Investigating bio-remediation capabilities of a constructed wetland through spatial successional study of the sediment microbiome

Abstract Constructed wetlands (CWs) are engineered environments designed to utilise natural processes to treat urban or industrial wastewater, with the core driver of the bioremediation process provided by the microorganisms present within. This study isolated 32 bacterial strains from sediment across the Sardar Bherry CW to find candidates with remediation properties and to understand how the physiochemical gradient from wastewater input influences the functional properties of the bacteria present. Bacterial isolates recovered closer to the wastewater effluence were more likely to be pathogenic, with increased haemolytic activity, causing high rates of fish mortality. In contrast, isolates recovered further from the wastewater source were observed to be non-pathogenic and have increased inhibitory effect against pathogenic strains. Extracellular proteins extracted from non-pathogenic isolates also appeared to be effective at inhibiting the growth of pathogenic bacteria, including multidrug resistant strains. Non-pathogenic isolates recovered across all sampling sites displayed the ability to reduce high levels of ammonia in solution during laboratory testing. Antibiogram assays of the recovered isolates showed a relatively high rate of multidrug resistant or marginally resistant bacteria across all sampling sites, highlighting a potential limitation within the CW bioremediation process in mitigating antibiotic resistant strains. This isolate based study provided an avenue to understand the influence of spatial succession from wastewater effluence on bacterial characteristics, as well as obtain candidates that can be further investigated for optimisation in bioremediation efforts. The cultured isolates can supplement future environmental sequencing studies by providing wet lab specimens to compare (meta)genomic information discovered within the CW ecosystem.