Ultrastructural Localization of Phycocyanin in the Acidophilic, Thermophilic Alga, Cyanidium Caldarium

Abstract

Although the general ultrastructure of Cyanidium caldarium, an acidophilic, thermophilic alga of questionable taxonomic rank, has been extensively studied (see review of literature in reference 1), some peculiar ultrastructural features of the chloroplast of this alga have not been noted by other investigators.Cells were collected and prepared for thin sections at the Yellowstone National Park and were also grown in laboratory cultures (45-52°C; pH 2-5). Fixation (glutaraldehyde-osmium), dehydration (ethanol), and embedding (Epon 812) were accomplished by standard methods. Replicas of frozenfracture d- etched cells were obtained in a Balzers apparatus. In addition, cells were examined after disruption in a French Press.

Thermophilic Microorganisms and Life at High Temperatures

“…Autotrophically grown cells possess much more extensive chloroplast development, and under many conditions virtually the whole cell may be filled with chloroplast (Figure 9.3). As noted by Edwards and Mainwaring (1973), the chloroplast contains nearly parallel, concentric, nonstacked thylakoids, and on the outer faces of both thylakoid membranes there are rows of phycobilisomes. The phycobilisomes of Cyanidium are similar to those of other algae where phycocyanin is present .…”

“…The relationship with the Rhodophyta seems the strongest, especially since there are already well-established unicellular red algae (e.g., Porphyridium, Phragmonema). There is also some support for this idea from immunodiffusion studies on glucose phosphorylase (Fredrick, 1976) and from ultra-Structural studies (Edwards and Mainwaring, 1973), although ultrastructural studies can also support the case that the chloroplast of Cyanidium may have originated from an endosymbiosis between a procaryotic bluegreen alga and a nonphotosynthetic eucaryotic organism (Edwards and Mainwaring, 1973).…”

“…In later work, Seckbach (1972) and Edwards and Mainwaring (1973) carried out electron microscopic studies on autotrophically grown Cyanidium. Autotrophically grown cells possess much more extensive chloroplast development, and under many conditions virtually the whole cell may be filled with chloroplast (Figure 9.3).…”

“…The phycobilisomes of Cyanidium are similar to those of other algae where phycocyanin is present . Edwards and Mainwaring (1973) between the Cyanidium chloroplast and certain unicellular blue-green algae in the manner in which the phycobilisomes associated with the chloroplast thylakoid membrane. Staehelin (1968) has studied the ultrastructure of the membrane and cell wall of Cyanidium by the freeze-etching technique.…”