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Centro de Investigaciones Biológicas del Noroeste (CIBNOR) 2013

Análisis de comunidades de microorganismos productores de hidrógeno de ambientes hipersalinos naturales y en microcosmos

Soria Andrade, Guadalupe Viridiana

Titre : Análisis de comunidades de microorganismos productores de hidrógeno de ambientes hipersalinos naturales y en microcosmos

Auteur : Soria Andrade, Guadalupe Viridiana

Etablissement de soutenance : Centro de Investigaciones Biológicas del Noroeste (CIBNOR)

Grade : Maestría en Ciencias en el Uso, Manejo y Preservación de los Recursos Naturales 2013

The simple composition of molecular hydrogen has significant influence on the function and structure of microbial ecosystem population through its strong control over the thermodynamics of redox reactions in metabolism. For fermentation and oxidation of small organic molecules, hydrogen production is often required. However, the community structure is expected to be distinctive according to environmental soil use conditions, so when we compare two different sites as ESSA_A1 and LSI_S3, we will find differences in both structure and hydrogen concentrations. Were performed a community structure analysis by PCR-DGGE technique using the Fe-Fe hydrogenase gene-hydA (which codes for the enzyme subunit A involved in hydrogen production) and the 16S rRNA (encoding the small 16S rRNA subunit) gene for both systems denominated microcosms and intact environmental samples. Were recorded differences between study sites ; salinities for ESSA_A1 were 5.3% and 28% for LSI_S3 ; hydrogen concentrations in situ were 0.0011% or 11 ppm for ESSA_A1 and 0.0055% or 55 ppm for LSI_S3. Structures and ecological estimates of the bacterial community and those of putative hydrogen producers were also different. The 16S rRNA gene phylotypes obtained suggest a greater stability and complexity in ESSA_A1 community where physicochemical parameters are manipulated with minimal fluctuations, as this site is part of an industrial process ; hence the community is less deteriorated, its higher stability for an increase in the functional redundancy of different operational taxonomic units (OTUs) in the community. It is speculated that low hydrogen concentrations in this site are the fast reactivity of molecular hydrogen generating a short retention time of this molecule in the community. When analyzing the number of OTUs obtained through ecological estimates, it suggests a greater community diversity and uniformity was found in ESSA_A1. Obtaining DGGE profiles and hydrogen concentrations in the treatment with formaldehyde suggests there are microorganisms that can use this compound as an energy or carbon source as methylotrophic bacteria although it should be confirmed. In the case of the functional gene (hydA), we found a community with greater values in ecological estimates in ESSA_A1, suggesting greater diversity and stability compared to LSI_S3, which helps us to support the hypothesis of differences in the putative hydrogen producing microorganism community. Moreover, higher hydrogen concentrations in LSI_S3 could be due to gas accumulation under salt crusts preventing gas dissipation into the atmosphere, which explains the greater values in the little diverse community found in this site. It is important to know from an ecological and biotechnological point of view a community of microorganisms involved in hydrogen generation and of those that are consumers within highly complex communities, as microbial mats.

Mots Clés : fermentación ; hidrógeno ; hidrogenasa


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