Bacteria sense many chemical signals in their environments and respond to them in various ways. One way thatthey respond is by swimming toward compounds that
provide food or a signal of a protective environment. Parales
and Harwood (pp 266–273) review bacterial chemotaxis to
aromatic molecules. Some of these compounds play a key
ecological role as plant-derived signals that initiate intimate
relationships, including tumor formation by
Agrobacterium tumefaciens and nodulation by Rhizobium.
Bacteria are also attracted to diverse aromatic pollutants,
such as benzene, naphthalene and chlorinated herbicides,
as a precedent to degradation of these compounds. It is
likely that the response to aromatic compounds and the
associated chemotactic signal transduction pathways
evolved to mediate response to plant-derived compounds,
but may now be exploited for human ends to deal with
environmental pollutants of related chemical structures.
Similarly, many bacteria can degrade or transform plantderived
alkaloid compounds, such as opiates from the
poppy plant, and these degradation abilities can be harnessed
for drug discovery or modeling transformation of drugs in
the human body. Rathbone and Bruce (pp 274–281) provide us with an insight into the pathways used by bacteria to confront the alkaloids they encounter in nature and survey the exploitation of these pathways to manipulate and create synthetic alkaloids for medicinal application and to construct biosensors for drug detection.