CARBOXYSOME CONTENT OF SYNECHOCOCCUS LEOPOLIENSIS (CYANOPHYTA) IN RESPONSE TO INORGANIC CARBON1

The carboxysome content of chemostat grown Synechococcus leopoliensis (Racib.) Komarek increases under inorganic carbon limitation. At growth rates of ca. 85%μ_max the carboxysome content (±SE) was 0.57 ± 0.09 carboxysomes·cell section^?1. Under severe carbon limitation (ca. 13%μ_max) this increased to 3.4 · 0.3 carboxysomes·cell section^?1. Corresponding to this change is a three order of magnitude decrease in the half-saturation constant of photosynthesis for dissolved inorganic carbon. Nitrogen and phosphorus limitation had no effect on carboxysome content or the kinetics of photosynthesis with respect to inorganic carbon. These results are discussed in light of the apparent lack of photorespiration in these organisms.     

OSCILLATORIA (TRICHODESMIUM) THIEBAUTII (CYANOPHYTA) IN THE CENTRAL NORTH ATLANTIC OCEAN12

Physiological rate measurements were made with Oscillatoria thiebautii (Gom.) Geitler in the subtropical north Atlantic Ocean between Spain and Bermuda during May and June of 1975. The near surface C:N fixation ratios averaged 6.5, and the cellular composition ratio was 6.2, suggesting that N₂ fixation is the major path of nitrogenous nutrition for this alga. Compared to other oceanic phytoplankters, it has a low affinity for orthophosphate at oceanic concentrations (k_s= 9.0); however, it has a high potential for utilizing phosphomonoesters (170–300 ng atoms P ·μg chl a^?1· h^?1). Maximal photosynthesis occurred at 450–700 μ Einstein · m^?2· s^?1, and was inhibited by full sunlight. Calculated cell division rates (ca. 180 days) suggest that relative to other phytoplankters in this oceanic region, O. thiebautii must be subjected to negligible grazing pressure. No major differences in C, N, chl a or ATP were observed between the tuft (fusiform) and puff (spherical) colonies. ATP concentrations relative to other cellular constituents varied greatly between colonies, suggesting a general inter-colony physiological variability in the open Atlantic. With increasing depth in the euphotic zone, there was no evidence for chromatic adaption. The observations that O. thiebautii represents only a small fraction of total phytoplankton biomass and that its growth rate is 10–100 times slower than that of the other indigenous phytoplankton, strongly suggest that N₂ fixation by this alga is a virtually insignificant component of the nitrogenous nutrition for the phytoplankton of the North Atlantic central gyre in late Spring.     

SIMAZINE-INDUCED INHIBITION IN PHOTOACCLIMATED POPULATIONS OF ANABAENA CIRCINALIS (CYANOPHYTA)1

The effects of the triazine herbicide, simazine, on photosynthetic oxygen evolution and growth rate in photoacclimated populations of Anabaena circinalis Rabenhorst were investigated. Chemostat populations were acclimated to photon flux densities (PFDs) of 50, 130, and 230 μmol·m^?2·s^?1 of photosynthetic active radiation (PAR), Decreases in chlorophyll a (Chl a). c-phycocyanin (CPC), and total carotenoid (TCar) contents and CPC: Chl a and CPC: TCar ratios of populations coincided with increasing PFD, Polynomial regression models that characterize inhibition of photosynthesis for populations acclimated to 50 and 130 μmol photons·m^?2·s^?1 PAR were distinct from the model for populations acclimated to 230 μmol photons·m^?2·s^?1 PAR. Simazine concentrations that, depressed oxygen evolution 50% compared to controls decreased with increasing PFD. Increases and decreases in both biomass and growth rate coincided with increasing PFD and simazine concentration, respectively. Simazine concentrations that depressed growth rate 50% compared to controls increased with decreasing PFD. The differences in photosynthetic and growth inhibition among photoacclimated populations indicate that sensitivity to photosystem II inhibitors is affected by alterations in pigment contents.     

