Ricardo Amils

Aminoglycoside-induced mistranslation in thermophilic archaebacteria

SummaryThe effect of selected aminoglycoside antibiotics on the translational accuracy of poly(U) programmed ribosomes derived from the thermophilic archaebacteria Thermoplasma acidophilum, Sulfolobus solfataricus, Thermococcus celer and Desulfurococcus mobilis has been determined. Under optimum temperature and ionic conditions for polyphenylalanine synthesis, the four species investigated are found to be markedly diverse in their response to the miscoding-inducing action of aminoglycoside antibiotics. T. acidophilum is sensitive to all of the compounds tested except streptomycin; S. solfataricus responds to paromomycin and to hygromycin B; T. celer is only affected by neomycin, and D. mobilis is refractory to all drugs. The only feature shared by the four species under study, and by all archaebacteria so far investigated, is their complete insensitivity to streptomycin. The structural and phylogenetic implications of the remarkable diversity encountered among archaebacterial ribosomes in their susceptibility to aminoglycosides are discussed.

A micromorphological and phylogenetic study of Sarcocornia (Chenopodiaceae) of the Iberian Peninsula

This study presents a comprehensive revision of the genus Sarcocornia (Chenopodiaceae) on the Iberian Peninsula based on macromorphological, micromorphological and phylogenetic data, and considering caryological, ecological and biogeographical information. Three species of Sarcocornia have been identified on the Iberian Peninsula: Sarcocornia perennis (Miller) A.J. Scott, Sarcocornia fruticosa (L.) A.J. Scott and Sarcocornia alpini (Lag.) Rivas-Martínez. Several authors have proposed that S. alpini is a specific and subspecific rank of S. perennis. Fuente, Rufo and Sánchez-Mata have recently described a new species, Sarcocornia hispanica. The micromorphological and molecular studies (sequence of the internal transcribed spacer region) indicate that there is a broad diversity within Sarcocornia in the Western Mediterranean. This article proposes a new species (Sarcocornia pruinosa) and subspecies (S. alpini subsp. carinata) in view of the new data.

Photosynthesis in Extreme Environments

Our ongoing exploration of Earth has led to continued discoveries of life in environments that have been previously considered uninhabitable. For example, we find thriving communities in the boiling hot springs of Yellowstone, the frozen deserts of Antarctica, the concentrated sulfuric acid in acid-mine drainages, and the ionizing radiation fields in nuclear reactors (González-Toril et al., 2003; Lebedinsky et al., 2007; Pointing et al., 2009). We find some microbes that grow only in brine and require saturated salts to live, and we find others that grow in the deepest parts of the oceans and require 500 to 1000 bars of hydrostatic pressure (Horikoshi, 1998; Ma et al., 2010). Life has evolved strategies that allow it to survive even beyond the daunting physical and chemical limits to which it has adapted to grow. To survive, organisms can assume forms that enable them to withstand freezing, complete desiccation, starvation, high levels of radiation exposure, and other physical or chemical challenges. Furthermore, they can survive exposure to such conditions for weeks, months, years, or even centuries. We need to identify the limits for growth and survival and to understand the molecular mechanisms that define these limits. Biochemical studies will also reveal inherent features of biomolecules and biopolymers that define the physico-chemical limits of life under extreme conditions. Broadening our knowledge both of the range of environments on Earth that are inhabitable by microbes and of their adaptation to these habitats will be critical for understanding how life might have established itself and survived. The diversity of life on Earth today is a result of the dynamic interplay between genetic opportunity, metabolic capability, and environmental change. For most of their existence, Earth’s habitable environments have been dominated by microorganisms and subjected to their metabolism and evolution. As a consequence of geological, climatologic, and microbial processes acting across geological time scales, the physical-chemical environments on Earth have been changing, thereby determining the path of evolution of subsequent life. For example, the release of molecular oxygen by cyanobacteria as a by product of photosynthesis as well as the colonization of Earth’s surface by metazoan life contributed to fundamental, global environmental changes. The altered environments, in turn, posed novel evolutionary opportunities to the organisms present, which ultimately led to the formation of our planet’s major animal and plant species.

Electrophoretic Techniques in Microbial Ecology

Classical microbial ecology analysis is limited by the unavoidable need for isolation of the microorganisms prior to their characterization. Although it is obvious that isolation of microorganisms is indispensable for their full characterization, it is now well recognised among microbiologists that only a small fraction of all bacteria have been isolated and characterised (Ward et al., 1992). Comparison of the percentage of culturable bacteria with total cell counts from different habitats showed enormous discrepancies (summarised by Amann et al., 1995).The introduction of molecular biology methods (such as fluorescent in situ hybridization, denaturing gradient gel electrophoresis or cloning) has enabled a significant advance in microbial ecology (Amann et al., 1995), especially in the study of extreme environments such as acidic habitats, in which conventional methods are severely limited, and some may even lead to equivocal conclusions, with occasionally grievous economic consequences.