Calcite precipitation induced by Bacillus cereus MRR2 cultured at different Ca2+ concentrations: Further insights into biotic and abiotic calcite

Biomineralization induced by microorganisms has become a hot spot in the field of carbonate sedimentology; however, the mechanisms involved still need to be explored. In this study, the bacterium Bacillus subtilis J2 (GenBank MG575432) was used to induce the precipitation of calcium carbonate minerals at Mg/Ca molar ratios of 0, 3, 6, 9, and 12. Bacillus subtilis J2 bacteria released ammonia to increase pH, but the ammonia released only made the pH increase to 8.25. Carbonic anhydrase was also produced to catalyze the hydration of carbon dioxide, and this process released carbonate and bicarbonate ions that not only increased pH but also elevated carbonate supersaturation. The biominerals formed at a Mg/Ca molar ratio of 0 were spherulitic, elongated, dumbbell-shaped, and irregularly rhombohedral calcite; at a Mg/Ca molar ratio of 3, the biominerals were calcite and aragonite, the weight ratio of calcite decreased from 26.7% to 15.6%, and that of aragonite increased from 73.3% to 84.4% with increasing incubation time. At higher Mg/Ca molar ratios, the biominerals were aragonite, and the crystallinity and thermal stability of aragonite decreased with increasing Mg/Ca molar ratios. FTIR results showed that many organic functional groups were present on/within the biominerals, such as C–O–C, N–H, C=O, O–H, and C–H. HRTEM-SAED examination of the ultra-thin slices of B. subtilis J2 bacteria showed that nano-sized minerals with poor crystal structure had grown or been adsorbed on the EPS coating. The EPS of the B. subtilis J2 strain contained abundant glutamic acid and aspartic acid, which could be deprotonated in an alkaline condition to adsorb Ca2+ and Mg2+ ions; this made EPS act as the nucleation sites. This study may provide some references for further understanding of the mechanism of biomineralization induced by microorganisms.

https://www.mdpi.com/2075-163X/9/4/218/pdf

Mechanism of Biomineralization Induced by Bacillus subtilis J2 and Characteristics of the Biominerals

The bio-precipitation of calcium and magnesium ions by free and immobilized Lysinibacillus fusiformis DB1-3 in the wastewater

Mercury-mediated toxicity remains one of the greatest barriers against microbial survival, even though bacterial resistance to mercury compounds can occur. However, the genetic and physiological adaptations of bacteria to mercury stress still remains unclear. Here, we show that the marine bacterium Pseudomonas stutzeri 273 is resistant to 50 μM Hg2+ and removes up to 94% Hg2+ from culture. Using gene homologous recombination and complementation, we show that genes encoding Hg2+-transport proteins MerT, MerP, the mercuric reductase MerA and the regulatory protein MerD are essential for bacterial mercuric resistance when challenged with Hg2+. Further, mercury stress inhibits flagellar development, motility, chemotaxis and biofilm formation of P. stutzeri 273, which are verified by transcriptomic and physiological analyses. Surprisingly, we discover that MerF, a previously reported Hg2+-transporter, determines flagellar development, motility and biofilm formation in P. stutzeri 273 by genetic and physiological analyses. Our results strongly indicate that MerF plays an integral role in P. stutzeri 273 to develop physiological responses to mercury stress. Notably, MerF homologs are also prevalent in different human pathogens. Using this unique target may provide novel strategies to control these pathogenic bacteria, given the role of MerF in flagella and biofilm formation. In summary, our data provide an original report on MerF in bacterial physiological development and suggest that the mer in marine bacteria has evolved through progressive, sequential recruitment of novel functions over time.

/pdf/genetic-and-physiological-adaptations-of-marine-bacterium-4q8j2nccn7.pdf

Genetic and Physiological Adaptations of Marine Bacterium Pseudomonas stutzeri 273 to Mercury Stress.

