RESUMEN
Four clones of the marine, unicellular, cyanobacteria Synechococcus spp., were examined for the spectral and biochemical features of their phycoerythrins (PE) and their photosynthetic characteristics. Two spectral types of PE which are distinct from known PEs were found. One PE type possessed absorption maxima at 500 and 545 nm and a fluorescence emission at 560 nm. Upon denaturation in acid-urea, two chromophore absorption maxima were obtained, one corresponding to phycourobilin (A(max) 500 nm) and one at 558 nm, ascribed to a phycoerythrobilin-like chromophore. The ratio of phycoerythrobilin-like to phycourobilin chromophores was 4.9:1.3. This PE possessed two subunits of M(r)s of 17.0 and 19.5 kD for the alpha and beta subunits, respectively. The other PE possessed a single symmetrical absorption at 551 nm and a fluorescence emission at 570 nm. This phycobiliprotein showed a single chromophore absorption band (A(max) 558 nm) and yielded two polypeptides, an alpha of 17.5 kD and a beta subunit of 20.8 kD. Both PEs showed a (alpha, beta)(n) structure. The presence of phycoerythrobilin-like chromophores (A(max) 558 nm) appears to be diagnostic of this marine cyanobacterial group. The features of these PEs combined with additional biochemical data, suggest a possible evolutionary link between the PE-containing marine Synechococcus group and the red algal chloroplast. When the Synechococcus clones were grown under low light intensity the PE-containing clones showed higher photosynthetic performance, larger photosynthetic units sizes, reaction center I to II ratios near unity, and steeper initial slopes of photosynthesis versus irradiance curves than a non-PE-containing clone. These findings demonstrate the high photosynthetic efficiency of PE-containing clones in low light environments common to middepth neritic and oceanic habitats.
RESUMEN
Twenty-one species (23 isolates) of marine diatoms were examined for their capacity to utilize analogs of cyanocobalamin for growth at the ecologically significant concentration of 4 ng 1-(1) . Yields due to the analogs were compared to those produced by B12 . Responses of the various clones to the analogs were not all-or-none, but varied continuously; thus, assigning the clones to the conventional B12 specificity types is a convenient but arbitrary classification. The use of 10 and 1% levels of response is suggested for such classification. At the 10% level of response, 11 clones had coliform, 4 lactobacillus, and 8 mammalian specificity patterns. At the 1% response level, 14 had coliform, 5 lactobacillus, and 4 mammalian specificities. All clones exceed the 10% response level on all benzimi-dazole-containine analogs tested. Few clones showed definite enough patterns of response to make them potentially useful for differential bioassay. The clones suggested are clone 675-D (Bidclulphia sp.?), clone F(;) -3 (Fragilaria sp.?), and the estuarine clone of Cyclotella nana (3H).
RESUMEN
Melosira nummuloides, clone Mel-3, shows a very high specificity with regard to its ability to take up organic substrates. Amino acids supplied in the medium at 1 X 10(-4) M are taken up at initial rates of the same order of magnitude as that of photoassirnilation of COj. However, sugars, sugar alcohols, or organic acids supplied at the same concentration are not taken up. The mechanism for uptake of amino acids appears to require energy, since tlie uptake of the amino acid analog α-aminoisobutyric acid is strongly inhibited by 2 f-dinitrophenul. The uptake mechanism does not appear to be inducible. The ability of M. numinuloides to utilize amino acids as a nitrogen source is quite restricted. Arginine, ghttamine, asparagine, proline, and glutamic acid were good nitrogen sources. Seventeen other amino acids, including α-aminoisobutyric acid, were unsatisfactory for growth, although they were rapidly taken up from the medium.
RESUMEN
By means of a medium containing dextran, nuclei were isolated in high yield from cells of Gymnodinium nelsoni, a marine dinoflagellate. Most of the DNA, but less than onetenth of the RNA, of the original cells was recovered in the purified nuclei. The nuclei appeared substantially intact as observed by light or electron microscopy. The isolated nuclei were capable of incorporating tritiated uridine triphosphate into material insoluble in cold acid. The general procedure was found to be applicable also to two species of diatoms.