Matrix is everywhere: extracellular DNA is a link between biofilm and mineralization in Bacillus cereus planktonic lifestyle

To date, the mechanisms of biomineralization induced by bacterial cells in the context of biofilm formation remain the subject of intensive studies. In this study, we analyzed the influence of the medium components on the induction of CaCO₃ precipitation by the Bacillus cereus cells and composition of the extracellular matrix (ECM) formed in the submerged culture. While the accumulation of extracellular polysaccharides and amyloids appeared to be independent of the presence of calcium and urea during the growth, the accumulation of extracellular DNA (eDNA), as well as precipitation of calcium carbonate, required the presence of both ingredients in the medium. Removal of eDNA, which was sensitive to treatment by DNase, did not affect other matrix components but resulted in disruption of cell network formation and a sixfold decrease in the precipitate yield. An experiment with a cell-free system confirmed the acceleration of mineral formation after the addition of exogenous salmon sperm DNA. The observed pathway for the formation of CaCO₃ minerals in B. cereus planktonic culture included a production of exopolysaccharides and negatively charged eDNA lattice promoting local Ca²⁺ supersaturation, which, together with an increase in the concentration of carbonate ions due to pH rise, resulted in the formation of an insoluble precipitate of calcium carbonate. Precipitation of amorphous CaCO₃ on eDNA matrix was followed by crystal formation via the ACC-vaterite-calcite/aragonite pathway and further formation of larger mineral aggregates in complex with extracellular polymeric substances. Taken together, our data showed that DNA in extracellular matrix is an essential factor for triggering the biomineralization in B. cereus planktonic culture.

Continuing progress in the field of two-dimensional correlation spectroscopy (2D-COS): Part III. Versatile applications

In this review, the comprehensive summary of two-dimensional correlation spectroscopy (2D-COS) for the last two years is covered. The remarkable applications of 2D-COS in diverse fields using many types of probes and perturbations for the last two years are highlighted. IR spectroscopy is still the most popular probe in 2D-COS during the last two years. Applications in fluorescence and Raman spectroscopy are also very popularly used. In the external perturbations applied in 2D-COS, variations in concentration, pH, and relative compositions are dramatically increased during the last two years. Temperature is still the most used effect, but it is slightly decreased compared to two years ago. 2D-COS has been applied to diverse systems, such as environments, natural products, polymers, food, proteins and peptides, solutions, mixtures, nano materials, pharmaceuticals, and others. Especially, biological and environmental applications have significantly emerged. This survey review paper shows that 2D-COS is an actively evolving and expanding field.

Short reaction times coupled with alkalization improves the release of phosphorus from Al-waste activated sludge

In this study, the performance and mechanism of P release from Al-waste activated sludge (WAS) via wet-chemical treatment at different reaction times were investigated. The maximum P release (46% of TP) was achieved at 20 min when the pH was maintained at 2 during acidic treatment. During alkali treatment, the maximum P concentration (363.96 mg/L, 46.07%) was achieved at 10 min when pH was initially adjusted to 12. Acidic treatment took twice as long to achieve the same efficiency of released P as the alkali treatment. Furthermore, P release mainly originated from Al-P and Ca-P during acidic treatment and Al-P dissolution during alkali treatment. The cost of chemical consumption was 483.96 USD/ton TS sludge with acidic treatment, which was 8.49 times higher than that of alkali treatment without pH control. Thus, short reaction times (ca. 10 min) coupled with alkalization provide an effective approach for improving P release from Al-WAS.

Adsorption of phenol over bio-based silica/calcium carbonate (CS-SiO2/CaCO3) nanocomposite synthesized from waste eggshells and rice husks

A bio-based Silica/Calcium Carbonate (CS–SiO2/CaCO3) nanocomposite was synthesized in this study using waste eggshells (ES) and rice husks (RH). The adsorbents (ESCaCO3, RHSiO2 and, CS-SiO2/CaCO3) characterized using XRD show crystallinity associated with the calcite and quartz phase. The FTIR of ESCaCO3 shows the CO−23 group of CaCO3, while the spectra of RHSiO2 majorly show the siloxane bonds (Si–O–Si) in addition to the asymmetric and symmetric bending mode of SiO2. The spectra for Chitosan (CS) show peaks corresponding to the C=O vibration mode of amides, C–N stretching, and C–O stretching. The CS–SiO2/CaCO3 nanocomposite shows the spectra pattern associated with ESCaCO3 and RHSiO2. The FESEM micrograph shows a near monodispersed and spherical CS–SiO2/CaCO3 nanocomposite morphology, with an average size distribution of 32.15 ± 6.20 nm. The corresponding EDX showed the representative peaks for Ca, C, Si, and O. The highest removal efficiency of phenol over the adsorbents was observed over CS–SiO2/CaCO3 nanocomposite compared to other adsorbents. Adsorbing 84–89% of phenol in 60–90 min at a pH of 5.4, and a dose of 0.15 g in 20 ml of 25 mg/L phenol concentration. The result of the kinetic model shows the adsorption processes to be best described by pseudo-second-order. The highest correlation coefficient (R2) of 0.99 was observed in CS-SiO2/CaCO3 nanocomposite, followed by RHSiO2 and ESCaCO3. The result shows the equilibrium data for all the adsorbents fitting well to the Langmuir isotherm model, and follow the trend CS-SiO2/CaCO3 > ESCaCO3 > RHSiO2. The Langmuir equation and Freundlich model in this study show a higher correlation coefficient (R2 = 0.9912 and 0.9905) for phenol adsorption onto the CS–SiO2/CaCO3 nanocomposite with a maximum adsorption capacity (qm ) of 14.06 mg/g compared to RHSiO2 (10.64 mg/g) and ESCaCO3 (10.33 mg/g). The results suggest good monolayer coverage on the adsorbent’s surface (Langmuir) and heterogeneous surfaces with available binding sites (Freundlich).

Effect of CO2 driven ocean acidification on calcification, physiology and ovarian cells of tropical sea urchin Salmacis virgulata - A microcosm approach

In the present study, we depict the structural modification of test minerals, physiological response and ovarian damage in the tropical sea urchin Salmacis virgulata using microcosm CO₂ (Carbon dioxide) perturbation experiment. S. virgulata were exposed to hypercapnic conditions with four different pH levels using CO₂ gas bubbling method that reflects ambient level (pH 8.2) and elevated pCO₂ scenarios (pH 8.0, 7.8 and 7.6). The variations in physical strength and mechanical properties of S. virgulata test were evaluated by thermogravimetric analysis, Fourier transform infrared spectroscopy, X-ray diffraction analysis and scanned electron microscopy analysis. Biomarker enzymes such as glutathione-S-transferase, catalase, acetylcholine esterase, lipid peroxidase and reduced glutathione showed physiological stress and highly significant (p < 0.01) towards pH 7.6 and 7.8 treatments. Ovarian cells were highly damaged at pH 7.6 and 7.8 treatments. This study proved that the pH level 7.6 and 7.8 drastically affect calcification, physiological response and ovarian cells in S. virgulata.