title: Microbial community adaptation to quaternary ammonium biocides as revealed by metagenomics.
abstract: Quaternary ammonium compounds (QACs) represent widely used cationic biocides that persist in natural environments. Although microbial degradation, sensitivity and resistance to QACs have been extensively documented, a quantitative understanding of how whole communities adapt to QAC exposure remain elusive. To gain insights into these issues, we exposed a microbial community from a contaminated river sediment to varied levels of benzalkonium chlorides (BACs, a family of QACs) for 3 years. Comparative metagenomic analysis showed that the BAC-fed communities were dramatically decreased in phylogenetic diversity compared with the control (no BAC exposure), resulting presumably from BAC toxicity, and dominated by Pseudomonas species (> 50% of the total). Time-course metagenomics revealed that community adaptation occurred primarily via selective enrichment of BAC-degrading Pseudomonas populations, particularly P. nitroreducens, and secondarily via amino acid substitutions and horizontal transfer of a few selected genes in the Pseudomonas populations, including a gene encoding a PAS/PAC sensor protein and ring-hydroxylating dioxygenase genes. P. nitroreducens isolates were reproducibly recoverable from communities after prolonged periods of no-BAC exposure, suggesting that they are robust BAC-degraders. Our study provides new insights into the mechanisms and tempo of microbial community adaptation to QAC exposure and has implications for treating QACs in biological engineered systems.
authors.affiliation: School of Civil and Environmental Engineering, Georgia Institute of Technology, Atlanta, GA, USA.
authors.forename: Seungdae
authors.initials: S
authors.lastname: Oh
authors.forename: Madan
authors.initials: M
authors.lastname: Tandukar
authors.forename: Spyros G
authors.initials: SG
authors.lastname: Pavlostathis
authors.forename: Patrick S G
authors.initials: PS
authors.lastname: Chain
authors.forename: Konstantinos T
authors.initials: KT
authors.lastname: Konstantinidis
mesh_terms: D000222:Adaptation, Physiological; D001419:Bacteria / Q000187:drug effects*; D001548:Benzalkonium Compounds / Q000494:pharmacology*; D044822:Biodiversity; D004202:Disinfectants / Q000494:pharmacology; D056186:Metagenomics; D008969:Molecular Sequence Data; D010802:Phylogeny
chemical_list: D001548:Benzalkonium Compounds; D004202:Disinfectants