Blue Green Algae

Blue green alga Spirulina platensis was subjected to different concentrations of NaCl, i.e. (0.1, 0.5, 5 and 10g/l) by using 1g/ l (as stock salt) that considered to be the control of the experiments according to their concentration in Zarrouk medium, in order to study the effect of NaCl concentrations on the photosynthesis pigments which are chlorophyll a, chlorophyll b, total chlorophyll, carotenoids, phycocyanin, allophycocyanin and phycobiliproteins. Sodium chloride caused different effects on photosynthetic pigments of the studied algae. In 10g/l NaCl, the maximum reduction of chlorophyll a, chlorophyll b, and total chlorophyll were 2.540, 0.808, and 3.349mg/1, respectively, while maximum reduction of phycocyanin, allophycocynin, and phycobiliproteins were 0.303, 0.232, and 0.535mg/1, respectively. Moreover, carotenoids induced to reach 1.182mg/l in 10g/l NaCl. Rising NaCl concentration up to 5 and 10g/l caused the induction of carotenoids as well as the inhibition of chlorophyll a, chlorophyll b, total chlorophyll, phycocyanin, allophycocyanin and phycobiliproteins and vice versa happen when NaCl concentration decreased to 0.1 and 0.5g/l.

Marine algae have been known and utilized from the ancient era. It is the source of chemical compounds mainly useful as a food for their richness in protein, fatty acids, minerals and vitamins. Physiologically active compounds also have a great potential to play an important role as cosmetic, medicine and as a pharmaceutical aid. In this review, the provided information will play an important role in the medicinal and cosmeceutical production in future.

In this study, the upper infralittoral zone of Antalya (Turkish Mediterranean coasts) was researched. 375 algae and five seagrasses were determined. There are (36 taxon) blue-green algae (Cyanophyceae), (198 taxon) red algae [Rhodellophyceae (1), Compsopogonophyceae (2), Bangıophyceae (5), Florideophyceae (190)], (74 taxon) brown algae (Fucophyceae), (67 taxon) green algae [Chlorophyceae (4), Ulvophyceae (18), Cladophorophyceae (23),Bryopsidophyceae (20), Dasycladophyceae(2)] and (5 taxon) seagrasses (Liliopsida). Bonnemaisonia clavata G. Hamel (Rhodophyceae) was given as new record for the Turkish Marines. Leibleinia epiphytica (Hieronymus) Anagnostidis & Komárek, Microchaete grisea Thuret, Calothrix scopulorum (Weber van Bosse & Mohr) C. Agardh (Cyanophyceae), Gelidiocolax christinae J. Feldman et G. Feldman, Falkenbergia hildenbrandii (Bornet) Falkenberg, Hydrolithon farinosum var. chalicodictyum (W.R. Taylor) Serio, Acrodiscus vidovichii (Meneghini) Zanardini, Ceramium codii (Richards) Feldmnn Mazoyer, Chondria mairei Feldmann Mazoyer, Polysiphonia paniculata Montagne (Rhodophyceae) and Ulva curvata (Kützing) De Toni (Ulvophyceae) were given as new record for the Turkish coasts of Mediterranean.

A field trail was conducted at South Port Said, Egypt, during the two successive summer seasons of 2013 and 2014 to study the physiological response of rice Giza 178 cultivar grown under saline soil conditions to decreasing the mineral nitrogen fertilizer from 145 to 72 or 107 kg N/ha with adding bio-fertilizers i.e. yeast extract, azolla, blue green alga and Rizobium rizobacter. Results indicated that plant height, leaf area index (LAI), crop growth rate (CGR), net assimilation rate (NAR), photosynthetic pigments, dehydrogenase activity (DHA), soluble sugars, antioxidant enzymes [catalase (CAT), polyphenol oxidase (PPO) and peroxidase (POD)], potassium content, panicle length, panicle weight, 1000-grain weight, grain and straw yields were increased when plants received 107 kg N/ha plus spraying yeast extract, followed by adding azolla, then blue green alga and Rizobium rizobacter without significant difference with the treatment of 145 kg N/ha. While, significant increases were recorded in proline, sodium contents, and sodium/potassium ratio in leaves when plants received 72 Kg N/ha with Rizobium rizobacter followed by blue green alga then azolla and finally yeast extract as compared with other treatments.

