Diversity of microbial communities colonizing the walls of a Karstic cave in Slovenia

Lava cave microbial communities within mats and secondary mineral deposits: implications for life detection on other planets

Lava caves contain a wealth of yellow, white, pink, tan, and gold-colored microbial mats; but in addition to these clearly biological mats, there are many secondary mineral deposits that are nonbiological in appearance. Secondary mineral deposits examined include an amorphous copper-silicate deposit (Hawai'i) that is blue-green in color and contains reticulated and fuzzy filament morphologies. In the Azores, lava tubes contain iron-oxide formations, a soft ooze-like coating, and pink hexagons on basaltic glass, while gold-colored deposits are found in lava caves in New Mexico and Hawai'i. A combination of scanning electron microscopy (SEM) and molecular techniques was used to analyze these communities. Molecular analyses of the microbial mats and secondary mineral deposits revealed a community that contains 14 phyla of bacteria across three locations: the Azores, New Mexico, and Hawai'i. Similarities exist between bacterial phyla found in microbial mats and secondary minerals, but marked differences also occur, such as the lack of Actinobacteria in two-thirds of the secondary mineral deposits. The discovery that such deposits contain abundant life can help guide our detection of life on extraterrestrial bodies.

Random transposon mutagenesis of Verrucomicrobium spinosum DSM 4136(T)

The Verrucomicrobia are a bacterial group of growing interest due to their environmental ubiquity as free-living and host-associated microbes. They also exhibit an unusual compartmentalized cell plan, shared with members of neighboring phyla that include the Planctomycete bacteria. However, Verrucomicrobia are currently difficult to study, due to a lack of available genetic tools that would permit robust testing of hypotheses formulated from ecological and genomic data. To our knowledge, there are no published studies describing the transformation of exogenous DNA into any members of the Verrucomicrobia (or the neighboring phylum containing Planctomycetes). Here, we present a procedure for the transformation of DNA into Verrucomicrobium spinosum DSM 4136(T) via electroporation and the first description of a random transposon mutant library in this organism. We anticipate that this approach could be applied successfully to other Verrucomicrobia, providing opportunities to test the role of predicted gene function in ecological interactions and identify genes associated with the distinctive Planctomycete-Verrucomicrobial cell plan.