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1. Microbial life in the nascent Chicxulub crater

   https://doi.org/10.1130/G46799.1  

   Schaefer, Bettina; Grice, Kliti; Coolen, Marco J.L.; Summons, Roger E.; Cui, Xingqian; Bauersachs, Thorsten; Schwark, Lorenz; Böttcher, Michael E.; Bralower, Timothy J.; Lyons, Shelby L.; et al (January 2020, Geology)

   Abstract The Chicxulub crater was formed by an asteroid impact at ca. 66 Ma. The impact is considered to have contributed to the end-Cretaceous mass extinction and reduced productivity in the world’s oceans due to a transient cessation of photosynthesis. Here, biomarker profiles extracted from crater core material reveal exceptional insights into the post-impact upheaval and rapid recovery of microbial life. In the immediate hours to days after the impact, ocean resurge flooded the crater and a subsequent tsunami delivered debris from the surrounding carbonate ramp. Deposited material, including biomarkers diagnostic for land plants, cyanobacteria, and photosynthetic sulfur bacteria, appears to have been mobilized by wave energy from coastal microbial mats. As that energy subsided, days to months later, blooms of unicellular cyanobacteria were fueled by terrigenous nutrients. Approximately 200 k.y. later, the nutrient supply waned and the basin returned to oligotrophic conditions, as evident from N2-fixing cyanobacteria biomarkers. At 1 m.y. after impact, the abundance of photosynthetic sulfur bacteria supported the development of water-column photic zone euxinia within the crater. 

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2. Mineralogy of microbially induced calcium carbonate precipitates formed using single cell drop-based microfluidics

   https://doi.org/10.1038/s41598-020-73870-y  

   Zambare, Neerja M.; Naser, Nada Y.; Gerlach, Robin; Chang, Connie B. (December 2020, Scientific Reports)

   null (Ed.)

   Abstract Microbe-mineral interactions are ubiquitous and can facilitate major biogeochemical reactions that drive dynamic Earth processes such as rock formation. One example is microbially induced calcium carbonate precipitation (MICP) in which microbial activity leads to the formation of calcium carbonate precipitates. A majority of MICP studies have been conducted at the mesoscale but fundamental questions persist regarding the mechanisms of cell encapsulation and mineral polymorphism. Here, we are the first to investigate and characterize precipitates on the microscale formed by MICP starting from single ureolytic E. coli MJK2 cells in 25 µm diameter drops. Mineral precipitation was observed over time and cells surrounded by calcium carbonate precipitates were observed under hydrated conditions. Using Raman microspectroscopy, amorphous calcium carbonate (ACC) was observed first in the drops, followed by vaterite formation. ACC and vaterite remained stable for up to 4 days, possibly due to the presence of organics. The vaterite precipitates exhibited a dense interior structure with a grainy exterior when examined using electron microscopy. Autofluorescence of these precipitates was observed possibly indicating the development of a calcite phase. The developed approach provides an avenue for future investigations surrounding fundamental processes such as precipitate nucleation on bacteria, microbe-mineral interactions, and polymorph transitions. 

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3. Non-Stratiform Dolomitization on the Margins of the Great Bank of Guizhou in the Xiliang area, south China

   Sears, Madison; Luczaj, John; Carney, Eryn; Lehrmann, Daniel (April 2024, Geological Society of America Abstracts with Programs)

