Saline systems最新文献

Microorganisms that adapt to moderate and high salt environments use a variety of solutes, organic and inorganic, to counter external osmotic pressure. The organic solutes can be zwitterionic, noncharged, or anionic (along with an inorganic cation such as K(+)). The range of solutes, their diverse biosynthetic pathways, and physical properties of the solutes that effect molecular stability are reviewed.

A hundred years have passed since the description of the genus Dunaliella, the unicellular green alga which is responsible for most of the primary production in hypersaline environments worldwide. The present paper provides an historical survey of research on Dunaliella, from the early work in the 19th century to the thorough taxonomic studies by Teodoresco, Hamburger, Lerche and others from the beginning of the 20th century onwards. It attempts to trace the origin of some of the most important breakthroughs that have contributed to our present understanding of this alga that plays such a key role in many hypersaline environments.

Background: A variety of strategies for survival of UV irradiation are used by cells, ranging from repair of UV-damaged DNA, cell cycle arrest, tolerance of unrepaired UV photoproducts, and shielding from UV light. Some of these responses involve UV-inducible genes, including the SOS response in bacteria and an array of genes in eukaryotes. To address the mechanisms used in the third branch of life, we have studied the model archaeon, Halobacterium sp. strain NRC-1, which tolerates high levels of solar radiation in its natural hypersaline environment.

Results: Cells were irradiated with 30-70 J/m(2) UV-C and an immunoassay showed that the resulting DNA damage was largely repaired within 3 hours in the dark. Under such conditions, transcriptional profiling showed the most strongly up-regulated gene was radA1, the archaeal homolog of rad51/recA, which was induced 7-fold. Additional genes involved in homologous recombination, such as arj1 (recJ-like exonuclease), dbp (eukaryote-like DNA binding protein of the superfamily I DNA and RNA helicases), and rfa3 (replication protein A complex), as well as nrdJ, encoding for cobalamin-dependent ribonucleotide reductase involved in DNA metabolism, was also significantly induced in one or more of our experimental conditions. Neither prokaryotic nor eukaryotic excision repair gene homologs were induced and there was no evidence of an SOS-like response.

Conclusion: These results show that homologous recombination plays an important role in the cellular response of Halobacterium sp. NRC-1 to UV damage. Homologous recombination may permit rescue of stalled replication forks, and/or facilitate recombinational repair. In either case, this provides a mechanism for the observed high-frequency recombination among natural populations of halophilic archaea.

Background: Freshwater anostracans inhabit ephemeral water bodies in which as the water level decreases due to evaporation the salt concentration increases. Thus, for most anostracans salinity becomes the major stress factor.

Results: We tested five concentrations of NaCl (0 to 8 g/l) on the life table demography of Branchipus schaefferi fed Chlorella (alga). Age-specific survivorship curves of male and female B. schaefferi showed nearly a similar pattern in that increased salt concentration resulted in decreased survivorship. The age-specific reproduction (m(x)) of females showed several peaks of cyst production at 0 and 1 g/l salinity while in treatments containing salt at 4 or 8 g/l, there were fewer peaks. Average lifespan, life expectancy at birth, gross and net reproductive rates, generation time and the rate of population increase were all significantly influenced by the salt concentration in the medium. The highest value of net reproductive rate (970 cysts/female) was in treatments containing 0 g/l of salt, while the lowest was 13 cysts/female at 8 g/l. The rate of population increase (r) varied from 0.52 to 0.32 per day depending on the salt concentration in the medium.

Conclusion: The low survival and offspring production of B. schaefferi at higher salinity levels suggests that this species is unlikely to colonize inland saline water bodies. Therefore, the temporary ponds in which it is found, proper conservative measures must be taken to protect this species.

Saline Systems addresses the publication needs of scientists conducting basic and applied research on coastal and inland saline environments and their flora and fauna. The journal covers research at all levels, from individual genes to whole genomes and entire ecosystems. Rapid progress in the molecular biology and microbial ecology of halotolerant and halophilic organisms and the sensitivity of many saline environments warrants an online journal with fast turnaround times. Many saline environments are threatened and the need for an Open Access journal to address the dissemination and sharing of knowledge on their conservation and management is compelling. Saline Systems provides an interdisciplinary forum for scientists working within all of the relevant fields.