Osmoprotectants in Halomonas elongata: high-affinity betaine transport system and choline-betaine pathway.

The osmoregulatory pathways of the moderately halophilic bacterium Halomonas elongata DSM 3043 have been investigated. This strain grew optimally at 1.5 to 2 M NaCl in M63 glucose-defined medium. It required at least 0.5 M NaCl for growth, which is a higher concentration than that exhibited by the H. elongata type strain ATCC 33173. Externally provided betaine, choline, or choline-O-sulfate (but not proline, ectoine, or proline betaine) enhanced the growth of H. elongata on 3 M NaCl-glucose-M63 plates, demonstrating the utilization of these compounds as osmoprotectants. Moreover, betaine and choline stimulated the growth of H. elongata DSM 3043 over the entire range of salinity, although betaine was more effective than choline at salinities below and above the optimum. We found that H. elongata DSM 3043 has at least one high-affinity transport system for betaine (K(m) = 3.06 microM and Vmax = 9.96 nmol of betaine min(-1) mg of protein(-1)). Competition assays demonstrated that proline betaine and ectoine, but not proline, choline, or choline-O-sulfate, are also transported by the betaine permease. Finally, thin-layer chromatography and 13C-nuclear magnetic resonance analysis showed that exogenous choline was taken up and transformed to betaine by H. elongata, demonstrating the existence of a choline-glycine betaine pathway in this moderately halophilic bacterium.     

Artificial hybridization within Saxifraga pentadactylis (Saxifragaceae)

Saxifraga pentadactylis subsp. almanzorii , an endemic to the subalpine nucleus of Sierra de Gredos (central Spain), differs from its closest relative, subsp. willkommiana , by its less showy petals. An artificial crossing program was carried out in order to assess the degree of reproductive isolation between the subspecies. To facilitate interpretation of the results, the program was extended to 10 other interspecific hybrid combinations within sect. Saxifraga . All the data gathered are congruent with the occurrence of two evolutionary scenarios. Interspecific crossings, rendering moderate to high seed-set (in obtaining the F₁), and vigorous but relatively sterile F₁ offspring, reveal reproductive barriers at the level of the F₁ fertility, probably originated as a byproduct of divergent evolution. In contrast, intraspecific crossings within S. pentadactylis resulted in seed-set values lower than expected (in obtaining the F₁), in a majority of weak non-viable F₁ offspring but also in a few fertile F₁ hybrid specimens which were able to originate F₂ offspring. This second pattern reveals reproductive barriers at the level of the F₁ vitality, probably arisen in a quite abrupt fashion. The lower P/O for subsp. almanzorii as compared to subsp. willkommiana , together with the rest of the evidence suggest that the reproductive barriers between them might be the product of active selection against hybridization achieved by incrementing the levels of autogamy in the former.     

The Jurassic succession in west-central Argentina: stratal patterns, sequences and paleogeographic evolution

Jurassic rocks in west-central Argentina are predominantly marine and marginal-marine siliciclastics, associated with prominent but volumetrically subordinate carbonates and evaporites. Facies developments were ruled by paleogeographic persistence within the southern-infratropical latitude belt (within 40–50°S) and by siliciclastic derivation from the Patagonian hinterland to the southwest. Minor volcanic and volcaniclastic supply arrived from the west, out of a magmatic belt related to Circum-Pacific convergence. Timing of the main marine-flooding events and general correspondence with the high-rank stratal packaging recorded in western North America, suggest that global eustasy was also a factor in controlling the local stratigraphic record. Early Jurassic sedimentation occurred within a series of semi-isolated depocentres linked to fault-bounded Triassic troughs. The Sinemurian-Toarcian deposits record depocentre expansion and coalescence. These trends were coeval with progressively more widespread marine invasions from the northwest and west, leading to an elongate marine seaway which connected central Patagonia with the Pacific domain. During the Aalenian-Bajocian the region was subject to a more subdued tectonism and the foreland side of the basin became fringed by an extensive clastic embankment. Bathonian and Early Callovian were times when coarse clastics prograded into the basin, while the marine embayment shrank as a result of stepwise forced regressions. During Late Callovian to Oxfordian globally rising sea-level, the depocentre witnessed the appearance of cosmopolitan invertebrates and a stratal pattern of basin widening and depositional underbalance, that promoted cratonward onlap and inception of widespread carbonate deposition. Ooidal-coralline carbonate development was terminated after a relatively sudden (Messinian-style) event that desiccated a large tract of the Andean basin, and favored massive precipitation of anhydrite. In the course of the Kimmeridgian the evaporite basin was largely flooded by siliciclastics and turned into a broad and featureless mudflat-salina complex, linked to a widespread erg and to an ephemeral drainage system. By the Tithonian, at a period of peak oceanic stand, marine connection was reinstated and recorded as the most widespread Jurassic transgression across the Neuquén-Aconcagua embayment. Shelfal deposition consisted of molluscs and ooid-dominated carbonate terraces that grew in pulses tuned to eustatic fluctuations. Like in other prolific petroleum provinces around the world the Tithonian basinal strata involve widespread euxinic deposits featuring unusually high organic content.     

