BIOFILM FORMATION ON METAL STRUCTURES, BY A DEEP-OCEAN BACTERIUM

Metals find their way into the marine environment through different ways, as components of bridges, piers, ships, plane and ship wrecks, etc. Exposure of metals to the aqueous environment leads to two major processes – corrosion and biofouling.

Corrosion leads to the destruction of the properties of the metal and its subsequent dissolution into the medium. Microorganisms are known to influence the corrosion processes by altering the properties of the metal at the interface between the metal, microbes and water. They accomplish this by adhering to the metal surface by using extracellular polymeric substances (EPS) and forming irreversible bonds with the metal – leading to the formation of biofilms. These biofilms can alter the corrosion process by slowing or hastening it, depending on the microbes that constitute the biofilms.

In this study, the effect of a deep-ocean bacterium - isolated from the rusticles that were retrieved from the wreck of the Titanic – on corrosion of mild steel coupons was examined. Environmental scanning electron microscope, weight loss measurements and spectroscopic techniques were used to study these effects. The bacteria were found to form biofilms on the metal surface and alter the corrosion process. Severe corrosion was seen in the samples that were subjected to constant shaking as opposed to those that were static. The difference in the corrosion rate was assessed at lower temperatures, similar to those that exist in the deep ocean. This gives us a better understanding of the biogeochemical processes that lead to the cycling of metals.