« Spirulina labyrinthiformis » Gomont: prima segnalazione nelle Terme di Segesta (Sicilia)

Abstract

First report of the presence of Spirulina labyrinthiformis Gomont in Thermae of Segesta (Sicily). – The study on the algal ecology of thermal waters in Segesta shows for the first time the occurrence of Spirulina labyrinthiformis Gomont. It is interesting to note the high population density of Spirulina against the other components of the algal microflora, represented by the species of Cyanophyceae and Bacillariophyceae and that of photosynthetic bacteria.     

Spirulina culture in sea-water

Summary Laboratory experiments using small raceway ponds have shown that Spirulina maxima can be adapted easily to grow in sea-water supplemented with nitrate, phosphate, bicarbonate, and Fe-EDTA. To prevent precipitate formation, phosphate was supplied by diffusion through a dialysis membrane; the amount of Na-bicarbonate added was low (100 ppm) and the pH was kept in the range 8.6–8.8 by bubbling CO₂ into the culture.No significant differences have been noticed in productivity or in the chemical composition of the biomass between cultures in sea-water and in the standard bicarbonate medium. Cultures subjected to light/dark cycles of 12/12 h showed a higher respiration rate in sea-water than in the bicarbonate medium.The higher weight loss in the sea-water medium in the dark was counterbalanced by an increased synthesis of carbohydrates during the light period.     

Two halophilic Ectothiorhodospira strains with unusual morphological,physiological and biochemical characters

Two strains belonging to the genus Ectothiorhodospira were isolated from enrichment cultures inoculated with sulfide-containing samples from the saltern of Trapani. Cells are motile short spirilla with internal stacks of membranes. During sulfide utilization they produce external globules of sulfur that are then completely oxidized to sulfate. These halophilic microorganisms need NaCl concentrations of 11% and 18% and a slightly alkaline pH. They are typical photoautotrophic bacteria, utilizing sulfide, sulfur and, only one of them, thiosulfate as photosynthetic electron donors; growth is stimulated by organic compounds. Neither of the two strains is capable of assimilatory sulfate reduction and neither grows in the dark. Pigments of the two strains are bacteriochlorophyll a and carotenoids of the normal spirilloxanthin series subgroup 1B. Quinones are Q8 and MK8 in a strain and Q8 and MK7 in the other one: the latter situation, with quinone side chains of different lengths, is atypical within phototrophic bacteria. For morphological, physiological and biochemical characters, at least one of these strains clearly stays apart from the six Ectothiorhodospira species described until now.List of abbreviations HPLC high performance liquid chromatography - TLC thin layer chromatography - Qn ubiquinone—number of isoprenoid units of the side chain - MKn menaquinone—number of isoprenoid units of the side chain - R_t retention time - R_f retention factor Dedicated to the memory of Professor Gino Florenzano who inspired this work