Bacterial oxidation of iron in the iron sulfide mineral pyrite is also an important part of the microbial leaching process, because the ferric iron produced, is itself an oxidant of ores. A major toxic form of mercury is methylmercury. The ability of bacteria to resist the toxicity of heavy metals is often due to the presence of specific plasmids that encode enzymes capable of detoxifying the metals. Hydrocarbons are generally stable in anoxic environments, but are subject to microbial attack in oxic habitats. Addition of inorganic nutrients is important for bioremediation of spilled oil.
Some algae can produce hydrocarbons.
The crown gall bacterium Agrobacterium enters into a unique relationship with higher plants. The crown gall plasmid has also found extensive use in the genetic engineering of crop plants. The bacteria induce the formation of root nodules, within which the nitrogen-fixing process occurs. The plant provides the organic energy source needed by the root nodule bacteria, and the bacteria provide fixed nitrogen for the growth of the plant.