Title: Iron and Manganese μMiners: The Characterization of Potential Siderophore Producing Cave Bacteria
Authors: Tammi R. Duncan1 and Diana E. Northup1
Affiliations: 1Department of Biology, University of New Mexico
Abstract: Iron is an essential survival requirement for all living organisms on Earth. Specifically, bacteria contribute to the cycling of iron by aerobic and anaerobic respiration of ferrous (Fe2+) and ferric (Fe3+) iron. To scavenge and absorb iron from the environment, bacteria produce and release siderophores, which are low-molecular-weight compounds with high affinity and selectivity for ferric iron. Some terrestrial caves contain deposits of ferromanganese oxides on their walls and are possibly good habitats in which to look for the production of siderophores by bacteria. Subterranean bacterial communities have been identified in association with secondary cave formations of caves in the Guadalupe Mountains, NM. Previous investigations of the diversity of these communities have been conducted in Lechuguilla and Spider Caves, and have led to the discovery of bacterial species related to iron- and manganese-oxidizing bacteria in ferromanganese deposits (FMD). We hypothesize that subterranean bacteria are mining reduced iron or manganese from the cave walls by using siderophores, providing the iron or manganese that they oxidize to form the FMD. To test this hypothesis, 173 isolated cultures of bacteria were collected, characterized, and tested for siderophore production from previously collected cultures inoculated with cave FMD on site in either Spider or Lechuguilla Cave. These isolates have been characterized by catalase and oxidase testing and Gram staining, and tested for siderophore production. The presence of isolates that produce siderophores would support our hypothesis that bacteria are mining the cave wall rock for reduced iron.