Photosynthetic metabolism in the cyanophytaOscillatoria rubescens D.C.

Short term¹⁴C labelling experiments and enzymatic activities related to primary pathways of photosynthesis have been studied in the cyanophytaOscillatoria rubescens D.C. from axenic cyclostat cultures. Responses of samples from cultures with different amounts of nitrogen are presented and compared. Variations in photosynthetic pigments are used to quantify the degree of nitrogen starvation at different levels.PEPcarboxylase activity remains low and is not affected by nitrogen starvation. RuBPcarboxylase activity is lowered to nearly two thirds of its normal metabolic rate by starvation but PEPcarboxykinase and aspartate aminotransferase activities are significantly higher in this case. Malate dehydrogenase is slightly altered and malic enzyme is never active. Starved algae replaced in fresh complete media fix rapidly¹⁴C in nitrogen compounds such as amino acids. Results are discussed in regard to both physiological and ecological characteristics ofO. rubescens. PEPcarboxykinase can play a role in making efficient use of HCO ₃ ^- .Abbreviations AAT aspartate aminotransferase - APC allophycocyanin - ASM 1 algal synthetic medium, 1st modification - DW dry weight - GAPDH glyceraldehyde 3-phosphate dehydrogenase - MDH malate dehydrogenase - PC phycocyanin - PE phycoerythrin - PEP phophoenolpyruvate - PEPC phosphoenolpyruvate carboxylase - PEPCK phophoenolpyruvate carboxykinase - PGA 3-phosphoglyceric acid - RuBPC ribulose bisphosphate carboxylase     

DEPRESSION OF MASTIGOCLADUS LAMINOSUS (CYANOPHYTA) NITROGENASE ACTIVITY UNDER NORMAL SUNLIGHT INTENSITIES1

The effect of light intensity (PAR) on the nitrogenase activity of Mastigocladus laminosus Cohn was studied by the acetylene reduction technique. Benthic mat from a thermal stream, Hot River, in Yellowstone National Park was used in both experimental and in situ incubations. This hot spring maintained a mean pH of 7.0, was essentially isothermal (ca. 50°C), and had virtually no upstream to downstream physicochemical gradients (P > 0.05). Two surveys of the stream showed that nitrogenase of the M. laminosus mat was significantly more active (P > 0.02) under low light intensities than under high intensities, 252 and 712 μE · m^?2· s^?1, respectively. Maximum activity of Hot River Mastigocladus (268 nmol C₂H₄· mg Chl a^?1· h^?1) occurred at 50% full midday light intensities; the rates at low light (mean = 247 nmol C₂H₄· mg Chl a^?1· h^?1) were significantly (P > 0.001) greater than those at high light (mean = 106). The results indicate that M. laminosus nitrogenase activity is low light adapted and suggest that the temporal pattern for nitrogen fixation might be significantly different from that of thermophilic Calothrix.     

NEW ENDOLITHIC CYANOPHYTES FROM THE NORTH ATLANTIC OCEAN. III. HYELLA PYXIS LUKAS & HOFFMAN SP. NOV.1

A new species of marine endolithic cyanophyte, Hyella pyxis Lukas and Hoffman (Order: Pleurocapsales), differs from other species of Hyella in its cell and filament dimensions, the manner in which its branches are initiated and the presence of gloeocapsin in the sheaths of colonies from the intertidal zone. Hyella pyxis colonies consist of a small cluster of coccoid cells located at the substrate surface and long, conspicuously branched filaments composed of cells that are longer than they are wide. Branches are initiated by the reorientation of the distal end of a filament cell or by the elongation of a filament cell, usually at one of its distal corners. Chromatic adaptation was not observed perhaps accounting for the relatively shallow depth limit of this species. Hyella pyxis was found within mollusk shells from the continental margin of eastern Florida to a depth of 50 m and carbonate rocks in the intertidal zone on Bermuda.     

中国吉林蓝藻门3新种

1　高山真枝藻　新种　图1Ｓｔｉｇｏｎｅｍａａｌｐｉｎｕｍ　Ｈ.Ｘ.Ｘｉａｏ,ｓｐ.ｎｏｖ.Ｆｉｇ.1ＳｐｅｃｉｅｓｎｏｖａｈａｂｉｔｕｓｉｍｉｌｌｉｍａＳ.ｎａｎｘｉｏｎｇｅｎｓｉＷ.Ｊ.Ｚｈｕ,ａｑｕｏｆｉｌｉｓ18～19μｍｃｒａｓｓｉｓ,ｖａｇｉｎｉｓａｄａｐｉｃｅｓｒａｍｕｌｏｒｕｍｆｕｌｖｉｓ,ｈｏｒｍｏｇｏｎｉｉｓｍａｊｏｒｉｂｕｓａｄａｐｉｃｅｓｒａｍｕｌｏｒｕｍｅｔａｄｌａｔｅｒｅｓｒａｍｕｌｏｒｕｍｐｏｓｉｔｉｓｄｉｆｆｅｒｔ.Ｔｈａｌｌｕｓｐｕｌｖｉｎａｔｕｓ,ｇｅｌａｔｉｎｏｓｕｓ,ｎｉｇｅｒ…     

Taxonomic notes on water bloom forming Microcystis species (Cyanophyta) from China—An example from samples of the Dianchi Lake

Ten common species of Microcystis, based on the examination of water samples from the Dianchi Lake, Yunnan, China, were morphologically described, and their taxonomy was also discussed. They are Microcystis aeruginosa, M. botrys, M. firma, M. flos-aquae, M. ichthyoblabe, M. novacekii, M. pseudofilamentosa, M. smithii, M. viridis and M. wesenbergii. Taxonomic status of other Microcystis species reported in China was also evaluated. Key words Cyanophyta, Microcystis, morphology, taxonomy, China.     

