[Real time history of 21st century bacteria: giants and martians]

We denominate "21st century bacteria" two types of strange and amazing creatures from the kingdom Protista, discovered between the last years of the twentieth and the present days: the giant bacteria and those with a possible Martian origin. Searching for them, bold investigators have travelled to distant and hostile lands, desolate places and deep waters, performing a kind of investigation that we only can describe as "investigation-adventure". This paper presents expeditions to the Red Sea, fishing the Epulopiscium; to Lake Mono, searching a bacteria able to growth with arsenic; to the Antarctic Circle, finding a meteorite with petrified alien microorganisms; and… to the quiet laboratory, a not less dangerous place.