In the industry, the microbes are referred to as Hydrocarbon Utilizing Microorganisms, or H.U.M. bugs.
The most common H.U.M. bugs found in petroleum products are Cladosporium Resinae and Pseudomonas Aeruginosa. H.U.M. bugs enter your fuel system from contaminated sources. Every stop in the commercial fuel distribution process has the potential for breeding these bugs, and it only takes a few microbes to start a problem in your boat fuel tank. H.U.M. bugs need water to sustain them and multiply. They don’t survive in pure fuel. Water shows up in fuel tanks and storage vessels from condensation on the inside of the tanks or by entering through breathers in moisture-laden air. In addition to creating a breeding ground for H.U.M. bugs, the water present in fuel combines with the sulfur in diesel fuel to form sulfuric acid. Since water is heavier than fuel, this sulfuric acid sits on the bottom of tanks, usually trapped in a “sludge” of H.U.M. bugs and their waste products.
http://felixmarine.net/article-fuel-polishing.html
I don’t know for sure, but maybe what I am talking about is not was the caller is talking about.
Well answers my question. Kind of creepy aren't they?