Molybdenum is reported to be very toxic to ruminants and shows evidence of spermatogenesis
toxicity in animals and insects. Hence, its removal is important. In this study, we report on the
first isolation of molybdenum-reducing bacterium from agricultural soil. The bacterium reduces
hexavalent molybdenum (sodium molybdate) to molybdenum blue (Mo-blue); a colloidal
product, which can be trapped and removed from solution. Phylogenetic analysis resulted in a
tentative identification of the bacterium as Serratia sp. strain MIE2. The optimum conditions for
Mo-blue production using the normal one-variable-at-a-time (OVAT) approach were 10 mM of
sodium molybdate, pH 6.0, a temperature of 35°C, ammonium sulphate at 10 g/L as the nitrogen
source and sucrose concentrations of between 30-50 g/L as the carbon source and electron donor
for molybdate. Studies on the effects of pesticides and solvents on Mo-blue production showed
that Mo-blue production from whole cells was relatively more affected by these xenobiotics
compared to the crude enzyme. Nevertheless, the strain was resistant to most of the xenobiotics
tested. Based on the strain MIE characteristics, the bacterium will be a suitable candidate for the
remediation of aquatic bodies and agricultural soils contaminated with molybdenum.