Search

Studying the crystallization sequence of calcium carbonate (CaCO3) polymorphs provides great insights into bacterial mineralization mechanisms, and carbonate rock genesis in recent geological history. CaCO3 biomineralization studies were conducted using Synechococcus sp. PCC 7942. Changes in bacterial optical density, polysaccharide content, carbonic anhydrase activity, pH, Ca2+, Mg2+, phosphate, and bicarbonate concentrations in medium, and precipitation levels were recorded, while precipitate morphology and polymorphisms were characterized. We identified an abnormal crystallization sequence order of carbonate polymorphs: calcite, aragonite, and vaterite, which failed to obey Ostwald’s rule. We investigated saturation indices (SI) and calculated calcite, aragonite, and vaterite quantities. Also, two mineralization studies were performed using PCC 7942 in the medium-plus different phosphates levels and extracellular polymeric substances (EPS) secreted by PCC 7942. Calcite was precipitated due to phosphate levels >7 µmol·L−1 and SIvaterite values aragonite values >2.3 and phosphate levels −1 exerted crucial roles in aragonite formation. Finally, decreased phosphate and Mg2+ levels promoted vaterite crystallization. We suggest this unique crystallization order may be attributed to changes in bacterial density and PO43− levels. Our study provides new insights into bacterial mineralization mechanisms.HIGHLIGHTSShow that calcite, aragonite, and vaterite crystallized in order in MICP.The abnormal crystallization sequence of CaCO3 polymorphs does not follow Ostward’s theory.The metabolic activity of Synechococcus sp. PCC 7942 and phosphate levels should be responsible for this unique crystallization order. Show that calcite, aragonite, and vaterite crystallized in order in MICP. The abnormal crystallization sequence of CaCO3 polymorphs does not follow Ostward’s theory. The metabolic activity of Synechococcus sp. PCC 7942 and phosphate levels should be responsible for this unique crystallization order.

Marine sediment is considered a vast sink for organic pollutants including polycyclic aromatic hydrocarbons (PAHs). However, little is known about the relationship between subcritical PAH allocation and benthic microbial patterns. Thus, we carried out a field investigation at the abandoned Yellow River Delta (AYRD) to deepen the understanding of PAHs' horizontal distribution and ecological roles on the continental shelf. The PAH level in the AYRD is relatively low and distance-independent, indicating it resulted from long-term, chronic, anthropogenic input. The combined application of diagnostic molecular ratios reported inconsistent PAH sources, which might be due to the low PAH concentrations and the complexity of contributing sources. Positive Matrix Factorization provided a more robust source classification and identified three main PAH sources-coal combustion and vehicle emissions, petrogenic process, and fossil fuels. The benthic microbiome did not show a significant response to PAHs in terms of microbial assemblage or alpha-diversity. However, Operational Taxonomic Units in some specific phyla, like Thaumarchaeota, Proteobacteria, Acidobacteria, and Chytridiomycota, correlated with the PAH source indicators, supporting the notion that PAH source indicators can act as a novel environmental indicator for microbial adaption. What's more, Microbial Ecological Networks show more connection at sites identified as biomass combustion by both Fluoranthene/(Fluoranthene + Pyrene) and Indeno(1,2,3-cd)pyrene/(Indeno(1,2,3-cd)pyrene + Benzo(ghi)perylene) compared to the ones identified as biomass combustion by Fluoranthene/(Fluoranthene + Pyrene) and petroleum combustion by Indeno(1,2,3-cd)pyrene/(Indeno(1,2,3-cd)pyrene + Benzo(ghi)perylene). Herein, we demonstrate that the PAHs' source indicator can serve as a novel indicator of the interactions between microorganisms, and thus, should be applied to the sustainable management effort in the offshore area.

Terrestrial fungi, especially arbuscular mycorrhizal (AM) fungi, enhance heavy metal sequestration and promote ecosystem restoration. However, their ecological functions were historically overlooked in discussions regarding water quality. As an AM fungi-derived stable soil protein fraction, glomalin-related soil protein (GRSP) may provide insights into the ecological functions of AM fungi associated with water quality in coastal ecosystems. Here, we first assessed the metal-loading dynamics and ecological functions of GRSP transported into aquatic ecosystems, characterized the composition characteristics, and revealed the mechanisms underlying Cu and Cd sequestration. Combining in situ sampling and in vitro cultures, we found that the composition characteristics of GRSP were significantly affected by the element and mineral composition of sediments. In situ, GRSP-bound Cu and Cd contributed 18.91–22.03% of the total Cu and 2.27–6.37% of the total Cd. Functional group ligands and ion exchange were the principal mechanisms of Cu binding by GRSP, while Cd binding was dominated by functional group ligands. During the in vitro experiment, GRSP sequestered large amounts of Cu and Cd and formed stable complexes, while further dialysis only released 25.74 ± 3.85% and 33.53 ± 3.62% of GRSP-bound Cu and Cd, respectively.