The Evolution of a Capacity to Build Supra-Cellular Ropes Enabled Filamentous Cyanobacteria to Colonize Highly Erodible Substrates

Several motile, filamentous cyanobacteria display the ability to self-assemble into tightly woven or twisted groups of filaments that form macroscopic yarns or ropes, and that are often centimeters long and 50-200 microm in diameter. Traditionally, this trait has been the basis for taxonomic definition of several genera, notably Microcoleus and Hydrocoleum, but the trait has not been associated with any plausible function.Through the use of phylogenetic reconstruction, we demonstrate that pedigreed, rope-building cyanobacteria from various habitats do not form a monophyletic group. This is consistent with the hypothesis that rope-building ability was fixed independently in several discrete clades, likely through processes of convergent evolution or lateral transfer. Because rope-building cyanobacteria share the ability to colonize geologically unstable sedimentary substrates, such as subtidal and intertidal marine sediments and non-vegetated soils, it is also likely that this supracellular differentiation capacity imparts a particular fitness advantage in such habitats. The physics of sediment and soil erosion in fact predict that threads in the 50-200 microm size range will attain optimal characteristics to stabilize such substrates on contact.Rope building is a supracellular morphological adaptation in filamentous cyanobacteria that allows them to colonize physically unstable sedimentary environments, and to act as successful pioneers in the biostabilization process

Desnutrição e sarcopenia em doentes hospitalizados

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Cyanobacterial diversity in extreme environments in Baja California, Mexico: a polyphasic study

Cyanobacterial diversity from two geographical areas of Baja California Sur, Mexico, were studied: Bahia Concepcion, and Ensenada de Aripez. The sites included hypersaline ecosystems, sea bottom, hydrothermal springs, and a shrimp farm. In this report we describe four new morphotypes, two are marine epilithic from Bahia Concepcion, Dermocarpa sp. and Hyella sp. The third, Geitlerinema sp., occurs in thermal springs and in shrimp ponds, and the fourth, Tychonema sp., is from a shrimp pond. The partial sequences of the 16S rRNA genes and the phylogenetic relationship of four cyanobacterial strains (Synechococcus cf. elongatus, Leptolyngbya cf. thermalis, Leptolyngbya sp., and Geitlerinema sp.) are alsopresented. Polyphasic studies that include the combination of light microscopy, cultures and the comparative analysis of 16S rRNA gene sequences provide the most powerful approach currently available to establish the diversity of these oxygenic photosynthetic microorganisms in culture and in nature

Penetration of ultraviolet radiation into shallow water sediments: High exposure for photosynthetic communities

Benthic photosynthetic microorganisms are widespread in shallow-water sediments, microenvironments that are commonly assumed to be virtually opaque to ultraviolet radiation (WR). We used a newly developed optical microprobe to measure the submillimeter penetration of solar UVR into a variety of these microenvironments. UVR lapping due to strong scattering occurred at the surface of some sediments, resulting in a surface maximum of scalar irradiance (E(0)) that could be significantly larger that the incident radiation. In the subsurface, E(0) was typically extinguished in a quasi-exponential manner, with attenuation coefficients (310 nm) ranging from 4 to 21 mm(-1), depending on sediment type. Ultraviolet B (at 310 nm) was extinguished to 1% of the incident between 1.25 and 0.23 mm from the surface. Within the euphotic zones of these sediments, however, the space-averaged UVB scalar irradiance was very high, between 15 and 33% of the incident. In natural waters, for example, the same parameter varies between 3 and 9% of the incident. Thus, in fact, photosynthesis in these environments must develop under strong UV stress, and it must be regarded as potentially labile to the effects of ozone depletion

Abordagem da hipertrigliceridemia severa na gravidez: a propósito de um caso clínico

RESUMO Durante a gravidez o metabolismo lipídico é afectado pelas hormonas placentárias de modo a assegurar um adequado aporte nutricional para o feto, constatando-se um aumento fisiológico dos níveis de triglicerídeos (TG), em particular no terceiro trimestre. Se o aumento do valor dos triglicerídeos for superior ao esperado na gravidez a paciente deve ser cuidadosamente monitorizada. A principal complicação da hipertrigliceridemia severa é a pancreatite aguda que está associada a uma mortalidade materno-fetal elevada (20%). Os autores apresentam o caso de uma mulher de 31 anos, com gestação de 34 semanas e hipertrigliceridemia severa (TG=1127 mg/dl). Foi internada e submetida a dieta pobre em gorduras, suplementos de ácidos gordos ómega 3 e a apertada vigilância clínica e analítica. O parto decorreu às 37 semanas de gestação sem complicações. O recém-nascido, do sexo feminino, pesava 3220 g e o score Apgar era de 9 ao primeiro minuto. Após o parto os níveis de TG maternos mostraram uma redução marcada. Este caso ilustra a importância do diagnóstico precoce e da instituição de medidas estratégicas relativamente simples na prevenção de pancreatite aguda em grávidas com hipertrigliceridemia severa

Light and Life: Exotic Photosynthesis in Binary Star Systems

The potential for hosting photosynthetic life on Earth-like planets within binary/multiple stellar systems was evaluated by modelling the levels of photosynthetically active radiation (PAR) such planets receive. Combinations of M and G stars in: (i) close-binary systems; (ii) wide-binary systems and (iii) three-star systems were investigated and a range of stable radiation environments found to be possible. These environmental conditions allow for the possibility of familiar, but also more exotic forms of photosynthetic life, such as infrared photosynthesisers and organisms specialised for specific spectral niches.Comment: Accepted for publication in: Astrobiolog