Cometabolism

For those pesticides that are cometabolized, ie, not utilized as a growth substrate, the assumption of first-order kinetics is appropriate. The more accurate kinetic expression is actually pseudo-first-order kinetics, where the rate is dependent on both the pesticide concentration and the numbers of pesticide-degrading microorganisms. However, because of the difficulties in enumerating pesticide-transforming microorganisms, first-order rate constants, or half-hves, are typically reported. Based on kinetic constants, it is possible to rank the relative persistence of pesticides. Pesticides with half-hves of <10 days are considered to be relatively nonpersistent pesticides with half-hves of >100 days are considered to be relatively persistent. 

Aerobic biodegradation of trichloroethylene occurs by cometabolism with aromatie eompounds (Ensley 1991) and thus requires a cosubstrate such as phenol (Nelson et al. 1987, 1988) or toluene (Fan and Scow 1993). Trichloroethylene degradation by toluene-degrading baeteria has been demonstrated in the presence, but not absence, of toluene (Mu and Scow 1994). Isoprene, a structural analog of trichloroethylene, has also been used as a cosubstrate for triehloroethylene oxidation by some bacteria (Ewers et al. 1990). One source of inhibition of degradation in the absence of cosubstrate may be the toxieity of triehloroethylene itself to indigenous bacteria. 

Alvarez-Cohen L, McCarty PL. 1991b. Product toxicity and cometabolic competitive inhibition modeling of chloroform and trichloroethylene transformation by methanotrophic resting cells. Appl Environ Microbiol 57 1031-1037. 

The oxidation of a number of chloroalkanes and chloroalkenes including dichlorometh-ane, chloroform, 1,1,2-trichloroethane, and 1,2,2-trichloroethene (Vannelli et al. 1990). Although the rate of cometabolism of trihalomethanes increased with levels of bromine substitution so also did toxicity. Both factors must therefore be evaluated in the possible application of this strain (Wahman et al. 2005). 

Rasche ME, MR Hyman, DJ Arp (1991) Factors limiting aliphatic chlorocarbon degradation by Nitrosomonas europaea cometabolic inactivation of ammonia monooxygenase and substrate specificity. Appl Environ Microbiol 57 2986-2994. 

Wahman DG, LE Katz, GE Speitel (2005) Cometabolism of trihalomethanes by Nitrosomonas europaea. Appl Environ Microbiol 71 7980-7986. 

Cometabolism merits, however, careful analysis since important metabolic principles underlie most of the experiments, even though confusion may have arisen as a result of ambiguous terminology. An attempt is therefore made to ignore semantic implications and to adopt a broad perspective in discussing this enviromnentally important issue. A pragmatic point of view has been adopted, and the following examples attempt to illustrate the kinds of experiments, which have been carried out under various conditions. 

Adriaens P, DD Focht (1991a) Evidence for inhibitory substrate interactions during cometabolism of 3,4-dichlorobenzoate hy Acinetobacter sp. strain 4-CBl. FEMS Microbiol Ecol 85 293-300. 

Adriaens P, DD Focht (1991b) Cometabolism of 3,4-dichlorobenzoate by Acinetobacter sp. strain A-CQ. Appl Environ Microbiol 57 173-179. 

Blasco R, M Mallavarapu, R-M Wittich, KN Timmis, DH Pieper (1997) Evidence that formation of protoanemonin from metabolites of 4-chlorobiphenyl degradation negatively affects the survival of 4-chlorobiphenyl-cometabolizing microorganisms. Appl Environ Microbiol 63 434. 

Hamamura N, C Page, T Long, L Semprini, DH Arp (1997) Chloroform cometabolism by butane-grown CF8, Pseudomonas butanovora, and Mycobacterium vaccae JOB5 and methane-grown Methylosinus tricho-sporium Appl Environ Microbiol 63 3607-3613. 

Hay AG, DD Focht (1998) Cometabolism of l,l-dichloro-2,2-bis(4-chlorophenyl)ethylene by Pseudomomas acidovorans M3GY grown on biphenyl. Appl Environ Microbiol 64 2141-2146. 

Hopkins GD, PL McCarty (1995) Field evaluation of in situ aerobic cometabolism of trichloroethylene and three dichloroethylene isomers using phenol and toluene as primary substrates. Environ Sci Technol 29 1628-1637. 

Horvath RS (1971) Cometabolism of the herbicide 2,3,6-trichlorobenzoate. J Agric Eood Chem 19 291-293. 

Megharaj M, A Jovcic, HE Boul, JH Thiele (1997) Recalcitrance of l,l-dichloro-2,2-bis(p-chlorophenyl) ethylene (DDE) to cometabolic degradation by pure cultures of aerobic and anaerobic bacteria. Arch Environ Contam Toxicol 33 141-146. 

Saflic S, PM Fedorak, JT Andersson (1992) Diones, sulfoxides, and snlfones from the aerobic cometabolism of methylbenzothiophenes by Pseudomonas strain BTl. Environ Sci Technol 26 1759-1764. 

Shiaris MP, JJ Cooney (1983) Replica plating method for estimating phenanthrene-utilizing and phenan-threne-cometabolizing microorganisms. Appl Environ Microbiol 45 706-710. 

The cometabolism of halogenated methanes has been examined in Nitrosomonas europaea and may putatively be mediated by ammonia monooxygenase. 

Safinowski M, C Griebler, RU Meckenstock (2006) Anaerobic cometabolic transformation of polycyclic and heterocyclic aromatic hydrocarbons evidence from laboratory and field studies. Environ Sci Technol 40 4165-4173. 

Hernandez BS, JJ Arensdorf, DD Focht (1995) Catabolic characteristic of biphenyl-ntilizing isolates which cometabolize PCBs. Biodegradation 6 75-82. 

Engesser KH, MA Rubio, DW Ribbons (1988a) Bacterial metabolism of side chain fluorinated aromatics cometabolism of 4-trifluoromethyl (TFM)-benzoate by 4-isopropylbenzoate grown Pseudomonas putida IT strains. Arch Microbiol 149 198-206. 

Drzyzga O, A Schmidt, K-H Blotevogel (1996) Cometabolic transformation and cleavage of nitrodiphenylamines by three newly isolated sulfate-reducing bacterial strains. Appl Environ Microbiol 62 1710-1716. 

Annweiler E, W Michaelis, RU Meckenstock (2001) Anaerobic cometabolic conversion of benzothiophene by a sulfate-reducing enrichment culture and in a tar-oil-contaminated aquifer. Appl Environ Microbiol 67 5077-5083. 

Hardison L, SS Curie, LM Ciuffeti, MR Hyman (1997) Metabolism of diethyl ether and cometabolism of methyl terf-butyl ether by a filamentous fungus, a Graphium sp. Appl Environ Microbiol 63 3059-3167. 

Fries MR, GD Hopkins, PL McCarty, LJ Forney, JM Tiedje (1998a) Microbial succession during a field evaluation of phenol and toluene as the primary substrates for trichloroethene cometabolism. Appl Environ Microbiol 63 1515-1522. 

Fries MR, LJ Forney, JM Tiedje (1998b) Phenol- and toluene-degrading microbial populations from an aquifer in which successful trichloroethene cometabolism occurred. Appl Environ Microbiol 63 1523-1530. 

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