Culture and molecular methods as complementary tools for water quality management

Area of Science:

• Environmental Microbiology
• Water Treatment Technology
• Analytical Chemistry

Background:

• Drinking water treatment plants (DWTPs) harbor complex bacterial communities.
• Understanding these microbial populations is crucial for ensuring water safety and treatment efficacy.
• Traditional culture-based methods and modern culture-independent techniques offer different insights into microbial diversity.

Purpose of the Study:

• To characterize bacterial communities in a full-scale DWTP using matrix-assisted laser desorption/ionization time of flight mass-spectrometry (MALDI-TOF MS).
• To compare MALDI-TOF MS identification results with previous 16S rRNA (V4) metabarcoding data.
• To evaluate the combined utility of culture-based and culture-independent methods for assessing microbial populations in DWTPs.

Main Methods:

• Sample collection across nine stages of the potabilization process in a DWTP.
• Isolation and identification of 1807 bacterial colonies using MALDI-TOF MS with a specialized Drinking Water Library.
• Comparison of MALDI-TOF MS data with existing 16S rRNA (V4) metabarcoding results.

Main Results:

• MALDI-TOF MS successfully identified 32% of isolates to at least the genus level.
• Both methods showed similar trends in bacterial diversity across treatment stages.
• Significant differences in taxa detection were observed, particularly at lower taxonomic levels.
• Bacterial diversity was high in raw water (river/groundwater) dominated by Proteobacteria.
• Diversity decreased post-chlorination, with Bacillus sp. (MALDI-TOF MS) and Obscuribacteraceae (metabarcoding) being prevalent.
• Flavobacterium was the most abundant taxon in decantation, sand filtration, and mixing chamber stages for both methods.

Conclusions:

• The study demonstrates the utility of MALDI-TOF MS for identifying bacterial isolates in DWTPs.
• Combining MALDI-TOF MS with metabarcoding provides a more comprehensive understanding of microbial communities.
• This integrated approach enhances insights into bacterial roles in water treatment and quality, aiding DWTP management.