Molecular mechanism of YbtA-mediated transcriptional regulation of divergent overlapping promoters ybtA and irp6 of Yersinia enterocolitica.

Genes of Yersiniae spp. involved in production of the siderophore yersiniabactin are located on the high-pathogenicity island (HPI). Their transcription is controlled by the AraC/XilS-like transcriptional regulator YbtA encoded within the HPI.

Transcriptional regulation of high pathogenicity island iron uptake genes by YbtA.

A large group of Enterobacteriaceae, including members of the genus Yersinia, produce the extracellular siderophore yersiniabactin enabling them to multiply under iron-depleted conditions. Genes, involved in yersiniabactin synthesis, transport and regulation are clustered in the high pathogenicity island (HPI). YbtA, an AraC-like transcriptional regulator, is presumed to be the central regulator of yersiniabactin production together with the ferric uptake regulator Fur.

Irp9, encoded by the high-pathogenicity island of Yersinia enterocolitica, is able to convert chorismate into salicylate, the precursor of the siderophore yersiniabactin.

The Irp9 protein of Yersinia enterocolitica participates in the synthesis of salicylate, the precursor of the siderophore yersiniabactin. In Pseudomonas species, salicylate synthesis is mediated by two enzymes: isochorismate synthase and isochorismate pyruvate-lyase. Both enzymes are required for complementation of a Yersinia irp9 mutant.

Molecular evidence for host-adapted races of the fungal endophyte Epichloë bromicola after presumed host shifts.

Host shifts of plant-feeding insects and parasites promote adaptational changes that may result in the formation of host races, an assumed intermediate stage in sympatric speciation. Here, we report on genetically differentiated and host-adapted races of the fungal endophyte Epichloë bromicola, which presumably emerged after a shift from the grass Bromus erectus to other Bromus hosts. Fungi of the genus Epichloë (Ascomycota) and related anamorphs of Neotyphodium are widespread endophytes of cool-season grasses.

Functional analysis of yersiniabactin transport genes of Yersinia enterocolitica.

Yersinia enterocolitica O:8, biogroup (BG) IB, strain WA-C carries a high-pathogenicity island (HPI) including iron-repressible genes (irp1-9, fyuA) for biosynthesis and uptake of the siderophore yersiniabactin (Ybt). The authors report the functional analysis of irp6,7,8, which show 98-99% similarity to the corresponding genes ybtP,Q,X on the HPI of Yersinia pestis. It was demonstrated that irp6,7 are involved in ferric (Fe)-Ybt utilization and mouse virulence of Y.

Epichloë grass endophytes increase herbivore resistance in the woodland grass Brachypodium sylvaticum.

Endophytic fungi of the genus Epichloë and their asexual Neotyphodium forms are thought to interact mutualistically with their host grasses, providing protection for the host against herbivores and pathogens mediated by fungal alkaloids. Most previous research has concentrated on agronomically important grasses, such as tall fescue, and its interactions with livestock grazers or invertebrate herbivores. In this study we focus on the woodland grass Brachypodium sylvaticum which is infected by the strictly host-specific endophyte Epichloë sylvatica.

Analysis of the gene for beta-fructosidase (invertase, inulinase) of the hyperthermophilic bacterium Thermotoga maritima, and characterisation of the enzyme expressed in Escherichia coli.

This is the first report describing the gene structure and the enzymatic properties of a beta-fructosidase of a hyperthermophilic organism. The bfrA gene of the ancestral bacterium Thermotoga maritima MSB8 codes for a 432-residue, polypeptide of about 50 kDa, with significant sequence similarity to other beta-fructosidases. On the basis of its primary structure, BfrA can be assigned to glycosyl hydrolase family 32.