The amino acid sequences of the cytochromes c553 from Porphyridium cruentum and Aphanizomenon flos-aquae

The amino acid sequences of cytochrome c₅₅₃ from the eukaryotic red alga Porphyridium cruentum and from the prokaryotic cyanobacterium Aphanizomenon flos-aquae have been determined from the tryptic and cyanogen bromide peptides. The results indicate that a charged region of these proteins has evolved with special rapidity to accomodate a rapid evolution of a binding site in the P₇₀₀ electron acceptor complex.     

Notes on the growth and sporulation of a natural population of Aphanizomenon flos-aquae

Aphanizomenon flos-aquae contributed regularly to the summer phytoplankton in Kinnego Bay, a highly eutrophic part of Lough Neagh. Growth of the alga was variable in different years, and was apparently related to the duration of depletion of dissolved nitrate-nitrogen in the water. Although four growth pulses occurred during the study period, sporulation was only observed during one of these, when the population was very dense although evenly distributed down the water column. It seems that Aphanizomenon overwintered in Kinnego Bay as vegetative filaments and that production of akinetes was not necessary for perennation of the species. The observed sporulation in 1973 may have been induced by the high pH values caused by dense phytoplankton crops; no other measured environmental factors were particularly unfavourable to growth of Aphanizomenon at this time.     

SPECIFIC ASSOCIATIONS OF THE BLUEGREEN ALGAE ANABAENA AND APHANIZOMENON WITH BACTERIA IN FRESHWATER BLOOMS1

Scanning electron micrographs and autoradiographs of Anabaena circinalis Rabenh. and Aphanizomenon flos-aquae (L.) Ralfs in samples from fresh-water communities show that bacteria are attached specifically at the polar region of heterocysts of these known N₂ fixers. This algal-bacterial association occurs most frequently during bloom conditions. The possible roles of this association in maintaining nuisance bloom conditions are discussed.     

Studies on marine algae of the British Isles. 8. Cystoseira tamariscifolia (hudson) papenfuss

The fine structure of the zoospores of Urospora penicilliformis (Roth) Aresch. (Chlorophyceae) is described. Of special interest is the flagellar apparatus. The proximal part of each of the 4 flagella is ribbon-shaped and contains nine wings attached to the peripheral double tubules. The flagellar root system originates from the flagellar bases and includes striated fibrous roots, passing close to the nucleus, and cruciate nine-stranded microtubular roots along the four corners of the cell. The Golgi bodies produce numerous vesicles, concentrating apically in the cell; they are presumed to be of importance for the attachment of the zoospore.     

Effects of thermal acclimation and photoacclimation on lipophilic pigments in an invasive and a native cyanobacterium of temperate regions

The freshwater cyanobacterium Cylindrospermopsis raciborskii spreads from tropical to temperate regions worldwide. This entails acclimation to varied light and temperature conditions. We studied the thermal and light acclimation of the photosynthetic machinery of C. raciborskii by monitoring alteration of the chlorophyll a and carotenoid content in German strains of C. raciborskii, in African and Australian strains of C. raciborskii, and in German strains of Aphanizomenon gracile, a native cyanobacterium belonging to the same order (Nostocales). Our results showed that temperate and tropical C. raciborskii strains did not differ in pigment acclimation to light and temperature. In contrast, the ratio of photoprotective carotenoids (namely the carotenoid glycoside 4-hydroxymyxol glycoside [aphanizophyll]) to chlorophyll a increased significantly more in C. raciborskii in comparison with A. gracile (1) with decreasing temperatures from 20 to 10°C and a moderate light intensity of 80?µmol photons m^?2?s^?1 and (2) with increasing light intensities at a suboptimal temperature of 15°C, compared to 20°C. We conclude that below 20°C photoinhibition is avoided by greater photoprotection in the invasive species C. raciborskii compared to the native species A. gracile.     

MONOSPECIFIC AGGREGATIONS OF TWO CYANOPHYTES IN A EUTROPHIC LAKE1

Microcystis incerta Lemmerman, and Lyngbya versicolor (Wartmann) Gomont, formed large monospecific aggregations on the surface of a lake rich in Aphanizomenon flos-awuae (L.) Ralfs. Neither of the two algae in the aggregations was found in the water beneath.     