吉林省蓝藻门两新种

报道了采自吉林省的蓝藻门2个新种：具翼单歧藻Tolypothrix alata,脆弱真枝藻Stigonema fragile。     

Carotenoids of Anacystis nidulans,structures of caloxanthin and nostoxanthin

Reinvestigation of the carotenoids of Anacystis nidulans has confirmed the occurrence of β,β-carotene (β-carotene), β,β-caroten-3-ol (cryptoxanthin), β,β-carotene-3,3′-diol (zeaxanthin) and 2R,3R,3′R-β,β-carotene-2,3,3′-triol (absolute configuration assigned in the present work). In addition the previously unknown 2R,3R,2′R,3′R-β,β-carotene-2,3,2′,3′-tetrol has been isolated. The triol and the tetrol are considered identical with caloxanthin and nostoxanthin, respectively, for which allenic structures have been suggested by others. The chirality of these compounds followed from CD and ¹H NMR considerations.     

A Light and Electron Microscopic Study of Anabaena volzii Lemm

Anabaena volzii Lemm. is a rare species of Cyanophyta. It possesses characteristics of prokary0tes. Young filaments of A. volzii consist of only vegetative cells. The filament leng- thens by the increase of its cell number owing to amitosis. A mature filament contains vegetative cells, heterocysts and akinetes; the latter two differentiate from the vegetative cells. Vegetative cells and heterocysts are short-cylindric shaped. An akinete in longitudinal sections of appear to be elliptical. Viewed with a transmission electron microscope, an electron-dense cell wall, plasmolemma, thylakoids (photosynthetic lamellae), nucleo-plasmic region and polyhedral bodies can be seen in the vegetative cell. The nucleo-plasmic region, which lacks a nuclear envelope, is surrounded or dissected, but often connected with the thylakoids. There are also some extremely electron-dense (if samples were post-fixed in osmic acid) cyanophycin granules in its cytoplasm. Heterocyst is larger than vegetative cells. Its remarkable features are a thick envelope, an electron-transparent cell wall and a distinctive plug-like body at both ends of the cell respectively. In the plug-like body is seen an irregular narrow channel. Somewhat dilated thylakoids in the heterocyst appear to be more winding and contorted (than those in vegetative cells), making a dedicate pattern. A long ellipticring-shaped membrane structure is formed in a heterocyst ,composed, of an electron-dense rod core surrounded by 14 concentric layers of lamellae. Akinete forms thick cell wall. A nucleo-plasmic region, fine and contorted thylakoids, many cyanophycin granules, and abundant ribosomes are found in akinetes.     

NOTE. NEW EUENDOLITHIC CYANOBACTERIA FROM THE BAHAMA BANK AND THE ARABIAN GULF: HYELLA RACEMUS SP. NOV.1

A new species of endolithic cyanobacteria, Hyella racemus sp. nov. (order Pleurocapsales), penetrates ooid grains in actively shoaling sands in shallow (0.5–5 m) waters of the Bahama carbonate platform and the Arabian Gulf. Hyella racemus is characterized by prolific branching, resulting in dense grape-like cell clusters that penetrate the carbonate substrate. The clusters radiate inward and form deep, isodiametric pits. Resin casts of these pits are framboid (raspberry-like) in shape. The borehole morphology conforms with the shape of the endolith body and can be identified in resin-cast preparations. Cell division is by cleavage with regular alternation of division planes. The sheath is tight, layered, and colorless or yellow-brown when under strong illumination. The new species is one of the most common endoliths in ooids of the Bahamas and the Arabian Gulf It differs from other members of this endolithic genus by its branching pattern and less prominent apical cells.     

VOLATILE ORGANIC SULFIDES FROM FRESHWATER ALGAE1

Dimethyl sulfide (DMS) was found to be the principle biogenic sulfur compound in a freshwater environment. Endemic and non-endemic algae were cultured under axenic and nonaxenic conditions in defined media. Sulfur gas analysis of culture fluids indicated that members of the Cyanophyta were probable sources of DMS whereas representatives of the divisions Chlorophyta, Xanthophyta and Bacillariophyta apparently did not produce this compound. Comparison of gaseous contents of young and old nonaxenic cultures of filamentous algae in the divisions Chlorophyta and Xanthophyta showed DMS occurred only in aged cultures and was probably produced by bacteria utilizing substances from senescent algal cells. Data suggest that the composition of the algal community determines whether DMS is algal and/or bacterial in origin.