Sedimentation is a major process for removal of particulate material from the water column and important determinant accounting for the stability of aquatic ecosystems. Gross sedimentation rates (GSR) in Lake Kinneret (Israel), regularly monitored from 1999 up-to-date with sedimentation traps, showed salient temporal and spatial variability. In the lake center, the annual mean GSR ranged from 1.9 to 6.0 g m-2 d-1. The accumulation rate of sediments at the lake centrum during the study averaged from 2.6 to 4.3 mm yr-1, in agreement with values obtained by sediment core dating. Organic matter (OM) content comprised 33-42% of the sinking particulate mater in sediment traps located in the lake centre and was 1.5-2 times lesser in peripheral stations. The highest seasonal values of OM content in traps were associated with collapse of algal blooms. Algae and their debris are the main component of OM and their fate in the water column can be well traced by photosynthetic pigments. Chlorophyte signature pigments display much lower degradability in the water column than those of diatoms and dinoflagellates and leave a relatively persistent residue in the buried sediments. Despite large variation in algal community composition, the ratio of OM sedimentation flux to primary production (i.e., the export ratio) alters only slightly throughout the stratified period. Approximately 20% of the OM supplied to the lake by primary production founds its way to the traps. A large decline of water level in recent years affected the processes of particle resuspension and offshore translocation, which caused prominent site-specific impacts on the sedimentation regime. We argue that changes in sedimentation rates observed in the lake are related to fluctuations of loads from the watershed and prominent water level fluctuations.

In this research, marine algae and seagrasses were investigated in the upper infralittoral zone of Mersin (Turkish Mediterranean coasts). A total of 396 algae and 5 seagrasses were determined. 36 of them belong to blue-green algae (Cyanophyceae), 204 to red algae [Rhodellophyceae (2), Compsopogonophyceae (2), Bangıophyceae (6), Florideophyceae(194)], 82 to brown algae (Fucophyceae), 74 to green algae [Chlorophyceae (7), Ulvophyceae (19), Trentepohlıophyceae (1), Cladophorophyceae (25), Bryopsidophyceae (20), Dasycladophyceae (2)] and 5 to seagrasses (Liliopsida).

In western cultures, certain cyanobacteria have been an accepted source of microalgal biomass for food for about 30 years, in particular Spirulina (Arthrospira) platensis and S. maxima. Beginning in the early 1980s, another species, Aphanizomenon flos-aquae was adopted for similar uses. This is harvested from Upper Klamath Lake, the largest freshwater lake system in Oregon. In 1998 the annual commercial production of Aphanizomenon flos-aquae was about 1 × 10 6 kg. Since this species is not cultured like Spirulina in outdoor ponds or raceways, it requires very different procedures for harvesting and processing. These are reviewed here and include extensive off-lake screens or on-lake barges, which dewater and concentrate the cells. Other procedures, such as those for removal of detritus and mineral materials, and those for monitoring and reducing the amounts of certain contaminant cyanobacteria, which can produce cyanotoxins, have also become important in quality control and marketing.

