Developing antibiotics-based strategies to efficiently enrich ammonia-oxidizing archaea from wastewater treatment plants.

The effects of five antibiotics (i.e., ampicillin, streptomycin, carbenicillin, kanamycin and tetracycline) on ammonia-oxidizing archaea (AOA) enrichment from anoxic activated sludge were investigated. The combined use of five antibiotics during 90-day cultivation could selectively inhibit nitrite-oxidizing bacteria (NOB) and ammonia-oxidizing bacteria (AOB) with AOA unaffected, as evidenced by the nitrite accumulation ratio of 100 % and the proportion of AOA in ammonia-oxidizing microbes over 91 %. The alternative use of five antibiotics was the optimal approach to screening for AOA during 348-day cultivation, which inhibited AOB growth at a level equivalent to the combined use of five antibiotics (the AOB-amoA gene decreased by over 99.90 %), further promoted AOA abundance (the much higher AOA-amoA to AOB-amoA gene copy number ratio (1453.30) than that in the groups with the combined use of five antibiotics (192.94)), eliminated bacterial adaptation to antibiotics and reduced antibiotic-resistant bacteria to form Nitrocosmicus-dominant community (42.35 % in abundance).