Transport-Induced Spatial Patterns of Sulfur Isotopes (δS) as Biosignatures.

Cave minerals deposited in the presence of microbes may host geochemical biosignatures that can be utilized to detect subsurface life on Earth, Mars, or other habitable worlds. The sulfur isotopic composition of gypsum (CaSO·2HO) formed in the presence of sulfur-oxidizing microbes in the Frasassi cave system, Italy, was evaluated as a biosignature. Sulfur isotopic compositions (δS) of gypsum sampled from cave rooms with sulfidic air varied from -11 to -24‰, with minor deposits of elemental sulfur having δS values between -17 and -19‰.

Susceptibility of Goethite to Fe-Catalyzed Recrystallization over Time.

Recent work has shown that iron oxides, such as goethite and hematite, may recrystallize in the presence of aqueous Fe under anoxic conditions. This process, referred to as Fe-catalyzed recrystallization, can influence water quality by causing the incorporation/release of environmental contaminants and biological nutrients. Accounting for the effects of Fe-catalyzed recrystallization on water quality requires knowing the time scale over which recrystallization occurs.

Metabolic diversity and ecological niches of Achromatium populations revealed with single-cell genomic sequencing.

Large, sulfur-cycling, calcite-precipitating bacteria in the genus Achromatium represent a significant proportion of bacterial communities near sediment-water interfaces at sites throughout the world. Our understanding of their potentially crucial roles in calcium, carbon, sulfur, nitrogen, and iron cycling is limited because they have not been cultured or sequenced using environmental genomics approaches to date. We utilized single-cell genomic sequencing to obtain one incomplete and two nearly complete draft genomes for Achromatium collected at Warm Mineral Springs (WMS), FL.

A food web analysis of the juvenile blue crab, Callinectes sapidus, using stable isotopes in whole animals and individual amino acids.

The stable isotope compositions (C and N) of plants and animals of a marsh dominated by Spartina alterniflora in the Delaware Estuary were determined. The study focused on the juvenile stage of the Atlantic blue crab, Callinectes sapidus, and the importance of marsh-derived diets in supporting growth during this stage. Laboratory growth experiments and field data indicated that early juvenile blue crabs living in the Delaware Bay habitat fed primarily on zooplankton, while marsh-dwelling crabs, which were enriched in C relative to bay juveniles, utilized marsh-derived carbon for growth.