Ceramium species, like most red algae, contain the pigments chlorophyll a, phycocyanin, and phycoerythrin to capture sunlight. Phycocyanin and phycoerythrin are water-soluble phycobilin proteins that absorb strongly in the green, yellow, and orange light ranges. Chlorophyll a absorbs strongly in the red and blue-violet wavelengths. In addition, some intertidal Ceramium species have high concentrations of carotenoids, photoprotective pigments that prevent tissue damage during bright sunlight.
Early photosynthetic pigment separation experiments in the 1920s by Arne Tiselius used an Atlantic species, Ceramium rubrum, for pigment extraction. C. rubrum was used as the study species because it was abundant off the coast of Sweden where Tiselius was living, and because it contains large quantities of phycocyanin and phycoerythrin that he was studying.
M. Ikawa et al. (1973) investigated various algae to determine the if any of them had antibiotic properties. Out of the 21 algae species they tested, Ceramium rubrum had the highest inhibitory response towards growth of the bacteria Bacillus subtilis. They found that this was due to an extremely high amount of free sulfur crystals contained in C. rubrum cells. Free sulfur is well-known to be inhibitory to Gram-positive bacteria (which B. subtilis is). When Gram-negative bacteria were tested with C. rubrum, there was no inhibitory effect. Other species of Ceramium were not tested.
This high level of reduced sulfur in C. rubrum cells could
be hugely important in protecting the alga from harmful biotic inteaction.
Bacterial diseases borne by Gram-positive bacteria will have a much
harder time attacking C. rubrum. In addition, the sulfur might
have some sort of anti-herbivory effect, in addition to an antibiotic
© 2005 Lynn Asbeck