Identifying the core bacterial and fungal communities within four agricultural biobeds used for the treatment of pesticide rinsates.

AIMS: This study evaluated the variability of bacterial and fungal communities within unique pesticide remediation biobeds. METHODS AND RESULTS: Four biobeds receiving different applied pesticide rinsates, were sampled throughout an operational season to determine pesticide removal efficacy and microbial communities. Biomixture samples collected from different biobed depths, were subjected to Illumina sequencing of the 16S rRNA (bacteria) and ITS2 (fungi) genes. Pesticide removal rates for all biobeds averaged 99%, with microbial community analysis revealing biobeds shared 60-70% of the most abundant bacterial and fungal orders, respectively. Though biobed depth did not greatly impact microbial community profile or diversity, bacterial and fungal taxa profiles between biobeds notably diverge at levels of genera and OTU. Biobed bacterial communities exhibited greater diversity than fungal communities between and within all biobeds. CONCLUSIONS: Biobeds receiving variable pesticide rinsates share a 'core' microbial community, exhibiting greater bacterial diversity relative to fungal diversity. Pesticide exposure increased bacterial diversity throughout the biobeds, while fungal diversity was variable, meriting further understanding of fungicide application to biobed fungal community stability. SIGNIFICANCE AND IMPACT OF THE STUDY: Biobeds achieve high treatment efficacy of unique pesticide rinsates, regardless of differentiation of specific genera in response to specific compounds; supporting biobeds as a robust engineered system for pesticide rinsates bioremediation.

Assessment of the microbial quality of irrigation water in a prairie watershed.

AIMS: To assess levels of faecal contamination in the Qu'Appelle River (Saskatchewan, Canada) and its suitability for irrigation, by using the Colilert-18/Quanti-Tray technology. METHODS AND RESULTS: Various sites located along the Qu'Appelle River were sampled weekly from May to August 2005-2007. A total of 594 freshwater samples were collected and analysed for enumeration of Escherichia coli using the Colilert-18. The false-positive rate for E. coli detection using Colilert-18 was at most 1.5%. Throughout the irrigation period (June to August), up to 85% of the water samples collected from one of the irrigation water-pumping sites exceeded the recommended limit of 100 CFU per 100 ml. Spikes in E. coli counts were generally concomitant with the sudden rise in river flows. A sub-sample of confirmed E. coli isolates were typed by randomly amplified polymorphic DNA (RAPD). RAPD analysis revealed a high degree of genetic diversity among E. coli isolates. A significant association between RAPD patterns and the month of E. coli isolation was demonstrated. CONCLUSIONS: Colilert-18 provides an effective means for assessing microbial quality of irrigation water. SIGNIFICANCE AND IMPACT OF THE STUDY: Qu'Appelle River is subject to variability of faecal contamination during irrigation times and monitoring throughout irrigation season is important for ensuring safe production practices.