The aim of this study is to improve root system and adventitious roots formation of date palm cv. Bartamoda plantlets during rooting stage and increasing survival percentage of plantlets during acclimatization stage. The plantlets were cultured on two type of media, 1/2 of Murashge and skoog medim (MS) salts or tap water supplemented with different levels of humic acid (0.0, 5.0, 10.0, 15.0 and 25.0 ml/l). The cultured plantlets were incubated under a 16h photoperiod of 4000 lux light intensity at a temperature of 27± 2 °C. Each treatment consisted of 9 replicates of one plantlet per tube. The measurements were recorded on plantlet height, number of leaves, number of root and root length(cm) after four months from culturing. The results showed that, using tap water as a nutrient medium was more effective than 1/2 MS salts of medium. On the other hand, the humic acid at 15 or 25 ml/l was superior compared with other concentrations. The survival percentage was 75% as the best result when the plantlets were cultured on 15 or 25 ml/l humic acid without significant differences in between.

This study was done to indicate the activity of secondary metabolites of cyanophyta algal extracts for Anabaena azolla which isolate from one of running water system in Hilla city nearby Babylon university campus and development in BG11 medium to study the effective of secondary metabolites in An.azolla extracts (cold water, hot water, acetone and ethanol extracts) to inhibition two species of fungi (Fusarium oxysporum and Penecillium expansum) also used of HPLC and FT-IR analysis to detected some of active secondary metabolites was done only for acetone and ethanol extracts also to preliminary statements that used of four extracts of blue green alga Anabaena azolla. The role of An.azolla extracts to inhibition growth of these fungi was detected through measured diameter and percentage of inhibition zone which was increased with concentrations and the results showed these extracts had high correlation ratio and fungi shows high sensitivity to these extract. The mode of mechanism action to inhibition was on fungi cell wall by inhibition active enzymes, excelled treatment for cold water extract. The most important active compounds had been detected in HPLC and FT-IR were phenolic compounds which consists of (Tannic acid, Gallic acid and Coummarin) and flavonoids compounds consists of (Kaempherol and Quercetin) these all compounds detected specially in acetone extract of An.azolla , also to introductory statements which were detected six of active groups in extracts like (Terpens, glycosides, saponins, alkaloids, phenols and flavonoids) .

The present study was designed to investigate the possible therapeutic effects of Balanites aegyptiaca (Heglig dates), Persea Americana (Avocado fruit) and Aphanizomenon flos-aquae (AFA) water extracts on some biochemical parameters such as ALAT, ASAT, alkaline phosphatase, acid phosphatase, triglycerides, cholesterol, LDL-cholesterol, HDL-cholesterol, total lipids and risk ratio 1&2 in streptozotocin diabetic rats. The results of the current study recorded a significant increase in serum ALAT, ASAT and ALP enzymes activities in diabetic group in comparison with the negative control group. Also a significant increase was observed in serum triglycerides, cholesterol, LDL-cholesterol, total lipids level and risk ratio 1 &2. On contrast, a significant decrease was recorded in serum ACP enzyme activity, HDL-cholesterol level in diabetic group. Rats treated with Balanites aegyptiaca, Persea Americana and AFA alone or mixed together showed an improvement in these parameters.

The phytoplankton species composition and abundance in Ogun River, Ogun state, Southwest Nigeria was studied for a period of seven months (December, 2011 - June, 2012), a total of forty-one genera belonging to five taxonomic groups were recorded from Ogun River. The phytoplankton species composition was surpassed by Chrysophyta with 15 species consisting of 36.6% followed by Chlorophyta with 14 consisting of 34.1%. This was followed by Cyanophyta (7 species) consisting of 17.1%, Euglenophyta with 3 species consisting of 7.3% and Pyrrophyta with 2 species consisting 4.92%. Cyanophyta was the highest in abundance consisting of 41% while the lowest in abundance was Pyrrophyta consisting of 1.5%. The low nature of phytoplankton abundance and diversity observed in this study must have been caused by the polluted nature of the water due to the anthropogenic activities carried out around its shores The dominance of Cyanophyta in this river is similar to findings from Lake Victoria, Lake Bishoftu, Lake Chaohu and the temple pond of Thirupour.

