Physiology and Cultivation of Algae and Cyanobacteria 7. 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 = toleance to high light, UV, desiccation • in marine Arcitic& Antarctic env. - rare Psychrophilic phototrophs Eukaryotic • 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 Chfprella vulgaris Beij 5.3 6.6 Chlorella pyrenoidosa Chick 3.1 6.6-7.4 Chant corallina Klein ex Wild 4.5 7.3 Sceuedesmus quadricauda (Turp.) Breb 3.1 6.S-7.0 Euglena mu tabHis Schmitz 2.8 5.0-6.4 Dunali el la 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 • Spiruiina 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,... Pafrnltal of pholosynlhelic microorganisms Dri ironmmilal pomrrmkr Prokar votes Liika notes High temperature Low temperature High salt concentration LowpH High pH High radiation levels Unicellular c^jano bacteria (Syricchococcus [ThertfJosyfKchococcits] sp.). photosynthesizeup to 73-74°Q the highest temperatures enabling photosynthesis 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 abo^e 250 g l_l Cyanobacteria are seldom, if at allj found in acidic environments Cyanobacteria^ especially Spiru occur massively in alkaline lakes, some of them are obligate alkaliphiles Cyanobacteria are often found in high radiation envkonments and tolerate high levels of visihle and ultraviolet radiation The most thermotolerant eukaryotic alga {Cyfttiidimi) 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 Unicellular green algae of the genus Diftiftliefki are found worldwide at salt concentrations up to NaQ saturation Specialized acidophilic photosyn-thetic eukaryotes (C}HtiidiiMiY D.flcidophiki) grow at pH values as low as 0-1 Many eukaryotic algae grow in high pH environments Some carotene id -rich eukaryotic microalgae grow in high ligbt environments