Marina Torreblanca

Classification of Non-alkaliphilic Halobacteria Based on Numerical Taxonomy and Polar Lipid Composition, and Description of Haloarcula gen. nov. and Haloferax gen. nov.

Summary A large number of halobacteria have been isolated from different hypersaline environments at different geographical sites and studied together with type culture collection strains with respect to several phenotypic features. Numerical processing of the data resulted in thirteen phenons. A representative of each was studied to determine its polar lipid composition. Our results show the existence of at least three groups with the taxonomic level of genus. Results obtained by other authors with regard to the genotypic relationships among halobacteria support this. Besides the existing genus Halobacterium we propose the two new genera Haloarcula and Haloferax for the nomenclatural accomodation of the three groups.

Production of halocin is a practically universal feature of archaeal halophilic rods

Antagonisms among members of nine phenons of halobacteria were detected by combining two methods based on the double layer technique. Inhibitory activities were not due to phages. The protein nature of the inhibitors indicated that they were halocins. With only one exception, all strains tested exhibited inhibitory activity against other halobacteria due to the production of halocins. A very wide range of activity spectra was detected and the numerical comparative analysis showed little grouping, due to the scarce similarities between them. This indicates that many different halocins are produced by this heterogeneous group of micro‐organisms. Our results show that halocin production should be considered as a practically general feature of halobacteria.

Halocin H6, a Bacteriocin from Haloferax gibbonsii

Summary: Haloferax gibbonsii strain Ma2.39 produces an inhibitor substance designated halocin H6. This halocin was isolated from culture supernatants of the producer strain. It appeared to be a non-inducible bacteriocin with a bactericidal mode of cation and typical ‘single-hit’ kinetics. The protein was purified by a combination of hydroxylapatite affinity chromatography, gel filtration and HPLC. Halocin H6 is a protein of M r 32000; it is heat resistant, non-salt-dependent (it retains its activity after exposure to distilled water) and sensitive to pronase but not to trypsin.

A halocin acting on Na+/H+ exchanger of Haloarchaea as a new type of inhibitor in NHE of mammals

The capability of halocin H6 (a bacteriocin-like protein produced by haloarchaeaHaloferax gibbonsii) to inhibit Na+/H+ exchange (NHE) in mammalian cells and its cardio-protective efficacy on the ischemic and reperfused myocardium were evaluated in the present study. H6 inhibits NHE activity (measured by a flow cytometry method) in a dose-dependent form of cell lines of mammalian origin (HEK293, NIH3T3, Jurkat and HL-1) as well as in primary cell culture from human skeletal muscle (myocytes and fibroblasts).In vivo, an ischemia-reperfusion model in dogs by coronary arterial occlusion was used (two hours of regional ischemia and three hours of reperfusion). In animals treated with halocin H6 there was a significant reduction of premature ventricular ectopic beats and infarct size, whereas blood pressure and heart rate remained unchanged. Up to date, halocin H6 is the only described biological molecule that exerts a, specific inhibitory activity in NHE of eukaryotic cells.ResumenEn el presente trabajo se evalúa la capacidad de la halocina H6 (una proteína tipo bacteriocina producida por la haloarchaeaHaloferax gibbonsii) para inhibir el intercambiador Na+/H+ (NHE) de céludas de mamífero y su posible eficacia cardioprotectora frente a los daños causados por isquemia-reperfusión del miocardio. En experimentosin vitro H6 inhibe la actividad de NHE (determinada por citometría de flujo) de forma dosis-dependiente tanto en líneas celulares de mamíferos (HEK293, NIH3T3, Jurkat y HL-1) como en cultivos primarios de miocitos y fibroblastos aislados de músculo esquelético humano. En experimentosin vivo se utilizó un modelo de isquemia-reperfusión en perros por oclusión de la arteria coronaria (dos horas de isquemia y tres de reperfusión). En animales tratados con halocina H6 se produjo una disminución significativa a nivel estadístico, tanto del número de latidos ectópicos ventriculares como del tamaño del infarto, mientras que no se produjeron cambios tanto en la presión sanguínea como en el ritmo cardíaco. Hasta la fecha la halocina H6 es la única molécula biológica descrita que ejerce una actividad inhibidora específica sobre el NHE de células eucariotas.

Microbial and nutrient pollution along the coasts of Alicante, Spain

Abstract A systematic study of some pollution indicators (faecal coliforms, enterococci, Nitrogen and Phosphorus) has been carried out for seven years along a tourist crowded coastal region of Spain (Alicante Province), evaluating the influence of sewage outfalls close to beaches. The study shows the importance of constant monitoring of pollution to achieve an adequate prevention policy. In general there is a tendency to improvement on this coast, attributable to a better sewage disposal network.

Mode of Action of Halocins H4 and H6: Are They Effective Against the Adaptation to High Salt Environments?

Halocins H4 and H6, two bacteriocins produced by halobacterial strains, are proteins able to kill other halobacterial strains than those which produce them. Although their physico-chemical features are quite distinct, their modes of action seem to be similar. Both halocins induce morphological changes and lysis in sensitive cells, affect light-induced pH changes and inhibit α-aminoisobutiric acid transport. All these factors lead us to suppose that the target of both halocins must be located at membrane level, affecting one or more of the mechanisms which take part in the complex machinery of regulation and maintenance of the electrochemical gradients steady state through the membrane. The fact that halobacteria live in extremely aggressive media considerably increases the effectiveness of substances such as halocin H4 and H6 to kill salt-dependent cells.

Isolation of the fibrocrystalline body, a structure present in haloarchaeal species, from Halobacterium salinarum.

Abstract. An organized structure, the fibrocrystalline body (FB), has been isolated from the archaeon Halobacterium salinarum. The structure is also present in, and can be isolated from, other extreme halophilic archaea. FB is present in the cytoplasm during the exponential growth and early stationary phases. This structure is affected by vincristine, an antitumoral drug, which targets tubulin. The drug causes fragmentation of the FB, changes in the cell shape, and growth inhibition. Taken together, these results point toward an important role in the life of the cell for this highly organized structure.