Some of the most popular fuel testing kits are those used to identify microbial contamination in diesel, jet fuel, and all other fuel derivatives. Microbiological contamination is sometimes known as “diesel bug” or “diesel fungus” in diesel fuel, and “jet fuel fungus” in jet fuel. Microbiological contamination consists of certain strains of bacteria, yeasts, and fungus that are deemed hazardous to fuel. These pollutants are especially common in middle distillate fuels.