   The Great Bank of Guizhou (GBG) is an isolated carbonate platform in the Nanpanjiang Basin. Contacts between limestone and dolomitized material cross-cut bedding and form an irregular lobe shaped body that extends from the interior and terminates toward the basin. Precursor carbonate facies include oolite grainstone and packstone (with some containing a microbial matrix), clotted microbialite boundstone, and massively dolomitized carbonate mudstone containing stromatolitic and fenestral fabrics indicating a range of high-energy subtidal shoal to intertidal tidal flat environments. The mudstones are present lower in the outcrop, followed by grainstones and packstones moving upwards. Samples range from partially to fully dolomitized, with partially dolomitized samples occurring near the dolomitization front. In partially dolomitized oolite, the ooids are selectively replaced by dolomite. The paragenetic sequence interpreted from petrography includes early marine intergranular cement, early fracturing associated with possible tepee formation, neomorphism of aragonitic mollusk shells and cortical laminae in ooids, anhedral replacement dolomite, dissolution forming dissolved ooids and vugs, late stage coarse euhedral dolomite cement within intergranular pores, vugs, and early fractures, twinned calcite fill of early fractures and vugs, late stage fractures filled with twinned calcite, and finally stylolites. Previous data from the western GBG using fluid inclusion and clumped isotope geothermometry indicates that dolomitization occurred with high temperatures at burial, within a spatially variable range of 90°C to 185°C. 87Sr/86Sr values of 0.707677 to 0.708601 are similar to the ratios found in Triassic seawater. δ18O (VPDB) values for dolomite range from -7.68‰ to -1.53‰, consistent with evaporative enrichment of seawater and high burial temperatures. The spatial distribution of the dolomite, strontium isotopes and oxygen isotopes are consistent with reflux dolomitization. In other areas, the platform interior contains evidence for hypersaline conditions and evaporite mineral precipitation also consistent with the reflux model. The geothermometry data indicates that early reflux dolomite was replaced at high temperatures during burial. 

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4. Quorum sensing inhibition as a promising method to control biofilm growth in metalworking fluids

   https://doi.org/10.1007/s10295-019-02181-7  

   Özcan, Safiye Selen; Dieser, Markus; Parker, Albert E.; Balasubramanian, Narayanaganesh; Foreman, Christine M. (April 2019, Journal of Industrial Microbiology & Biotechnology)

   Microbial contamination in metalworking systems is a critical problem. This study determined the microbial communities in metalworking fluids (MWFs) from two machining shops and investigated the effect of quorum sensing inhibition (QSI) on biofilm growth. In both operations, biofilm-associated and planktonic microbial communities were dominated by Pseudomonadales (60.2–99.7%). Rapid recolonization was observed even after dumping spent MWFs and meticulous cleaning. Using Pseudomonas aeruginosa PAO1 as a model biofilm organism, patulin (40 µM) and furanone C-30 (75 µM) were identified as effective QSI agents. Both agents had a substantially higher efficacy compared to α-amylase (extracellular polymeric substance degrading enzyme) and reduced biofilm formation by 63% and 76%, respectively, in MWF when compared to untreated controls. Reduced production of putatively identified homoserine lactones and quinoline in MWF treated with QS inhibitors support the effect of QSI on biofilm formation. The results highlight the effectiveness of QSI as a potential strategy to eradicate biofilms in MWFs. 

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5. Influence of environment and mineralogy on euendolithic microboring patterns

   https://doi.org/10.1002/dep2.70029  

   Lincoln, Tyler; Lingappa, Usha; Hibner, Brianna; Trower, Elizabeth J (November 2025, The Depositional Record)

   Abstract Euendolithic microorganisms, capable of bioerosion in carbonate substrates, play an important role in modern marine ecosystems and have a fossil record extending into deep time. Understanding the factors driving microboring behaviour is essential for interpreting their ecological impact and reconstructing ancient environmental conditions. In this study, we conducted field incubation experiments across multiple sites at Little Ambergris Cay in the Turks and Caicos Islands, examining microboring density in abiotic optical calcite and aragonite under varying conditions of light, subaerial exposure, current energy, substrate mineralogy and trace metal content. We observed sinuous tunnels within 1 week of incubation in transparent calcite, with longer deployment times (2.5–5 months) resulting in meaningful increases in boring density. We also documented boring activity in dark conditions, suggesting potential for enhanced mineral dissolution at night when geochemical conditions are more optimal. Trace metal analysis of our experimental substrates revealed Fe/Ca and Mn/Ca ratios exceeding western Atlantic sea water estimates by 1–3 orders, with calcites more enriched in Mn than aragonites, offering preliminary support for the novel hypothesis that dissolution of CaCO₃minerals might be a useful source of trace metals for euendoliths. Sea water chemistry varied across sites, particularly between restricted interior and open platform sites. A comparison of boring densities suggests that trace metal abundance, mineralogy, local sea water CaCO₃mineral saturation state (Ω) and subaerial exposure (e.g. intertidal vs. shallow subtidal) may all influence microboring. These findings offer new perspectives on the euendolithic lifestyle, showing how substrate selection and temporal partitioning of dissolution activity balance metabolic costs with environmental constraints. They also enhance our ability to interpret the fossil record and bioerosion dynamics under changing conditions. 

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