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. Such subaerial mats could have supported a substantial aerobic biosphere, including nitrification and methanotrophy, and promoted methane emissions and oxidative weathering under ostensibly anoxic Precambrian atmospheres. High C-turnover rates and cell abundances would have made these mats prime locations for early microbial diversification. Growth of landmass in the late Archean to early Proterozoic Eons could have reorganized biogeochemical cycles between land and sea impacting atmospheric chemistry and climate.

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

Reactive Fe(III) minerals can influence methane (CH4 ) emissions by inhibiting microbial methanogenesis or by stimulating anaerobic CH4 oxidation. The balance between Fe(III) reduction, methanogenesis, and CH4 oxidation in ferruginous Archean and Paleoproterozoic oceans would have controlled CH4 fluxes to the atmosphere, thereby regulating the capacity for CH4 to warm the early Earth under the Faint Young Sun. We studied CH4 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). Iron reduction, methanogenesis, CH4 oxidation, and microbial taxonomy were monitored in treatments amended with ferrihydrite or goethite. After three dilutions, Fe(III) reduction persisted only in bottles with ferrihydrite. Enhanced CH4 production was observed in the presence of goethite, highlighting the potential for reactive Fe(III) oxides to inhibit methanogenesis. Supplementing the media with hydrogen, nickel and selenium did not stimulate methanogenesis. There was limited evidence for Fe(III)-dependent CH4 oxidation, although some incubations displayed CH4 -stimulated Fe(III) reduction. 16S rRNA profiles continuously changed over the course of enrichment, with ultimate dominance of unclassified members of the order Desulfuromonadales in all treatments. Microbial diversity decreased markedly over the course of incubation, with subtle differences between ferrihydrite and goethite amendments. These results suggest that Fe(III) oxide mineralogy and availability of electron donors could have led to spatial separation of Fe(III)-reducing and methanogenic microbial communities in ferruginous marine sediments, potentially explaining the persistence of CH4 as a greenhouse gas throughout the first half of Earth history.

Degradation of oil by fungi isolated from Gulf of Mexico beaches.

Fungi of the Ascomycota phylum were isolated from oil-soaked sand patties collected from beaches following the Deepwater Horizon oil spill. To examine their ability to degrade oil, fungal isolates were grown on oiled quartz at 20°C, 30°C and 40°C. Consistent trends in oil degradation were not related to fungal species or temperature and all isolates degraded variable quantities of oil (32-65%). Fungal isolates preferentially degraded short (

Same, same but different: symbiotic bacterial associations in GBR sponges.

Symbioses in marine sponges involve diverse consortia of microorganisms that contribute to the health and ecology of their hosts. The microbial communities of 13 taxonomically diverse Great Barrier Reef (GBR) sponge species were assessed by DGGE and 16S rRNA gene sequencing to determine intra and inter species variation in bacterial symbiont composition. Microbial profiling revealed communities that were largely conserved within different individuals of each species with intra species similarity ranging from 65-100%. 16S rRNA gene sequencing revealed that the communities were dominated by Proteobacteria, Chloroflexi, Acidobacteria, Actinobacteria, Nitrospira, and Cyanobacteria. Sponge-associated microbes were also highly host-specific with no operational taxonomic units (OTUs) common to all species and the most ubiquitous OTU found in only 5 of the 13 sponge species. In total, 91% of the OTUs were restricted to a single sponge species. However, GBR sponge microbes were more closely related to other sponge-derived bacteria than they were to environmental communities with sequences falling within 50 of the 173 previously defined sponge-(or sponge-coral) specific sequence clusters (SC). These SC spanned the Acidobacteria, Actinobacteria, Proteobacteria, Bacteroidetes, Chloroflexi, Cyanobacteria, Gemmatimonadetes, Nitrospira, and the Planctomycetes-Verrucomicrobia-Chlamydiae superphylum. The number of sequences assigned to these sponge-specific clusters across all species ranged from 0 to 92%. No relationship between host phylogeny and symbiont communities were observed across the different sponge orders, although the highest level of similarity was detected in two closely related Xestospongia species. This study identifies the core microbial inhabitants in a range of GBR sponges thereby providing the basis for future studies on sponge symbiotic function and research aiming to predict how sponge holobionts will respond to environmental perturbation.