The role of microbial community composition and groundwater chemistry in determining isoproturon degradation potential in UK aquifers

Abstract

The community response of indigenous sandstone, chalk and limestone groundwater microorganisms to the addition of the commonly used herbicide isoproturon was examined. The addition of 100 microg l(-1) isoproturon generally caused an increase in species diversity determined by chemotaxonomic analysis (fatty methyl ester analysis) of isolates resulting from incubation of cultures at 18 degrees C for 4 days. Amongst the groundwater samples to which isoproturon was added, isoproturon degradation rates were correlated with increasing dominance of a few species. However, the changes in community profile associated with isoproturon degradation varied from site to site. Repeated sub-culturing with 100 microg l(-1) isoproturon and sterile groundwater was carried out to examine whether this level of pesticide could exert a selection pressure, and hence stimulate more rapid degradation. Significantly increased degradation was observed in a groundwater sample from the chalk, but not in sandstone, or limestone samples. The addition of filter-sterilised sandstone groundwater to bacteria on filter paper from slow degrading limestone sites significantly improved their degrading performance. The addition of filter-sterilised limestone groundwater to the sandstone bacteria reduced their degradation rate only slightly. The data suggested that the nature of the indigenous community does influence pesticide degradation in groundwater, but that the groundwater chemistry may also play a role.

Microbial communities in UK aquifers: current understanding and future research needs

“…Some findings suggest no correlation (e.g. Johnson et al 2000) whereas others identify enhanced biodegradation when there has been previous exposure to, for example, isoproturon (Johnson et al 1998(Johnson et al , 2000(Johnson et al , 2004 or BTEX (Fahy et al 2006). The key factors determining whether a bacterial community can degrade pollutants appear to be the makeup of the community itself and the groundwater chemistry (Johnson et al 2004).…”

“…The key factors determining whether a bacterial community can degrade pollutants appear to be the makeup of the community itself and the groundwater chemistry (Johnson et al 2004). Johnson et al (2004) found that the presence of isoproturon changed the community structure, and degradation was accompanied by an increase in the proportion of a few dominant species, although different degrading taxa were found in different samples. This suggests that there is some flexibility in the community composition (functional redundancy) and that some functions can be carried out by different organisms.…”

“…This suggests that there is some flexibility in the community composition (functional redundancy) and that some functions can be carried out by different organisms. Water chemistry was demonstrated to play a role in providing the right environment for degradation (in chalk, limestone and sandstone aquifer samples), as addition of filtered groundwater from a fast degrading site was able to stimulate the degradation of isoproturon by bacterial populations from slow degrading limestone samples, and vice versa (Johnson et al 2004).…”

“…Johnson et al (2004) examined the microbial response to isoproturon in different rock types and found that uncontaminated samples were all dominated by Pseudomonas (γ-Proteobacteria) (ranging from 93% of the isolates in sandstone to 49% and 43% in chalk and limestone). All other common organisms (making up more than 10% of the isolates) were either α-or β-Proteobacteria or unidentifiable.…”

“…Estimates of bacterial density range from 10 2 to 10 6 cells per cm 3 water or from 10 4 to 10 8 cells per cm 3 sediment (Pickup et al 2001;Johnson et al 2004;Griebler & Lueders 2009;Sorensen et al 2013). However, the microbial community also includes archaea, fungi, other microeukaryotic organisms and viruses (see Table 1 for examples).…”