Diverse microbial communities inhabiting ferromanganese deposits in Lechuguilla and Spider Caves

Abstract

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 beta- and gamma-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.

The impact of host rock geochemistry on bacterial community structure in oligotrophic cave environments

“…Such geomicrobial activity is thought to be indicated by the presence of corrosion residues: areas of fabric and mineralogical change in the bedrock, characterized by a color change and softening or powdering of the rock (Boston et al, 2001;Canaveras et al, 2001;Northup et al, 2003). While these residues do contain an observable microbial population, a mechanism of formation remains to be determined Northup et al, 2003).…”

Comparative microbial community composition from secondary carbonate (moonmilk) deposits: implications for the Cansiliella servadeii cave hygropetric food web

“…Several clades within the Sphingomonadales were comprised of clones from both moonmilk sites, and were more closely related to each other than to previously retrieved environmental clones or cultured strains. Schabereiter-Gurtner et al (2004) retrieved similar alphaproteobacterial groups from cave-wall rock and Paleolithic paintings in Spain, and Northup et al (2003) found these genera from caves in New Mexico. Gurtner et al, 2002b;Schabereiter-Gurtner et al, 2002a;Schabereiter-Gurtner et al, 2004;Ikner et al, 2007).…”

“…16S rRNA gene sequences were retrieved from moonmilk to evaluate the microbial diversity, which was expected to be high based on previous research of natural, cave-wall habitats (e.g., Northup et al, 2003;Chelius & Moore, 2004;Van de Kamp, 2004;Barton et al, 2007) and cave-walls with Paleolithic paintings or system having been anthropogenically impacted (e.g., Groth & Saiz-Jimenez, 1999; Schabereiterdella Foos percolating waters extractions during the summer (0.38 ± 0.14 mg/l Chl a), but nothing was detected from samples collected in the winter. Only moonmilk collected from the summer had detectable quantities of chlorophyll, with a composition of 0.14 ± 0.09 µg/l Chl a.…”

“…1). They have also been identified from naturally oligotrophic, but not associated with cave paintings, cave-wall surfaces (e.g., Northup et al, 2003;Barton et al, 2007). The general phylogenetic similarities, even in the absence of high sequence identities, may indicate that the cave habitat, irrespective of geochemical or mineralogic conditions, may be a common habitat for these betaproteobacterial groups.…”

“…Chemolithoautotrophic microbial processes control metal and nutrient cycling in karst aquifer systems (e.g., Sarbu et al, 1996;Northup et al, 2003;Opsahl & Chanton, 2006;Gray & Engel, 2013) and support rich and biologically diverse ecosystems with complex trophic-level interactions and food webs in…”