Elmi Fatemeh, Etemadifar Zahra, Emtiazi Giti
Department of Cell and Molecular Biology & Microbiology, Faculty of Biological Science and Technology, University of Isfahan, Isfahan, 8174673441, Iran.
Microb Ecol. 2023 Feb;85(2):698-707. doi: 10.1007/s00248-022-01977-y. Epub 2022 Feb 21.
Urease-producing bacteria are abundant in soils, which can precipitate calcium carbonate nanocrystals by enzymatic hydrolysis of urea in the presence of calcium ions. This process is known as microbially induced calcium carbonate precipitation (MICP), and it has received much attention in recent years as an eco-friendly technology. Therefore, the purpose of the present study was to isolate local extremophile bacterial strains capable of producing calcium carbonate. Among a total of 44 isolated urease-producing strains from sandy soils, one strain with a high level of urease activity (8.16 U/ml) and production of a large amount of calcium carbonate (410 mg/100 ml) was selected for further investigation. 16S rRNA gene sequencing showed that this strain had 99.66% sequence identity to Bhargavaea cecembensis. The SEM-EDX and XRD analyses indicated that irregular vaterite and aggregated nanocalcite were the dominant polymorphs produced by this strain. The size of these nanocalcite crystals ranged between 25 and 42 nm. The selected strain showed high levels of tolerance to different conditions of temperature, pH, and salinity. This strain grows at high temperatures up to 50 °C, alkaline pH (9-11), and high concentrations of NaCl (20-25% w/v). Flow cytometry analysis demonstrated 96% cell viability of the isolated strain after desiccation stress. Bhargavaea was first reported in 2009 as a new genus, and it belongs to the Firmicutes. So far, there has been no report on its MICP potential. The present study is the first one to report nanocrystal calcium carbonate precipitation in polyextremophile Bhargavaea cecembensis, which makes it a suitable candidate for bio-cementation under extreme circumstances.
产脲酶细菌在土壤中大量存在，它们能够在钙离子存在的情况下通过脲酶对尿素的酶促水解作用沉淀碳酸钙纳米晶体。这个过程被称为微生物诱导碳酸钙沉淀（MICP），近年来作为一种环保技术受到了广泛关注。因此，本研究的目的是分离能够产生碳酸钙的本地嗜极细菌菌株。在从沙质土壤中分离出的总共44株产脲酶菌株中，选择了一株脲酶活性高（8.16 U/ml）且能产生大量碳酸钙（410 mg/100 ml）的菌株进行进一步研究。16S rRNA基因测序表明，该菌株与巴氏芽孢杆菌的序列同一性为99.66%。扫描电子显微镜-能谱仪（SEM-EDX）和X射线衍射（XRD）分析表明，不规则的球霰石和聚集的纳米方解石是该菌株产生的主要多晶型物。这些纳米方解石晶体的尺寸在25至42纳米之间。所选菌株对不同的温度、pH和盐度条件表现出高度耐受性。该菌株能在高达50°C的高温、碱性pH（9 - 11）和高浓度NaCl（20 - 25% w/v）条件下生长。流式细胞术分析表明，分离出的菌株在干燥胁迫后细胞活力为96%。巴氏芽孢杆菌于2009年首次作为一个新属被报道，它属于厚壁菌门。到目前为止，尚未有关于其MICP潜力的报道。本研究是首次报道嗜极端多菌巴氏芽孢杆菌中纳米晶碳酸钙沉淀的研究，这使其成为极端环境下生物胶结的合适候选菌株。
