Ciprofloxacin consumption and phenomenal transformation to a culturable nanometer-sized- bacterium by a Klebsiella strain SG01

Antimicrobial resistance is a global crisis. Biodegradation by bacteria is an effective strategy to remove the micropollutant from the environment. In this study, we demonstrate that a persistent fluoroquinolone, ciprofloxacin (CIP) can be degraded by a multidrug-resistant Klebsiella sp. SG01 and used as its only carbon source. SG01’s ability to consume or degrade more than 50% of CIP (~2g/L) within 48 h exceeded previous published data on CIP-biodegradation. The degradation was quantified using UV-vis spectroscopy and the degraded product was less toxic than the parent compound as tested against a susceptible Escherichia coli K12. SG01 changes into nano-sized cells as culturable nanobacterium, passes through a 0.22 µm pore-size filter while growing on ciprofloxacin, and shows a shorter generation time than cells grown on glucose or rich medium. The nano-sized-bacterium reverses to its micrometer-sized form within an hour of culture transfer to nutrient-rich Luria broth. The basis for the changed growth phenotype of nano-SG01 cells and metabolic changes was partially established by the whole-genome transcriptome.