The little bacteria that can - diversity, genomics and ecophysiology of 'Dehalococcoides' spp. in contaminated environments.
Bottom Line: Recent genome sequencing projects revealed a large number of genes that are potentially involved in reductive dechlorination.Molecular approaches towards analysis of diversity and expression especially of reductive dehalogenase-encoding genes are providing a growing body of knowledge on biodegradative pathways active in defined pure and mixed cultures as well as directly in the environment.Moreover, several successful field cases of bioremediation strengthen the notion of dedicated degraders such as Dehalococcoides spp. as key players in the restoration of contaminated environments.
Affiliation: Laboratory of Microbiology, Wageningen University, Dreijenplein 10, 6703 HB, Wageningen, the Netherlands.Show MeSH
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Mentions: In spite of all the information obtained in physiological studies very little is known about the diversity, distribution and functioning of Dehalococcoides in different environments although they were detected at several contaminated locations. Hendrickson and co‐authors have demonstrated the presence of Dehalococcoides spp. in soil and groundwater samples from 24 sites scattered throughout North America and Europe (Hendrickson et al., 2002). Up to 200 µM PCE could be dechlorinated, and complete dechlorination to ethene could be correlated to the presence of Dehalococcoides spp. in the sampling locations. Recently, we conducted a large‐scale survey focusing on presence, activity and dechlorination potential of Dehalococcoides spp. in river sediments and floodplain soils from different polluted locations in Europe (Fig. 3) (Taş, 2009). Almost all of the tested sediment and soil samples showed the capacity to dechlorinate HCB and/or chlorinated ethenes irrespective of the in situ contaminant levels. Nevertheless, the HCB transformation rates observed in the laboratory‐scale microcosms and the number of 16S rRNA gene copies of Dehalococcoides spp. in the environmental samples did not show a strong correlation. In these river systems, Dehalococcoides spp. relative abundance was furthermore shown to change significantly along temporal and spatial gradients, but was also found to be influenced by other environmental factors such as water temperature (Taşet al., 2009).
Affiliation: Laboratory of Microbiology, Wageningen University, Dreijenplein 10, 6703 HB, Wageningen, the Netherlands.