Viability of dried filaments, survivability and reproduction under water stress, and survivability following heat and UV exposure in Lyngbya martensiana, Oscillatoria agardhii, Nostoc calcicola, Hormidium fluitans, Spirogyra sp. and Vaucheria geminata

Response of short-term heat shock on photosynthetic activity of soil crust cyanobacteria

Short-term heat exposure in tropical regions can generate severe stress in the photosynthetic activity of soil crust cyanobacteria. We investigated the responses of two filamentous cyanobacteria, Scytonema tolypothrichoides and Tolypothrix bouteillei, to 1hr exposure at 35, 45, and 55 °C using variable chlorophyll fluorescence. Protocols for maximum quantum yield (F_V/F_M) and dark recovery of chlorophyll a fluorescence (OJIP) transient were applied. Heat exposure caused damage to the donor side of PSII, indicated by a decrease in F_V/F_M and a rapid increase in F₀. After heat stress, photochemical energy utilization (φ_Po, φ_ETo, and φ_RE1o) declined and energy dissipation (φ_DIo) increased. At 45 °C, the photosynthetic apparatus was reversibly damaged, since full recovery was observed after 7 days of relaxation. S. tolypothrichoides was more resistant to heat stress than T. bouteillei, confirming better adaptation to higher temperatures as observed in growth experiments.

Grazing livestock are exposed to terrestrial cyanobacteria

While toxins from aquatic cyanobacteria are a well-recognised cause of disease in birds and animals, exposure of grazing livestock to terrestrial cyanobacteria has not been described. This study identified terrestrial cyanobacteria, predominantly Phormidium spp., in the biofilm of plants from most livestock fields investigated. Lower numbers of other cyanobacteria, microalgae and fungi were present on many plants. Cyanobacterial 16S rDNA, predominantly from Phormidium spp., was detected in all samples tested, including 6 plant washings, 1 soil sample and ileal contents from 2 grazing horses. Further work was performed to test the hypothesis that ingestion of cyanotoxins contributes to the pathogenesis of some currently unexplained diseases of grazing horses, including equine grass sickness (EGS), equine motor neuron disease (EMND) and hepatopathy. Phormidium population density was significantly higher on EGS fields than on control fields. The cyanobacterial neurotoxic amino acid 2,4-diaminobutyric acid (DAB) was detected in plant washings from EGS fields, but worst case scenario estimations suggested the dose would be insufficient to cause disease. Neither DAB nor the cyanobacterial neurotoxins β-N-methylamino-L-alanine and N-(2-aminoethyl) glycine were detected in neural tissue from 6 EGS horses, 2 EMND horses and 7 control horses. Phormidium was present in low numbers on plants where horses had unexplained hepatopathy. This study did not yield evidence linking known cyanotoxins with disease in grazing horses. However, further study is warranted to identify and quantify toxins produced by cyanobacteria on livestock fields, and determine whether, under appropriate conditions, known or unknown cyanotoxins contribute to currently unexplained diseases in grazing livestock.

Studies on conjugation of Spirogyra using monoclonal culture

We succeeded in inducing conjugation of Spirogyra castanacea by incubating algal filaments on agar plate. Conjugation could be induced using clone culture. The scalariform conjugation was generally observed, while lateral conjugation was rarely. When two filaments formed scalariform conjugation, all cells of one filament behaved as male and those of other filament did as female. Very rarely, however, zygospores were formed in both of pair filaments. The surface of conjugation tube was stained with fluorescently labeled-lectins, such as Bandeiraea (Griffonia) simplicifolia lectin (BSL-I) and jacalin. BSL-I strongly stained the conjugation tubes, while weakly did the cell surface of female gamete first and then that of male gamete. Jacalin stained mainly the conjugation tubes. Addition of jacalin inhibited the formation of papilla, suggesting some important role of jacalin-binding material at the initial step of formation of the conjugation tubes.

