CAREER: Investigating the relationship between giant sulfur bacteria and microfossil-bearing phosphorites.

Phosphatic mineral deposits are well known for their exquisite preservation of soft tissue ? including fossilized cells. Large septate filaments interpreted as the oldest eukaryotes are preserved in 1.6 billion-year-old phosphorites from the Vindhyan Basin in Central India, and the oldest putative metazoans are preserved as phosphatized symmetrical cell clusters in the 600-milion-year-old Doushantuo Formation in southern China. Interestingly, large vacuolate sulfur-oxidizing bacteria are thought to mediate modern phosphogenesis, and commonly possess morphologies that closely resemble both the Vindhyan filaments and the Doushantuo globular microfossils. Could the Vindhyan or Doushantuo microfossils represent vacuolated sulfur bacteria, rather than eukaryotes? Could these microfossils provide evidence of the ancient mediation of phosphorites by sulfur bacteria? In the case of the Doushantuo microbiota, some microfossils are clearly eukaryotic, and likely metazoan in origin, while others cannot be easily interpreted as animals ? but are the bacterial and animal interpretations mutually exclusive? Other ancient and recent phosphorite deposits also possess structures that might well represent fossilized sulfur bacteria, but criteria for their recognition are not yet established. The PI?s research group will: 1) investigate newly-discovered modern sulfur bacteria that are partially entombed in phosphatic minerals; 2) perform phosphatization experiments with modern sulfur bacteria to investigate the taphonomy of phosphatized bacteria; 3) compare modern phosphatized sulfur bacteria with ancient microfossils from Proterozoic and Phanerozoic phosphorites; and 4) use observations of modern sulfur bacteria to develop new criteria for differentiating fossils of giant sulfur bacteria from those of microbial eukaryotes - including embryonic metazoans.The research component of this proposal is tied closely to an education and outreach plan that develops new undergraduate and graduate courses as the foundation of a geobiology curriculum at the University of Minnesota. A graduate student who will work on the projects describer herein will also be supported and mentored throughout the grant period. The education and outreach plan also increases research opportunities for military veterans through the establishment of a summer research experience for student veterans, as well as providing outreach to high school students and underrepresented minorities through participation in the NSF-funded North Star STEM Alliance, the UMN Exploring Careers in Engineering and Physical Science Program, and the annual meeting of the Society for the Advancement of Chicanos and Native Americans in Sciences.