Abstract:
Reverse-osmosis (RO) drinking water poses unique microbiological challenges due to its ultra-low biomass, residual disinfectants, and minimal nutrients. This dissertation (i) develops and validates DNA-based protocols to recover trace microbes, (ii) examines how magnesium remineralization influences regrowth and community shifts, and (iii) characterizes real-world biofilm formation in RO-fed shower plumbing. Key findings include a superior 0.2 µm polycarbonate filter for DNA recovery, evidence that carbon—not magnesium—is growth-limiting, and the identification of core biofilm taxa (e.g., Blastomonas, Porphyrobacter). These insights offer new strategies for monitoring and managing biological stability in advanced water systems.

Bio:
Ratna Putri is an environmental microbiologist and bioinformatician at KAUST, with over ten years’ experience spanning academia and industry. She earned her B.Sc. in Microbiology (ITB, Indonesia), an M.Sc. in Marine Environmental Health & Biotechnology (Ghent University) before coming to pursue her Ph.D here at KAUST. Her research integrates advanced molecular methods (DNA extraction, qPCR, flow cytometry) and bioinformatics to unravel microbial dynamics in ultra-low-biomass water systems, biogenic H₂S in oil reservoirs, and biofilm ecology in desalination contexts.