Fossils from Doushantuo Formation

Posted by Judy Arbique Dec 27, 2006

Fossils found in the Doushantuo Formation in southern China may be fossils of a giant bacteria known as Thiomargarita, rather than eggs and embryos as originally believed.

The fossils which first made their appearance on the cover of the journal Nature in 1998 showed evidence of reductive cell division and were identified as embryos; however, in 2005, Samantha Joye and Karen Kalanetra, marine biologists at the University of Georgia, found that Thiomargarita, a large vacuolate sulfur-oxidizing bacteria can multiply by reductive cell division, a process rarely seen in bacteria.

In the same year, Heide Schulz, from the University of Hannover in Germany, who first discovered Thiomargarita, showed that the bacterium promotes deposition of a mineral known as phosphorite. The Doushantuo Formation is rich in the mineral phosphorite. Jake Bailey, a graduate student in earth sciences at the University of Southern California proposed in the December 20, 2006 edition of the journal Nature that the fossils may be Thiomargarita, the world’s largest known living bacterium. Bailey found similarities in the sizes and morphologies of Thiomargarita and the fossils believed to be metazoan eggs and embryos from the Doushantuo Formation. Bailey also proposed that Thiomargarita is responsible for production of the phosphorite deposits in the Doushantuo Formation.

Sources:

University of Southern California

Bailey JV, SB Joye, KM Kalanetra, BE Flood and FA Corsetti. Evidence of giant sulphur bacteria in Neoproterozoic phosphorites. Nature. 20 December 2006.