02601nas a2200241 4500008004100000022001400041245005900055210005400114260001200168520187700180653001302057653001902070653001702089653001502106653003102121100001702152700002102169700002602190700002302216700003302239700001702272856007002289 2024 eng d a0030-129900aThe underground network: Facilitation in soil bacteria0 aunderground network Facilitation in soil bacteria c06/20243 a

Our understanding of the fundamental role that soil bacteria play in the structure and functioning of Earth's ecosystems is ever expanding, but insight into the nature of interactions within these bacterial communities remains rudimentary. Bacterial facilitation may enhance the establishment, growth, and succession of eukaryotic biota, elevating the complexity and diversity of the entire soil community and thereby modulating multiple ecosystem functions. Global climate change often alters soil bacterial community composition, which, in turn, impacts other dependent biota. However, the impact of climate change on facilitation within bacterial communities remains poorly understood even though it may have important cascading consequences for entire ecosystems. The wealth of metagenomic data currently being generated gives community ecologists the ability to investigate bacterial facilitation in the natural world and how it affects ecological systems responses to climate change. Here, we review current evidence demonstrating the importance of facilitation in promoting emergent properties such as community diversity, ecosystem functioning, and resilience to climate change in soil bacterial communities. We show that a synthesis is currently missing between the abundant data, newly developed models and a coherent ecological framework that addresses these emergent properties. We highlight that including phylogenetic information, the physicochemical environment, and species-specific ecologies can improve our ability to infer interactions in natural soil communities. Following these recommendations, studies on bacterial facilitation will be an important piece of the puzzle to understand the consequences of global change on ecological communities and a model to advance our understanding of facilitation in complex communities more generally.

10abacteria10aclimate change10afacilitation10aresilience10astress-gradient hypothesis1 aJorna, Jesse1 aAdams, Byron, J.1 aAanderud, Zachary, T.1 aFrandsen, Paul, B.1 aTakacs-Vesbach, Cristina, D.1 aKéfi, Sonia uhttps://nsojournals.onlinelibrary.wiley.com/doi/10.1111/oik.1029901983nas a2200133 4500008004100000245011300041210007100154260001200225490000700237520149300244100002101737700002201758856006901780 2019 eng d00aUnimodal productivity–diversity relationships among bacterial communities in a simple polar soil ecosystem0 aUnimodal productivity–diversity relationships among bacterial co c07/20190 v213 a

Unlike other macroecological principles, relationships between productivity and diversity have not been effectively tested for microbial communities. Here we describe an experiment in which the availability of resources to soil bacterial communities was manipulated in a model system, the McMurdo Dry Valleys of Antarctica. Mannitol additions were used to simulate a productivity gradient such that a response in bacterial biomass production, taxonomic diversity and functioning (e.g., enzyme activity) were induced. Resource amendment induced a positive linear response in microbial productivity (P < 0.001) but a unimodal (hump‐shaped) response in microbial diversity at multiple taxonomic scales (P = 0.035). Putative oligotrophic (e.g., phyla Nitrospirae and Cyanobacteria) and copiotrophic (e.g., phylum Proteobacteria) taxa were apparent through substantial community turnover along the resource gradient. Soil enzyme activity was inversely related to bacterial biomass but positively related to diversity, suggesting the latter may be a stronger control over enzyme‐mediated decomposition. The mechanisms behind this pattern are consistent with macroecological theory of a shift from environmental (e.g., stress tolerance) to biotic (e.g., competition) drivers with increasing resource availability. This evidence is among the first of its kind to document a significant unimodal productivity–diversity relationship for soil bacteria.

1 aGeyer, Kevin, M.1 aBarrett, John, E. uhttps://onlinelibrary.wiley.com/doi/full/10.1111/1462-2920.1463904687nas a2200181 4500008004100000022001400041245015900055210006900214260001200283300001600295490000700311520405500318100001204373700001804385700002904403700001804432856005504450 2016 eng d a0099-224000aUltrastructural and Single-Cell-Level Characterization Reveals Metabolic Versatility in a Microbial Eukaryote Community from an Ice-Covered Antarctic Lake0 aUltrastructural and SingleCellLevel Characterization Reveals Met c06/2016 a3659 - 36700 v823 a

The McMurdo Dry Valleys (MCM) of southern Victoria Land, Antarctica, harbor numerous ice-covered bodies of water that provide year-round liquid water oases for isolated food webs dominated by the microbial loop. Single-cell microbial eukaryotes (protists) occupy major trophic positions within this truncated food web, ranging from primary producers (e.g., chlorophytes, haptophytes, and cryptophytes) to tertiary predators (e.g., ciliates, dinoflagellates, and choanoflagellates). To advance the understanding of MCM protist ecology and the roles of MCM protists in nutrient and energy cycling, we investigated potential metabolic strategies and microbial interactions of key MCM protists isolated from a well-described lake (Lake Bonney). Fluorescence-activated cell sorting (FACS) of enrichment cultures, combined with single amplified genome/amplicon sequencing and fluorescence microscopy, revealed that MCM protists possess diverse potential metabolic capabilities and interactions. Two metabolically distinct bacterial clades (Flavobacteria and Methylobacteriaceae) were independently associated with two key MCM lake microalgae (Isochrysis and Chlamydomonas, respectively). We also report on the discovery of two heterotrophic nanoflagellates belonging to the Stramenopila supergroup, one of which lives as a parasite ofChlamydomonas, a dominate primary producer in the shallow, nutrient-poor layers of the lake.

