Photosynthetic organisms prokaryotic

Genes encoding glucose transporters have recently been cloned from three photosynthetic organisms, the prokaryotic cyanobacterium Synechocystis [208,209], the... 

Fig. 2. An evolution diagram illustrating a suggestion of common ancestry of some present-day organisms. The essential features of present-day photosynthesis may have originated in the prebiotic era and is preserved in its most primitive form in (at least some) present-day phototrophs. The heterotrophs may have developed parallel with the aerobic nonphotosynthetic bacteria, some l to 1.5 x 109 years after the emergence of the cyanobacteria. The eukaryotic photosynthetic organisms developed much later, perhaps some 1.5 to 0.5 x 109 years ago. The archaebacteria are primitive organisms that seem to have no evolutionary relation with the present prokaryotes.21 Little is known about their energy metabolism. Tentatively, they are considered as a very early form of cellular life.

Algae are members of the plant kingdom and contain chloroplasts similar to those of higher plants, but prokaryotic photosynthetic organisms do not have chloroplasts. In prokaryotes, the photochemical reactions occur in the plasma membrane, which has extensive invaginations resembling the cristae of the mitochondrial inner membrane (fig. 15.3). Table 15.1 summarizes the main distinctions between the various types of photosynthetic organisms. 

Blue-green algae (= cyanobacteria) are prokaryotes which are responsible for the production of metabolites with antiviral, fungicidal and cytotoxic activities [40, 41]. These photosynthetic organisms are frequently found living within host invertebrates, most notably the sponges. Aspects of the chemistry of such associations will be discussed in subsequent sections... 

We include in this term all of the photosynthetic organisms, which are prokaryotes such as Cyanobacteria or... 

Until recently, phytochromes were thought to be restricted to photosynthetic organisms. -" However, recent studies based on DNA sequencing databases uncovered many phytochrome-like genes in prokaryotic organisms, such as Synechocystis, Bradyrhizobium, and Ddnicoccus. Protein sequence comparison shows that the chromophore bearing N-terminal domains are conserved in all known phytochromes. 

Even in prokaryotes, many species contain a complex internal membrane structure. This is especially true in photosynthetic organisms such as purple non-sulphur bacteria and cyanobacteria (Figure 6.1). Moreover, in some organisms membrane (or organelle) formation can be induced (Table 6.1) - thus providing a convenient experimental system from which to isolate membranes and in which to study membrane biogenesis. 

Ascidians play host to a range of organisms. These relationships may be commensal, symbiotic, or parasitic. Symbiotic relationships which involve exchange of metabolic products between the host and guest probably have the greatest influence on secondary metabolism and chemical ecology. Photosynthetic symbionts are the most common and consequential of these guests. Two unicellular symbionts frequently reported are the prokaryotes Synechocystis and Prochloron.13(1 Ascidians pass symbionts to their larvae, and neither have been cultivated independently of one another. 

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