Identification of chlorophyll b in extracts of prokaryotic algae by fluorescence spectroscopy.

Abstract

Solvent extracts of three different prokaryotic algae from three species of didemnid ascidians contained pigments identified, on the basis of their fluorescence excitation (E) and fluorescence emission (F) spectral maxima (measured in nm) at 77 K, as chlorophyll a (E 449, F 678) and chlorophyll b (E 478, F 658). The release of algae on cutting or freezing Diplosoma virens was accompanied by a strong unidentified acid that converted these pigments to pheophytins. This unexpected finding provided further confirmation of the identity of the chlorophylls on the basis of the fluorescence spectra at 77 K of pheophytin a (E 415, F 669) and pheophytin b (E 439, F 655). There was no evidence for the presence of the fluorescent bilin pigments found in other prokaryotic blue-green algae. Chlorophyll a/b ratios ranged from 2.6 to 12.0 in algae from different ascidians. The photosynthetic membranes were not organized into appressed thylakoids or grana in the algae from any of the three species of ascidians. The relationship between these observations and those in higher eukaryotic organisms is discussed.Several species of colonial ascidians in the family Didemnidae (Phylum Chordata, Subphylum Urochordata) from the Great Barrier Reef of northeastern Australia harbor bright green, unicellular algae in their cloacal cavities. Earlier studies of these algae showed that they are prokaryotic, with an ultrastructure resembling that of blue-green algae, but that they apparently lack the phycobilin pigments and the phycobilosomes characteristic of the blue-green algae (1). Similar prokaryotic algae have been reported growing on the surface of an unidentified didemnid ascidian from Baja California, and the presence of chlorophylls a and b in these algae was provisionally established on the basis of chromatography and room temperature absorbance spectra (2,3 (Hartmeyer), Trididemnum Cyclops (Michaelsen), and juvenile colonies of Didemnum ternatanum (Gottschaldt) were collected at low tide from coral rocks immediately behind the reef front. Larger, older colonies of D. ternatanum were found attached to branches of staghorn coral in deeper water along the front edge of the reef. The specimens collected in July were identified at the Heron Island Research Station laboratory by Patricia Kott Mather. Samples were embedded as previously described (4) for later electron microscopic study.Differences were noted in the ease with which the algae are removed from their ascidian hosts. Those from Diplosona mrens were released readily by applying pressure to the ascidian colony after it had been cut in two. The algae from this ascidian were either expressed into cold, filtered sea water, or into cold 0.1 M Tris.HCl buffer at pH 8.3, and then sedimented by centrifugation. Algae were much more difficult to extract from the other two ascidians, and consequently were isolated in relatively small quantities from these species. In Didemnum ternatanum their release is accompanied by the breakage of many of the algal cells and by embedment of the ...

Supramolecular structure of stacked and unstacked regions of the photosynthetic membranes of Prochloron sp., a prokaryote

“…Our electron micrographs of thin sections closely resemble those published previously (4)(5)(6)8 lc) and in freeze-fracture replicas (Fig. id).…”

“…Although previous studies have led to some controversi about the organization of the photosynthetic membranes in Prochloron (4)(5)(6)8), virtually all of the published results support the following conclusions: The photosynthetic lamellae are typical closed thylakoids. As in the cyanobacteria, the thylakoids are the only observable membrane system in the cytoplasm and they are not enclosed by an envelope membrane.…”

“…The similarity of the architecture of the thylakoids of Prochloron to that of green algal and plant chloroplasts also provides additional evidence of an evolutionary relationship between Prochioron and the chloroplasts of green plants. Prochloron, a unicellular photosynthetic prokaryote, is found in association with didemnid ascidians in marine environments (1)(2)(3)(4)(5)(6)(7)(8). Members of the genus Prochloron and the cyanobacteria are prokaryotes that carry out photosynthesis in a manner similar to that of eukaryotic plants.…”

Chemical properties of the test of ascidians in relation to predation

“…Intercellular acidity of ascidian tests has been observed in connection with investigations on Prochloron symbionts in the family Didemnidae which are either embedded in the test, or contained in the common cloacal cavity or loosely associated on the surface (Thinh and Griffiths, 1977;Thorne et al, 1977). All symbionts, but especially those embedded in the test, would be subjected to a low pH if reports of intercellular acidity in the ascidian test are accurate.…”

Revisiting chlorophyll extraction methods in biological soil crusts – methodology for determination of chlorophyll a and chlorophyll a + b as compared to previous methods

“…Unfortunately, the Chl a /Chl b ratio in algae, chlorolichens (photobiont: green algae), and bryophytes (i.e. liverworts and mosses) is variable, thus not facilitating the proportional quantification of both 20 groups; nevertheless, it allows tentative estimates on the relevance of eukaryotic Chl b -comprising partners (Thorne et al, 1977).…”