SignificanceCyanobacteria were responsible for the origin of oxygenic photosynthesis, and have since come to colonize almost every environment on Earth. Here we show that their ecological range is not limited by the presence of sunlight, but also extends down to the deep terrestrial biosphere. We report the presence of microbial communities dominated by cyanobacteria in the continental subsurface using microscopy, metagenomics, and antibody microarrays. These cyanobacteria were related to surface rock-dwelling lineages known for their high tolerance to environmental and nutritional stress. We discuss how these adaptations allow cyanobacteria to thrive in the dark underground, a lifestyle that might trace back to their nonphotosynthetic ancestors.

Ooids are one of the common constituents of ancient carbonate rocks, yet the role that microbial communities may or may not play in their formation remains unresolved. To search for evidence of microbial activity in modern and Holocene ooids, samples collected from intertidal waters, beaches and outcrops in the Bahamas and in Shark Bay in Western Australia were examined for their contents of lipid biomarkers. Modern samples from Cat and Andros islands in the Bahamas and from Carbla Beach in Hamelin Pool, Western Australia, showed abundant and notably similar distributions of hydrocarbons, fatty acids (FAs) and alcohols. A large fraction of these lipids were bound into the carbonate matrix and only released on acid dissolution, which suggests that these lipids were being incorporated continuously during ooid growth. The distributions of hydrocarbons, and their disparate carbon isotopic signatures, were consistent with mixed input from cyanobacteria together with small and variable amounts of vascular plant leaf wax [C27 -C35 ; δ(13) C -25 to -32‰Vienna Pee Dee Belemnite (VPDB)]. The FAs comprised a complex mixture of C12 -C18 normal and branched short-chain compounds with the predominant straight-chain components attributable to bacteria and/or cyanobacteria. Branched FA, especially 10-MeC16 and 10-MeC17 , together with the prevalence of elemental sulfur in the extracts, indicate an origin from sulfate-reducing bacteria. The iso- and anteiso-FA were quite variable in their (13) C contents suggesting that they come from organisms with diverse physiologies. Hydrogen isotopic compositions provide further insight into this issue. FAs in each sample show disparate δD values consistent with inputs from autotrophs and heterotrophs. The most enigmatic lipid assemblage is an homologous series of long-chain (C24 -C32 ) FA with pronounced even carbon number preference. Typically, such long-chain FA are thought to come from land plant leaf wax, but in this case, their (13) C-enriched isotopic signatures compared to co-occurring n-alkanes (e.g., Hamelin Pool TLE FA C24 -C32 ; δ(13) C -20 to -24.2‰ VPDB; TLE n-alkanes δ(13) C -24.1 to -26.2 -‰VPDB) indicate a microbial origin, possibly sulfate-reducing bacteria. Lastly, we identified homohopanoic acid and bishomohopanol as the primary degradation products of bacterial hopanoids. The distributions of lipids isolated from Holocene oolites from the Rice Bay Formation of Cat Island, Bahamas were very similar to the beach ooids described above and, in total, these modern and fossil biomarker data lead us to hypothesize that ooids are colonized by a defined microbial community and that these microbes possibly mediate calcification.

Trade tensions, resource nationalism, and various other factors are increasing concerns regarding the supply reliability of nonfuel mineral commodities. This is especially the case for commodities required for new and emerging technologies ranging from electric vehicles to wind turbines. In this analysis, we use a conventional risk-modeling framework to develop and apply a new methodology for assessing the supply risk to the U.S. manufacturing sector. Specifically, supply risk is defined as the confluence of three factors: the likelihood of a foreign supply disruption, the dependency of U.S. manufacturers on foreign supplies, and the ability of U.S. manufacturers to withstand a supply disruption. The methodology is applied to 52 commodities for the decade spanning 2007-2016. The results indicate that a subset of 23 commodities, including cobalt, niobium, rare earth elements, and tungsten, pose the greatest supply risk. This supply risk is dynamic, shifting with changes in global market conditions.

Little Salt Spring (Sarasota County, FL, USA) is a sinkhole with groundwater vents at ~77 m depth. The entire water column experiences sulfidic (~50 μM) conditions seasonally, resulting in a system poised between oxic and sulfidic conditions. Red pinnacle mats occupy the sediment-water interface in the sunlit upper basin of the sinkhole, Furthermore, our observations of the production of 2-methyl hopanoids by Cyanobacteria under conditions of low oxygen and low light are consistent with the recovery of these structures from ancient black shales as well as their paucity in modern marine environments.

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Archaeal ANaerobic MEthanotrophs (ANME) facilitate the anaerobic oxidation of methane (AOM), a process that is believed to proceed via the reversal of the methanogenesis pathway. Carbon isotopic composition studies indicate that ANME are metabolically diverse and able to assimilate metabolites including methane, methanol, acetate, and dissolved inorganic carbon (DIC). Our data support the interpretation that ANME in marine sediments at methane seeps assimilate both methane and DIC, and the carbon isotopic compositions of the tetrapyrrole coenzyme F430 and the membrane lipids archaeol and hydroxy‐archaeol reflect their relative proportions of carbon from these substrates. Methane is assimilated via the methyl group of CH3‐tetrahydromethanopterin (H4MPT) and DIC from carboxylation reactions that incorporate free intracellular DIC. F430 was enriched in 13C (mean δ13C = −27‰ for Hydrate Ridge and −80‰ for the Santa Monica Basin) compared to the archaeal lipids (mean δ13C = −97‰ for Hydrate Ridge and −122‰ for the Santa Monica Basin). We propose that depending on the side of the tricarboxylic acid (TCA) cycle used to synthesize F430, its carbon was derived from 76% DIC and 24% methane via the reductive side or 57% DIC and 43% methane via the oxidative side. ANME lipids are predicted to contain 42% DIC and 58% methane, reflecting the amount of each assimilated into acetyl‐CoA. With isotope models that include variable fractionation during biosynthesis for different carbon substrates, we show the estimated amounts of DIC and methane can result in carbon isotopic compositions of − 73‰ to − 77‰ for F430 and − 105‰ for archaeal lipids, values close to those for Santa Monica Basin. The F430 δ13C value for Hydrate Ridge was 13C‐enriched compared with the modeled value, suggesting there is divergence from the predicted two carbon source models.

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