Biologia 68/5: 830—837, 2013Section BotanyDOI: 10.2478/s11756-013-0215-1Growth characteristics of selected thermophilic strainsof cyanobacteria using crossed gradients of temperature and light*František Hindák 1 , Jana Kvíderová 2,3 & Jaromír Lukavský 2,41 Slovak Academy of Sciences, Institute of Botany, Dúbravská cesta 9, SK–84523, Bratislava, Slovakia;e-mail: frantisek.hindak@savba.sk2 Academy of Sciences of Czech Republic, Institute of Botany, Department of Plant Ecology, Dukelská 135, CZ–37982 T?eboň,Czech Republic3 University of South Bohemia, Faculty of Science, Centre for Polar Ecology, Branišovská 31, CZ–37005 ?eské Budějovice,Czech Republic; e-mail: kviderova@butbn.cas.cz4 Bioref inery Research Centre of Competence, Dukelská 135, CZ–37982 T?eboň, Czech Republic;e-mail: lukavsky@botany.cas.czAbstract: Growth requirements of 10 possibly thermophilic strains of cyanobacteria were compared under a wide spectrumof light and temperature conditions (7–80 W m −2 , 12–40 ? C). The strains were isolated from dif ferent localities: six of thermalsprings in Slovakia (4 from Pieš?any, 2 from Sklené Teplice), one from thermal waters in Rupite, Bulgaria, 2 strains froma hypersaline lake Chott-el-Djerid, Tunisia, and one strain from the tropical island of Cebu, Philippines. Although thecrossed gradient unit allowed only sub-optimal temperature range with respect to thermophile def inition, i.e. optimumtemperature above 45 ? C, there were dif ference among the strains. The most thermophilic and high-light tolerant strainwas Synechococcus bigranulatus strain Lukavský 2005/66, with a peak above 45 ? C; the second was Chroococcidiopsisthermalis strain Hindák 2008/9, and Isocystis sp. strain Hindák 2006/1. The temperature requirements of other strainswere similar; the least thermophilic were both Slovakian strains of the genus Hapalosiphon. Growth was not limited below80 W m −2 , except for H. fontinalis strain Hindák 2008/3, which prefers lower irradiance. Hapalosiphon delicatulus strainHindák 2007/20, isolated from a bark tree on the tropical island of Cebu was rather mesophilic than thermophilic andshade–preferring. The CCA revealed that the ecologically similar strains originated from the same or nearby localities.There were no signif icant correlations between temperature optima in culture and in nature. Bulgarian and Tunisian strainspreferred higher irradiances.Key words: Cyanobacteria; crossed gradients of temperature and light; growth; thermal springsIntroductionThermophiles (organisms with growth optima of 45–50 ? C or higher) are interesting and important organ-isms adapted to temperatures in the approximate rangeof 40 to 70 ? C (Berenguer 2011). They were common,and even monopolistic, in the distant past, but arenow usually found in thermal springs (Gold 1992,1999; Hindák 2008a; Hindák & Hindáková 2006, 2007;Lukavský et al. 2011). This is advantageous becausethermal springs are relatively very stable, and havebeen so for maybe thousands of years, and thus residentorganisms have had enough time to adapt. Such adapta-tions include modif ications of membranes, protein andnucleic acid structures, and the production of specif iccompounds. Increased temperatures lead to a decreasein the unsaturated/saturated fatty acid ratio (Maslovaet al. 2004; Satoh et al. 1979). Maslova et al. (2004) fur-*Electronic supplementary materials are available in the online version of the articlether discussed a possible role of hexadecanoic acids inthe adaptation of Synechococcus to high temperatures.Increased thermal stability of proteins is due to a higherrigidity resulting from hydrophobic forces and internalstructural changes (Kumar et al. 2007). Nucleic acidchanges include increased C+G content in RNA, struc-tural stabilization by base modif ication or small ligandbinding, generation of compact tertiary structures, in-teractions with ribosomal proteins, and ef f i cient DNArepair and RNA turnover (Grosjean & Oshima 2007).For biotechnological applications, modif ied bio-chemical pathways and the production of unusualmetabolic products could have potential, so thermalsprings could serve as reservoirs for new strains possess-ing novel characteristics (Pulz & Gross 2004). Thermo-tolerant Phormidium sp. produced anti-microbial com-pounds against G − and G + bacteria, also Candida albi-cans and Cladosporidium resinae (Fish & Codd 2004).Another strain of Phormidium sp. was immobilized incalcium alginate and used to treat dye-rich wastewa-ter (Ertugrul et al. 2008). Some unusual Fe-proteins,c ? 2013 Institute of Botany, Slovak Academy of Sciences