Vegetative survival of some wall and soil blue-green algae under stress conditions

Lyngbya major (a wall alga), survived throughout year, maximally to >80 % at atmospheric temperature (AT) of 17-36 degrees C and relative humidity (RH) 60-100 % in rainy and spring seasons, but the survival was 43-64 % in winter when AT decreased to 5 degrees C and RH was 65-98 %, and 15-23 % in summer when AT reached 48 degrees C and RH was 23-60 %. All soil algae (Lyngbya birgei, Aphanothece pallida, Gloeocapsa atrata, Oscillatoria subbrevis, O. animalis) survived >90 % in rainy season when soil moisture content (SMC) was 89-100 %. Lowering of SMC to a minimum of 55 % in spring and 39 % in winter led L. birgei, O. subbrevis and O. animalis to survive from 75, 66, and 65 %, respectively, in spring and 12, 14, and 20 % in winter, and A. pallida and G. atrata not at all in both seasons. All soil algae did not survive in summer when SMC was 12-30 %. Myxosarcina burmensis survived only in rainy and spring seasons when pond water temperature (PWT) was 19-25 degrees C and 18-26 degrees C, respectively, and not in winter and summer when PWT was 2-14 degrees C and 25-36 degrees C, respectively. L. major and A. pallida survived almost equally well under both submerged and air-exposed conditions for 15 d but less if submerged for more time than air-exposed on moist soil surface, while L. birgei, G. atrata, O. subbrevis, and O. animalis survived submergence in liquid medium better and longer than air-exposure on moist soil surface. Pond alga M. burmensis survived submergence better than air-exposure, true to its aquatic habitat. All algae survived less and died without forming any resistant cells when exposed to physical and physiological water stress (imposed by growing them on highly agarized media or in salinized liquid media), light stress (at 0, 2 and 10 micromol m(-2) s(-1) light intensity) or following UV shock (0.96-3.84 kJ/m(2)). A. pallida and G. atrata cells did not divide on 8 % agarized solid media, in > or =0.3 mol/L salinized liquid media, and in darkness. The presence of sheath over L. major and L. birgei filament cells and mucilage cover over A. pallida and G. atrata cells protect them against physical desiccation to some extent but not against UV shock.

Survival and reproduction in some algae under stress conditions

Pithophora oedogonia and Cladophora glomerata survived lowest 60 and 58%, respectively, in June when the pond diurnal water temperature (PDWT) increased to a maximum of 28 degrees C. The lowering of PDWT only by 1 degrees C in July improved survivability of both algae to their almost maximum level of 100 and 96%, respectively. Further lowering of PDWT to 17-22 degrees C in November initiated akinete formation in P. oedogonia. The process of akinete initiation, maturation and germination continued till April when PDWT increased to 20-24 degrees C, but not beyond that in May when PDWT was 21-26 degrees C. By this time, probably all akinetes have germinated in situ, and the alga was entirely vegetative. P. oedogonia population is not synchronous in nature, since during the 5-6-month reproductive season, some filaments were in active vegetative stage, some had akinete initiation, some had completed akinete formation, and some had akinetes germinating. C. glomerata grew dense vegetative in November and initiated (zoo)sporangial primordia formation (to some extent) in February (when PDWT was lowest, viz. 10-14 degrees C) till April. Meanwhile, no (zoo)-sporangial primordia either produced any zoospore or germinated into a germ tube; and all released their cytoplasmic content and died (along with some vegetative cells) with an increase in PDWT to 21-26 degrees C in May. Vaucheria geminata vegetative patches appeared on the soil surface, 2nd week of January by lowering of atmospheric diurnal temperature (ADT) to 9-16 degrees C in the 1st week. The alga started sexual reproduction by the 2nd week of March (when ADT increased to 20-23 degrees C) and completed the process of reproduction by the 1st week of April (when ADT increased to 24-26 degrees C) and died thereafter. P. oedogonia, C. glomerata and V. geminata survived better and longer in submerged conditions than air-exposed (which was true for P. oedogonia and C. glomerata aquatic habitat and also indicated that the soil alga V. geminata could survive to some extent if submerged in rain water). P. oedogonia formed akinetes and C. glomerata (zoo)sporangial primordia only in submerged condition and not when air-exposed on moist soil surface. V. geminata did not complete the life cycle both under submerged and air-exposed conditions. Vegetative survival in P. oedogonia, C. glomerata, V. geminata, Aphanothece pallida, Gloeocapsa atrata, Scytonema millei, Myxosarcina burmensis, Phormidium bohneri, Oscillatoria animalis, O. subbrevis, Lyngbya birgei, L. major, Microcoleus chthonoplastes and Rhizoclonium crassipellitum, reproduction in P. oedogonia, C. glomerata and V. geminata, cell division in A. pallida and G. atrata, heterocyst and false branch formation in S. millei, all, were adversely affected at approximately 28.5 degrees C for t12 h at light intensity of approximately 160 micromol m(-2) s(-1); high intensity does not ameliorate high temperature damage to any algae. The presence of liquid water, than its absence, outside the different algae moderated the severity of heat to some extent but not when the heat was severe.