Air-grown Synechococcus R-2 (PCC 7942) cultures grown in BC-11 medium are very alkaline (outside pH is 10.0) and use HC0,-as their inorganic carbon source. The cells showed a dependente on Na+ for photosynthesis, but low Na+ conditions (1 mo1 m-3) were sufficient to support saturating photosynthesis. The intracellular dissolved inorganic carbon in the light was greater than 20 mo1 m-3 in both low-Na+ conditions and in BC-11 medium containing the usual [Na+] (24 mo1 m-,, designated high-Na+ conditions). l h e electrochemical potential for HC0,-in the light was in excess of 25 kJ mol-', even in high-Na+ conditions. The Na+-motive force was greater than -12 kJ mol-' under both Na+ conditions. On thermodynamic grounds, an Na+-driven co-port process would need to have a stoichiometry of 2 or greater (22Na+i,,/HC03-'i,), but we show that Nat or K+ fluxes cannot be linked to HC0,-transport. Na+ and K+ fluxes were unaffected by the presence or absence of dissolved inorganic carbon. In low-Na+ conditions, Na+ fluxes are too low to support the observed net C-carbon fixation rate. Active transport of HC0,-hyperpolarizes (not depolarizes) the membrane potential. 14 Cyanobacteria (Cyanophyta, the blue-green algae) generally live in alkaline environments where Abbreviations: c (subscript), refers to the control-treated cells; CAI' S, 3-(cyclohexylamino)-~-propane-sulfonic acid; AG, Gibbs free energy; AG,,o, Gibbs free energy of transport process; AHC03-,,, electrochemical potentiallgradient for bicarbonate; ApH+,,, electrochemical potential/ gradient of protons; ApNati,,, electrochemical potential/gradíent of sodium; DIC, dissolved inorganic carbon (CO, + H,C03 + HC0,-+ CO,2-); e (subscript), refers to the experimental treatment cells; in (subscript), inward; i (subscript), refers to the inside of the cells; K,,,, one-half maximum rate of photosynthesis; o (subscript), refers to the outside of the cells or bulk electrolyte. 1573 www.plant.org on August 13, 2015 -Published by www.plantphysiol.org Downloaded from

Marine algae have been known and utilized from the ancient era. It is the source of chemical compounds mainly useful as a food for their richness in protein, fatty acids, minerals and vitamins. Physiologically active compounds also have a great potential to play an important role as cosmetic, medicine and as a pharmaceutical aid. In this review, the provided information will play an important role in the medicinal and cosmeceutical production in future.

In this research, marine algae and seagrasses were investigated in the upper infralittoral zone of Hatay (Turkish Mediterranean coasts). A total of 377 algae and 5 seagrasses were determined. 30 of them belong to blue-green algae (Cyanophyceae), 201 to red algae [Rhodellophyceae (2), Compsopogonophyceae (2), Bangıophyceae (5), Florideophyceae (192)], 73 to brown algae (Fucophyceae), 73 to green algae [Chlorophyceae (5), Ulvophyceae (19), Trentepohlıophyceae (1), Cladophorophyceae (24), Bryopsidophyceae (22), Dasycladophyceae (2)] and 5 to seagrasses (Liliopsida).

The blue green alga Oscillatoria limnetica was isolated from lotic ecosystem. The isolated microalga species was cultivated in BG-11 media for biomass production and to test the effect of organophosphorus glyphosate on carbohydrate, total protein, shikimik acid, flavonoid and superoxide dismutase enzyme. Adversely depleting of the cellular activities of O. limnetica causing by glyphosate treatments, leading to a marked decrease in the carbohydrates, proteins, flavonoid and maximum reduction was 30.980mg/l, 22.39mg/l and 0.48 µg/g dry wt., respectively at 20mg/l of glyphosate.The shikimik acid pathway was inhibited by glyphosate, leading to an accumulation of shikimic acid. The shikimic acid content increased and the highest content was 1.38mg/l at 20mg/l. Also, superoxide dismutase enzyme activity increased along with increasing glyphosate concentrations and maximum activity was 3.14 units/ml in 20mg/l.

