Influence of temperature and salinity on carbon and nitrogen content in Dunaliella viridis teodoresco under nitrogen sufficiency

Cell carbon and nitrogen in D. viridis are strongly dependent on the culturing conditions. Both elements increase with increasing salinity. At 31°C cell carbon is maximum and cell nitrogen minimum. This temperature was described previously (Jiménez, C., Niell, F. X. & Fernandez, J. A. (1990). Hydrobiologia, 197, 165-72) as the optimal one for achieving the maximum oxygen evolution. These results point out a possible competence for the reducing power during carbon and nitrogen assimilation processes, and under conditions of high photosynthesis (carbon assimilation) there is a partial inhibition of nitrate reduction, making C:N ratio maximum under conditions of maximum net photosynthesis.The study of cell glycerol, nitrate, structural proteins and free amino acids indicates that all of these solutes accumulate in the cells as a result of the high salinity adaptation.     

Purification,characterization and biological activity of three forms of ferredoxin from the sulfate-reducing bacterium Desulfovibrio gigas

Three forms of ferredoxin FdI, FdI′, and FdII have been isolated from Desulfovibrio gigas, a sulfate reducer. They are separated by a combination of DEAE-cellulose and gel filtration chromatographic procedures. FdI and FdI′ present a slight difference in isoelectric point which enables the separation of the two forms over DEAE-cellulose, while FdII is easily separated from the two other forms by gel filtration. The three forms have the same amino acid composition and are isolated in different aggregation states. Molecular weight determinations by gel filtration gave values of 18 000 for FdI and FdI′ and 24 000 for FdII, whereas a value of 6000 is determined when dissociation is accomplished with sodium dodecyl sulfate. The electronic spectra are different and their ultraviolet-visible absorbance rations are 0.77, 0.87 and 0.68 respectively for FdI, FdI′ and FdII. Despite these differences, the physiological activities of the three forms are similar as far as the reduction of sulfite by molecular hydrogen is concerned.     

Molecular Genetics of Cystinuria: Identification of Four New Mutations and Seven Polymorphisms, and Evidence for Genetic Heterogeneity

A cystinuria disease gene (rBAT) has been recently identified, and some mutations causing the disease have been described. The frequency of these mutations has been investigated in a large sample of 51 Italian and Spanish cystinuric patients. In addition, to identify new mutated alleles, genomic DNA has been analyzed by an accurate and sensitive method able to detect nucleotide changes. Because of the lack of information available on the genomic structure of rBAT gene, the study was carried out using the sequence data so far obtained by us. More than 70% of the entire coding sequence and 8 intron-exon boundaries have been analyzed. Four new mutations and seven intragenic polymorphisms have been detected. All mutations so far identified in rBAT belong only to cystinuria type I alleles, accounting for ~44% of all type I cystinuric chromosomes. Mutation M467T is the most common mutated allele in the Italian and Spanish populations. After analysis of 70% of the rBAT coding region, we have detected normal sequences in cystinuria type II and type III chromosomes. The presence of rBAT mutated alleles only in type I chromosomes of homozygous (type I/I) and heterozygous (type I/III) patients provides evidence for genetic heterogeneity where rBAT would be responsible only for type I cystinuria and suggests a complementation mechanism to explain the intermediate type I/type III phenotype.     

Biological diversity and cultural heritage

In this paper some examples of the development of communities of microorganisms and plants on historic buildings and montiments are shown. When the building stones differ from the surrounding natural substrata, an increase in the biological diversity of the area is produced. In some cases, monuments can come to constitute a true refuge for a few species when the natural habitat is threatened. It is suggested that biological diversity, when it does not represent a threat for the cultural heritage, should be considered worthy of preservation.     

Understanding the role of DNA methylation in successful biological invasions: a review

Biological invasions provide a unique opportunity to investigate rapid adaptation and evolution as the introduced taxa adapt to biogeographic contexts or habitats in which they have not evolved. The capacity of populations to evolve is generally thought to be constrained by their existing heritable genetic variation, which is usually associated with variation in genomic DNA nucleotide sequences. However, there is increasing acceptance that a range of mechanisms—collectively termed ‘epigenetics’ can alter gene function and affect ecologically important traits. Epigenetic processes may mediate adaptive phenotypic plasticity and provide heritable variation on a finer timescale than DNA sequence-based mutations. This review focuses on DNA methylation, a well-studied epigenetic mechanism known to be associated with biological adaptation to environmental stress. We explore the role of DNA methylation in characterising the adaptive potential of invasive species. We also provide an overview of studies focused on DNA methylation and invasive species to date, and identify knowledge gaps and potential ways to advance understanding of epigenetic-based adaptation. A summary of the literature suggests that DNA methylation could play a key role in the success of invasive species. Introduced populations with reduced genetic diversity often display increased DNA methylation variation in comparison with native populations, which could create phenotypic diversity when it is most required. Recent data show that DNA methylation could contribute to adaptation through both phenotypic plasticity and heritable variation, particularly through clonal reproduction. From a methodological perspective, recent advances in molecular techniques provide an exciting opportunity to explore the functional relevance of DNA methylation to successful biological invasions. Gaining a greater understanding of the adaptive and evolutionary processes that contribute to invasion success is critical for preventing and managing the future introduction, establishment and spread of invasive species.