Motility in Oscillatoria salina as affected by different factors

All 3-10-d-old Oscillatoria salina filaments glide with the speed of 323-330 microm/min (BG 11 medium, pH 7.5, 21 +/- 2 degrees C, continuous light intensity of approximately 30 micromol m(-2) s(-1)) in a culture chamber. However, a time bound progressive decrease in gliding speed and in percentage of gliding filaments occurred, depending upon the severity of different stress factors studied, viz. water stress (2-8% agarized media, liquid media with 0.2-1 mol/L NaCl, blot-dryness of filaments for > or = 5 min), temperature shock (5, 40 degrees C for > or = 5 min; 35 degrees C for > or = 15 min), darkness and low light intensity (2, 10 micromol m(-2) s(-1)), UV exposure (0.96-3.84 kJ/m2), pH extremes (< or = 6.5 and > or = 9.5), lack of all nutrients from liquid medium (double distilled water), presence of 'heavy' metals (1, 25 ppm Fe, Cu, Zn, Ni, Co, Hg) or organic substances in liquid medium (25, 250 ppm 2,4-D, captan, urea, DDT, thiourea). This feature of the alga (i.e. reduction in speed and percentage of gliding filaments depending upon severity of stress conditions) may thus be suggested to be used in assessing water quality.

Survival of blue-green and green algae under stress conditions

Terrestrial blue-green algae Scytonema millei, Phormidium bohneri and Lyngbya mesotricha survived to 100 % at atmospheric temperatures of 5-36 degrees C and relative humidity 55-100 % in rainy, winter and spring seasons but the survival was 15-25 % in summer when atmospheric temperature reached 48 degrees C and relative humidity was < or =23 %. Microcoleus chthonoplastes maximum survival was =80 % in rainy season followed by a decrease to =1/2 and 1/4 level in winter and spring, respectively; it disappeared in summer but a few cells and/or trichomes enclosed within sheath may be surviving sticking to soil, not evident microscopically, since the population reappeared at the same place with the onset of rain. Terrestrial green alga Rhizoclonium crassipellitum survived only in spring and died at the onset of summer without forming any dormant cell and/or reproductive structure. Only P. bohneri survived better and longer under submerged conditions in liquid medium than air-exposed on moist soil surface in the culture chamber, while the other algae fared almost equally or slightly better air-exposed on moist soil surface (or even on 2 % agarized medium) than when suspended in liquid medium, indicating that air exposure rather than submerged conditions was needed for most of the terrestrial algae to survive. Water stress imposed on growing algae either on high-agar-solid media or in 0.2-0.6 mol/L NaCl liquid media in the culture chamber reduced vegetative survival in all; it resulted in death without any dormant cell remaining. When stored in desiccators over fused CaCl2, M. chthonoplastes died within 1/2 month, R. crassipellitum and L. mesotricha within 1 month, P. bohneri within 1/2 month, and S. millei not even within 1 1/2 month, indicating their survival pattern against atmospheric dryness to be wide; it also explained the M. chthonoplastes absence in summer and S. millei presence throughout the year. At increased atmospheric humidity the desiccation-sensitive algae (e.g., M. chthonoplastes) survived better than a desiccation-resistant alga (here S. millei). All algae survived considerable darkness (S. millei > 1 1/2 month; P. bohneri, M. chthonoplastes and R. crassipellitum >1 month, and L. mesotricha >1/2 month), and low light intensity of 2 and 10 micromol m(-2)s(-1) which explains their prolific growth in shady places. All algae were differently sensitive to wet heat (45 degrees C for 5-40 min) and to UV shock (0.96-3.84 kJ/m2).

