The aim of this study was to characterize the behaviour of a PAH-degrading bacterium to determine whether mineralization plateaus as a result of substrate removal, a decrease in microbial activity or nutrient availability in sterile soils over time. To investigate this, the mineralization of 14C-phenanthrene was measured until it plateaued; subsequently, additional 14C-phenanthrene, catabolic inocula or nutrients were introduced and mineralization was measured for a further 10 d. Cell numbers were also measured together with 14C-uptake into microbial biomass. Freshly added 14C-phenanthrene was rapidly metabolised by the microorganisms. Neither the addition of a catabolic inoculum nor nutrients affected the extent of 14C-phenanthrene mineralization. Cell numbers remained constant over time, with only a small amount of the 14C-activity incorporated into the microbial biomass. This study indicated that the termination of mineralization was due to the removal of available phenanthrene and not decreasing cellular activity or cell death. The mineralization values also correlated with 14C-phenanthrene extractability using β-cyclodextrin. Mineralization can estimate the microbial availability of 14C-contaminants in soil.
Semple was the senior and corresponding author of this paper. Dew/Doick/ Rhodes were postgraduate students, supervised by Semple. Numerous studies have assumed that mineralisation of chemicals is a measure of bioavailability and as a comparator for its chemical determination (see Paper 1 above); this paper addressed this assumption. RAE_import_type : Journal article RAE_uoa_type : Earth Systems and Environmental Sciences