Experimental evidence that clay inhibits bacterial decomposers: Implications for preservation of organic fossils

Abstract

Exceptionally preserved organic fossils are commonly associated with clay-rich horizons or directly with clay minerals. It has been posited that interactions between clay minerals and organic tissues inhibit enzymatic reactions or protect carcasses in such a way that decay is inhibited. However, interactions between clay minerals and the biological agents of decay, especially bacteria, may be at least as important to preservation potential. Here we show that clays of particle size < 2 μm in suspensions exceeding 10 mg/ml in concentration inhibit the growth of Pseudoalteromonas luteoviolacea, a marine heterotrophic bacterium involved in the decay of marine animals. Such clay-microbe interactions can contribute to exceptional preservation and specific examples may play a role in shaping the distribution of Konservat-Lagerstätten through time.

Soft‐Bodied Fossils Are Not Simply Rotten Carcasses – Toward a Holistic Understanding of Exceptional Fossil Preservation

“…[94] Clay minerals have long been implicated in having a role in the processes that suppressed the breakdown of tissues in Burgess Shale type localities [97] and experimental evidence suggests that clay mineralogy has a profound impact on tissue decay. [13] …”

“…[28,29] Sediment mineralogy, particularly of clays, may also play a role in tissue stabilization. [13,26,30,31] Early cementation of the surrounding sediment promotes exceptional preservation by eliminating pore space and may create a cast of soft tissue anatomy. Early precipitation of carbonate at the sediment surface [32] or the presence of microbial mats [33] may have promoted preservation in Burgess Shale-type deposits, for example, and microbial mats are a common feature of deposits preserving muscle tissue.…”

“…The pathways travelled by exceptional fossils prior to discovery are complex, and understanding preservation is an active field of research based on investigations of fossil specimens and taphonomic experiments on extant organisms. [13] Following discovery, further biological information can be lost or modified during excavation and preparation of a fossil; the method used to remove surrounding matrix may create artifacts and should be taken into account when analyzing important features. [14] A key hurdle to interpreting fossils correctly is determining which characters are missing because they were originally absent in vivo and which characters have failed to survive all of the processes involved in fossilization.…”

An Akouemma hemisphaeria Organic Macrofossils Colony Hosting Biodiversity Assemblage on the Seafloor of Okondja Basin (Gabon) dated at 2.2 Ga

“…Support for the role of authigenic clay precipitation in organism preservation comes both from experiments [51][52][53][54] and from field studies of modern environments [21,[55][56][57]. These show that microbial mediation of clay minerals is common for the preservation of microorganisms and soft-body macroorganisms.…”

Russia–UK Collaboration in Paleontology: Past, Present, and Future

“…In addition marine waters were characterized by a higher concentration of alkalis, which promoted precipitation of carbonate cements, reducing diffusion and slowing degradation (Gaines et al 2012a). Recent studies suggest that the composition of clay minerals in the early oceans may also have served to inhibit bacterial activity (Wilson and Butterfield 2014;McMahon et al 2016;Naimark et al 2016 (Ivantsov 1999;Ivantsov et al 2005). The Middle Cambrian Zelenotsvetnaya Formation on the Ukukit River on the Siberian Platform has yielded rhabdopleurids with preserved zooids (Sennikov 2016).…”