Abstract
Microbially induced calcium carbonate (CaCO3) precipitation (MICP) is a process where microbes induce condition favorable for CaCO3 formation through metabolic activities by increasing the pH or carbonate ions when calcium is near. The molecular and ecological basis of CaCO3 precipitating (CCP) bacteria has been poorly illuminated. Here, we showed that increased pH levels by deamination of amino acids is a driving force toward MICP using alkalitolerant Lysinibacillus boronitolerans YS11 as a model species of non-ureolytic CCP bacteria. This alkaline generation also facilitates the growth of neighboring alkaliphilic Bacillus sp. AK13, which could alter characteristics of MICP by changing the size and shape of CaCO3 minerals. Furthermore, we showed CaCO3 that precipitates earlier in an experiment modifies membrane rigidity of YS11 strain via upregulation of branched chain fatty acid synthesis. This work closely examines MICP conditions by deamination and the effect of MICP on cell membrane rigidity and crystal formation for the first time.
Highlights
Calcium carbonate precipitating (CCP) bacteria contribute to the geochemical cycle as they precipitate carbonate minerals, including calcium carbonate in nature (Douglas and Beveridge 1998)
We demonstrate that the precipitated calcium carbonate can modify membrane rigidity in bacteria by upregulating branched chain amino acid (BCAA) and branched chain fatty acid (BCFA) synthesis
Strain YS11 at density of 1 × 106 colony-forming unit (CFU)/ml was transferred into 25 ml of calcium acetate (CaAc) medium (15.8 mM calcium acetate, .4% yeast extract, .5% glucose) or sodium acetate (NaAc) medium (15.8 mM sodium acetate, .4% yeast extract, .5% glucose) in a 50-ml flask to observe the growth on Ca-rich or Ca-poor condition
Summary
Calcium carbonate precipitating (CCP) bacteria contribute to the geochemical cycle as they precipitate carbonate minerals, including calcium carbonate in nature (Douglas and Beveridge 1998). There are four main environmental parameters that govern reaction kinetics for calcium carbonate precipitation: (1) pH, (2) calcium (Ca2+) ion concentration, (3) dissolved inorganic carbon (DIC) concentration, and [4] nucleation site availability (Hammes and Verstraete 2002) Bacteria influence these parameters through their metabolic activity, the production of biofilm, and Bacteria can form biofilms in most environmental niches, and most biofilm communities in nature. Previous studies have shown that EPS formed by biofilms is crucial when investigating bacterial physiological functions and activities (Giuffre et al 2013; Braissant et al 2003). These ex situ research efforts have found that EPS could regulate spatial position of precipitation during mineralization. Exploring the relationship between pH increasing bacteria involved in multispecies biofilm and calcium carbonate formation is important for understanding integral mechanisms of microbially induced calcium carbonate formation (MICP)
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