Calcium carbonate (CaCO3) biomineralization has been investigated due to its wide range of scientific and technological implications, however, the molecular mechanisms of this important geomicrobiological process are largely unknown. Here, a urease-positive marine actinobacterium Brevibacterium linens BS258 was demonstrated to effectively form CaCO3 precipitates. Surprisingly, this bacterium could also dissolve the formed CaCO3 with the increase of the Ca2+ concentration. To disclose the mechanisms of biomineralization, the genome of B. linens BS258 was further completely sequenced. Interestingly, the expression of three carbonic anhydrases was significantly up-regulated along with the increase of Ca2+ concentration and the extent of calcite dissolution. Moreover, transcriptome analyses revealed that increasing concentration of Ca2+ induced KEGG pathways including quorum sensing (QS) in B. linens BS258. Notably, most up-regulated genes related to QS were found to encode peptide/nickel ABC transporters, which suggested that nickel uptake and its associated urease stimulation were essential to boost CaCO3 biomineralization. Within the genome of B. linens BS258, there are both cadmium and lead resistance gene clusters. Therefore, the sequestration abilities of Cd2+ and Pb2+ by B. linens BS258 were checked. Consistently, Pb2+ and Cd2+ could be effectively sequestered with the precipitation of calcite by B. linens BS258. To our knowledge, this is the first study investigating the microbial CaCO3 biomineralization from both genomic and transcriptomic insights, which paves the way to disclose the relationships among bacterial metabolisms and the biomineralization.

/pdf/genomic-and-transcriptomic-insights-into-calcium-carbonate-w1bqil3l7x.pdf

Genomic and Transcriptomic Insights into Calcium Carbonate Biomineralization by Marine Actinobacterium Brevibacterium linens BS258.

This article presents a research study on the deposition process of Ca2+ induced by Synechocystis sp. PCC6803 in BG11 liquid medium with different Ca2+ concentrations and different pH. The changes of Ca2+ concentrations were measured by using atomic absorption method and the corresponding dynamical models were studied. Minerals and cells were analyzed by high resolution transmission electron microscope, selected area electron diffraction, scanning electron microscope, energy dispersive X-ray spectroscope, X-ray diffraction. The selected area electron diffraction patterns were analyzed by Digital Micrograph 3.7 software. The result showed that Ca2+ concentrations decreased faster in the experimental group. The changes of calcium carbonate precipitation were fitting to an exponential model. PH 7 and Ca2+ concentration of 1.5 g/L were most conducive to calcium carbonate precipitation in the corresponding gradient range. The result of high-resolution transmission electron microscopy showed that minerals in th...

Bio-precipitation of Calcite with Preferential Orientation Induced by Synechocystis sp. PCC6803

Abstract Objective To identify the alterations of CD8 + T cells in blood and labial salivary glands (LSGs) of patients with Primary Sjögren’s syndrome (pSS). Methods Blood samples from 24 pSS patients were assayed for CD38 + HLA-DR + CD8 + (activated CD8 + , aCD8 + ) T cells and serum IFN-γ and TNF-α, using flow cytometry and ELISA respectively, and compared with samples from 27 healthy controls. Immunohistochemistry was used to count CD8 + T cells in LSG tissues of 24 pSS patients and of 6 control patients with normal pathology. Results pSS patients had more aCD8 + T cells than aCD4 + T cells (medians 33.13% vs . 9.43%, p &lt; 0.0001), and had an increased level of aCD8 + T cells (medians 33.13% vs . 16.48%, p &lt; 0.0001) and serum IFN-γ (medians 1026 pg/mL vs . 0.00 pg/mL, p &lt; 0.0001) compared to the healthy controls. The levels of aCD8 + T cells and IFN-γ were both significant positively correlated with European League Against Rheumatism Sjögren’s Syndrome Disease Activity Index, IgG, anti-nuclear antibodies, rheumatoid factor. The LSGs focus score (FS) ≥1 group had more CD8 + T cell counts than 0≤ FS &lt;1 group and control group (medians 256/mm 2 vs . 126/mm 2 and 256/mm 2 vs . 64/mm 2 respectively, both p &lt; 0.05). Conclusion The aCD8 + T cells and IFN-γ are positively correlated with each other, and predominantly elevated in the blood of pSS patients. In the LSG tissues of pSS, CD8 + T cell counts increase with severity of the lesions. CD8 + T cells may play crucial role in the pathogenesis of pSS. Key Points • Primary Sjögren’s syndrome (pSS) is a chronic and systemic autoimmune disease. pSS patients had elevated blood levels of CD38 + HLA-DR + CD8 + T cells and IFN-γ. • The CD38 + HLA-DR + CD8 + T cells positively correlated with disease parameters and serum IFN-γ. • The salivary glands of pSS patients had appreciable CD8 + lymphocyte infiltration. CD8 + T cells may play crucial role in the pathogenesis of pSS. 

/pdf/alterations-of-cd8-t-cells-in-the-blood-and-salivary-glands-26jl777j.pdf

Alterations of CD8+ T cells in the blood and salivary glands of patients with primary Sjögren’s syndrome

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Bio-precipitation of Calcite with Preferential Orientation Induced by Synechocystis sp. PCC6803

Alterations of CD8+ T cells in the blood and salivary glands of patients with primary Sjögren’s syndrome