Calcareous deposit formation under cathodic polarization and marine biocalcifying bacterial activity.

CaCO3 precipitation can occur through bacterial activity (biomineralization) but can also take place in abiotic conditions in seawater at a steel surface under cathodic polarization. In this work, we used two biocalcifying bacterial strains: Pseudoalteromonas sp. and Virgibacillus halodenitrificans isolated in a previous work from marine environment for their ability to induce CaCO3 precipitation. Motility experiments were performed to evaluate the bacterial behaviour in the absence or presence of an applied electric current of -600 µA/cm2 in a solid medium. As no alteration of bacterial growth or CaCO3 crystal formation were observed, we studied both strains in liquid cultures at different applied currents densities: -100, -200 and -600 µA/cm2. The deposits formed on the cathode surface were characterized by µ-Raman spectroscopy and X-ray diffraction. The strain ability to biocalcify in the presence of electric current, in the liquid medium, was evaluated by monitoring bacterial growth, pH evolution, CaCO3 production and metabolic characterization for 7 days. Our results show that neither bacterial growth, enzymatic pathways or CaCO3 production were altered by the electric current. Moreover, bacterial activity modified drastically the nature of the compounds formed on the cathode surface. It favoured Mg-containing calcite, hindering the formation of both aragonite and brucite.

High Throughput Proteomic Exploration of Hypothermic Preservation Reveals Active Processes within the Cell Associated with Cold Ischemia Kinetic.

The demand for organs to be transplanted increases pressure on procurement centers, to the detriment of organ quality, increasing complications. New preservation protocols are urgently needed, requiring an in-depth understanding of ischemia-reperfusion mechanisms. We performed a proteomic analysis using LC-MS/MS-TOF data analyzed through R software and Cytoscape's ClueGO application, comparing the proteome of kidney endothelial cells, key cell type, subjected to 3, 6, 12, 19, and 24 h of cold ischemia and 6 h reperfusion. Critical pathways such as energy metabolism, cytoskeleton structure/transport system, and gene transcription/translation were modulated. Important time windows were revealed: a-during the first 3 h, central proteins were upregulated within these pathways; b-the majority of these upregulations were maintained until 12 h cold ischemia time (CIT); c-after that time, the overall decrease in protein expression was observed; d-at reperfusion, proteins expressed in response to cold ischemia were all downregulated. This shows that cold ischemia is not a simple slowing down of metabolism, as deep changes take place within the proteome on major pathways. Time-sensitive expression of key protein reveals possible quality biomarkers as well as potential targets for new strategies to maintain or optimize organ quality.

New Biocalcifying Marine Bacterial Strains Isolated from Calcareous Deposits and Immediate Surroundings.

Marine bacterial biomineralisation by CaCO3 precipitation provides natural limestone structures, like beachrocks and stromatolites. Calcareous deposits can also be abiotically formed in seawater at the surface of steel grids under cathodic polarisation. In this work, we showed that this mineral-rich alkaline environment harbours bacteria belonging to different genera able to induce CaCO3 precipitation. We previously isolated 14 biocalcifying marine bacteria from electrochemically formed calcareous deposits and their immediate environment. By microscopy and µ-Raman spectroscopy, these bacterial strains were shown to produce calcite-type CaCO3. Identification by 16S rDNA sequencing provided between 98.5 and 100% identity with genera Pseudoalteromonas, Pseudidiomarina, Epibacterium, Virgibacillus, Planococcus, and Bhargavaea. All 14 strains produced carbonic anhydrase, and six were urease positive. Both proteins are major enzymes involved in the biocalcification process. However, this does not preclude that one or more other metabolisms could also be involved in the process. In the presence of urea, Virgibacillus halodenitrificans CD6 exhibited the most efficient precipitation of CaCO3. However, the urease pathway has the disadvantage of producing ammonia, a toxic molecule. We showed herein that different marine bacteria could induce CaCO3 precipitation without urea. These bacteria could then be used for eco-friendly applications, e.g., the formation of bio-cements to strengthen dikes and delay coastal erosion.

Looking at the past through a telescope: adults postdated their earliest childhood memories.

Our previous studies have consistently shown a telescoping error in children's dating of earliest childhood memories. Preschool children through adolescents systematically date their earliest memories at older ages, in comparison with the age estimates provided by their parents or by themselves previously. In the current study, we examined the dating of earliest childhood memories in two samples of college adults and collected independent age estimates from their parents. Consistent with our findings with children, adults significantly postdated their earlier memories by approximately 12 months (Study 1) and 6 months (Study 2). The actual age of earliest memories was 2.5 years after adjusted for telescoping errors, 1 year earlier than what is commonly believed at 3.5 years. These findings challenge commonly held theoretical assumptions about childhood amnesia and highlight critical methodological issues in the study of childhood memory.