This is not a new problem. When I was a new apprentice in the late 1960s the L188 fleet (of a South Pacific operator) had a hell of a problem with the lower wing planks rotting out from this microbial contamination. We were told that the "bugs" lived in the water phase and "ate" the kerosene to live, producing corrosive products as they did so. Our stated strategy was to carry out scrupulous water drains to keep the water phase at a minimum and introduce various (unknown to me) chemicals to aid in killing the bugs.
The end result for this little black duck was that I spent a lot of time inside the tanks grinding off corrosion to the extent that one aircraft had a doubler fitter to the inboard lower wings to make up for the dramatically reduced plank thickness. The rego lent itself to an obvious acronym - XX-ECC, obviously "'ere comes corrosion"!! OTOH, the "tank allowance" and overtime were quite welcome!!