Bacterial degraders, assessment

Several HPLC methods for the assessment of flavins in urine are available, the majority being published before 1989 (for review, see 1) (18,26,33,70,71). HPLC has been shown to be a fast, sensitive, simple, and reproducible analytical method for urinary flavins (Table 5). Using fluorescence detection, flavin concentrations as low as 0.05 to 0.30 Ag/mL and as high as 2 to 12 p,g/mL RF can be measured without concentration or dilution, respectively. No special pretreatment procedure is necessary for HPLC of urine samples. Fresh urine samples are injected either directly or after centrifugation, to remove most of the sediment. Due to bacterial degradation, the stability of riboflavin in fresh urine is limited at room temperature, even in the dark. Consequently, all flavin-containing urine samples should be stabilized by acidification (acetic or oxalic acid) and/or adding a small amount of toluene. 

The subsequent fate of the assimilated carbon depends on which biomass constituent the atom enters. Leaves, twigs, and the like enter litterfall, and decompose and recycle the carbon to the atmosphere within a few years, whereas carbon in stemwood has a turnover time counted in decades. In a steady-state ecosystem the net primary production is balanced by the total heterotrophic respiration plus other outputs. Non-respiratory outputs to be considered are fires and transport of organic material to the oceans. Fires mobilize about 5 Pg C/yr (Baes et ai, 1976 Crutzen and Andreae, 1990), most of which is converted to CO2. Since bacterial het-erotrophs are unable to oxidize elemental carbon, the production rate of pyroligneous graphite, a product of incomplete combustion (like forest fires), is an interesting quantity to assess. The inability of the biota to degrade elemental carbon puts carbon into a reservoir that is effectively isolated from the atmosphere and oceans. Seiler and Crutzen (1980) estimate the production rate of graphite to be 1 Pg C/yr. 

Boyd, E.M., Meharg, A.A., Wright, J. and Killham, K. (1997b) Assessment of toxicological interactions of benzene and its primary degradation products (catechol and phenol) using a /wx-modified bacterial bioassay. Environmental Toxicology and Chemistry, 16, 849-856. 

Figure k. Diphenamid, MBC and EPTC degradation by mixed bacterial cultures obtained from history (P) and non-history (NP) soils, respectively. EPTC degradation was assessed by measuring evolution. 

For many years, traditional microbiological techniques such as direct microscopy and enrichment cultivation have been used to study microbial diversity in contaminated ecosystems. Assessing the bacterial diversity by direct microscopy is very difficult due to the simple morphology of bacteria and the lack of conspicuous traits that distinguish them from each other. Isolation of oil-degrading bacteria was, and still is, an essential discipline in biodegra-... 

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