Effect and removal of Cr(VI) and Cd(II) heavy metals on some Synechocystis sp. strains isolated from different freshwaters: Estimation of metal removal in terms of proteins and thiols

In the present study 15 cyanobacterial isolates were isolated from freshwaters such as Mogan Lake, Kurtboğazı Damm, Uncalı Stream, Bafa Lake, Hatim Stream, Harikalar Diyarı Pond and Kızılırmak River. Isolates were identified according to their morphologies, cell divison physiology and 16S rRNA as Synechocystis sp. Identified isolates were exposed to 5-50 ppm Cr(VI) and Cd(II) concentrations and the aliveness of the isolates were determined by chlorophyll-a analysis and EC50 values. Synechocystis sp. BASO670 was selected as the most protected its aliveness to Cr(VI) and Cd(II) and this strain was used at each experiments. Dead, immobilized dead and immobilized alive biomass of the Synechocystis sp. BASO670 were used for biosorption of Cr(VI) and Cd(II) and the effect of parameters such as pH, biomass, temperature, metal concentrations and time on biosorption was investigated. As a result optiumum conditions for Cr(VI) biosoption of different biomasses of Synechocystis sp. BASO670 were; pH 2, 0,05 g (dead biomass)- 30 bead (immobilized biomass), 25 oC, 100 ppm metal concentrations and 60 min, optiumum conditions for Cd(II) were; pH 7, 0,05 g (dead biomass) - 30 beads (immobilized biomass), 25 oC, 100 ppm metal concentrations and 60 min. Maximum biosorption for both metals were determined at immobilized dead biomass of Synechocystis sp. BASO670. Synechocystis sp. BASO670 was exposed to 10 ppm Cr(VI), 10 ppm Cd(II) and 10 ppm Cr(VI) and 10 ppm Cd(II) metal mixture for bioaccumulation and as a result, this isolate was accumulate high percentage of Cd(II) than Cr(VI). Isolate wich was exposed to metals at the same conditions of bioaccumulation was also analysed by scanning electrom microscope (SEM) and elemental analysis were determined. As a result cells exposed to Cr(VI) and Cd(II), produced more exopolysaccharides and morphological defects were determined at cells exposed to metal mixture whwn compared with control. Also, protein profiles by SDS-PAGE of Synechocystis sp. BASO670 isolate which was exposed to metals at the same conditions of bioaccumulation, were determined by SDS-PAGE. When compared with control, some differences at protein values, a different protein synthesis at the cells exposed to Cr(VI) and some missing proteins at the cells exposed to metal mixture were detected. Also Synechocystis sp. BASO670 was evaluated with metals at the same conditions of bioaccumulation and total thiol, non-protein thiol and protein binded thiol values were determined. It was determined an increase especially at the protein binded thiols levels of the isolate exposed to metals.