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Our previous study reported that Saccharomyces cerevisiae could induce calcium carbonate (CaCO3) precipitation, but the associated mechanism was unclear. In the present study, Saccharomyces cerevisiae was cultured under various conditions, including the presence of different organic acids and initial pH, and the yields of CaCO3 formation induced by the different organic acids were compared. The metabolism of organic acid by the metabolites of S. cerevisiae was also assessed in vitro. The SEM-EDS and XRD results showed that only acetate acid, pyruvic acid, and α-ketoglutaric acid could induce CaCO3 formation, and the weight order of the produced CaCO3 was pyruvic acid, acetate acid, α-ketoglutaric acid. In addition, the presence of only yeast metabolites and the initial neutral or alkaline environment also limited the CaCO3 formation. These results illustrated that organic acid oxidation intracellularly, especially the tricarboxylic acid cycle, was the major mechanism, and the CaCO3 yield was related to the amount of CO2 produced by the metabolism of organic acids. These findings will deepen the knowledge of the mineralization capacity of S. cerevisiae and provide a theoretical basis for the future application of yeast as an alternative microorganism in MICP.
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SignificanceThe conservation of historical relics against microbial biodeterioration is critical to preserving cultural heritages. One major challenge is our limited understanding of microorganisms' dispersal, colonization, and persistence on relics after excavation and opening to external environments. Here, we investigate the ecological and physiological profiles of the microbiome within and outside the Dahuting Han Dynasty Tomb with a 1,800-y history. Actinobacteria dominate the microbiome in this tomb. Via interkingdom signaling mutualism, springtails carry Actinobacteria as one possible source into the tomb from surrounding environments. Subsequently, Actinobacteria produce cellulases combined with antimicrobial substances, which helps them to colonize and thrive in the tomb via intrakingdom competition. Our findings unravel the ecology of the microbiomes colonizing historical relics and provide help for conservation practices.
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Actinobacteria , Microbiota , BacteriasRESUMEN
In this study, we tested a possible mechanism of the association between math anxiety and math achievement: the mediating role of math-specific grit (i.e., sustaining effort in the face of adversity when learning math). In Study 1, a sample of 10th grade students (N = 222) completed a battery of personality and attitude questionnaires, and math achievement was indexed by curriculum-based examination scores. Mediation analyses indicated that math-specific grit, but not domain-general grit, mediated the relationship between math anxiety and math achievement. In Study 2, we replicated and extended the above findings with another sample of 11th grade students (N = 465). Mediation analyses indicated that math-specific grit and math-specific procrastination played sequential mediating roles in the relationship between math anxiety and math achievement. That is, individuals with higher math anxiety were less gritty in math learning, possibly further leading them to be more procrastinated in performing math work, which may finally result in worse math achievement. In summary, the current study provides the first evidence that math-specific grit may mediate the relationship between math anxiety and math achievement. Furthermore, it also demonstrated the value of math-specific grit over domain-general grit in predicting math success, which invites a broader investigation on subject-specific grit.
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Information on pigment sizes in mural samples is a key factor in determining the suitable processes of possible restoration and conservation on ancient murals and is also significant for the investigation of a mural's historic value and analysis of its technical process. Thus, in this paper, the green painted layers composed of different pigment sizes were analyzed by laser-induced breakdown spectroscopy. First, a parametric study was undertaken to optimize the LIBS signal to noise ratio and decrease fluctuations. Then, the variation of LIBS signal with pigment size was studied on simulated mural samples. Finally, a classifiable model of pigment sizes was built by coupling with the PCA method and was successfully applied to classify pigment sizes on real mural pieces.