PHOTOREGULATION OF PHYCOBILISOME STRUCTURE DURING COMPLEMENTARY CHROMATIC ADAPTATION IN THE MARINE CYANOPHYTE PHORMIDIUM SP. C861

Changes in the molecular structure of phycobilisomes during complementary chromatic adaptation were studied in the marine cyanophyte Phormidium sp. C86. This strain forms phycoerythrin (PE)-less phycobilisomes under red light but synthesizes PE-rich phycobilisomes under green light. Analysis of phycobiliprotein composition and electron microscopic examination of phycobilisomes in ultra-thin sections of cells and of isolated phycobilisomes were performed for cells acclimated to red and green light, respectively. The structure of phycobilisomes formed under red light conditions was typically hemidiscoidal. Phycobilisomes in cells acclimated to green light were twice as large in size as those in cells acclimated to red light. This increase in phycobilisome size was a result of the increase in the molar ratio of antenna pigment (PE and phycocyanin) to allophycocyanin, from 3.5 to 11.3. Pigment composition and fine structure of phycobilisomes formed under green light were similar to those of “nonhemidiscoidal” phycobilisomes reported in Phormidium persicinum. These results suggest that changes occur not only in the molecular species of peripheral rods but also in the structure of rods and probably of cores in relation to their connection with rods during chromatic adaptation of Phormidium sp. C86.     

ASSOCIATION OF PLEUROCAPSA AND CALOTHRIX (CYANOPHYTA) IN A THERMAL STREAM1,2

A crustose, nodular mat, primarily composed of Calothrix sp. and Pleurocapsa sp., occurs in some alkaline hot springs of the western United States. Together, these species constituted ca. 71% of the mat biomass; the remainder was partitioned between other cyanophytes and bacteria. Their temperature growth ranges in culture were 24–50 C (Calothrix) and 30–55 C (Pleurocapsa). Both clonal cultures had maximal growth rates at 45 C (Pleurocapsa, 1.28 doublings/24 h; Calothrix 2.30). Calothrix grew at approximately twice the rate of Pleurocapsa throughout their coincidental temperature range. The relative proportions of Calothrix (42%) and Pleurocapsa (27%) were constant in a thick mat (ca. 1 mm) regardless of season; however, a thin mat (ca. 0.5 mm) contained significantly more Pleurocapsa (71%) and less Calothrix (5%). Analysis of 10 μm thick microtome sections showed that Pleurocapsa dominated the innermost region (substrate side) of the nodule mat while Calothrix abundance increased from ca. 3% in this region to 80–96% at the surface of thick mat samples (ca. 0.8–2.3 mm). Our proposed that the grazing pressure exerted by an ostracod population accounts for the continued coexistence of and the observed spatial relationships between these species appears most consistent with the observations.     

吉林省蓝藻门单歧藻属三新种

报道了采自吉林省五女峰的蓝藻门单歧藻属三新种,纤细单岐藻、长枝单岐藻、普通单岐藻。     

吉林省蓝藻门二新种

报道了采自吉林省五女峰的蓝藻门二新种,即:颗粒伪枝藻、绚丽裂须藻。     

Observations on a new species of Symphyonemopsis Tiwari & Mitra,viz. S. Pantii n. sp. (Cyanophyta,Stigonematales)

The paper describes the morphology and reproduction of a new species of Symphyonemopsis viz. S. pantii n. sp. isolated from enrichment cultures of a soil sample collected from the campus of Sangeet Samiti, Allahabad (India). Thalli grow as dark blue-green, small, wooly patches on soil surface but as cushion-like growths on agar plates. It has a prostrate and erect system. The latter bears secondary branches of almost equal breadth. It possesses both false and true branches. Usually true branches are reverse V-shaped. The alga shows formation of hormocysts and akinetes. In old cultures usually the main filament becomes multiseriate. The crescent-shaped stages of hormocysts are also present here. Cells of the present alga are constricted at the cross-walls On comparison it was found to come close to Symphyonemopsis katniensis Tiwari et Mitra but differs in certain fundamental characters. It is, therefore, described as a new species viz. S. pantii n. sp. (Cyanophyta, Stigonematales, Mastigocladaceae).     

Black algae

Many species of cyanophytes, especially those growing on tiles and walls exposed to air and sunlight, appear black due to the presence of pigments in the mucilaginous cell-walls. Such pigments may serve a protective role against adverse effects of ultraviolet light but, overlying the ordinary intracellular blue-green pigments, they make the algal clumps look black. Among the most familiar of such algae are species of Gloeocapsa, which by discolouring pale surfaces of public or private premises can constitute a nuisance responsible for a considerable loss of financial value.     

吉林省蓝藻门三新种

报道了采自吉林省五女峰的蓝藻门3个新种：集安蓝柄藻、紫红柄球藻、扩展真枝藻。