Physiology of acid stream algae

Abstract

Sixteen axenic cultures of algae from acid streams of known water chemistry were produced without the use of antibiotics. These included four strains of Euglena mutabilis (Durham Culture Collection No. D464, D640, D641, D642). Strain D464, isolated from Brandon Acid Stream, Co, Durham, was selected for detailed study; the pH of the stream was 2.6.The optimum yield of E. mutabilis D464 in the basal medium at pH 2.6, occurred at a photon flux density of 100 µmol m(^-1)s(^-1). All four strains (D464, D640, D641, D642) had optimum yields between pH 3.4 and 4.0. Adaptation to low and high pH was checked with strain D464 and it was found that this strain could be adapted to grow at pH 1.5. and at pH 8.5.The nutritional requirements and tolerance to heavy metals of strains D464, D640 and D641 was investigated under standard growth conditions and was found that Na (10 mg 1(^-1) to 25 mg l(^-1)) improved yield. Strains D464, D640 and D641 grew in the vitamin-free basal medium, however in the strain chosen for detailed study (D464) adding vitamin B(_1) and B(_12) improved yield. Heterotrophic and photoheterotrophic growth was investigated using strains D464, D640 and D641 and was found that they utilize the following organic carbon substrates, glucose, fructose, sucrose, glycerol, lactic acid and acetate. Yield was least in acetate. These strains also utilized β-alanine, Dl-asporagine, glycyl-glycine, urea, uric acid and ethanol-amine as sole nitrogen source in the presence of light but not in the dark. Using strain D464 phosphatase activity was checked and was found that this strain had both acid and alkaline cell surface phosphatase activity. All three strains (D464, D640, D641) tested showed tolerance to varying concentrations of different heavy metals. Tolerance in the diminishing order appears to be as follows: Al>Mn>Pb>Ni>Co>Zn>Cu>Fe>Cd. Factors influencing Zn toxicity were investigated using strain D464 and it was found that Zn toxicity influenced by the size of the inoculum, The pH and the composition of growth medium. Na and Ca (above 10 mg 1(^-1)) increased toxicity to Zn, while CI (up to and including 75 mg 1 (^-1) ) and glycyl-glycine reduced Zn toxicity. K (160 mg l(^-1)), Mg (200 mg l(^-1)) and Mn (80 mg l(^1)) had no effect on Zn toxicity in strain D464.