02314nas a2200265 4500008004100000245012500041210006900166260001200235490000700247520147000254653001501724653001101739653001701750653001801767653001101785653004001796100002201836700001501858700002301873700002201896700002401918700002101942700002101963856006401984 2020 eng d00aEnergetic and environmental constraints on the community structure of benthic microbial mats in Lake Fryxell, Antarctica0 aEnergetic and environmental constraints on the community structu c02/20200 v963 a

Ecological communities are regulated by the flow of energy through environments. Energy flow is typically limited by access to photosynthetically active radiation (PAR) and oxygen concentration (O2). The microbial mats growing on the bottom of Lake Fryxell, Antarctica, have well-defined environmental gradients in PAR and (O2). We analyzed the metagenomes of layers from these microbial mats to test the extent to which access to oxygen and light controls community structure. We found variation in the diversity and relative abundances of Archaea, Bacteria and Eukaryotes across three (O2) and PAR conditions: high (O2) and maximum PAR, variable (O2) with lower maximum PAR, and low (O2) and maximum PAR. We found distinct communities structured by the optimization of energy use on a millimeter-scale across these conditions. In mat layers where (O2) was saturated, PAR structured the community. In contrast, (O2) positively correlated with diversity and affected the distribution of dominant populations across the three habitats, suggesting that meter-scale diversity is structured by energy availability. Microbial communities changed across covarying gradients of PAR and (O2). The comprehensive metagenomic analysis suggests that the benthic microbial communities in Lake Fryxell are structured by energy flow across both meter- and millimeter-scales.

10aAntarctica10aenergy10aLake Fryxell10amicrobial mat10aOxygen10aPhotosynthetically Active Radiation1 aDillon, Megan, L.1 aHawes, Ian1 aJungblut, Anne, D.1 aMackey, Tyler, J.1 aEisen, Jonathan, A.1 aDoran, Peter, T.1 aSumner, Dawn, Y. uhttps://academic.oup.com/femsec/article/96/2/fiz207/569719602205nas a2200205 4500008004100000245012400041210006900165260001200234300001300246490000700259520150700266100002201773700001501795700002301810700002201833700002401855700002101879700002101900856007801921 2020 eng d00aEnvironmental control on the distribution of metabolic strategies of benthic microbial mats in Lake Fryxell, Antarctica0 aEnvironmental control on the distribution of metabolic strategie c04/2020 ae02310530 v153 a

Ecological theories posit that heterogeneity in environmental conditions greatly affects community structure and function. However, the degree to which ecological theory developed using plant- and animal-dominated systems applies to microbiomes is unclear. Investigating the metabolic strategies found in microbiomes are particularly informative for testing the universality of ecological theories because microorganisms have far wider metabolic capacity than plants and animals. We used metagenomic analyses to explore the relationships between the energy and physicochemical gradients in Lake Fryxell and the metabolic capacity of its benthic microbiome. Statistical analysis of the relative abundance of metabolic marker genes and gene family diversity shows that oxygenic photosynthesis, carbon fixation, and flavin-based electron bifurcation differentiate mats growing in different environmental conditions. The pattern of gene family diversity points to the likely importance of temporal environmental heterogeneity in addition to resource gradients. Overall, we found that the environmental heterogeneity of photosynthetically active radiation (PAR) and oxygen concentration ([O2]) in Lake Fryxell provide the framework by which metabolic diversity and composition of the community is structured, in accordance with its phylogenetic structure. The organization of the resulting microbial ecosystems are consistent with the maximum power principle and the species sorting model.

1 aDillon, Megan, L.1 aHawes, Ian1 aJungblut, Anne, D.1 aMackey, Tyler, J.1 aEisen, Jonathan, A.1 aDoran, Peter, T.1 aSumner, Dawn, Y. uhttps://journals.plos.org/plosone/article?id=10.1371/journal.pone.023105302611nas a2200253 4500008004100000245011600041210006900157260001200226520177500238653001202013653002502025653003202050653001402082653002402096100002102120700002202141700002802163700002102191700002302212700002102235700001502256700002302271856006302294 2019 eng d00aEnvironmental controls on bacteriohopanepolyol profiles of benthic microbial mats from Lake Fryxell, Antarctica0 aEnvironmental controls on bacteriohopanepolyol profiles of benth c07/20193 a

Bacteriohopanepolyols (BHPs) are pentacyclic triterpenoid lipids that contribute to the structural integrity and physiology of some bacteria. Because some BHPs originate from specific classes of bacteria, BHPs have potential as taxonomically and environmentally diagnostic biomarkers. For example, a stereoisomer of bacteriohopanetetrol (informally BHT II) has been associated with anaerobic ammonium oxidation (anammox) bacteria and suboxic to anoxic marine environments where anammox is active. As a result, the detection of BHT II in the sedimentary record and fluctuations in the relative abundance of BHT II may inform reconstructions of nitrogen cycling and ocean redox changes through the geological record. However, there are uncertainties concerning the sources of BHT II and whether or not BHT II is produced in abundance in non‐marine environments, both of which are pertinent to interpretations of BHT II signatures in sediments. To address these questions, we investigate the BHP composition of benthic microbial mats from Lake Fryxell, Antarctica. Lake Fryxell is a perennially ice‐covered lake with a sharp oxycline in a density‐stabilized water column. We describe the diversity and abundance of BHPs in benthic microbial mats across a transect from oxic to anoxic conditions. Generally, BHP abundances and diversity vary with the morphologies of microbial mats, which were previously shown to reflect local environmental conditions, such as irradiance and oxygen and sulfide concentrations. BHT II was identified in mats that exist within oxic to anoxic portions of the lake. However, anammox bacteria have yet to be identified in Lake Fryxell. We examine our results in the context of BHPs as biomarkers in modern and ancient environments.

10aanammox10abacteriohopanepolyol10abacteriohopanetetrol isomer10abiomarker10aMcMurdo Dry Valleys1 aMatys, Emily, D.1 aMackey, Tyler, J.1 aGrettenberger, Christen1 aMueller, Elliott1 aJungblut, Anne, D.1 aSumner, Dawn, Y.1 aHawes, Ian1 aSummons, Roger, E. uhttps://onlinelibrary.wiley.com/doi/full/10.1111/gbi.12353