Tesis doctoral de Lorena Victoria Escudero Gonzalez
Presence of arsenic in drinking and irrigation waters is a serious concern of great economic, social, and environmental importance in numerous locations across south america (mainly in the northern chile and argentina). As respiring microorganisms that reduce as(v) to as(iii) are diverse and can be involved in the as mobilization from the sediment to drinking water sources. The present phd thesis explores the links between the microbial metabolism and the biogeochemical cycling of as in saline systems of northern chile. On the one hand, the microbial diversity and the distribution and diversity of arsenic functional genes (i.E., Arsenate reductases arra and arsc) were studied in saline environments with high (e.G., Salar de ascotán) and low (e.G., Laguna tebenquiche) as concentrations. On the other hand, characterization of microbial enrichments and bacterial pure cultures were carried out to link bacterial activity and the origin of arsenic minerals in the environment. the 16s rrna gene clone libraries showed consistent differences in bacterial community composition in saline environments with high and low concentrations of as. As functional genes were amplified with specific primers previously described in the literature and methodological improvements were conducted in this work to optimize the amplification in hypersaline, as-rich natural samples. The gen arra is present in anaerobic microorganims that respire as (v) to as (iii). The gen arsc, in turn, is used for detoxification trough membrane pumps. Most of the sequences found formed new clusters distantly related to previously known sequences obtained from environments with presence of as, within the firmicutes. Both 16s rdna and arsenic functional genes showed firmicutes and gammaproteobacteria as the predominant bacterial groups in water and sediment samples of salar de ascotán. along a set of natural samples with increasing arsenic concentrations we found a positive relationship between arsenic concentration and abundance of arsenic reducing bacteria determined by mpn. The gen arra was detected throughout the gradient. Conversely, the gen arsc was only found in the samples with the lowest arsenic concentrations. These data showed a widespread occurrence of bacteria related to the arsenic cycling, suggesting a key role of arsenic reducing bacteria in the arsenic mobilization to the aqueous phase. finally, through classical microbiology studies we obtained a new strain of shewanella from sediments of ascotán that reduced both as and sulfate under anaerobic conditions, a specific trait not previously reported in other shewanella spp isolated from environments contaminated with arsenic. In addition, these studies gave further clues for a better comprehension of the arsenic cycle at the geological level. We showed that the presence and activity of arsenic reducing bacteria was linked to the formation of sulfurous arsenic minerals at a large scale, giving further evidence for the biological origin of the wide arsenic mineral layers found in salar de ascotán.
Datos académicos de la tesis doctoral «Estudio de los genes implicados en el metabolismo del arsénico en cultivos y en sistemas naturales«
- Título de la tesis: Estudio de los genes implicados en el metabolismo del arsénico en cultivos y en sistemas naturales
- Autor: Lorena Victoria Escudero Gonzalez
- Universidad: Autónoma de barcelona
- Fecha de lectura de la tesis: 30/03/2009
Dirección y tribunal
- Director de la tesis
- Carles Pedrós Alió
- Tribunal
- Presidente del tribunal: ricard Guerrero moreno
- Antonio Ventosa ucero (vocal)
- (vocal)
- (vocal)