IMPORTANCE Single-cell eukaryotes called protists play critical roles in the cycling of organic matter in aquatic environments. In the ice-covered lakes of Antarctica, protists play key roles in the aquatic food web, providing the majority of organic carbon to the rest of the food web (photosynthetic protists) and acting as the major consumers at the top of the food web (predatory protists). In this study, we utilized a combination of techniques (microscopy, cell sorting, and genomic analysis) to describe the trophic abilities of Antarctic lake protists and their potential interactions with other microbes. Our work reveals that Antarctic lake protists rely on metabolic versatility for their energy and nutrient requirements in this unique and isolated environment.

1 aLi, Wei1 aPodar, Mircea1 aMorgan-Kiss, Rachael, M.1 aKelly, R., M. uhttp://aem.asm.org/lookup/doi/10.1128/AEM.00478-1600496nas a2200133 4500008004100000022001400041245011800055210006900173260001200242300001400254490000700268100002100275856006600296 2016 eng d a0006-356800aUnraveling ecosystem responses to climate change on the Antarctic continent through Long-Term Ecological Research0 aUnraveling ecosystem responses to climate change on the Antarcti c10/2016 a799 - 8000 v661 aPriscu, John, C. uhttps://academic.oup.com/bioscience/article/66/10/799/223616600488nas a2200145 4500008004100000245007700041210006900118260001200187300001200199490000700211100002100218700001700239700001700256856006900273 2013 eng d00aUnderstanding Terrestrial Ecosystem Response to Antarctic Climate Change0 aUnderstanding Terrestrial Ecosystem Response to Antarctic Climat c01/2013 a33 - 330 v941 aLevy, Joseph, S.1 aLyons, Berry1 aAdams, Byron uhttp://onlinelibrary.wiley.com/doi/10.1002/2013EO030009/abstract00578nas a2200133 4500008004100000245011000041210006900151100001800220700002000238700001700258700002200275700002300297856012400320 2007 eng d00aUnique similarity of faunal communities across aquatic terrestrial interfaces in a polar desert ecosystem0 aUnique similarity of faunal communities across aquatic terrestri1 aAyres, Edward1 aWall, Diana, H.1 aAdams, Byron1 aBarrett, John, E.1 aVirginia, Ross, A. uhttps://mcm.lternet.edu/content/unique-similarity-faunal-communities-across-aquatic-terrestrial-interfaces-polar-desert00662nas a2200157 4500008004100000245014000041210006900181260001700250300001200267100002000279700002600299700001400325700002200339700002000361856012300381 2004 eng d00aUnderstanding the functions of biodiversity in soils and sediments will enhance global ecosystem sustainability and societal well-being0 aUnderstanding the functions of biodiversity in soils and sedimen bIsland Press a249-2541 aWall, Diana, H.1 aBardgett, Richard, D.1 aCovich, A1 aSnelgrove, P.V.R.1 aWall, Diana, H. uhttps://mcm.lternet.edu/content/understanding-functions-biodiversity-soils-and-sediments-will-enhance-global-ecosystem00562nas a2200169 4500008004100000245007600041210006900117260001200186300001200198490000700210653001100217653002400228100002000252700002000272700002300292856007700315 2000 eng d00aThe use of anhydrobiosis by soil nematodes in the Antarctic Dry Valleys0 ause of anhydrobiosis by soil nematodes in the Antarctic Dry Vall c08/2000 a460-4670 v1410aBiggie10asurvival strategies1 aTreonis, Amy, M1 aWall, Diana, H.1 aVirginia, Ross, A. uhttp://onlinelibrary.wiley.com/doi/10.1046/j.1365-2435.2000.00442.x/full00602nas a2200157 4500008004100000245010300041210006900144300001200213490000800225100001700233700002400250700001500274700001500289700001500304856012500319 2000 eng d00aUV radiation and potential biological effects beneath the perennial ice cover of an antarctic lake0 aUV radiation and potential biological effects beneath the perenn a155-1650 v4271 aKepner, R.L.1 aWharton, Robert, A.1 aCollier, R1 aCockell, C1 aJeffrey, W uhttps://mcm.lternet.edu/content/uv-radiation-and-potential-biological-effects-beneath-perennial-ice-cover-antarctic-lake