The complex role of microbial metabolic activity in fossilization

Abstract

Bacteria play an important role in the fossilization of soft tissues; their metabolic activities drive the destruction of the tissues and also strongly influence mineralization. Some environmental conditions, such as anoxia, cold temperatures, and high salinity, are considered widely to promote fossilization by modulating bacterial activity. However, bacteria are extremely diverse, and have developed metabolic adaptations to a wide range of stressful conditions. Therefore, the influence of the environment on bacterial activity, and of their metabolic activity on fossilization, is complex. A number of examples illustrate that simple, general assumptions about the role of bacteria in soft tissue fossilization cannot explain all preservational pathways: (i) experimental results show that soft tissues of cnidaria decay less in oxic than anoxic conditions, and in the fossil record are found more commonly in fossil sites deposited under oxic conditions rather than anoxic environments; (ii) siderite concretions, which often entomb soft tissue fossils, precipitate due to a complex mixture of sulfate‐ and iron reduction by some bacterial species, running counter to original theories that iron reduction is the primary driver of siderite concretion growth; (iii) arthropod brains, now widely accepted to be preserved in many Cambrian fossil sites, are one of the first structures to decay in taphonomic experiments, indicating that their fossilization processes are complex and influenced by bacterial activity. In order to expand our understanding of the complex process of bacterially driven soft tissue fossilization, more research needs to be done, on fossils themselves and in taphonomic experiments, to determine how the complex variation in microbial metabolic activity influences decay and mineralization.

Time-dependent microbial shifts during crayfish decomposition in freshwater and sediment under different environmental conditions

“…Mineral precipitation is often an important step in the preservation of soft bodied organisms 82 . In all experiments, the precipitation of calcite crystals was detected at the inner side of the crayfish carapaces, though to different extents.…”

Biofilms as agents of Ediacara-style fossilization

“…Ediacara-style fossilization is not only distinctive of Ediacara Biota macroorganisms but also of microbial mats and biofilms or “matgrounds” that carpeted the Ediacaran seafloor and are similarly recorded as a variety of moldic textures, known as textured organic surfaces (TOS), in Ediacara fossil assemblages 28 . The characteristic spatial and ecological association of Ediacara macrofossils and microbial mat and biofilm textures across a wide range of Ediacara-style fossil deposits 29 – 31 has led to the suggestion that matgrounds, in addition to fostering the habitability of the Ediacara seafloor 32 – 39 and shaping the ecology of Ediacara communities 28 , 40 – 42 , may have also played a critical role in their fossilization 5 , 43 – 49 . Previous work has highlighted that bacteria may readily undergo silicification via Bitter Springs-style fossilization (i.e., permineralization of filamentous and coccoid microorganisms in cherts 50 – 53 ).…”

New Efforts toward Aminothiazolylquinolones with Multitargeting Antibacterial Potential

“…All the above damage to membrane, DNA, DNA gyrase, and antioxidant defense system would bring a devastating disaster for bacteria and induce metabolic inactivation. Metabolically active cells can reduce the redox indicator to pink fluorescent resofurin from blue Alamar Blue in the presence of functional enzymes. − Hence, the fluorescent spectrum was applied to assess the effects of ATQ 17a on bacterial metabolic activity. The results in Figure S14 revealed that the metabolic activity of P. A. evidently declined with enhancing content of compound 17a .…”