The study of microbial biotransformation reactions has
focused largely on chemical substances of particular interest
to humans. The terms ‘biotransformation’, ‘biocatalysis’ and
‘biodegradation’ have been used almost interchangeably,
depending on the interest of the people studying the
reactions. In this issue, there are excellent descriptions of
biodegradation reactions for the biotransformation of
potentially toxic compounds. Examples include the
nitroaromatic explosives, such as 2,4,6-trinitrotoluene
(TNT), the PCBs, and the phosphotriester pesticides and
nerve agents. In the case of PCBs, Abraham et al. point out
that these materials have apparently been co-opted as final
electron acceptors in anaerobic sediments where electron
acceptors are probably deficient. This represents a specific
adaption to the chemical environment. With TNT, Heiss
and Knackmuss (pp 282–287) tell a somewhat different
story of apparently non-specific reduction of nitroaromatic
explosives to generate intermediates that react to oligomerize
and condense with soil organic material. Whatever the
intent of the soil microbes, these reactions have potential
utility by rendering the compounds less leachable and
bioavailable and, thus, can be construed as environmental
detoxification. In the case of synthetic phosphotriester
compounds, microbial hydrolysis offers a dramatic
reduction in toxicity and, thus, has broad applications.
Phosphotriester pesticides such as paraoxon have been
shown to be excellent substrates for the phosphotriesterase
from Pseudomonas diminuta, which has been extensively
studied by Raushel (pp 288–295) and is the subject of the
review on this topic in this issue. The review points out that
the most toxic of the synthetic organophosphate compounds are military nerve agents such as soman and VX.