Carwash metagenomics

Vehicle washing produces effluent contaminated with a range of pollutants such as heavy metals, polyaromatic hydrocarbons (PAHs), total petroleum hydrocarbons-gasoline range organics (TPH-GRO), and in some instances, phosphate based-detergents (Tekere, Sibanda, and Maphangwa 2016; Aikins and Boakye 2015). These pollutants have potential to exert selective pressure on microbial communities found therein. Some studies suggest that environmental bacterial community composition is determined by geochemical parameters such as pH, total organic carbon (TOC), nutrient availability, and presence (and concentration) of gases and metals (Lu, Wilson, and Kampbell 2006). However, (Wu et al. 2017) found bacterial diversity to be strongly related to soil pH, with higher diversity in neutral samples and lower diversity in acidic samples and concluded that pH was the primary determinant of bacterial community composition while (Lozupone and Knight 2007) analysed the environmental distribution of bacterial gene sequences using 16S rRNA sequence analysis and found salinity to be the major determinant of environmental microbial community composition. Whichever geochemical parameter is the primary determinant of microbial community composition, fact remains that the presence of contaminants in the environment may translate either to reduced microbial species abundance (Xie et al. 2016), increased species diversity (Siam and Ghobrial 2000), or increased tolerance of the microbes to the pollutant, resulting in neither an increase or decrease in species diversity (Wakelin et al. 2014), depending on the nature of the pollutants and their impacts on the resident microbes.Sequencing of the 16S rRNA gene has been extensively used to study bacterial community diversity of different environments including oil-contaminated soils (Peng, Zi, and Wang 2015), extreme environments created by mine tailings (Liu et al. 2014), coral reefs (Zhang et al. 2015), residential kitchens and the indoor environment (Flores et al. 2013; Stanish et al. 2015), and in the food processing industry (Reynisson et al. 2010). However, far less is currently known about the diversity of microbial communities found within carwash effluents, microbial niches that are characterised by a wide array of potentially toxic chemical substances, and which have the potential to impact environmental water sources. In addition, actual car washing frequencies, washing chemicals/detergents, effluent flow rates and the origin of microbial inocula (since some microbes are conveyed into those carwashes by cars) all vary among carwashes. Because of this variation, one might expect the microbial taxa found in effluents from different carwashes to be different. To our knowledge, a study of the microbial community composition of carwashes is yet to be made. To understand the diversity of bacterial communities found in carwash effluents, we compared the composition of bacterial communities in 10 carwash effluent samples using targeted 16S rRNA gene sequencing.