the bacterial wall and essential for DNA uptake, can be a limiting factor for transformation efficiency., Competing Interests: The authors declare no competing financial interests.

The crystal structure of a hypothetical protein AQ_1354 (gi 2983779) from the hyperthermophilic bacteria Aquifex aeolicus has been determined using X-ray crystallography. As found in many structural genomics studies, this protein is not associated with any known function based on its amino-acid sequence. PSI-BLAST analysis against a non-redundant sequence database gave 68 similar sequences referred to as 'conserved hypothetical proteins' from the uncharacterized protein family UPF0054 (accession No. PF02310). Crystallographic analysis revealed that the overall fold of this protein consists of one central alpha-helix surrounded by a four-stranded beta-sheet and four other alpha-helices. Structure-based homology analysis with DALI revealed that the structure has a moderate to good resemblance to metal-dependent proteinases such as collagenases and gelatinases, thus suggesting its possible molecular function. However, experimental tests for collagenase and gelatinase-type function show no detectable activity under standard assay conditions. Therefore, we suggest either that the members of the UPF0054 family have a similar fold but different biochemical functions to those of collagenases and gelatinases or that they have a similar function but perform it under different conditions.

We report the construction of a versatile Gateway-based co-expression vector set for producing multiprotein complexes in Escherichia coli . The set consists of two groups of three vectors (pCoGW and pCo0GW), each having a specific antibiotic resistance gene, a compatible origin of replication and allowing cloning of up to two genes, each under control of its own T7 promoter. To validate the set, 33 (co-)expression plasmids encoding fluorescent protein (GFP, DsRed and ECFP) have been generated. Protein expression levels were quantified and (co-)expression visualized by fluorescent microscopy. The results illustrate the applicability of these vectors in co-expression studies. [ABSTRACT FROM AUTHOR]