Nutrient stress causes akinete differentiation in cyanobacterium Anabaena torulosa with concomitant increase in nitrogen reserve substances

Addition of nitrogen source (nitrate), carbon sources (acetate, citrate and fructose), depletion of nutrients (phosphate-free nitrate medium), dilution of medium (2, 4 and 8 times diluted nitrate medium) under unaerated conditions induced akinete differentiation in Anabaena torulosa. Aerated cultures under the same conditions did not differentiate akinetes. The amounts of reserve metabolites--glycogen and cyanophycin (multi-L-arginyl-poly-L-aspartic acid) granule polypeptide (CGP)--were determined in unaerated and aerated cultures, and at different stages of growth and akinete differentiation. The addition of nitrate, acetate, citrate and fructose under unaerated conditions resulted in the accumulation of glycogen and CGP in higher amounts after 4 d (akinete initiation); the CGP content further changed at mature free akinetes phase. Higher accumulation of reserve products was also observed under nutrient deficiency (phosphate-depleted or diluted media) after 4 d of cultivation. Under aerated conditions reserve product accumulation was considerably lower. Thus a low accumulation of reserve products in aerated cultures showed that aeration probably somehow relieves the organism from a nutritional stress.

Vegetative survival and reproduction under submerged and air-exposed conditions and vegetative survival as affected by salts, pesticides, and metals in aerial green alga Trentepohlia aurea

Trentepohlia aurea vegetative cells do not survive submerged conditions for more than 5 months, but can survive air-exposed conditions for more than 1 year. Disintegration and rapid death of algal cells was observed to a higher extent under submerged than air-exposed condition. Under submerged conditions T. aurea did not form any sporangium while prolific formation occurred under air-exposed conditions. Under submerged conditions algal cells formed few-celled, filamentous, cytoplasmic type setae. Vegetative cells were resistant to some extent to various levels of salt (NaCl, < or = 0.8 mol/L), pesticides (DDT, 2,4-D or captan, 2000 ppm) and 'heavy' metals (zinc or nickel, 200 ppm; cobalt, < or = 100 ppm.)

Cell differentiation and colony alteration of an edible terrestrial cyanobacterium Nostoc flagelliforme, in liquid suspension cultures

Morphological characteristics of an edible terrestrial cyanobacterium Nostoc flagelliforme in liquid suspension cultures under photoautotrophic conditions are presented. Different cell forms alternated in a regular manner during the experimentation period (30 d). N. flagelliforme exhibited a very complex life cycle in terms of colony morphology, including mainly 4 different colony morphological forms, viz. hormogonia, filaments, seriate colonies and aseriate colonies. Under laboratory conditions it formed spherical colonies on solid media but not threadlike colonies as it did under natural conditions. The overall life span of the alga was not altered by the existence of different nitrogen sources in the media despite the depression of some cell forms or colony morphologies. Compared with growth on the medium with urea and ammonium as nitrogen sources, the alga on standard medium had a short period of hormogonia and aseriate colony, suggesting that both ammonium and urea could stimulate the formation of hormogonia, at the same time inhibiting the formation of heterocystous cells. The new information on the growth and morphology of N. flagelliforme could be potentially used for the scale-up or field cultivation.

Effectiveness ofCyanothece spp. andCyanospira capsulata exocellular polysaccharides as antiadhesive agents for blocking attachment ofHelicobacter pylori to human gastric cells

The effect of cyanobacterial polysaccharides (from Cyanothece spp. and Cyanospira capsulata) on the binding of Helicobacter pylori to gastric epithelial cells was evaluated. The antiadhesive action on Kato III and HeLa S3 human gastric cell lines was established.

Zoosporangia survival, dehiscence and zoospore formation, and motility in the green alga Rhizoclonium hieroglyphicum as affected by different factors

Urea at 200 ppm (probably serving as a nitrogen source), liquid Bold's basal medium at pH 7.5, temperature of about 22 degrees C and light intensity of about 40 micromol m(-2) s(-1) for 16 h a day induced rapid and/or abundant zoospores formation and zoosporangia dehiscence and favored zoospore liberation, speed and motility time period in the green alga Rhizoclonium hieroglyphicum. However, factors such as water stress (2 and 4 % agarized media, liquid media with 0.2-0.4 mol/L NaCl, 5-60 min blot-dryness of filaments), pH extremes of liquid media (at < or =6.5 and > or =9.5), temperature shock in liquid media (5 and 35 degrees C for > or =5 min), UV exposure (0.96-3.84 kJ/m2), lack of all nutrients from liquid medium (double distilled water), darkness, and presence of "heavy" metals (1-25 ppm Cu, Fe, Zn, Hg, Ni, Co) or organic substances (200-600 ppm captan or DDT, 800 and 1000 ppm 2,4-D, 50 and 400 ppm indole-3-acetic acid (3-IAA), 1000 and 2000 ppm urea, 100 and 200 ppm thiourea) in liquid media decreased and/or delayed at various levels either zoosporangia survival, zoospore formation or zoosporangia dehiscence and/or the rate of zoospore liberation from zoosporangia, zoospore speed and time period of motility in the media or totally inhibited all these processes. 3-IAA at 50 and 400 ppm induced zoosporangial papilla to grow into a tube-like projection of about 30-120 microm in length. Zoosporangial dehiscence rather than zoospore formation or zoosporangia survival, and zoospore motility period rather than zoospore speed are probably more sensitive to various adverse environmental factors. The rate of zoospores liberation from zoosporangium (possibly related directly to some extent on the zoospore number inside) is probably independent of zoospore speed in the medium.