Importance of interspecific competition in the abundance of Aphanizomenon flos-aquae (Cyanophyceae)

The population dynamics of Aphanizomenon flos-aquae var. klebahnii Elenk. (Cyanophyceae) was studied in an artificial pond for 32 months from May 2002 to December 2004. Our previous in vitro study showed that the lower limits of water temperature and pH for its growth are within the ranges of 11°–14°C and 7.1–7.4, respectively, and it appeared that these findings are applicable to the emergence and disappearance of Ap. flos-aquae in the pond. Based on the change in the water temperature, the emergence of Ap. flos-aquae in 2004 was expected to be in late April, whereas emergence occurred after a 1-month lag period. During this period, Ankistrodesmus falcatus (Corda) Ralfs (Chlorophyceae) dominated the phytoplankton assemblage, which raised the possibility that the growth of Ap. flos-aquae was restricted by the existence of An. falcatus. We conducted mixed cultures of Ap. flos-aquae and An. falcatus at four temperatures (14°, 19°, 24°, and 29°C). After 18 days of incubation, An. falcatus dominated at 14° and 29°C whereas Ap. flos-aquae dominated at 19°C. This result indicates that a slightly higher water temperature than the growth threshold value is needed for Ap. flosaquae to outcompete An. falcatus, which agrees with the field observation. Contrary to the results of the mixed culture, the summer phytoplankton assemblage was dominated by Ap. flos-aquae, and the population of An. falcatus was less or almost absent. This variation seemed to be partly caused by the difference in nutrient conditions; concentrations of dissolved inorganic nitrogen and phosphorus in the pond were far lower than those in the culture medium. The lack of nitrogen fixation of An. falcatus seemed to be a growth disadvantage during the summer when the concentration of dissolved inorganic nitrogen was low.     

The formation and degradation of cyanobacterium Aphanizomenon flos-aquae blooms: the importance of pH, water temperature, and day length

Investigation of annual changes in phytoplankton community structure in a small artificial eutrophic pond was carried out from May 2002 to April 2003. A heavy bloom of Aphanizomenon flos-aquae var. klebahnii Elenk. (Cyanobacteria) persisted in most of the water column from June to the end of October. In November, the A. flos-aquae bloom suddenly crashed and green algae were predominant until the end of spring. Weekly monitoring suggested strong involvement of the changes in abiotic factors in the cyanobacterial bloom degradation. To clarify the effects of pH, water temperature, and day length on the growth of A. flos-aquae, laboratory batch experiments were conducted. The results showed that A. flos-aquae could not grow below pH 7.1 and 11°C, and the growth tended to be suppressed under a 10L:14D photoperiod. pH, water temperature, and day length are vital factors in the growth of A. flos-aquae and, additionally, grazing by cyclopoid copepods also seemed important in bloom collapse.     

Characterization of human monocyte activation by a water soluble preparation of Aphanizomenon flos-aquae.

Aphanizomenon flos-aquae (AFA) is a fresh-water microalgae that is consumed as a nutrient-dense food source and for its health-enhancing properties. The current research characterizes the effect of a water soluble preparation from AFA on human monocyte/macrophage function and compares the effect of AFA with responses from known agents that modulate the immune system. At 0.5 μg/ml the AFA extract robustly activated nuclear factor kappa B (NF-kappa B) directed luciferase expression in THP-1 human monocytic cells to levels at 50% of those achieved by maximal concentrations (10 μg/ml) of bacterial lipopolysaccharide (LPS). In addition, the AFA extract substantially increased mRNA levels of interleukin-1β(IL-1β) and tumor necrosis factor-(TNF-), and enhanced the DNA binding activity of NF-kappa B. The effects of AFA water soluble preparation were similar to the responses displayed by LPS, but clearly different from responses exhibited by tetradecanoyl phorbol acetate (TPA) and interferon-gamma (INF-γ). Pretreatment of THP-1 monocytes with factors known to induce hyporesponsiveness suppressed both AFA-dependent and LPS-dependent activation. These results suggest that the macrophage-activating properties of the AFA water soluble preparation are mediated through pathways that are similar to LPS-dependent activation.