Collapsing Aged Culture of the Cyanobacterium Synechococcus elongatus Produces Compound(s) Toxic to Photosynthetic Organisms
Figure 1
Different fates of aged cultures of the cyanobacterium S. elongatus.
(A) Cultures maintained at stationary phase were characterized by dark blue-green pigmentation up to about 3 months (culture No. 1). Older cultures either rapidly collapsed (culture No. 2), or gradually acquired a yellowish color (culture No. 3) and further survived. Cultures No. 1 and 2 are about 3 months old, whereas culture No. 3 is 6 months old. (B) Conditioned medium (CM) of a collapsing culture induced rapid cell death of exponentially growing cells of S. elongatus in contrast to medium from non-collapsing cultures, which did not affect viability. Cells were inoculated into fresh medium (FM) as a control. 5 µl of undiluted cultures or cultures diluted 1∶100 or 1∶1000 were 'spotted' on solid growth medium, following exposure to the different media (see Methods).
