Glucose and plant exudate enhanced enumeration of bacteria capable of degrading polycyclic aromatic hydrocarbons.

Enumerating environmental microbial isolates capable of polycyclic aromatic hydrocarbon (PAH) degradation can provide insight into the microbe-plant interactions that facilitate PAH removal. We examined a known PAH degrader ( Pseudomonas putida G7), a nondegrader ( Agrobacterium tumefaciens LBA4404), and several microorganisms isolated from the environment by using a PAH cocktail in an enumeration medium with or without 0.025% (m/v) glucose and (or) root exudates. Compared with the standard most probable number (MPN), the addition of glucose and root exudates in a modified MPN method resulted in a 3- to 11-fold enhancement of PAH degraders being enumerated among microorganisms found in PAH-contaminated soils. High-performance liquid chromatography analysis verified that PAH levels were reduced using this modified enumeration method. Low levels of glucose, perhaps in concert with other materials in exudates, may promote microbial metabolism, thereby enhancing PAH degradation.