Copyright © 2014 ISSR Journals. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. ABSTRACT: Cyanobacteria are among the earliest of inhabitants of Planet Earth and are highly diverse members of the current global biodiversity and are making significant contributions to the Carbon and Nitrogen bio-geochemical cycles, particularly in the deep oceans. Cyanobacteria in recent year have gained importance because of their potential use in various areas of research. This diverse group has application in various fields like biotechnology, pharmacology, agriculture etc. Due to presence of wide spectrum of bioactive compounds cyanobacteria has possesses antiviral, antibacterial, antifungal and anticancer activities. Several strains of cyanobacteria are also rich in food supplements. Further nitrogen fixing capacity of cyanobacteri...

50 days' free access before August 07, 2021 https://authors.elsevier.com/c/1dGJs_V0xP0EGg ............................................................................................................... Outbreaks of cyanobacterial harmful algal blooms present a serious threat to ecosystem safety and human well-being. Removal of toxic cyanobacterial biomass from freshwaters and its safe utilization is a worldwide problem. We showed that regulation of intracellular carbon flow by applying nitrogen deprivation strategy with light and inorganic carbon manipulation during the cultivation of cyanobacterium Microcystis allows efficiently convert its biomass into the biofuel feedstock. The proteomic analysis demonstrated that highly efficient feedstock production can be achieved during Microcystis culturing by nitrogen deprivation, which slows down the catabolic consumption of carbohydrates in cells. Further, we developed a novel approach that allows converting the natural Microcystis biomass into carbohydrate-rich feedstock by maintaining a high rate of carbohydrate production at minimal biomass losses. The yield attains 0.22 g ethanol per gram dry biomass, which is in the range of the ethanol yield of sugarcane, but higher than the values of sugarcane waste. The suggested approach provides cost-effective technology for sustainable green energy production from nuisance cyanobacterial biomass. The massive removal of toxic cyanobacterial biomass for bioethanol productions can mitigate the harmful cyanobacterial blooms in eutrophic lakes, and positively affect their restoration.
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Marine algae and seagrasses were researched in the upper infralittoral zone of Adana (Turkish Mediterranean coasts) ın this study. 381 algae and 5 seagrasses (Liliopsida) were determined (Total 386 taxa). 27 of them belong to blue-green algae (Cyanophyceae), 204 to red algae [Rhodellophyceae (2), Compsopogonophyceae (2), Bangiophyceae (5), Florideophyceae(195)], 78 to brown algae (Fucophyceae), 72 to green algae [Chlorophyceae (7), Ulvophyceae (18), Trentepohlıophyceae (1), Cladophorophyceae (22) Bryopsidophyceae (22), Dasycladophyceae (2)]. Ceramium siliquosum (Kützing) Maggs & Hommersend var. zostericola f. zostericola, C. tenuicorne (Kützing) Waern (Rhodophyceae), Bryopsis adriatica (J. Agardh) Meneghini (Bryopsidophyceae) are given as newly record for the Mediterranean shores of Turkey.

