18S rRNA genes (SSU rDNA) of five newly sequenced species were used as molecular markers to infer phylogenetic relationships within the euglenoids. Two members of the order Euglenales ( Lepocinclis ovata Playfair , Phacus similis Christen), two of the order Eutreptiales ( Distigma proteus Ehrenberg , D. curvata Pringsheim) and Gyropaigne lefévrei Bourelly et Georges of the order Rhabdomonadales were used in parsimony, maximum likelihood, and distance analyses. All trees derived from SSU rRNA data strongly supported the monophyletic origin of the Euglenozoa, with kinetoplastids as sister clade to the euglenoids and Petalomonas cantuscygni Cann et Pennick diverging at the base of the monophyletic euglenoid lineage. The data also supported the theory that phagotrophic euglenoids arose prior to osmotrophs and phototrophs. A lineage of Peranema trichophorum Ehrenberg and all sequenced Euglenales formed a sister clade to the osmotrophs. This suggests that the evolution of phototrophy within the euglenoids radiated from a single event.

In order to reconstruct the evolution of euglenid flagellates, euglenozoan SSU rDNA data have been used to investigate phylogenetic relationships with a focus on osmotrophic taxa and especially on the Rhabdomonadales. The dataset consisting of the SSU rDNAs of osmotrophic, phagotrophic and phototrophic taxa was used in parsimony, maximum-likelihood and distance analyses. Five genera make up the Rhabdomonadales, all of them osmotrophic : Gyropaigne, Menoidium, Parmidium, Rhabdomonas and Rhabdospira. According to our analyses they form a strongly supported monophyletic assemblage which is characterized by a low sequence divergence compared to the euglenids in general. Closest relatives are the members of the osmotrophic genus Distigma. All primary osmotrophic species constitute a larger monophyletic group with the phototrophic euglenids and the phagotroph Peranema trichophorum. The combination of three rhabdomonadalian species Rhabdomonas gibba, Rhabdomonas spiralis and Rhabdospira spiralis with nearly identical SSU rDNA sequences is strongly recommended. The phagotroph Petalomonas cantuscygni branches at the bottom of the euglenid subtree with significantly weaker support. The inter-relationship of the three distinct euglenozoan taxa (euglenids, kinetoplastids and diplonemids) could not be convincingly resolved by this study.

L-Arginine C atabolism , Cyanophycin, U ltrastru ctu ral Analysis U ltrastru ctural and im m unocytochem ical investigations gave evidence th at cyanophycin (m ulti-L-arginyl-poly-L-aspartate) granules accum ulate in the cy anobacterium Synechocystis sp. strain PCC 6803 under n u trien t deficient grow th conditions, especially u n d e r phosphate lim itation. Besides nu trient deficiency, grow th o f Synechocystis PC C 6803 on L-arginine or lasparagine as sole N -source also led to high increase of cyanophycin synthesis, while grow th on the com bination of L-arginine or L-asparagine w ith nitrate only caused m inor cyanophycin accum ulation. G row th of Synechocystis PC C 6803 on L-arginine as sole N -source caused substantial m orphological and physiological changes, such as severe thylakoid m em brane degradation with partial loss of pigm ents and photo sy nth etic activity leading to a phenotype alm ost like th at seen under n u trien t deficiency. In con trast to the wild type, th e PsbO -free Synechocystis PC C 6803 m utant could grow on L-arginine as sole N -source w ith only m inor m orphological and physiological changes. D ue to its fairly balanced grow th, the m u tan t accu m ulated only few cyanophycin granules. L-arginine degrading activity (m easured as ornithine and am m onium form ation) was high in the P sbO -free m u tan t b u t n o t in the wild type when cells w ere grown on L-arginine as sole N -source. In b oth cells types the L-arginine degrading activity was high (although in the P sbO -free m u ta n t abo u t twice as high as in wild type), w hen cells were grown on L-arginine in co m bination with nitrate, and as ex p ected very low w hen cells were grown on n itrate as sole N -source. Thus, n et cyanophycin accum ulation in Synechocystis PCC 6803 is reg u lated by the relative co n cen tratio n o f L-arginine to the total nitrogen pool, and the intracellular L-arginine concen tratio n is greatly influenced by the activity of the L-arginine degrading enzym e system which in p a rt is reg u lated by the activity status of photosystem II. These results suggest a com plex in terre latio n b etw een cyanophycin synthesis, L-arginine catabolism , and in addition photosynthesis in Synechocystis PC C 6803.

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The aim of this study was to isolate and characterize the paramylon synthesizing enzyme from Euglena gracilis Klebs. A method for enzyme solubilization with high synthase activity using the zwitterionic detergent 3‐[(3‐cholamidopropyl)‐dimethylammonio]‐1‐propane sulfonate is presented. Fractionated purification showed that the main enzyme activity was associated with the paramylon granula fraction, isolated from heterotrophically grown cells of E. gracilis. Further purification by sucrose density centrifugation resulted in a large enzyme complex with an apparent molar mass of 670 kDa (native). The complex remained active throughout the isolation procedures and produced beta‐1,3‐glucan in vitro. Two polypeptides of 37 and 54 kDa could be identified by photoaffinity labeling with [32P]‐UDP‐glucose as substrate after SDS‐PAGE.