Lechuguilla cave microbiome

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Introduction

Lechuguilla Cave is a deep and expansive cave in New Mexico, USA. The cave and its microbiome have attracted interest from microbiologists because, despite several million years of isolation from the terrestrial environment, bacterial isolates from the cave display widespread resistance to modern clinical antibiotic drugs. This discovery sheds new light on the origin of antibiotic resistance genes, and it offers new opportunities for developing effective next-generation antibiotic drugs.

Geology

Lechuguilla Cave is located in Carlsbad Caverns National Park, New Mexico. It formed between four and seven million years ago through hypogenic speleogenesis [1]. Hydrogen sulfide from hydrocarbons in the nearby Delaware Basin became oxidized to sulfuric acid, and acidified groundwater infiltrated upward into the carbonate rock of the Capitan Formation, thereby forming Lechuguilla Cave [2].

After formation, the aquifer dropped leaving the cave hydrologically isolated from phreatic groundwater. The cave is also hydrologically isolated from above by the impermeable rock of the Yates Formation that overlies the Capitan Formation [3]. As a result, the influx of terrestrial water occurs very slowly and in negligible quantities. The cave and its biota have remained effectively isolated from the terrestrial environment and human activity. Water infiltrating into the cave today would have left the surface long before the advent of human antibiotic use in agriculture and medicine [4].

Cave Environment and Biodiversity

Lechuguilla Cave is an extreme environment defined by darkness and limited nutrients. Nonetheless, diverse microbial communities inhabit the aphotic and oligotrophic surfaces of the cave in rich biofilms. These communities are anchored by chemolithoautotrophic primary producers who oxidize ferromanganese substances in the rock, leaving distinctive deposits of ferromanganese ores nearby [5]. These chemolithoautotrophs support secondary populations of chemoheterotrophic bacteria, archaea, and fungi [6].


Several fungal and bacterial phyla have been isolated from the cave. These include the fungi Penicillium, Aspergillus, Cylindrocladium, Rhizopus, Mycelia sterilia, Mucor, Paecileomyces, Fusarium, and Epicoccum; and the bacteria Bacillus, Actinomycetes, Arthrobacter, Chryseomonas luteola, Rhodococcus, and Staphylococcus [8].

References