EMA amplicon based taxonomic characterisation of the viable bacterial community present in untreated and SODIS treated roof harvested rainwater
Illumina next generation sequencing coupled with the viability dye ethidium monoazide bromide (EMA) was utilised to characterise and compare the viable bacterial community present in roof harvested rainwater pre and post treatment. The diversity and relative abundance of the viable bacterial community present in roof harvested rainwater before (tank 1) and after solar disinfection treatment (SODIS CPC 1) for eight h, was also determined. Taxonomic assignments were made using the Ribosomal Database Project whereafter alpha and beta diversity indices were calculated to investigate the effect of SODIS treatment on the viable bacterial population present in roof harvested rainwater. Alpha diversity indices, including species richness and Shannon diversity were significantly (p 0.05) lower in the SODIS CPC 1 treated rainwater samples in comparison to tank 1 rainwater samples, indicating a significant difference in the species richness after treatment. The tank 1 rainwater samples were dominated by the families Nocardiaceae (16.5% and Pseudomonadaceae (8.9% while the SODIS CPC 1 rainwater samples were dominated by Nocardiaceae (44.0% and Micrococcaceae (31.7% On the genus level, Rhodococcus (17.1% and Pseudomonas (9.2% dominated in the tank 1 rainwater samples, while Rhodococcus (48.0% and Arthrobacter (35.2% were the most abundant in the SODIS CPC 1 rainwater samples. While, viable opportunistic pathogenic bacteria such as Pseudomonas and Clostridium XI were detected in both the tank 1 and SODIS CPC 1 rainwater samples, beta diversity analysis, using the Bray Curtis distance metric system, indicated that there was a significant shift (PERMANOVA, p 0.05) in the viable bacterial community after SODIS treatment. Based on the results obtained, EMA amplicon based taxonomic analysis could be utilised as an alternative culture independent method for the initial monitoring and profiling of the viable and viable but non culturable whole bacterial community in water sources.