A device for cathodic protection against corrosion of at least one metal structure in contact with an electrolytic medium comprising a sedimentary soil, said protective device dispensing with the need for a sacrificial metal and means for connection to an electrical distribution network, said protection device including: - at least two microbial anode systems each comprising microorganisms and an electrode configured to be in contact with said microorganisms and said electrolytic medium, said microorganisms having the ability to supply electrons to the electrode by degradation of oxidizable ambient resources following oxidation-reduction reactions, the electrode of each microbial anode system being configured to be buried at least partially in said sedimentary soil of the electrolytic medium and the free electrochemical potential of each microbial anode system being lower than the free electrochemical potential of the metal of said at least one metal structure to be protected; - at least one connecting means configured to connect each microbial anode system to said at least one metal structure and configured to let the electrons circulate from the electrode of each microbial anode system up to said at least one metal structure; so that a protective galvanic current is applied through the electrolytic medium from at least one of the microbial anode systems up to said at least one metal structure when said at least one microbial anode system is in contact with said electrolytic medium and is connected by said at least one connecting means to said at least one metal structure, said protection device being characterized in that it further includes: ∘ a system for measuring the current of electrons circulating in each connecting means allowing determining the variations in depletion of the oxidizable ambient resources which are in the environment close to the microbial anode system to which the connecting means is connected, ∘ a control system allowing stopping and activating the circulation of the current of electrons circulating in each connecting means. - at least two microbial anode systems each comprising microorganisms and an electrode configured to be in contact with said microorganisms and said electrolytic medium, said microorganisms having the ability to supply electrons to the electrode by degradation of oxidizable ambient resources following oxidation-reduction reactions, the electrode of each microbial anode system being configured to be buried at least partially in said sedimentary soil of the electrolytic medium and the free electrochemical potential of each microbial anode system being lower than the free electrochemical potential of the metal of said at least one metal structure to be protected; - at least one connecting means configured to connect each microbial anode system to said at least one metal structure and configured to let the electrons circulate from the electrode of each microbial anode system up to said at least one metal structure; ∘ a system for measuring the current of electrons circulating in each connecting means allowing determining the variations in depletion of the oxidizable ambient resources which are in the environment close to the microbial anode system to which the connecting means is connected, ∘ a control system allowing stopping and activating the circulation of the current of electrons circulating in each connecting means.