Viability of dried vegetative cells or filaments, survivability and/or reproduction under water and light stress, and following heat and UV exposure in some blue-green and green algae

Vegetative cells in dried, mucilagenous mass of Gloeocapsa aeruginosa and Aphanothece nidulans, reticulum of Hydrodictyon reticulatum, mucilagenous mass of Chroococcus minor, and filaments of Oedogonium sp. and Scytonema hofmanni died within 1/2, 1/2, 1/2, 1, 3 and 6 h, respectively, while dried vegetative filaments of Phormidium foveolarum retained under similar storage conditions viability for 4 d. P. foveolarum tolerated 1 mol/L NaCl. The resistance to desiccation in P. foveolarum exhibited similar dependence as that to heat or UV light. The water stress imposed on growing algae either on high-agar solid media or in NaCl-containing liquid media reduced at various levels or altogether inhibited the survival of vegetative parts in all, the cell division in C. minor, G. aeruginosa and A. nidulans, formation of heterocyst and false branch in S. hofmanni, oogonium in Oedogonium sp., and daughter net in H. reticulatum. Heat or UV shock of any level also produced similar effects as that by water stress. P. foveolarum tolerated low light level of 10 and 2 mumol m-2 s-1 and no light longer than the rest of other algae studied. Tolerance of microalgal forms to water, heat or UV stress depends primarily upon cell-wall characteristics or cell-sap osmotic properties rather than their habitats, morphology and prokaryotic or eukaryotic nature.

Fatty acid composition of six freshwater wild cyanobacterial species

Hydroxy, n-saturated, branched, dioic, and unsaturated fatty acids in six freshwater wild cyanobacteria (Chroococcus minutus, Lyngbya ceylanica, Merismopedia glauca, Nodularia sphaerocarpa, Nostoc linckia, and Synechococcus aeruginosus) collected from different lakes and springs of Israel have been identified by gas chromatography-mass spectrometry (GC-MS).

Evaluation of Tolypothrix germplasm for phycobiliprotein content

Twenty Tolypothrix strains, including 15 strains of T. tenuis, three strains of T. ceylonica and one strain each of T. nodosa and T. bouteillei, were evaluated for their phycobiliprotein content and composition. Significant differences among the Tolypothrix strains were found at both inter- and intra-specific levels in the production of phycobiliprotein constituents--phycocyanin (PC), allophycocyanin (APC) and phycoerythrin (PE). Four specific parameters, viz. PC or PE content, total phycobiliprotein and total protein content, and percentage of phycobiliproteins, in a mixture of total proteins were used to select four T. tenuis and one T. ceylonica strain as useful for phycobiliproteins production.

Vegetative survival, akinete and zoosporangium formation and germination in some selected algae as affected by nutrients, pH, metals, and pesticides

Lack of nitrogen, phosphorus, or all nutrients, extremes of pH (< 4, > 11), presence of 'heavy' metals (Co, Cu, Zn, Hg, Pb; 0.5-10 ppm) or pesticides (carbofuran, 2,4-D, dithane, phorate, or bavistin; 1-50 ppm) decreased to various extent or completely inhibited the survival or vegetative cells in all studied algae. The formation of akinetes, their viability and germination in Anabaena iyengarii, Westiellopsis prolifica, Nostochopsis lobatus and Pithophora oedogonia and the formation of zoosporangia, their viability, and the germination of zoospores in Cladophora glomerata and Rhizoclonium hieroglyphicum was affected. The formation of viable akinetes or zoosporangia was shown to be directly linked with vegetative cell survival and growth; it could not be induced by any chemical stress imposed.