Effects of Endogenous Substrates on Adaptation of Anaerobic Microbial Communities to 3-Chlorobenzoate

Abstract

Lengthy adaptation periods in laboratory studies evaluating the potential for contaminant biodegradation in natural or engineered environments may indicate that the native microbial communities are not metabolizing the contaminants in situ. In this study, we characterized the adaptation period preceding the biodegradation of 3-chlorobenzoate in anaerobic communities derived from lake sediment and wastewater sludge digesters. The importance of alternative mechanisms of adaptation of the anaerobic communities to 3-chlorobenzoate was evaluated by monitoring the concentrations of metabolic substrates and products as well as the levels of total small subunit (SSU) rRNA and SSU rRNA from populations thought to be important in 3-chlorobenzoate mineralization. The anaerobic environments from which the 3-chlorobenzoate-degrading communities were derived contained different levels of endogenous substrates. Increasing methane levels in the digester and sediment communities and decreasing chemical oxygen demand concentrations in the sediment community during the adaptation periods revealed that endogenous substrates were preferentially utilized relative to 3-chlorobenzoate. Methane and chemical oxygen demand concentrations leveled off concomitantly with the onset of 3-chlorobenzoate biodegradation, suggesting that depletion of the preferentially degraded endogenous substrates stimulated 3-chlorobenzoate metabolism. Consistent with these observations, adaptation to 3-chlorobenzoate occurred more rapidly in digester samples that were depleted of endogenous substrates compared to samples that contained high levels of these biodegradable compounds. Other potential adaptation mechanisms, e.g., genetic change or selective population enrichment, appeared to be less important based on the reproducibility and relative lengths of the adaptation events, trends in the SSU rRNA levels, and/or amplification of SSU rRNA genes from key populations.

Effect of biomass adaptation to biodegradation of dissolved organic carbon in water

“…However the rate of biodegradation is highly variable and dependent of many parameters including the chemical structure and concentration of the organic substance, temperature, salinity, pH, concentration of oxygen, inorganic nutrients, and concentration of microorganisms (Becker et al 2006;Brandt et al 2003Brandt et al , 2004Kulp et al 2007;Sanchez et al 2007;Spain et al 1980;Spain and Veld 1983;Steiner and Sauer 2001;Swindoll et al 1988;Wiggins and Alexander 1988). When a change in some of environmental factors occurs the biological systems are not able to react quickly (Somova et al 2005).…”

“…Several causes of this problem may be named including low detection limits of DOC and insufficient adaptation of biomass to the specific organic substances in the samples. The biomass adaptation has been mentioned in earlier studies of degradation of chemicals in wastewater and soil environments (Becker et al 2006;Brandt et al 2003Brandt et al , 2004Kulp et al 2007;Sanchez et al 2007;Spain et al 1980;Spain and Veld 1983;Steiner and Sauer 2001;Swindoll et al 1988;Wiggins and Alexander 1988) however the importance of this phenomenon for BDOC measurements has not been sufficiently addressed in drinking water systems. The knowledge is important not only to improve reproducibility of BDOC measurements but also to better understand the performances of biological filters for removal of DOC from water sources with variable water quality.…”

Microbial transformation of chlorinated benzoates

“…2 The conversion of 4-CBc to 4-hydroxybenzoate by hydrolytic dechlorination. FcbA = 4-chlorobenzoate-coenzyme A ligase; FcbB = 4-chlorobenzoyl-coenzyme A dehalogenase; FcbB (Ferrer et al 1986;Chae et al 2000) and chloride with intermediate formation of benzoate (Suflita et al 1982;Genthner et al 1989b;Townsend et al 1997;Becker et al 2005Becker et al , 2006. A three membered coculture converting 3-CBc to methane, CO 2 and Cl -is one of the best reported examples (Dolfing andTiedje 1986, 1991).…”

“…3. The measured methane yields from the mineralization of 3-CBc range from 93 to 122% of the theoretical production based on added 3-CBc, indicating a stoichiometric conversion (Genthner et al 1989b;Townsend et al 1997;Becker et al 2006). Enrichment cultures developed with 3-CBc have the capacity to remove chlorine groups in the meta position, consequently 3,5-DCBc (with both chlorine groups in the meta position) is also completely mineralized (Suflita et al 1982).…”

Effect of biostimulation on biodegradation of dissolved organic carbon in biological filters

“…These results showed that bacterial release into the effluent sample may be due to substrate concentration limitation after biodegradation. The rate of biodegradation is highly variable and depends on many parameters including chemical structure and concentration of the organic substance in water samples, applied oxidant (ozone, chlorine) dose, temperature, salinity, pH, concentration of oxygen, and inorganic nutrients and concentration of active microorganisms (Becker et al, 2006;Brandt et al, 2003Brandt et al, , 2004Kulp et al, 2007;Sanchez et al, 2007;Spain et al, 1980;Spain and Veld, 1983;Steiner and Sauer, 2001;Swindoll et al, 1988). Some organic compounds, especially aromatic compounds are rather resistant to natural biodegradation and biodegradation of a compound of the mixture can be strongly influenced by the presence of other components in the mixture (Tsai and Juang, 2006).…”