title: Bacterial Active Community Cycling in Response to Solar Radiation and Their Influence on Nutrient Changes in a High-Altitude Wetland.
abstract: Microbial communities inhabiting high-altitude spring ecosystems are subjected to extreme changes in solar irradiance and temperature throughout the diel cycle. Here, using 16S rRNA gene tag pyrosequencing (cDNA) we determined the composition of actively transcribing bacteria from spring waters experimentally exposed through the day (morning, noon, and afternoon) to variable levels of solar radiation and light quality, and evaluated their influence on nutrient recycling. Solar irradiance, temperature, and changes in nutrient dynamics were associated with changes in the active bacterial community structure, predominantly by Cyanobacteria, Verrucomicrobia, Proteobacteria, and 35 other Phyla, including the recently described Candidate Phyla Radiation (e.g., Parcubacteria, Gracilibacteria, OP3, TM6, SR1). Diversity increased at noon, when the highest irradiances were measured (3.3-3.9 H', 1125 W m-2) compared to morning and afternoon (0.6-2.8 H'). This shift was associated with a decrease in the contribution to pyrolibraries by Cyanobacteria and an increase of Proteobacteria and other initially low frequently and rare bacteria phyla (< 0.5%) in the pyrolibraries. A potential increase in the activity of Cyanobacteria and other phototrophic groups, e.g., Rhodobacterales, was observed and associated with UVR, suggesting the presence of photo-activated repair mechanisms to resist high levels of solar radiation. In addition, the percentage contribution of cyanobacterial sequences in the afternoon was similar to those recorded in the morning. The shifts in the contribution by Cyanobacteria also influenced the rate of change in nitrate, nitrite, and phosphate, highlighted by a high level of nitrate accumulation during hours of high radiation and temperature associated with nitrifying bacteria activity. We did not detect ammonia or nitrite oxidizing bacteriain situ, but both functional groups (NitrosomonaandNitrospira) appeared mainly in pyrolibraries generated from dark incubations. In total, our results reveal that both the structure and the diversity of the active bacteria community was extremely dynamic through the day, and showed marked shifts in composition that influenced nutrient recycling, highlighting how abiotic variation affects potential ecosystem functioning.
authors.affiliation: Programa de Biodiversidad and Departamento de Biología, Facultad de Ciencias Naturales y Exactas, Observatorio de Ecología Microbiana, Universidad de Playa Ancha Valparaíso, Chile.
authors.forename: Verónica
authors.initials: V
authors.lastname: Molina
authors.affiliation: Centro de Investigación Marina Quintay, Facultad de Ecología y Recursos Naturales, Universidad Andres Bello Valparaíso, Chile.
authors.forename: Klaudia
authors.initials: K
authors.lastname: Hernández
authors.affiliation: Laboratorio de Complejidad Microbiana y Ecología Funcional and Departamento de Biotecnología, Facultad de Ciencias del Mar y Recursos Biológicos, Universidad de Antofagasta, AntofagastaChile; Centre for Biotechnology and BioengineeringSantiago, Chile.
authors.forename: Cristina
authors.initials: C
authors.lastname: Dorador
authors.affiliation: Centro de Investigación y Gestión de Recursos Naturales, Instituto de Química y Bioquímica, Facultad de Ciencias, Universidad de Valparaíso Valparaíso, Chile.
authors.forename: Yoanna
authors.initials: Y
authors.lastname: Eissler
authors.affiliation: Centre for Biotechnology and BioengineeringSantiago, Chile; Departamento de Ciencias Farmacéuticas, Facultad de Ciencias, Universidad Católica del NorteAntofagasta, Chile.
authors.forename: Martha
authors.initials: M
authors.lastname: Hengst
authors.affiliation: Laboratorio de Complejidad Microbiana y Ecología Funcional and Departamento de Biotecnología, Facultad de Ciencias del Mar y Recursos Biológicos, Universidad de Antofagasta, AntofagastaChile; Centre for Biotechnology and BioengineeringSantiago, Chile.
authors.forename: Vilma
authors.initials: V
authors.lastname: Pérez
authors.affiliation: Fish and Stable Isotope Ecology Laboratory, Instituto de Ciencias Naturales Alexander von Humboldt, Facultad de Ciencias del Mar y Recursos Biológicos, Universidad de Antofagasta Antofagasta, Chile.
authors.forename: Chris
authors.initials: C
authors.lastname: Harrod
keywords: 16S RNA gene pyrosequencing; PAR; UVR; extreme ecosystem; phototrophic bacteria; rare microbial biosphere; solar radiation