Premium
Microbial F e( III ) oxide reduction potential in C hocolate P ots hot spring, Y ellowstone N ational P ark
Author(s) -
Fortney N. W.,
He S.,
Converse B. J.,
Beard B. L.,
Johnson C. M.,
Boyd E. S.,
Roden E. E.
Publication year - 2016
Publication title -
geobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.859
H-Index - 72
eISSN - 1472-4669
pISSN - 1472-4677
DOI - 10.1111/gbi.12173
Subject(s) - chemistry , enrichment culture , microbial mat , population , mesophile , biochemistry , microbiology and biotechnology , food science , bacteria , environmental chemistry , biology , cyanobacteria , genetics , demography , sociology
Chocolate P ots hot springs ( CP ) is a unique, circumneutral pH , iron‐rich, geothermal feature in Y ellowstone N ational P ark. Prior research at CP has focused on photosynthetically driven Fe( II ) oxidation as a model for mineralization of microbial mats and deposition of A rchean banded iron formations. However, geochemical and stable F e isotopic data have suggested that dissimilatory microbial iron reduction ( DIR ) may be active within CP deposits. In this study, the potential for microbial reduction of native CP Fe( III ) oxides was investigated, using a combination of cultivation dependent and independent approaches, to assess the potential involvement of DIR in F e redox cycling and associated stable Fe isotope fractionation in the CP hot springs. Endogenous microbial communities were able to reduce native CP Fe( III ) oxides, as documented by most probable number enumerations and enrichment culture studies. Enrichment cultures demonstrated sustained DIR driven by oxidation of acetate, lactate, and H 2 . Inhibitor studies and molecular analyses indicate that sulfate reduction did not contribute to observed rates of DIR in the enrichment cultures through abiotic reaction pathways. Enrichment cultures produced isotopically light F e( II ) during DIR relative to the bulk solid‐phase F e( III ) oxides. Pyrosequencing of 16S rRNA genes from enrichment cultures showed dominant sequences closely affiliated with Geobacter metallireducens , a mesophilic Fe( III ) oxide reducer. Shotgun metagenomic analysis of enrichment cultures confirmed the presence of a dominant G. metallireducens ‐like population and other less dominant populations from the phylum Ignavibacteriae , which appear to be capable of DIR . Gene (protein) searches revealed the presence of heat‐shock proteins that may be involved in increased thermotolerance in the organisms present in the enrichments as well as porin–cytochrome complexes previously shown to be involved in extracellular electron transport. This analysis offers the first detailed insight into how DIR may impact the Fe geochemistry and isotope composition of a F e‐rich, circumneutral p H geothermal environment.