Preliminary characterization of two Spirulina strains from the North Adriatic Sea (Italy)

Cyanobacteria and microalgae are photoxygenic microorganisms that can be found in different habitats worldwide, even those considered extreme. To cope with the typical environmental conditions where they live, but also to face sudden possible environmental changes, these microorganisms can adopt several strategies, including the production of bioactive compounds (e.g., Andersen, 1992; Whitton, 2012; Sciuto & Moro, 2015; Malcata et al., 2018). Many of the compounds produced by cyanobacteria and microalgae can be employed in different human fields (e.g., Levasseur et al., 2020; Alvarez et al., 2021; Kiran & Venkata Mohan, 2021), and projects aiming at finding new biomolecules and/or new exploitation ways of these photoxygenic microorganisms are increasing in the last years. Since the capability to produce some compounds by cyanobacteria and microalgae varies according to the taxa and there can be differences even among strains belonging to a same genus and/or species (e.g., Lauritano et al., 2016; Levasseur et al., 2020), the correct identification and characterization of these photoxygenic microorganisms are at the base of every more practical study. Nevertheless, cyanobacterial and microalgal biodiversity and potentialities are still underestimated, in particular for some taxa (e.g., Gaignard et al., 2019) and/or habitats (e.g., Jaspars et al., 2016; Cordeiro et al., 2020). In this context, the research project “Biotechnological potentials of microalgae for environmental sustainability” has been recently founded by the European Social Fund (ESF) - Italian National Operational Programme (NOP) on Research and Innovation 2014-2020, with the aim of isolating several cyanobacterial and microalgal strains from the environment and of characterizing them to understand their potentialities, with a focus on marine and transitional water habitats. Here we present the preliminary data obtained during the characterization of two Spirulina strains from the North Adriatic Sea (Italy). More precisely, the two cyanobacterial strains (temporarily tagged as strain KS5 and strain KS6) were sampled from a microbial biofilm growing on the glass walls of an artificial aquarium, filled in with water taken from Santa Maria del Mare (Venice Lagoon) and used to grow the seagrass Cymodocea nodosa (Ucria) Ascherson. In order to better identify and characterize these two cyanobacterial strains, molecular analyses were carried out, as well as morphological (light microscopy and scanning electron microscopy) and ultrastructural (transmission electron microscopy) observations. Biochemical analyses are, instead, still underway. Strain phylogeography and problems regarding the systematics of the genus Spirulina Turpin ex Gomont will also be discussed.