Algae & cyanobacteria in extreme environment Prokaryotic and eukaryotic phototrophs in extremes of •Temperature •Salinity •Low & High pH •Radiation Algae & cyanobacteria in extreme environment Extremophiles • Organisms with optimal growth conditions found beyond "normal" environment (Kristjansson & Hreggvidsson 1995). - "normal" envoronment » Temp. 4 - 40°C » pH 5 - 8.5 » Salinity betw. that of freshwater and seawater Thermophiles, Psychrophiles, Halophiles. Acidophiles, Alkaliphiles, Radiation-resistant oxygenic phototrophs Thermophilic phototrophs • Photosynthesis - not compatible with high Temp • Archeal life - up to 114°C or higher • Heterotrophic eubacteria - up to 95 °C • Thermophilic cyanobacteria - up to 74 °C • Eukaryotic phototrophs - up to 57 °C Thermophilic phototrophs Prokarvotic • hot springs, geothermal areas (max for cyanob. 74°C) • unicellular - Thermosynechococcus (max. 73-74°C) • filamentous - Mastigocladus laminosus, Phormidium sp., Oscillatoria sp.) max. 55-64°C Eukarvotic • Cyanidium caldarium 45-57°C (pH 2-4, atmosph. pure C02) Psychrophilic phototrophs • Arctic & Antarctic zones, high altitudes • low water T phytoplancton, in & on ice, in freshwater, saline streams & lakes, within rocks • relat. high diversity (low temp, potentially cause no specific problems for photosynth. function) - regul. lipid composition of membranes to adjust fluidity -> func. till cytoplasmic water unfrozen Psychrophilic phototrophs Prokarvotic • unicellular & filamnetous cyanob. - ice-shelf mats - Oscillatoria, Nostoc - ice-bound pools - Oscillatoria, Lyngbya, Phormidium - freshwater - Phormidium, Synechococcus • not true psychrophiles (growth optimum 15-35°C) • survival = tolerance to high light, UV, desiccation • in marine Arctic& Antarctic env. - rare Psychrophilic phototrophs Eukarvotic • red, pink, green, yellow patches on melting snow • snow algae, Chlamydomonas nivalis • "water-melon snow" = Chloromonas, Ankistrodesmus, Raphidonema, Mycanthococcus • main activity in spring & summer • abundant in marine Arctic&Antarctic env. - ice-shelf diatoms - Nitzschia, Pinnularia, Navicula Halophilic phototrophs • may thrive at NaCI cone, up to saturat. • salt lakes, hypersaline lagoons Prokarvotic • filamentous - Microcoleus chthonoplastes (up to 220g/l) • unicellular - Aphanothece, Phormidium, Spirulina • maintain intracellular ionic cone, at relat. low level; for osmotic equilibrium organic solutes are accumulated (sucrose, trehalose, glucosylglycerol) Halophilic phototrophs Eukarvotic • Dunaliella var.sp. - var. cone, tolerate up to 330g/l • Na+ is effectively excluded from cells • K+ is accumulated • for osmotic balance glycerol is accumulated - changes in metabolism & affinity of enzymes to glycerol, low membrane permeability to glycerol Acidophilic phototrophs • sulfataric fields (Naples Italy; Iceland; Yellowstone) • need to protect chlorophylls, DNA, ATP,..(unstable at low pH) • maintain intracellular medium at pH neutral - surface barrier extremely impermeable to protones; +other mechanisms e.g. protone pumps Prokarvotic • cyanobac. generaly pH neutral to alkaline • filamentous - Oscillatoria, Spirulina • unicell. - Aphanocapsa, Chroococcus Acidophilic phototrophs Eukaryotic • Cyanidium caldarium (thermoacidophil, Rhodophyceae) - tolerate 1N H2S04, growth optimum pH 0-4 • Dunaliella salina, Chlamydomonas acidophila, Pinularia • maintain intracell. pH near neutral - var. mechanisms - protone pumps, accumulation H2S04in vacuoles (pH 0.5) Acidophilic phototrophs Table 1. Intracellular pH values measured in Cyanidium caldariwn and in acidophilic chlorophytes. Data