Light as an energy source in continuous cultures of bacteriorhodopsin-containing halobacteria

The role of light as an energy source for slightly aereated cultures of halobac­ teria was studied, using continuous cultures with low nutrient concentrations and a low oxygen supply. A series of experiments were carried out with non­ illuminated and differently illuminated cultures and with ditferent oxygen transfer rates. Under low oxygen availability, light proved to be a decisively important energy source that allowed the populations to reach higher growth rates and much higher population densities. Oxygen inftuenced the growth over only a minimal level, below which neither the illuminated nor the dark cultures were atfected by the oxygen transfer rate. From these results, it appears that the bacteriorhodop­ sin-mediated energy supply could have a very important role for the ecology of halobacteria in their microaerophilic habitats. In the illuminated cultures, cells that originated purple colonies on plates appeared. These cells, which could be bacteriorhodopsin-constitutive mutants, are now being studied

Taxonomic Study of Non-alkaliphilic Halococci

Ninety-six extremely halophilic, non-alkaliphilic cocci were isolated from several salterns in different geographical areas of Spain. These strains, together with seven reference strains of the genus Halococcus, were characterized by means of 114 phenotypic features, the results being analysed by numerical techniques using the simple matching (SsM) coefficient and the unweighted pair group clustering (UPGMA) algorithm. At the 70% similarity level, four phenons were obtained. Phenon A contained 87 strains, including all the reference strains, and was considered to comprise members of the only named species of the genus Halococcus, H . rnorrhuae. Phenons B and C , which included five and seven strains respectively, showed greater metabolic versatility than phenon A. The four strains belonging to phenon D were significantly different from the other phenons in that they produced acid from glucose and were able to use most of the organic compounds tested. The results indicate that there is phenotypic diversity among the members of the genus Halococcus and that phenon D may constitute a new taxon

Susceptibility of halobacteria to heavy metals

Sixty-eight halobacteria, including both culture coUection strains and fresh isolates from widely dift'ering geographical areas, were tested for susceptibility to arsenate, cadmium, chromium, cobalt, copper, lead, mercury, nickel, silver, and zinc ions by an agar dilution technique. The culture collection strains showed dift'erent susceptibilities, clustering into five groups. Halobacterium medilerranei and Halobacterium volcanii were the most metal tolerant, whereas Haloarcula californiae and Haloarcula sinaiiensis had the highest susceptibilities of the culture collection strains. Dift'erent patterns of metal susceptibility were found for all the halobacteria tested, and there was a uniform susceptibility to mercury and silver. All strains tested were multiply metal tolerant

A Taxonomic Study of Heterotrophic Halophilic and Non- halophilic Bacteria from a Solar Saltern

A total of 564 strains of heterotrophic non-halophilic, marine, moderately halophilic and extremely halophilic bacteria was isolated from a saltern located near Huelva, SW Spain, facing the Atlantic Ocean. With the exception of the extremely halophilic bacteria, these were analysed by numerical techniques using the simple matching (SsM) coefficient and clustering was achieved using the unweighted pair group method with averages (UPGMA) algorithm. At the 72-504 similarity level, a different number of phenons was found for each salinity group of bacteria. Of the 154 non-halophilic strains, the majority were recovered in 10 phenons, representing members of the genera Staphylococcus, Bacillus and Micrococcus. The 1 38 marine strains, with the exception of 24 strains, clustered into 12 phenons; seven phenons were assigned to the suprageneric grouping Pseudomonas-Alteromonas-Deleya, and the other phenons to Micrococcus, Staphylococcus, Bacillus and Vibrio. The 140 moderately halophilic strains grouped into eight phenons, with only 1 1 strains left unassigned. The majority of these isolates were assigned to the genus Deleya (two phenons) and they showed great similarity with the recently described species D. halophila, isolated from hypersaline soils. Four phenons comprised microorganisms with phenotypic characteristics very similar to the moderately halophilic Vibrio costicola. Two phenons were assigned to the genera Flavobacterium and Acinetobacter but these strains were not similar to previously described species. Of the 145 extremely halophilic isolates studied, the most important group was identified as belonging to the species Halobacterium salinarium (86 strains), followed by H. saccharovorum (20 strains), H. vallismortis (19 strains), Haloarcula hispanica ( I 2 strains) and Halobacterium mediterranei (7 strains). Only one coccus was isolated, with characteristics very similar to those of Halococcus morrhuae

