Figure 4

Microbial cells present in the different layers of the WG7 sample: (row A) top-most layer of the microbial mat; (row B) sub-surface layer 1 (from a depth of 1–2 mm); (row C) sub-surface layer 2 (from a depth of 3–4 mm); and (row D) diatom cells and borax crystals in sub-surface layer 3 (from a depth of 5–8 mm); (Column I) images were taken using phase contrast microscopy; (column II, except for row D) images were taken using laser scanning confocal microscopy, at 488 nm excitation and 630–650 nm detection; (column III, except for row D) used differential interference contrast to modify the image from column II; and (column IV, except for row D) used laser scanning confocal microscopy (543 nm excitation and long pass 650 nm detection) to further modify the image from column II. Photographs in row D were taken using phase contrast microscopy.