were derived from Seckbach (2000a), Beardall and Entwisle (1984), and Pick (1999) Alga External pH Internal pH Cyanidium caldariwn 2.1 6.6 Chlorella saccharophila 4.0 7.1 Chlprella vulgaris Beij 5.3 6.6 Chlorella pyrenoidosa Chick 3.1 6.6-7.4 Chara corallina Klein ex Wild 4.5 7.3 Scenedesmus quadrlcauda (Turp.) Breb 3.1 6.S-7.0 Euglena mu tabHis Schmitz 2.8 5.0-6.4 Dunaliella acidophils 0.5-3.0 6.2-7.2 Alkaliphilic phototrophs • photosynthetic C02 consumption leads to increase pH in most phototrophs up to pH 9-10 during day • alkaline lakes, soda lakes • mechanism - info about halophills - limited info on adaptations to high pH Alkaliphilic phototrophs Prokarvotic • soda lakes • Spirulina platensis (pH 11) • Microcystis aerugnosa (pH 10) • Plectonema nostocorum (pH 13; 80%max.growth at pH 11) Eukarvotic • diatoms Cyclotella, Nitzschia, Coscinodiscus, Navicula • spec, of Nannochloris, Chlamydomonas, Dunaliella • unknown mechanism of adaptation Radiation-resistant phototrophs • photosynthesis -&- light • high light intens.; UV radiation (affects aminoacids, DNA,..) • protection - active - moving away - passive - protective compounds - Carotenoids - quench excited singlet oxygen - absorb visible light above 400nm - UV protection - indirect - mycosporine-like aminoacids - MAAs • var. derivates absorb at 310, 320, 360nm Radiation-resistant phototrophs Prokarvotic • cyanobacteria in Antarctica - Nostoc, Synechococcus - protection - carotenoid pigments (canthaxanthin, myxoxanthophyll), -MAAs - intracell.& extracell. -alkaloid (scytonemin) - mechanisms to repair UV-induced damage Radiation-resistant phototrophs Eukarvotic • Dunaliella salina (p-carotene - 8-12% DW) • C. nivalis (astaxanthin) • aplanospores of snow algae (falvonoids as antioxidants) • MAAs sunscreens widely found (UV absorb.) - dinoflagellates, cryptomonades,... lb bio 2. Oxygenic photosynthesis in extreme environments: comparison of the abilities to prokaryo-tic and eukaryotic microorganisms to live under different environmental extremes. For details see Sections 4-9 Potential of photosynthefic microorganisms Environmental parameter Proka notes Lukanoles High temperature Low temperature High salt concentration Low pH High pH High radiation levels Unicellular cyano bacteria {Syttechococcits [Ther ft losytiechococ ens] sp.). photosynthesize up to 73-74°C, the highest temperatures enab ling p hot osynthesis Cyanobacteria are abundantly found in the Arctic and Antarctic, and grow slowly at near-freezing temperatures. They are psychrotolerant rather than truly psychrophilic Cyanobacteria are abundantly found at high salt concentrations, but seldom develop massively at salt concentrations above 250 g l-1 Cyanobacteria are seldom, if at all, found in acidic environments Cyanobacteria. especially Spiri/foiii;, occur massively in alkaline lakes, some of them are ob ligate alkaliphi les Cyanobacteria are often found in high radiation environments and tolerate high levels of visible and ultraviolet radiation The most thermot olerant eukaryotic alga [Cytjriidimt) is capable of photosynthesis up to 57°C Eukaryotic algae, especially diatoms and green algae, grow in the cold ocean in or around sea ice; snow algae develop in melting snow and may be true psychrophiles LInicellular green algae of the genus DmaUella are found worldwide at salt concentrations up to NaCl saturation Specialized acidophilic photosyn-thetic eukaryotes \Cytmidium> D.iJcidophHtj) grow at pH values as low as 0-1 Many eukaryotic algae grow in high pH environments Some carotenoid-rich eukaryotic microalgae grow in high light environments