title: Self-preservation strategies during bacterial biomineralization with reference to hydrozincite and implications for fossilization of bacteria.
abstract: The induction of mineralization by microbes has been widely demonstrated but whether induced biomineralization leads to distinct morphologies indicative of microbial involvement remains an open question. For calcium carbonate, evidence suggests that microbial induction enhances sphere formation, but the mechanisms involved and the role of microbial surfaces are unknown. Here, we describe hydrozincite biominerals from Sardinia, Italy, which apparently start life as smooth globules on cyanobacterial filaments, and evolve to spheroidal aggregates consisting of nanoplates. Complementary laboratory experiments suggest that organic compounds are critical to produce this morphology, possibly by inducing aggregation of nanoscopic crystals or nucleation within organic globules produced by metabolizing cells. These observations suggest that production of extracellular polymeric substances by microbes may constitute an effective mechanism to enhance formation of porous spheroids that minimize cell entombment while also maintaining metabolite exchange. However, the high porosity arising from aggregation-based crystal growth probably facilitates rapid oxidation of entombed cells, reducing their potential to be fossilized.
authors.affiliation: School of GeoSciences, University of Edinburgh, West Mains Road, Edinburgh EH9 3JW, UK bryne.ngwenya@ed.ac.uk.
authors.forename: Bryne T
authors.initials: BT
authors.lastname: Ngwenya
authors.affiliation: School of GeoSciences, University of Edinburgh, West Mains Road, Edinburgh EH9 3JW, UK.
authors.forename: Marisa
authors.initials: M
authors.lastname: Magennis
authors.affiliation: Department of Chemical and Geological Sciences, University of Cagliari, Via Trentino 51, 09127 Cagliari, Italy.
authors.forename: Francesca
authors.initials: F
authors.lastname: Podda
authors.affiliation: School of Chemistry, University of Edinburgh, West Mains Road, Edinburgh EH9 3JW, UK.
authors.forename: Andrei
authors.initials: A
authors.lastname: Gromov
mesh_terms: D018407:Bacterial Physiological Phenomena; D000458:Cyanobacteria / Q000502:physiology*; D005580:Fossils; D007558:Italy
keywords: biomineralization; fossilization; nucleation