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Sulfur organomineralization

Elemental sulfur (S(0)) is an important intermediate in the biogeochemical cycle of this element. Although it is thermodynamically stable under a very limited range of Eh-pH conditions, S(0) is prevalent in a number of low-temperature environments. We are studying the role of organics in the formation and stabilization of elemental sulfur S(0), a process we called S(0) organomineralization. We found that the oxidation of sulfide in the presence of organics leads to the formation of S(0) minerals with unexpected morphologies and crystal structures. We are now working on deciphering the molecular mechanisms of this phenomenon, investigating evidence of it in different sulfidic natural environments, and elucidation whether some bacteria could be using S(0) organomineralization to stabilize extracellular stores of sulfur as an energy source.

Lab members involved: Brandi Cron Kamermans, Chrissie Nims

Figure: SEM image of organomineralized S(0)

Related publications: 

Formation and stabilization of elemental sulfur through organomineralization, Geochimica and Cosmochimica Acta (2019)

Self-assembly of biomorphic carbon/sulfur microstructures in sulfidic environments, Nature Communications (2016)

Kamermans et al., Elemental sulfur formation processes in a subsurface environment (Frasassi, Italy) (In Prep.)

Kamermans et al., Formation of extracellular S(0) by Sulfuricurvum kujiense through organomineralization (In Prep.)

Collaborators:

Alexis Templeton (University of Colorado at Boulder), Jennifer Macalady (Penn State University)

False Biosignatures

Interactions between sulfide and organics can produce organic-sulfur "biomorphs", which are microstructures with morphologies and sizes reminiscent of microorganisms and composed of organic carbon and sulfur. We are studying the possibility for such biomorphs to have formed in Precambrian sulfidic environments. We are also investigating the preservation potential of such "false biosignatures" in the rock record by performing experimental fossilization experiments (experimental silicification and diagenesis). Eventually, this work will help test the biogenicity of putative microbial fossils in the Precambian geological record.

Lab members involved: Chrissie Nims, Julia Lafond

Figure: STEM images (left) and XEDS maps (right) of organic-sulfur spherical biomorphs at different stages of silicification

Related publications: 

Nims et al., Experimental silicification of carbon-sulfur biomorphs (In Prep.)

The biological mechanisms at the origin of whiting events

The origin of marine carbonate muds (micrites) has been a topic of considerable uncertainty and research for decades. One source of mud, the apparently spontaneous precipitation of very fine suspended calcium carbonate particles, called a whiting, has been observed to occur and persist for many days in marine environments, most notably in the Bahamas. We are investigating the biological mechanisms at the origin of seasonal whiting events in the water column of meromictic Fayetteville Green Lake (NY). These mechanisms involve calcium carbonate nucleation at the surface of cyanobacterial cells (Synnechococcus), as well as on extracellular polymers produced by diatoms.

Lab members involved: Chloe Stanton

Figure: SEM image of calcite crystals closely associated with extracellular fibrils produced by diatoms

Related publications: 

Stanton et al., Field investigation of bio-induced calcium-carbonate precipitation mechanisms at the origin of whiting events (In Prep.)

Collaborators:

Lee Kump (Penn State University)

Phosphate recyling using biomineralizing bacteria

Modern agricultures rely heavily on the use of phosphate fertilizers, currently extracted from mined phosphatic rocks (phosphorites). However, recent projections have suggested that these phosphate reserves may be entirely depleted within the next 50 years. The recycling of phosphate from human waste (e.g. urine) would not only provide us with necessary nutrient for fertilizer production, but it would also decrease the excess amount of phosphate being released into waterways causing eutrophication. We are working on finding new processes to recycle phosphate from human waste using the natural capabilities of phosphate-biomineralizing bacteria.

Lab members involved: Claire Webster

In-vivo Raman characterization of sulfur compounds in biological samples

Raman spectromicroscopy is frequently applied to environmental samples for the detection of S(0), as a practical non-destructive micron-scale method for use on wet material and living cells. Recent technical advances enable the acquisition of ultra-low frequency (ULF) Raman measurements in the 10-100 cm-1 range using a single-stage spectrometer. We use ULF Raman spectroscopy as a powerful method for the micron-scale determination of S(0) structure in natural and laboratory systems, with a promising potential to shine new light on environmental microbial and chemical sulfur cycling mechanisms. 

Lab members involved: Chrissie Nims

Figure: Raman spectra of reference standards of solid cyclooctasulfur allotropes: α-S8 (yellow), β-S8 (blue), and γ-S8 (green)

Related publications: 

Nims et al., Low frequency Raman Spectroscopy for micron-scale and in-vivo characterization of elemental sulfur in microbial samples, Scientific Reports (2019)

Collaborators:

Maxwell Wetherington (Penn State University)

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