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Il Lago di Cadagno è teatro di una scoperta sullo sviluppo della vita nelle prime fasi del nostro pianeta. Nel laghetto alpino ticinese ricercatori internazionali hanno infatti osservato il ruolo centrale di alcuni batteri per la fissazione dell'azoto negli oceani primordiali, un processo importantissimo.
Che il Lago di Cadagno, a quasi 2mila metri d'altezza, poco sopra il Ritom in Leventina, fosse fuori dal comune lo si era capito già oltre un secolo fa. Per il colore, per il numero di pesci e la biodiversità. Merito di una caratteristica rara: gli strati d'acqua non si mischiano (meromissi), ed è questo che ha attirato anche la ricerca a cui ha partecipato la biochimica Lenny Winkel, professoressa al politecnico di Zurigo e ricercatrice all'Eawag, istituto svizzero di ricerca sull'acqua: “500 milioni fa gli oceani avevano una struttura biochimica simile. Sul fondo c'è poco ossigeno, e nonostante ciò si trovano batteri che svolgono un ruolo importante per l'ambiente”.
In un articolo pubblicato oggi (venerdì) su Nature Communications i ricercatori spiegano come la fissazione dell'azoto - una delle sostanze più importanti per la vita - avvenga non solo tramite cianobatteri, ma anche grazie a un gruppo di batteri dello zolfo, che tra l'altro danno il colore rosso chiaro all'acqua del lago. Ma che rilevanza ha questa novità osservata per la prima volta nel lago ticinese? “L'azoto era ed è presente sulla terra come gas... ma ci vuole un'organismo che lo catturi e lo renda disponibile anche agli organismi. Questo processo per gli scienziati è rilevante” spiega ancora Winkel.
Fluorescenza di batteri di zolfo viola in acqua dolce del lago Cadagno (in verde e viola) e la loro fissazione dell'azoto monocellulare misurata da nanoSIMS (pannelli inferiori)
La ricerca è stata svolta sotto la guida di scienziati del Max Planck Institut germanico, ma la collaborazione con atenei svizzeri è stata importante, sottolinea la professoressa Winkel. Oltre all'Eawag è stata coinvolta anche la SUPSI. Sul posto ci sono i laboratori del Centro Biologia Alpina di Piora, e le conoscenze locali sono preziose per gli scienziati internazionali che sono arrivati, e che di certo ancora arriveranno al Lago di Cadagno.
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