Anaerobic microbial communities

Yang, Y., Pesaro, M., Sigler, W., and Zeyer, J., 2005, Identification of microorganisms involved in reductive dehalogenation of chlorinated ethenes in an anaerobic microbial community. Water Res. 39 3954-3966. 

Soil columns with an undefined anaerobic microbial community were supplied with a mixture of the most prominent aromatic contaminants benzene, toluene, ethylbenzene and o,w,j3-xylene. 

Stams AIM, de Bok FAM, Plugge CM, van Eekert MHA, Dolling J, Schraa G. Exocellular electron transfer in anaerobic microbial communities. Environ Microbiol 2006 8 371-382. 

Rossetti S, LL Blackall, M Majone, P Hugenholtz, JJ Plumb, V Tandoi (2003) Kinetic and phylogenetic characterization of an anaerobic dechlorinating microbial community. Microbiology (UK) 149 459-469. 

Shih C-C, ME Davey, J Zhou, JM Tiedje, CS Criddle (1996) Effects of phenol feeding pattern on microbial community structure and cometabolism of trichloroethylene. Appl Environ Microbiol 62 2953-2960. Somsamak P, HH Richnow, MM Haggblom (2005) Carbon isotope fractionation during anaerobic biotransformation of methyl ferf-butyl ether and ferf-amyl methyl ether. Environ Sci Technol 39 103-109. Somsamak P, RM Cowan, MM Haggblom (2001) Anaerobic biotransformation of fuel oxygenates under sulfate-reducing conditions. EEMS Microbiol Ecol 37 259-264. 

Figure 25. Early steps of anaerobic degradation of indole by Desulfobacterium indolicum and hypothetical metabolic steps of indole degradation by a denitrifying microbial community.

Based on the previous publications, azo dye can be reduced by azoreductase-catalyzed reduction under anaerobic conditions. But still there is a speculation whether bacterial flavin reductases are responsible for the azo reductase activity observed with bacterial cell extracts. In a published report, it is reported that flavin reductases are indeed able to act as azo reductases [24]. Bacteria produce extracellular oxidative enzymes, which are relatively nonspecific enzymes catalyzing the oxidation of a variety of dyes. It was reported that so many diverse groups of bacteria play a role in decolorization. It has been also reported that mixed microbial community could reduce various azo dyes, and members of the y-proteabacteria and sulfate reducing bacteria (SRB) were found to be prominent members of mixed bacterial population by using molecular methods to determine the microbial population dynamics [1],... 

Nealson KH, Saffarini D (1994) Iron and manganese in anaerobic respiration environmental significance, phylogeny, and regulation. Ann Rev Microbio 48 311-343 Nealson KH, Stahl DA (1997) Microorganisms and biogeochemical cycles what can we learn from layered microbial communities Rev Mineral 35 5-34... 

Again, the absence of monitoring data does not necessarily indicate a lack of cresols in the environment. Cresols are widely occurring natural and anthropogenic products. However, biodegradation is probably the dominant mechanism responsible for the rapid removal of cresols from surface waters (see Section 5.3.2.2). Nevertheless, cresols may persist in extremely oligotrophic waters, in waters with limited microbial communities, and/or under anaerobic conditions such as in some sediments and groundwater aquifers. 

Differences in rates of transformation and/or utilization between the two systems are possibly due to a) constant input vs. single input of p-coumaric acid and nutrient solution, b) aerobic (open system) vs. more anaerobic (closed system) conditions, c) little chance for accumulation of transformation products and/or toxic microbial byproducts (constant flushing of system) vs. potential build up of transformation products and/or toxic microbial byproducts (closed system), d) different microbial communities both in terms of species (air-dried soil vs. autoclaved-inoculated soil) and numbers (10s vs. 108), and e) input of p-coumaric acid (53 pg/mL/h or 187 pg/h vs. 58 pg/mL one time addition) added to different amounts of soil (60 g of soil for the flow-through system vs. 1 g of soil for the test tube system). 

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