To date, different kinds of biosensing elements have been used effectively for environmental monitoring. Microbial cells seem to be well-suited for this task: they are cheap, adaptable to variable field conditions and give a measurable response to a broad number of chemicals. Among different
pollutants,
heavy metals are still a major problem for the environment. A reasonable starting point for the selection of a biorecognition
element to develop a biosensor for metals could be that of a microorganism that exhibits good mechanisms to cope with metals. Pseudomonads are characterized by the secretion of
siderophores (e.g.,
pyoverdine), low-molecular weight compounds that chelate Fe3+ during
iron starvation.
Pyoverdine is easily detected by colorimetric assay, and it is suitable for simple online measurements. In this work, in order to evaluate
pyoverdine as a biorecognition
element for
metal detection, the influence of
metal ions (Fe3+, Cu2+, Zn2+), but also of temperature, pH and nutrients, on microbial growth and
pyoverdine regulation has been studied in P. fluorescens. Each of these variables has been shown to influence the synthesis of
siderophore: for instance, the lower the temperature, the higher the production of
pyoverdine. Moreover, the concentration of
pyoverdine produced in the presence of metals has been compared with the maximum allowable concentrations indicated in international regulations (e.g., 98/83/EC), and a correlation that could be useful to build a colorimetric biosensor has been observed.