Sugar (ribose), spice (peroxidase) and all things nice (laccase hair‐dyes)

Abstract

The removal of pollutants from the environment has been declared a priority by a number of Environmental Protection Agencies (Roze et al., 2009). A great number of aerobic pathways have been deciphered and their relevance in microbiology and biotechnology has been reviewed several times (Garmendia et al., 2008; Siezen and Galardini, 2008; Govantes et al., 2008; Atlas and Bragg, 2009). In the area of biodegradation the role anaerobes and fungi play in removal of pollutants is of mounting interest. Microbial Biotechnology is publishing a number of new titles in this area, and here we have extracted some of the main conclusions. Tas and colleagues (2009) have dealt with mineralization of polychlorinated chemicals, which are harmful contaminants due to their persistence and their chronic toxicity to living organisms. Dehalococcoides spp. can anaerobically transform chlorinated xenobiotics to less‐ or even non‐noxious derivatives via reductive dechlorination. Tas and colleagues (2009) have reviewed the biology of this genus, focusing on its genetic peculiarities, its variability and, of course, its biodegradative properties. Dehalococcoides can replace chlorine by hydrogen atoms in recalcitrant halogenated compounds, using them as electron acceptors during anaerobic respiration. More than 100 16S rRNAs from environmental Dehalococcoides spp., are available, most of them corresponding to uncultured strains. In addition to the standard problems of cultivating anaerobic microbes, these coccoids usually grow in microbial communities where they can find a H2 supplier needed for thriving. The full genome sequences of several Dehalococcoides strains show that they have very small genomes which are highly similar. Moreover, they exhibit a large number of putative dehalogenase‐encoding genes (rdh), reaching up to 1.7% of the coding sequences in Dehalococcoides sp. Further work, combining transcriptional and proteomic techniques, will identify which proteins are really essential for the degradation of polychorinated xenobiotics. Jeon and colleagues (2009) also report in Microbial Biotechnology issues related with the attack of halogenated chemicals. They detail the discovery of four HAD (Halodehalogenases) defluorinases from different microbial genomes. Some of these dehalogenases have enhanced activities and this appears to arise from their sequence diversity (less than 30% sequence identity for HADs) (Prudnikova et al., 2009; Rye et al., 2009). The set of new dehalogenase were elucidated via biochemical characterization of 163 potential dehalogenases from the sequenced genomes of five common soil bacteria. Their discovery and characterization will be imperative to the future use of these enzymes in the biodegradation of halogenated chemicals. Another area of interest is the anaerobic degradation of monoaromatic compounds such as benzene, toluene, ethylbenzene and the xylene isomers (BTEX; Dou et al., 2008a; Wolicka et al., 2009). Anaerobic BTEX degradation has been shown to occur under denitrifying, sulfate‐reducing, iron‐reducing, manganese‐reducing and methanogenic conditions (Dou et al., 2008a,b; Barton and Fauque, 2009). These activities are of the relevance in removal of pollutants from contaminated aquifers and soils, and they are considered an important remediation strategy for hydrocarbon‐contaminated sites. New approaches based on isotopes are being taken, in fact, recently, compound‐specific isotope analysis was successfully used to distinguish between the effects of non‐degradative processes of mass loss such as sorption, volatilization, and dilution and those of biodegradation for aromatic hydrocarbons in the field (Fischer et al., 2008; Vogt et al., 2008). Compound‐specific isotope analysis is based on the fact that, in most chemical reactions, lighter isotopomers react faster than heavier ones, leading to a kinetic isotope effect. Herrmann and colleagues (2008) in Environmental Microbiology Reports, suggest that two‐dimensional isotope fractionation analyses are a valuable tool for identifying and monitoring anaerobic biodegradation of xylene isomers. They explored the carbon and hydrogen isotope fractionation of benzylsuccinate synthase (Bss)‐initiated degradation pathways for xylene isomers in order to obtain further information on the variability of isotope fractionation processes associated with Bss that might be important for the assessment of anaerobic degradation of xylene and toluene in the environment. The use of combined carbon and hydrogen isotope fractionation analyses may therefore be useful to monitor anaerobic xylene degradation at contaminated sites; this sort of technology will allow invaluable in situ monitoring of bioremediation processes.