File:Laguna Negra microbialites.jpg

English: Composite CLSM images of a resin-embedded black pustular microbialite, stained with calcein. Images were obtained with concomitant excitations at 405, 488, and 543 nm and collection between 425 and 475 nm, 500 and 530 nm, and 560 and 660 nm, respectively. Fluorescence emission between 500 and 530 nm emerges specifically from calcein (in green). (A) Mineral aggregates (Min. and white arrow) are observed in blue. Their surfaces are partially stained with calcein, hence indicating the presence of free Ca2+ ion. Inside and surrounding the mineral aggregate, diatom frustules (x) and living diatoms (Diat.) are visible thanks to their photosynthetic pigments. Some Rivularia filaments (Riv.) seem to be separated from the mineralized aggregates, while other filaments are close but not entombed in the aggregate and occur with diatoms. Calcein stained the space inside the filaments, i.e., between the sheath and the cells. In (B) yellow/light green dots are observed in one of the Rivularia filament (*). Calcein also strongly stained the contours of the pigmented c1 cocci-shaped cell colonies that were found closely associated with the mineral aggregates (white arrow). (C) Close up view of calcein-stained Rivularia filaments. The dye also stained some other filamentous microorganisms associated with the Rivularia sheath (F. mic.). Inside the Rivularia filament, some green dots are distinguishable (***). (D) Image of two transversally-cut Rivularia filaments, where calcein fluorescence (*) was also found between the cells and the sheath (sh.); as in (C), calcein also stained the c1 colonies.