Ronholm J, Schumann D, Sapers H M, Izawa M, Applin D, Berg B, Mann P, Vali H, Flemming R L, Cloutis E A, Whyte L G
Department of Natural Resource Sciences, McGill University, Sainte-Anne-de-Bellevue, QC, Canada.
Geobiology. 2014 Nov;12(6):542-56. doi: 10.1111/gbi.12102. Epub 2014 Sep 24.
Precipitation of calcium carbonate (CaCO3(s) ) can be driven by microbial activity. Here, a systematic approach is used to identify the morphological and mineralogical characteristics of CaCO3(s) precipitated during the heterotrophic growth of micro-organisms isolated from polar environments. Focus was placed on establishing mineralogical features that are common in bioliths formed during heterotrophic activity, while in parallel identifying features that are specific to bioliths precipitated by certain microbial phylotypes. Twenty microbial isolates that precipitated macroscopic CaCO3(s) when grown on B4 media supplemented with calcium acetate or calcium citrate were identified. A multimethod approach, including scanning electron microscopy, high-resolution transmission electron microscopy, and micro-X-ray diffraction (μ-XRD), was used to characterize CaCO3(s) precipitates. Scanning and transmission electron microscopy showed that complete CaCO3(s) crystal encrustation of Arthrobacter sp. cells was common, while encrustation of Rhodococcus sp. cells did not occur. Several euhedral and anhedral mineral formations including disphenoid-like epitaxial plates, rhomboid-like aggregates with epitaxial rhombs, and spherulite aggregates were observed. While phylotype could not be linked to specific mineral formations, isolates tended to precipitate either euhedral or anhedral minerals, but not both. Three anhydrous CaCO3(s) polymorphs (calcite, aragonite, and vaterite) were identified by μ-XRD, and calcite and aragonite were also identified based on TEM lattice-fringe d value measurements. The presence of certain polymorphs was not indicative of biogenic origin, although several mineralogical features such as crystal-encrusted bacterial cells, or casts of bacterial cells embedded in mesocrystals are an indication of biogenic origin. In addition, some features such as the formation of vaterite and bacterial entombment appear to be linked to certain phylotypes. Identifying phylotypes consistent with certain mineralogical features is the first step toward discovering a link between these crystal features and the precise underlying molecular biology of the organism precipitating them.
碳酸钙（CaCO₃(s)）的沉淀可由微生物活动驱动。在此，采用一种系统方法来确定从极地环境分离出的微生物在异养生长过程中沉淀的CaCO₃(s)的形态和矿物学特征。重点在于确定异养活动期间形成的生物岩中常见的矿物学特征，同时并行识别特定微生物系统型沉淀的生物岩所特有的特征。鉴定出了20种微生物分离株，它们在添加醋酸钙或柠檬酸钙的B4培养基上生长时会沉淀出宏观的CaCO₃(s)。采用了包括扫描电子显微镜、高分辨率透射电子显微镜和微X射线衍射（μ-XRD）在内的多方法途径来表征CaCO₃(s)沉淀。扫描电子显微镜和透射电子显微镜显示，节杆菌属细胞完全被CaCO₃(s)晶体包裹很常见，而红球菌属细胞则不会被包裹。观察到了几种自形和他形矿物形态，包括似双楔面体的外延板、带有外延菱形的似菱形聚集体和球粒聚集体。虽然系统型与特定矿物形态没有关联，但分离株倾向于沉淀自形或他形矿物，而非两者皆有。通过μ-XRD鉴定出了三种无水CaCO₃(s)多晶型物（方解石、文石和球霰石），并且基于透射电子显微镜晶格条纹d值测量也鉴定出了方解石和文石。某些多晶型物的存在并不表明其生物成因，尽管一些矿物学特征，如晶体包裹的细菌细胞或嵌入中晶体内的细菌细胞铸模是生物成因的迹象。此外，一些特征，如球霰石的形成和细菌包埋似乎与某些系统型有关。识别与某些矿物学特征一致的系统型是发现这些晶体特征与沉淀它们的生物体精确潜在分子生物学之间联系的第一步。
