TY - JOUR T1 - Differential incorporation of bacteria, organic matter, and inorganic ions into lake ice during ice formation JF - Journal of Geophysical Research: Biogeosciences Y1 - 2019 A1 - Santibáñez, Pamela A1 - Alexander B. Michaud A1 - Trista J. Vick-Majors A1 - D’Andrilli, Juliana A1 - Amy Chiuchiolo A1 - Hand, Kevin P. A1 - John C. Priscu AB -

The segregation of bacteria, inorganic solutes, and total organic carbon between liquid water and ice during winter ice formation on lakes can significantly influence the concentration and survival of microorganisms in icy systems, and their roles in biogeochemical processes. Our study quantifies the distributions of bacteria and solutes between liquid and solid water phases during progressive freezing. We simulated lake ice formation in mesocosm experiments using water from perennially (Antarctica) and seasonally (Alaska and Montana, USA) ice covered lakes. We then computed concentration factors and effective segregation coefficients, which are parameters describing the incorporation of bacteria and solutes into ice. Experimental results revealed that, contrary to major ions, bacteria were readily incorporated into ice and did not concentrate in the liquid phase. The organic matter incorporated into the ice was labile, amino acid-like material, differing from the humic-like compounds that remained in the liquid phase. Results from a control mesocosm experiment (dead bacterial cells) indicated that viability of bacterial cells did not influence the incorporation of free bacterial cells into ice, but did have a role in the formation and incorporation of bacterial aggregates. Together, these findings demonstrate that bacteria, unlike other solutes, were preferentially incorporated into lake-ice during our freezing experiments, a process controlled mainly by the initial solute concentration of the liquid water source, regardless of cell viability.

VL - 124 UR - https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2018JG004825 JO - J. Geophys. Res. Biogeosci. ER - TY - JOUR T1 - Diversity and Distribution of Freshwater Aerobic Anoxygenic Phototrophic Bacteria across a Wide Latitudinal Gradient JF - Frontiers in Microbiology Y1 - 2017 A1 - Ferrera, Isabel A1 - Sarmento, Hugo A1 - John C. Priscu A1 - Amy Chiuchiolo A1 - José M. González A1 - Grossart, Hans-Peter AB -

Aerobic anoxygenic phototrophs (AAPs) have been shown to exist in numerous marine and brackish environments where they are hypothesized to play important ecological roles. Despite their potential significance, the study of freshwater AAPs is in its infancy and limited to local investigations. Here, we explore the occurrence, diversity and distribution of AAPs in lakes covering a wide latitudinal gradient: Mongolian and German lakes located in temperate regions of Eurasia, tropical Great East African lakes, and polar permanently ice-covered Antarctic lakes. Our results show a widespread distribution of AAPs in lakes with contrasting environmental conditions and confirm that this group is composed of different members of the Alpha- and Betaproteobacteria. While latitude does not seem to strongly influence AAP abundance, clear patterns of community structure and composition along geographic regions were observed as indicated by a strong macro-geographical signal in the taxonomical composition of AAPs. Overall, our results suggest that the distribution patterns of freshwater AAPs are likely driven by a combination of small-scale environmental conditions (specific of each lake and region) and large-scale geographic factors (climatic regions across a latitudinal gradient).

VL - 8 UR - http://journal.frontiersin.org/article/10.3389/fmicb.2017.00175/full JO - Front. Microbiol. ER - TY - JOUR T1 - Early diverging lineages within Cryptomycota and Chytridiomycota dominate the fungal communities in ice-covered lakes of the McMurdo Dry Valleys, Antarctica JF - Scientific Reports Y1 - 2017 A1 - Rojas-Jimenez, Keilor A1 - Wurzbacher, Christian A1 - Bourne, Elizabeth Charlotte A1 - Amy Chiuchiolo A1 - John C. Priscu A1 - Grossart, Hans-Peter AB -

Antarctic ice-covered lakes are exceptional sites for studying the ecology of aquatic fungi under conditions of minimal human disturbance. In this study, we explored the diversity and community composition of fungi in five permanently covered lake basins located in the Taylor and Miers Valleys of Antarctica. Based on analysis of the 18S rRNA sequences, we showed that fungal taxa represented between 0.93% and 60.32% of the eukaryotic sequences. Cryptomycota and Chytridiomycota dominated the fungal communities in all lakes; however, members of Ascomycota, Basidiomycota, Zygomycota, and Blastocladiomycota were also present. Of the 1313 fungal OTUs identified, the two most abundant, belonging to LKM11 and Chytridiaceae, comprised 74% of the sequences. Significant differences in the community structure were determined among lakes, water depths, habitat features (i.e., brackish vs. freshwaters), and nucleic acids (DNA vs. RNA), suggesting niche differentiation. Network analysis suggested the existence of strong relationships among specific fungal phylotypes as well as between fungi and other eukaryotes. This study sheds light on the biology and ecology of basal fungi in aquatic systems. To our knowledge, this is the first report showing the predominance of early diverging lineages of fungi in pristine limnetic ecosystems, particularly of the enigmatic phylum Cryptomycota.

VL - 7 UR - https://www.nature.com/articles/s41598-017-15598-w IS - 1 JO - Sci Rep ER - TY - JOUR T1 - Evidence of form II RubisCO ( cbbM) in a perennially ice-covered Antarctic lake JF - FEMS Microbiology Ecology Y1 - 2012 A1 - Weidong Kong A1 - Jenna M. Dolhi A1 - Amy Chiuchiolo A1 - John C. Priscu A1 - Rachael M. Morgan-Kiss VL - 82 UR - http://onlinelibrary.wiley.com/doi/10.1111/j.1574-6941.2012.01431.x/full IS - 2 ER - TY - JOUR T1 - Microbial dynamics and flagellate grazing during transition to winter in Lakes Hoare and Bonney, Antarctica JF - FEMS Microbiology Ecology Y1 - 2012 A1 - Jill Thurman A1 - Jacqueline Parry A1 - Philip J. Hill A1 - John C. Priscu A1 - Trista J. Vick-Majors A1 - Amy Chiuchiolo A1 - Johanna Laybourn-Parry VL - 82 UR - http://onlinelibrary.wiley.com/doi/10.1111/j.1574-6941.2012.01423.x/full IS - 2 ER -