Phylogenetic and structural diversity of aromatically dense pili from environmental metagenomes.

Electroactive type IV pili, or e-pili, are used by some microbial species for extracellular electron transfer. Recent studies suggest that e-pili may be more phylogenetically and structurally diverse than previously assumed. Here, we used updated aromatic density thresholds (≥9.

Mesophilic microorganisms build terrestrial mats analogous to Precambrian microbial jungles.

Development of Archean paleosols and patterns of Precambrian rock weathering suggest colonization of continents by subaerial microbial mats long before evolution of land plants in the Phanerozoic Eon. Modern analogues for such mats, however, have not been reported, and possible biogeochemical roles of these mats in the past remain largely conceptual. We show that photosynthetic, subaerial microbial mats from Indonesia grow on mafic bedrocks at ambient temperatures and form distinct layers with features similar to Precambrian mats and paleosols.

Rates and pathways of CH oxidation in ferruginous Lake Matano, Indonesia.

This study evaluates rates and pathways of methane (CH ) oxidation and uptake using C-based tracer experiments throughout the oxic and anoxic waters of ferruginous Lake Matano. Methane oxidation rates in Lake Matano are moderate (0.36 nmol L  day to 117 μmol L  day ) compared to other lakes, but are sufficiently high to preclude strong CH fluxes to the atmosphere.

Decrypting the sulfur cycle in oceanic oxygen minimum zones.

Here we present ecophysiological studies of the anaerobic sulfide oxidizers considered critical to cryptic sulfur cycling in oceanic oxygen minimum zones (OMZs). We find that HS oxidation rates by microorganisms in the Chilean OMZ offshore from Dichato are sufficiently rapid (18 nM h), even at HS concentrations well below 100 nM, to oxidize all sulfide produced during sulfate reduction in OMZs. Even at 100 nM, HS is well below published half-saturation concentrations and we conclude that the sulfide-oxidizing bacteria in OMZs (likely the SUP05/ARTIC96BD lineage of the gammaproteobacteria) have high-affinity (>10 g wet cells h) sulfur uptake systems.

Shifting microbial communities sustain multiyear iron reduction and methanogenesis in ferruginous sediment incubations.

Reactive Fe(III) minerals can influence methane (CH ) emissions by inhibiting microbial methanogenesis or by stimulating anaerobic CH oxidation. The balance between Fe(III) reduction, methanogenesis, and CH oxidation in ferruginous Archean and Paleoproterozoic oceans would have controlled CH fluxes to the atmosphere, thereby regulating the capacity for CH to warm the early Earth under the Faint Young Sun. We studied CH and Fe cycling in anoxic incubations of ferruginous sediment from the ancient ocean analogue Lake Matano, Indonesia, over three successive transfers (500 days in total).