Tufa-forming biofilms of German karstwater streams: microorganisms, exopolymers, hydrochemistry and calcification - Tufas and Speleothems: Unravelling the Microbial and Physical Controls - page 99

Fig. 11. Different structural EPS domains in tufa-forming biofilms of both karstwater streams, Deinschwanger
and Westerh¨ fer Bach. a, d, g: Cell-associated EPS glycoconjugates, stained with N-acetylglucosamine-specific lectins,
originated of filamentous cyanobacteria. b, e, h: Sheet-like EPS glycoconjugates stained with fucose-specific lectin
form structures between cells of cyanobacteria and non-phototrophic prokaryotes. c, f, i: Diffuse and cloud-like EPS
glycoconjugates stained with amino sugar- and fucose-specific lectins. a - c, f, h - i: Westerh¨ fer Bach lower stream site
WB3; d - e, g: Deinschwanger Bach northern side tributary site DB 2. Colour allocation: red, lectin-specific EPS
glycoconjugates; blue, autofluorescence of chla; pink, autofluorescence of cyanobacteria for d - f; green, bacteria
(SYTO9) for g - i; green, calcein-stained calcite. All images were shown as Maximum Intensity Projections of LSM data
sets. Scale bar is 20 mm.

cloud-like signals (Fig. 11c, f, i) which covered
more or less large areas of tufa-forming biofilms.
Most of the lectins suitable for the detection
of cyanobacteria-associated EPS glycoconjugates
bind also to the cloud-like or sheet-like structures
(Fig. 11b, d, g). One possible explanation is that
these flat sheets have their origin at the end of
filamentous cyanobacterial cells forming exten-
ded 3-dimensional structures. Alternatively, the for-
mation of these sheet-like structures may be the
result of sloughing and release of EPS produced

by cyanobacteria due to their mobility. Another
possibility is that the activity of potential grazers
like protozoa or nematodes could have an influence
on the spatial arrangement of these extended sheet-
like structures. Some lectins bound to cloud-like
structures but also to diatom-associated EPS glyco-
conjugates. Diatoms formed during winter and early
spring time a substantial part of the photosynthetic
active community, but were quantitatively of
lower importance during the rest of the seasonal suc-
cession. Stalk-like EPS structures similar to those