title: Water stress impacts on bacterial carbon monoxide oxidation on recent volcanic deposits.
abstract: Water availability oscillates dramatically on young volcanic deposits, and may control the distribution and activity of microbes during early stages of biological succession. Carbon monoxide (CO)-oxidizing bacteria are among the pioneering colonists on volcanic deposits and are subjected to these water stresses. We report here the effects of water potential on CO-oxidizing bacteria in unvegetated (bare) and vegetated (canopy) sites on a 1959 volcanic deposit on Kilauea Volcano (Hawai'i). Time course measurements of water potential showed that average water potentials in the surface layer (0-1 cm) of canopy soil remained between -0.1 and 0 MPa, whereas dramatic diurnal oscillations (for example, between -60 and 0 MPa) occur in bare site surface cinders. During a moderate drying event in situ (-1.7 to 0 MPa), atmospheric CO consumption by intact bare site cores decreased 2.7-fold. For bare and canopy surface samples, maximum potential CO oxidation rates decreased 40 and 60%, respectively, when water potentials were lowered from 0 to -1.5 MPa in the laboratory. These observations indicated that CO oxidation is moderately sensitive to changes in water potential. Additional analyses showed that CO oxidation resumes within a few hours of rehydration, even after desiccation at -150 MPa for 63 days. Samples from both sites exposed to multiple cycles of drying and rewetting (-80 to 0 MPa), lost significant activity after the first cycle, but not after subsequent cycles. Similar responses of CO oxidation in both sites suggested that active CO-oxidizing communities in bare and canopy sites do not express differential adaptations to water stress.
authors.affiliation: Department of Biological Sciences, Louisiana State University, Baton Rouge, LA 70803, USA.
authors.forename: Carolyn F
authors.initials: CF
authors.lastname: Weber
authors.forename: Gary M
authors.initials: GM
authors.lastname: King
mesh_terms: D018407:Bacterial Physiological Phenomena; D002248:Carbon Monoxide / Q000378:metabolism*; D003681:Dehydration; D019015:Geologic Sediments / Q000382:microbiology; D006254:Hawaii; D010084:Oxidation-Reduction; D012988:Soil Microbiology; D013312:Stress, Physiological
chemical_list: D002248:Carbon Monoxide