The astrobiology primer: An outline of general knowledge - Version 1, 2006

Peer reviewe

Descubriendo la riqueza de las Cuevas: La Cueva de Villa Luz, en Tabasco

Sabías que…La Cueva de Villa Luz es famosa por su singular ambiente, rico en compuestos de azufre. Esta cueva se encuentra entre las más peligrosas para los humanos, ya que en su interior hay grandes concentraciones de gas sulfhídrico, muy tóxico, que le da a la cueva el típico olor a huevo podrido. La Villa Luz es el típico ejemplo de una cueva cuyo desarrollo y crecimiento se encuentran aún activos, debido a la acción del ácido sulfúrico. Este ácido es generado por el desecho metabólico de las colonias de bacterias, que obtienen sulfuro de hidrógeno de las rocas. El ácido sulfúrico es un elemento natural que interviene en varios procesos biogeoquímicos responsables de la formación de la cuev

Geomicrobiology of Cave Ferromanganese Deposits: A Field and Laboratory Investigation

Unusual ferromanganese deposits are found in several caves in New Mexico. The deposits are enriched in iron and manganese by as much as three orders of magnitude over the bedrock, differing significantly in mineralogy and chemistry from bedrock-derived insoluble residue. The deposits contain metabolically active microbial communities. Enrichment cultures inoculated from the ferromanganese deposits produced manganese oxides that were initially amorphous but developed into crystalline minerals over an 8-month period and beyond; no such progression occurred in killed controls. Phylogenetic analyses of sequences from clone libraries constructed from culture DNA identified two genera known to oxidize manganese, but most clones represent previously unknown manganese oxidizers. We suggest that this community is breaking down the bedrock and accumulating iron and manganese oxides in an oligotrophic environment

Diverse microbial communities inhabiting ferromanganese deposits in Lechuguilla and Spider Caves

Lechuguilla Cave is an ancient, deep, oligotrophic subterranean environment that contains an abundance of low‐density ferromanganese deposits, the origin of which is uncertain. To assess the possibility that biotic factors may be involved in the production of these deposits and to investigate the nature of the microbial community in these materials, we carried out culture‐independent, small subunit ribosomal RNA (SSU rRNA) sequence‐based studies from two sites and from manganese and iron enrichment cultures inoculated with ferromanganese deposits from Lechuguilla and Spider Caves. Sequence analysis showed the presence of some organisms whose closest relatives are known iron‐ and manganese‐oxidizing/reducing bacteria, including Hyphomicrobium, Pedomicrobium, Leptospirillum, Stenotrophomonas and Pantoea. The dominant clone types in one site grouped with mesophilic Archaea in both the Crenarchaeota and Euryarchaeota. The second site was dominated almost entirely by lactobacilli. Other clone sequences were most closely related to those of nitrite‐oxidizing bacteria, nitrogen‐fixing bacteria, actinomycetes and β‐ and γ‐Proteobacteria. Geochemical analyses showed a fourfold enrichment of oxidized iron and manganese from bedrock to darkest ferromanganese deposits. These data support our hypothesis that microorganisms may contribute to the formation of manganese and iron oxide‐rich deposits and a diverse microbial community is present in these unusual secondary mineral formations