Uptake of the lipophilic cation, tetraphenylphosphonium (TPP+), which is often used as a membrane potential probe, was studied in the cyanobacterium Synechococcus R-2 (PCC 7942) to determine if the technique was valid for these cells. Lipophilic cation probes are notorious for giving inconsistent estimates of membrane potential (ΔΨ) using the Nernst equation (ETPP+=ΔΨ). It is necessary to correct for the large amounts of TPP+ bound to the surface of the cells. The rate of equilibration of intracellular TPP+ is very fast (t½≈1–3 min), hence the permeability of the plasmalemma to TPP+ (PTPP+≈10–50 nm s−1) is very high. There appears to be an active uptake of TPP+ with a pH optimum at about pHo 7.5. TPP+ does not readily uncouple Synechococcus cells. Carbonyl cyanide p-trifluoromethoxyphenylhydrazone (FCCP) and dinitrophenol depolarized ETPP+, but monensin made ETPP+ more negative. Accumulation of TPP+ is not affected by [K+] in the medium in a way consistent with it acting as a reporter of the membrane potential. Addition of K+, NH4+ and HCO3− altered the uptake rate of TPP+ in a way consistent with electrogenic uptake of these ions but the effects were smaller than those found using the 86Rb+/valinomycin and 201TI+ probes. A comparison has been made with ΔΨ determinations using other membrane potential probes. ETPP+ was often close to the value of the membrane potential obtained using other methods under control conditions but effects of experimental treatments are sometimes inconsistent with those found using other ΔΨ probes. The TPP+ method is therefore unreliable and could be seriously misleading.

ABSTRACT. Biodiversity and distribution of cyanobacteria at Dronning Maud Land, East Antarctica.The current study describes the biodiversity and distribution of cyanobacteria from the natural habitats of Schirmacher land, East Antarctica surveyed during 23 rd Indian Antarctic Expedition (2003–2004). Cyanobacteria were mapped using the Global Positioning System (GPS). A total of 109 species (91 species were non-heterocystous and 18 species were heterocystous) from 30 genera and 9 families were recorded; 67, 86 and 14 species of cyanobacteria were identified at altitudes of sea level>100 m, 101–150 m and 398–461 m, respectively. The relative frequency and relative density of cyanobacterial populations in the microbial mats showed that 11 species from 8 genera were abundant and 6 species (Phormidium angustissimum, P. tenue, P. uncinatum Schizothrix vaginata, Nostoc kihlmanii and Plectonema terebrans) could be considered as dominant species in the study area.

Blue green alga Spirulina platensis was subjected to different concentrations of NaCl, i.e. (0.1, 0.5, 5 and 10g/l) by using 1g/ l (as stock salt) that considered to be the control of the experiments according to their concentration in Zarrouk medium, in order to study the effect of NaCl concentrations on the photosynthesis pigments which are chlorophyll a, chlorophyll b, total chlorophyll, carotenoids, phycocyanin, allophycocyanin and phycobiliproteins. Sodium chloride caused different effects on photosynthetic pigments of the studied algae. In 10g/l NaCl, the maximum reduction of chlorophyll a, chlorophyll b, and total chlorophyll were 2.540, 0.808, and 3.349mg/1, respectively, while maximum reduction of phycocyanin, allophycocynin, and phycobiliproteins were 0.303, 0.232, and 0.535mg/1, respectively. Moreover, carotenoids induced to reach 1.182mg/l in 10g/l NaCl. Rising NaCl concentration up to 5 and 10g/l caused the induction of carotenoids as well as the inhibition of chlorophy...

In western cultures, certain cyanobacteria have been an accepted source of microalgal biomass for food for about 30 years, in particular Spirulina (Arthrospira) platensis and S. maxima. Beginning in the early 1980s, another species, Aphanizomenon flos-aquae was adopted for similar uses. This is harvested from Upper Klamath Lake, the largest freshwater lake system in Oregon. In 1998 the annual commercial production of Aphanizomenon flos-aquae was about 1 × 10 6 kg. Since this species is not cultured like Spirulina in outdoor ponds or raceways, it requires very different procedures for harvesting and processing. These are reviewed here and include extensive off-lake screens or on-lake barges, which dewater and concentrate the cells. Other procedures, such as those for removal of detritus and mineral materials, and those for monitoring and reducing the amounts of certain contaminant cyanobacteria, which can produce cyanotoxins, have also become important in quality control and marketing.