Complete sequence of a new HLA-B35 allele found in a tribe of Mapuche Indians in the south of Argentina

The nucleotide sequence data reported in this paper have been submitted to the GenBank nucleotide sequence database and have been assigned the accession number U17107. The nameB*3509 was officially assigned by the WHO Nomenclature Committee in December 1994     

Hydroxyl Radicals and a Thylakoid-Bound Endopeptidase are Involved in Light- and Oxygen-Induced Proteolysis in Oat Chloroplasts

The hypothesis that light- and oxygen-induced proteolysis inchloroplasts is mediated by active oxygen species was examined.In order to determine whether or not H₂O₂ and/or ^{dot}OH radicalsare involved in these degradative processes we compared thedegradation of proteins in isolated oat chloroplasts exposedto white light at 80 W m^-2 with that in chloroplasts incubatedin darkness in the absence or presence of H₂O₂ or a ^{dot}OH-generatingsystem composed by ascorbic acid, FeCl₃ and H₂O₂ (Asc-Fe-H₂O₂).Light enhanced the rate of degradation of at least 18 polypeptides,while proteolysis was almost negligible in darkness in the abscenceof additives. H₂O₂ had a very small effect. However, Asc-Fe-H₂O₂-treatedchloroplasts in darkness showed a pattern of protein degradationalmost identical to that observed in the light. A thylakoid-boundendopeptidase (EP), the activity of which increased under photooxidativeenvironmental conditions and treatment with an ^{dot}OH-generatingsystem, was partially purified and characterized as a serinetypeprotease. Treatments with inhibitors of serine-type proteaseprevented both light- and Asc- Fe-H₂O₂-induced proteolysis.EP was more active against both soluble and membranous proteinsthat had been pretreated with Asc-Fe-H₂O₂ than against untreatedproteins. It is proposed that a high dose of light irradiationpromotes proteolysis by increasing the formation of ^{dot}OH,which may modify proteins such that they become more susceptibleto EP-catalyzed hydrolysis. ¹Fisiología Vegetal, Dept. de Biología Vegetal,Universidad de Alcalá de Henares, Present address: 28871Alcalá de Henares (Madrid), España.     

Coccoid Helicobacter pylori Not Culturable In Vitro Reverts in Mice

An experimental rodent model was used to demonstrate the viability of the coccoid form of Helicobacter pylori. Concentrated suspensions were prepared for the two different morphologies: at 2 days incubation for the bacillary forms and at 20 days incubation for the “dormant” forms. The strains used for incubation were two fresh isolates from humans with duodenal ulceration, and two collection strains. Five hundred microliters of culture (OD₅₅₀ = 5 Mc Farland) of Helicobacter pylori with bacillary (2-5×10⁹ CFU/ml) and coccoid (0 CFU/ml) morphology were inoculated intragastrically in BALB/c mice. The gastric mucosa of the mice was colonized by Helicobacter pylori with the administration of fresh bacillary and coccoid cultures and not with the established cultures. Helicobacter pylori was isolated at 1 week after inoculation with the administration of fresh bacillary cultures, while fresh coccoid Helicobacter pylori was recovered in mice stomachs after 2 weeks of inoculation. After colonization, histopathologic changes occurred after 1 month from inoculation; all colonized mice showed a systemic antibody response to Helicobacter pylori. These results support the thesis of the viability of coccoid Helicobacter pylori non-culturable in vitro and confirm that concentrated bacterial suspensions are able to colonize and to produce gastric alterations in this suitable animal model.     

Effects of oxygen level on metabolism and development of seedlings of Trapa natans and two ecologically related species

Seeds of the water plant Trapa natans L. (water chestnut) can germinate in strict anoxia. The seedlings show seminal roots growing upwards while shoot buds remain quiescent until O₂ becomes available. Trapa seedlings are highly tolerant to anoxia. The rate of ethanol fermentation was 21.2 μmol (g FW)⁻¹ h⁻¹, while production of lactate was negligible and lower than that of succinate. The seminal root of Trapa compares better to the rice coleoptile rather than to the rice root, both functionally and as to the metabolic response to anoxia. The anaerobic germination of Nuphar luteum L. and Scirpus mucronatus L. was also characterized by a limited developmental program.     

Construction of Novel Shuttle Vectors for Use between Moderately Halophilic Bacteria andEscherichia coli

Shuttle vectors useful for the genetic manipulation of several moderately halophilic bacteria have been constructed. These vectors are based on the minimal replicon of pCM1, a cryptic plasmid fromChromohalobacter marismortui,combined with the useful properties of pUC18 plasmid (i.e., small size, high copy number, multiple cloning sites,lacZfragment), as well as with the trimethoprim resistance gene as a selection marker for moderate halophiles. These vectors can be efficiently transferred by RP4-mediated conjugation fromEscherichia colito the moderate halophilesChromohalobacter marismortui, Deleya halophila, Halomonas elongata, Halomonas subglaciescola,andVolcaniella eurihalina.