RESUMO
In this paper, we report the presence of sedimentary microbial ecosystems in wetlands of the Salar de Atacama. These laminated systems, which bind, trap and precipitate mineral include: microbial mats at Laguna Tebenquiche and Laguna La Brava, gypsum domes at Tebenquiche and carbonate microbialites at La Brava. Microbial diversity and key biogeochemical characteristics of both lakes (La Brava and Tebenquiche) and their various microbial ecosystems (non-lithifying mats, flat and domal microbialites) were determined. The composition and abundance of minerals ranged from trapped and bound halite in organic-rich non-lithifying mats to aragonite-dominated lithified flat microbialites and gypsum in lithified domal structures. Pyrosequencing of the V4 region of the 16s rDNA gene showed that Proteobacteria comprised a major phylum in all of the microbial ecosystems studied, with a marked lower abundance in the non-lithifying mats. A higher proportion of Bacteroidetes was present in Tebenquiche sediments compared to La Brava samples. The concentration of pigments, particularly that of Chlorophyll a, was higher in the Tebenquiche than in La Brava. Pigments typically associated with anoxygenic phototrophic bacteria were present in lower amounts. Organic-rich, non-lithifying microbial mats frequently formed snake-like, bulbous structures due to gas accumulation underneath the mat. We hypothesize that the lithified microbialites might have developed from these snake-like microbial mats following mineral precipitation in the surface layer, producing domes with endoevaporitic communities in Tebenquiche and carbonate platforms in La Brava. Whereas the potential role of microbes in carbonate platforms is well established, the contribution of endoevaporitic microbes to formation of gypsum domes needs further investigation.
Assuntos
Bacteroidetes/isolamento & purificação , Sedimentos Geológicos/microbiologia , Lagos/microbiologia , Microbiota , Proteobactérias/isolamento & purificação , Áreas Alagadas , Bacteroidetes/genética , Carbonato de Cálcio/análise , Sulfato de Cálcio/análise , Chile , Clorofila/análise , Sedimentos Geológicos/química , Proteobactérias/genética , RNA Ribossômico 16S/genéticaRESUMO
The relation between birthweight and parity of the mother was examined in Nicaraguan patients from the capital Managua. 7431 births were taken into consideration from 1989-1991. 564 (= 7.6%) of these newborns were born to mothers with more than 5 deliveries. A positive correlation between the increasing number of the parity and the birthweight can be demonstrated in our patients until parity 10, however there are decreases in the birthweight of female newborns between parity 3 to 4 and 5 to 6 and in males between parity 6 to 7 and parity 8 to 9. The average age of a Nicaraguan primipara is 20.7 years and increases by 1.9-2.4 years until parity 5. From parity 6 to parity 15 it increases only by 0.7-1.2 years.