One locally microalga species Oscillatoria limnetica was isolated from the artificial canal around University of
Babylon in Al-Hilla city. The isolated microalga species was cultivated in BG-11 media for biomass production and to test
their ability to degrade glyphosate that is the widely used organophosphorus herbicide by high performance liquid
chromotography analysis. HPLC appeared to be an effective technique to follow decrease of glyphosate in biodegradation
process.
Removal efficiencies of glyphosate were evaluated and compared. The results confirmed the high efficiencies of
O.limnetica for the removal of the target contaminant.
There were significant differences in the rate of glyphosate removal from the medium after 3, 5, 7, 14 and 35 days in
all treatments. It was 97.5% after seven days at 5 mg/l treatment, 57.9% and 37.1% after fourteen days at 10 mg/l and 15
mg/l treatments, respectively and 99.9% after thirty five days at 20 mg/l treatment. Maximum removal efficiency
percentages of isolated species were increased to reach their maximum in all treatments after thirty five days.

Permeabilities of ammonia (NH3), methylamine (CH3NH2) and ethylamine (CH3CH2NH2) in the cyanobacterium (cyanophyte)Synechococcus R-2 (Anacystis nidulans) have been measured. Based on net uptake rates of DCMU (dichlorophenyldimethylurea) treated cells, the permeability of ammonia was 6.44±1.22 μm sec−1 (n=13). The permeabilities of methylamine and ethylamine, based on steady-state14C labeling were more than ten times that of ammonia (P methylamine=84.6±9.47 μm sec−1 (76),P ethylamine=109±11 μm sec−1 (55)). The apparent permeabilities based on net uptake rates of methylamine and ethylamine uptake were significantly lower, but this effect was partially reversible by ammonia, suggesting that net amine fluxes are rate limited by proton fluxes to an upper limit of about 700 nmol m−2 sec−1. Increasing concentrations of amines in alkaline conditions partially dissipated the pH gradient across the cell membrane, and this property could be used to calculate the relative permeabilities of different amines. The ratio of ethylamine to methylamine permeabilities was not significantly different from that calculated from the direct measurements of permeabilities; ammonia was much less effective in dissipating the pH gradient across the cell membrane than methylamine or ethylamine. An apparent permeability of ammonia of 5.7±0.9 μm sec−1 could be calculated from the permeability ratio of ammonia to methylamine and the experimentally measured permeability of methylamine. The permeability properties of ammonia and methylamine are very different; this poses problems in the interpretation of experiments where14C-methylamine is used as an ammonia analogue.

Specialized chemical probe techniques need to be used to measure the membrane potential (∆ψ i,o ) or the intracellular pH (pH i ) of the cyanobacterium Synechococcus R-2 (PCC7942). The pH i of Synechococcus is essentially a set point (≈7.3) over a wide range of extracellular pH (pH o ) from 7 to 11. Maintenance of the pH i is strongly Na +dependent and the cells cannot tolerate acid pH o . The 86 Rb + -valinomycin method of measuring the ∆ψ i,o has inherent limitations, the most obvious being that the valinomycin treatment itself might alter the membrane potential. 201 Tl + has been found in Synechococcus to distribute across the plasmalemma passively, and so the accumulation ratio of the ion ([Tl + ] i /[Tl + ] o or Tl + i,o ) can be used to calculate the apparent ∆ψ i,o . The two types of probe give comparable results in Synechococcus. Polarizations of the ∆ψ i,o of cells, because of electrogenic transport of ions, can be detected from its effects upon the uptake rate of permeant cations using both the 86 Rb + -valinomycin and 201 Tl + methods. HCO 3 hyperpolarized ∆ψ i,o , whereas NH 4 + , CH 3 NH 3 + , and K + led to depolarization. Most active transport systems, including the HCO 3 pump, in cyanophytes appear to be ATP binding cassette (ABC) type ATP pumps. Few cotransport (H + or Na + ) driven mechanisms have been identified. A substantial proportion of the power available from photosynthesis and respiration is used to maintain ionic gradients and the membrane potential and in the light a large part (≈10%) is used to import inorganic carbon.