A filter-plate method for the recovery and cultivation of microorganisms utilizing volatile organic compounds

Abstract

The recovery on solid media of microorganisms able to utilize complex mixtures such as petroleum hydrocarbons (PHCs) as their sole source of carbon and energy can be difficult due to differing solubilities of the PHC components. The inability to get adequate amounts of these compounds to partition into the solid media during preparation, without the use of surfactants, is a problem. To deal with these problems, an easy, inexpensive, and rapid method was developed for recovery and cultivation of microorganisms that are capable of growing on PHCs and other types of volatile and relatively insoluble substrates as sole sources of carbon and energy. This method involves introduction of the substrate to the microorganisms in the vapor phase by placing the growth substrate on a filter pad in the lid of a petri dish containing a minimal agar medium and microorganisms. The plate is incubated inverted, so the substrate/filter pad is below the microorganisms; growth can occur only if the microbes can utilize the volatilized compounds. This method has been used with a variety of volatilized hydrocarbon compounds, such as benzene, naphthalene, and alpha-pinene, to cultivate and enumerate both pure and mixed cultures of microorganisms. The filter pad method may be of use in the evaluation of microorganisms for their application to biofiltration applications.