Xenoestrogen
Xenoestrogens are a type of xenohormone that imitates estrogen. They can be either synthetic or natural chemical compounds. Synthetic xenoestrogens include some widely used industrial compounds, such as PCBs, BPA, and phthalates, which have estrogenic effects on a living organism even though they differ chemically from the estrogenic substances produced internally by the endocrine system of any organism. Natural xenoestrogens include phytoestrogens which are plant-derived xenoestrogens. Because the primary route of exposure to these compounds is by consumption of phytoestrogenic plants, they are sometimes called "dietary estrogens". Mycoestrogens, estrogenic substances from fungi, are another type of xenoestrogen that are also considered mycotoxins.
Xenobiotic
Microorganisms may be a viable solution to the issue of environmental pollution by the production of xenobiotics; a process known as bioremediation. Microorganisms are able to adapt to xenobiotics introduced into the environment through horizontal gene transfer, in order to make use of such compounds as energy sources. This process can be further altered to manipulate the metabolic pathways of microorganisms in order to degrade harmful xenobiotics under specific environmental conditions at a more desirable rate. Mechanisms of bioremediation include both genetically engineering microorganisms and isolating the naturally occurring xenobiotic degrading microbes. Research has been conducted to identify the genes responsible for the ability of microorganisms to metabolize certain xenobiotics and it has been suggested that this research can be used in order to engineer microorganisms specifically for this purpose. Not only can current pathways be engineered to be expressed in other organisms, but the creation of novel pathways is a possible approach.