A simple¹⁴C-respirometric method for assessing microbial catabolic potential and contaminant bioavailability

Abstract

This paper describes the validation and application of a simple flask-based (14)C-respirometer system designed to assess mineralisation of (14)C-labelled substrates under defined conditions. Validation of this respirometer system indicated stoichiometric CO(2) trapping up to a maximum of 400 micromol of CO(2) (in a single trap). Polycyclic aromatic hydrocarbon (PAH)-degrading bacteria were used to measure growth-linked biodegradation of [(14)C]naphthalene to (14)CO(2). A (14)C activity balance of 101.7+/-8.9% (n=6), after 74 h incubation time and 10 respirometer-opening events, indicated the suitability of the system for monitoring substrate mineralisation. This respirometric apparatus was then successfully applied to assess: (i) the PAH catabolism of microbes in a field contaminated soil, where naphthalene and phenanthrene were rapidly mineralised and (ii) soil-associated organic contaminant bioavailability, where increased soil-phenanthrene contact time resulted in a reduction in phenanthrene mineralisation in the soil. The described respirometer system differs from existing respirometer systems in that the CO(2) trap can be removed and replaced quickly and easily. The system is efficient, reproducible, adaptable to many situations, easy to construct and simple to use, it therefore affords advantages over existing systems.

Influence of Wood Biochar on Phenanthrene Catabolism in Soils

“…However it is worthy to note that 14 C-phenanthrene was spiked directly into aqueous solution of the respirometer assay and not into soil. Furthermore, the slurry method used enables agitation which tends to aid distribution of microorganisms evenly [4,27], and facilitates degradation of phenanthrene, while soil particles separate into suspension [27]. In so doing, microorganisms adhere to BC particles to reduce distance to substrate and mineralise phenanthrene [9,46,47], whilst presence of microbes on pore sites and native SOM may attenuate sorption capacity of biochar [20].…”

“…Results of biochar analysis are shown in Table 2. of soil) with toluene as the carrier solvent [27]. The mineralisation of 14 C-phenanthrene was determined by measuring the evolution of 14 CO 2 using modified 250 mL Schott bottles containing 1 M NaOH (1 mL) as a CO 2 trap, which was replaced daily [27].…”

“…of soil) with toluene as the carrier solvent [27]. The mineralisation of 14 C-phenanthrene was determined by measuring the evolution of 14 CO 2 using modified 250 mL Schott bottles containing 1 M NaOH (1 mL) as a CO 2 trap, which was replaced daily [27]. After 1, 20, 60 and 100 d aging in the dark at 21 ± 1 °C, respirometers were prepared in triplicate, with 10 ± 0.2 g soil (w/w) and 30 [28] recommend a 1:3 soil:liquid ratio for greater reproducibility and overall extents of mineralisation.…”

Polycyclic Aromatic Hydrocarbon Degradation of Phytoplankton-Associated Arenibacter spp. and Description of Arenibacter algicola sp. nov., an Aromatic Hydrocarbon-Degrading Bacterium

“…Decane, n-hexadecane, and anthracene were not mineralized. Using the validated and highly sensitive flask-based 14 C-respirometer system of Reid et al (17), detectable mineralization of phenanthrene and naphthalene occurred within 2 days and continued up until day 40, at which time these incubations were terminated (Fig. 1).…”

“…To compare the rate and extent at which strain TG409 T could mineralize 14 C-labeled phenanthrene and naphthalene, a highly sensitive 14 Crespirometer system (17) was used. This is a flask-based system designed to monitor substrate mineralization for up to 10 weeks with multiple respirometer-opening events.…”