Precipitation of Carbonate Minerals Induced by the Halophilic Chromohalobacter Israelensis under High Salt Concentrations: Implications for Natural Environments

Zuozhen Han,Dan Li,Peiyuan Li,Huaxiao Yan,Hui Zhao

doi:10.3390/min7060095

Abstract

The precipitation of carbonate minerals induced by halophilic bacteria has aroused wide concern. The study aimed to investigate the characterization and process of biomineralization in high salt systems by halophilic Chromohalobacter israelensis LD532 (GenBank: KX766026) bacteria, isolated from the Yinjiashan Saltern in China. Carbonate minerals were induced in magnesium sulfate and magnesium chloride medium, respectively. The mineral phase, morphology, and elemental composition of minerals were analyzed using X-ray p owder diffraction, scanning electron microscopy, and energy dispersive X-ray detection. Cells and ultrathin slices were studied using high resolution transmission electron microscopy, selected area electron diffraction, and energy dispersive X-ray detection. The carbonic anhydrase and ammonia released from LD532 bacteria increased pH of the medium and promoted the carbonate precipitation. Magnesium calcite and aragonite were induced by LD532 bacteria in magnesium chloride medium at an Mg/Ca molar ratio of 2, while Magnesium calcite and monohydrocalcite were precipitated in magnesium sulfate medium at the same Mg/Ca ratio, only monohydrocalcite were formed in both control groups. The morphologies and compositions of minerals in MgSO4 and MgCl2 solutions displayed significant differences, indicating different Mg2+ could affect physiological and biochemical activities of LD532 bacteria and thus affect the mineral deposition. Further study showed the nucleation sites were located on extracellular polymeric substances and intracellular vesicles of LD532 bacteria. This study is beneficial to the mechanism of carbonate biomineralization in natural salt environments.

Highlights

Carbonate minerals are widely distributed in the Earth’s crust and play an important role in the study of early diagenesis of marine sediments, calcification and the formation of cavernous chemical deposits [1]
LD532 bacterium can move in the semisolid medium (Table 1), indicating that the bacteria are motile
Bacteria commonly derive their motility from external structures called flagella

Summary

Introduction

Carbonate minerals are widely distributed in the Earth’s crust and play an important role in the study of early diagenesis of marine sediments, calcification and the formation of cavernous chemical deposits [1]. Minerals 2017, 7, 95 research findings on bioliths, such as stromatolites, oncolites, dendrites, and thrombolites [2,3,4,5,6,7,8,9,10], many researchers have investigated the ability of bacteria to precipitate minerals in natural environments and the laboratory. The role of microorganisms in the precipitation of a wide variety of carbonates generally has been acknowledged in recent years [11]. Interactions between microorganisms and minerals are a type of geological activities that occur widely in natural environments, and mineral dissolution and precipitation are almost inseparable from the role of microorganisms. Carbonate precipitation induced by different species of bacteria was a very common event in natural environments [5]. The morphology and mineralogy of carbonate minerals can be influenced by sulfate-reducing bacteria, which can produce copious amounts of extracellular polymeric substances (EPS) and increase the alkalinity by sulfate reduction and consumption of organic acids [13,14]

Methods

Results

Discussion

Conclusion