Precipitation of amorphous CaCO3 (aragonite-like) by cyanobacteria: A STXM study of the influence of EPS on the nucleation process

被引：223

作者：

Obst, M. ^{[1
,2
]}

Dynes, J. J. ^{[2
,3
]}

Lawrence, J. R. ^{[3
]}

Swerhone, G. D. W. ^{[3
]}

Benzerara, K. ^{[4
]}

Karunakaran, C. ^{[1
]}

Kaznatcheev, K. ^{[1
]}

Tyliszczak, T. ^{[5
]}

Hitchcock, A. P. ^{[2
]}

机构：

[1] Canadian Light Source, Saskatoon, SK S7H 0X4, Canada

[2] McMaster Univ, BIMR, Hamilton, ON L8S 4M1, Canada

[3] Environm Canada, Saskatoon, SK S7N 3H5, Canada

[4] CNRS & IPGP, IMPMC, ULR 7590, Paris, France

[5] Univ Calif Berkeley, Lawrence Berkeley Lab, Adv Light Source, Berkeley, CA 94720 USA

来源：

GEOCHIMICA ET COSMOCHIMICA ACTA | 2009年 / 73卷 / 14期

基金：

加拿大自然科学与工程研究理事会; 瑞士国家科学基金会;

关键词：

X-RAY MICROSCOPY; ADVANCED LIGHT-SOURCE; CALCIUM-CARBONATE; STRUCTURAL-CHARACTERIZATION; MICROBIAL BIOFILMS; FRESH-WATER; S-LAYER; KINETICS; BIOMINERALIZATION; TRANSMISSION;

D O I：

10.1016/j.gca.2009.04.013

中图分类号：

P3 [地球物理学]; P59 [地球化学];

学科分类号：

0708 ; 070902 ;

摘要：

An amorphous or nanocrystalline calcium carbonate (ACC) phase with aragonite-like short-range order was found to be a transient precursor phase of calcite precipitation mediated by cyanobacteria of the strain Synechococcus leopoliensis PCC 7942. Using scanning transmission X-ray microscopy (STXM), different Ca-species such as calcite, aragonite-like CaCO3, and Ca adsorbed on extracellular polymers were discriminated and mapped, together with various organic compounds, at the 30 nm-scale. The nucleation of the amorphous aragonite-like CaCO3 was found to take place within the tightly bound extracellular polymeric substances (EPS) produced by the cyanobacteria very close to the cell wall. The aragonite-like CaCO3 is a type of ACC since it did not show either X-ray or electron diffraction peaks. The amount of aragonite-like CaCO3 precipitated in the EPS was dependent on the nutrient supply during bacterial growth. Higher nutrient concentrations (both N and P) during the cultivation of the cyanobacteria resulted in higher amounts of precipitation of the aragonite-like CaCO3, whereas the amount of Ca2+ adsorbed per volume of EPS was almost independent of the nutrient level. After the onset of the precipitation of the thermodynamically stable calcite and loss of supersaturation the aragonite-like CaCO3 dissolved whereas Ca2+ remained sorbed to the EPS albeit at lower concentrations. Based on these observations a model describing the temporal and spatial evolution of calcite nucleation on the surface of S. leopoliensis was developed. In another set of STXM experiments the amount of aragonite-like CaCO3 precipitated on the cell surface was found to depend on the culture growth phase: cells in the exponential growth phase adsorbed large amounts of Ca within the EPS and mediated nucleation of ACC, while cells at the stationary/death phase neither adsorbed large amounts of Ca2+ nor mediated the formation of aragonite-like CaCO3. It is suggested that precipitation of an X-ray amorphous CaCO3 layer by cyanobacteria could serve as a protection mechanism against uncontrolled precipitation of a thermodynamically stable phase calcite on their surface. (c) 2009 Elsevier Ltd. All rights reserved.

引用

页码：4180 / 4198

页数：19