Simultaneous species-specific PCR detection and viability testing of poly(vinyl alcohol) cryogel-entrapped Rhodococcus spp. after their exposure to petroleum hydrocarbons

A method of simultaneous species-specific PCR detection and viability testing of poly(vinyl alcohol) cryogel-entrapped Rhodococcus spp. was developed that allowed the estimation of immobilized Rhodococcus opacus and Rhodococcus ruber survival after their exposure to petroleum hydrocarbon mixture. Spectrophotometric INT assay revealed high tolerance of gel-immobilized rhodococci to petroleum hydrocarbons, while among two Rhodococcus strains studied, R. ruber tolerated better to hydrocarbons compared to R. opacus. These findings were confirmed by respirometry results that showed increased respiratory activity of gel-immobilized Rhodococcus strains after 10-day incubation with 3% (v/v) petroleum hydrocarbon mixture. Moreover, jointly incubated rhodococcal strains demonstrated higher oxidative activities toward petroleum hydrocarbons than individual strains. Both Rhodococcus species were recovered successfully in cryogel granules using 16S rDNA-targeted PCR, even though the granules were previously stained with INT and extracted with ethanol. The method developed can be used for rapid detection and monitoring of gel-immobilized bacterial inocula in bioreactors or contaminated soil systems.