Numerical taxonomy of moderately halophilic Gram-negative rods

A study was made of 516 randomly selected isolates of moderately halophilic bacteria from solar salterns showing salinities between 8.8 and 40.0% (w/v) total salts, located in S.E. Spain. After purification, many cytological, physiological, biochemical, nutritional and an ti biot ic sensitivity characters were determined for 106 selected saltern isolates and two reference strains. Data were coded and analysed by numerical techniques using the Jaccard coefficient ( S J ) ,a nd clusters of strains were obtained by average linkage (UPGMA) analysis. Nine major phenons were found at the 72.5 % similarity level. The properties of each phenon are given, their taxonomic affinities are discussed, and typical reference strains are suggested. Almost all the strains were related to genera known to contain marine species. A large number of the strains could be tentatively assigned to the genus Vibrio, suggesting that this may be an abundant taxon of moderately halophilic Gram-negative rods in solar salterns

Isolation and partial characterization of a plasmid in the extremely halophilic archaebacterium Halococcus morrhuae CCM 537

The extremely halophilic archaebacterium Halococcus morrhuae CCM 537 was found to contain’’ a plasmid, pHM2, of 6.0 kb. A restriction map was constructed. Southern hybridization of pHM2 DNA to DNA extracted from other Halococcus sp. strains revealed the presence of a similar plasmid in one other strain. A plasmid of Halobacterium trapanicum shared common sequences with pHM2. Other plasmids from halobacteria displayed no homology with pHM2. The characterization of pHM2 may make it useful for the development of cloning vectors for extremely halophilic archaebacteria

Characterization of a plasmid from moderately halophilic eubacteria

A plasmid has been isolated for the first time from moderately halophilic eubacteria. Halomonas elongata, Halomonrrs halmphila, Deleya halophila and Vibrio costkola were found to harbour an 11.5 kbp plasmid (pMH1). The plasmid was isolated and characterized after transformation into Escherichia coh'JM101 cells. A restriction map was constructed, and unique restriction sites for EcoRI, EcoRV and ClaI were detected. The occurrence of such a plasmid in the original halophilic strains was confirmed by Southern hybridization. The plasmid carries genetic determinants that mediate resistance to kanamycin, tetracycline, and neomycin. This property, together with its relatively small size, its stability in E colicells, and the presence of unique restriction sites, makes pMHl a good candidate for the development of a cloning vector for moderate halophiles

Microbes and Society

El món microbià es compon de moltes espècies que pertanyen a grups molt diversos. La majoria dels microbis són commensals inofensius i molts d'altres són esencials en el desenvolupament i manteniment de la vida i dels ecosistemes. Cal considerar processos com ara el reciclatge de la matèria orgànica, la mineralitzación, per la qual els bacteris retornen a l'atmosfera els gasos necessaris per a la vida, o la fixació de nitrogen i carboni convertint aquests gasos en formes metabolitzables pels nostres organismes. També hi ha microorganismes patògens que, desafortunadament, són els més famosos ciutadans d'aquesta comunitat. La forta perspectiva antropocèntrica imperant en bona part de la història té a veure amb aquesta consideració hostil vers els microbis. En aquest article comentem la interacció microbis i societat esmentant el potencial humà per modificar la vida i controlar els ecosistemes naturals trencant sovint les pautes de l'evolució per causa d'aquestes modificacions. La conseqüència del ràpid creixement demogràfic, es relaciona directament amb les malalties emergents i un augment de les infeccions nosocomials. A la vegada, noves situacions socials i polítiques indueixen fenòmens preocupants com el bioterrorisme. Els efectes indesitjables dels microorganismes patògens i la seva utilització com a instruments perjudicials, no poden amagar els avantatges de convertirlos en aliats quan es coneixen les seves utilitats.The microbial world is composed of many species belonging to very diverse groups. Most microbes are harmless commensals, while many others are essential for the development and maintenance of life and a wide range of ecosystems. Processes such as the decomposition of organic matter, mineralization, the return to the atmosphere of gases needed by various life forms for nitrogen and carbon fixation, and the conversion of those gases into forms that can be metabolized by other organisms are undertaken by microorganisms. There are also pathogenic microorganisms that, unfortunately, are the most famous citizens of this community. The dominant anthropocentric view during large periods of history has been responsible for our hostility towards microbial life. In this paper, we discuss the interaction between microbes and society, the human potential to modify life and control natural ecosystems, and the frequent interruption of evolution that results from these modifications. The rapid growth of the human population has led to the emergence of several new diseases and an increased incidence of nosocomial infections. At the same time, current sociopolitical conditions have made bioterrorism an issue of very real concern. Nonetheless, the harmful effects of pathogenic microorganisms and their perverse use are not reason to forget their benefits and usefulness

Convenio Marco con la Universidad de Huelva, España.

. El presente acuerdo tiene como objetivo desarrollar programas de estudios conjuntos, intercambio y cooperación en el campo de la docencia, formación de estudiantes e investigació