Journal article
Induction of Escherichia coli into a VBNC state by continuous-flow UVC and subsequent changes in metabolic activity at the single-cell level
- Abstract:
- A viable but non-culturable (VBNC) state of bacteria induced by disinfection in water treatment poses serious health risks because of possible resuscitation of VBNC cells during transportation. In this study, a setup using continuous-flow ultraviolet (UVC) irradiation ranging from 0 to 172.2 mJ cm-2 was designed to simulate real-world disinfection in both drinking water (SDW) and reclaimed water (SRW) treatment plants. A systematic investigation of UVC-induced VBNC bacteria, including occurrence, resuscitation, and time-dependent recovery of metabolic activity during post-incubation, was conducted. Different techniques including two new ones of "single cell culture" and D2O-labeled single-cell Raman spectroscopy were employed to gain comprehensive insights into VBNC cells. Heterotrophic plate counts (HPC) and 5-cyano-2,3-ditoyl tetrazolium chloride flow cytometry (CTC-FCM) assay demonstrated that exposure to continuous-flow UVC can induce E. coli into a VBNC state. Membranes integrity and 16S rRNA transcription level of VBNC bacteria were demonstrated to be unaffected by UVC exposure even at a high dose of 172.2 mJ cm-2. Resuscitation of VBNC bacteria was identified in a more accurate way based on "single cell culture." Finally, time-dependent evolution of metabolic activity of UVC-treated cells during post-incubation was examined by D2O-labeled Raman spectroscopy at a high-resolution of single-cell level. C-D Raman bands resulting from incorporation of D2O-derived D into bacterial biomass were used as a sensitive and quantitative indicator of bacterial metabolic activity. A lower UVC dose, longer post-incubation time, and higher initial number of bacteria were demonstrated to result in a faster recovery of metabolic activity. Heterogeneous metabolic activity and subpopulation with higher metabolic activity were also revealed by single-cell Raman, even for UVC-treated cells losing cultivability. The comprehensive assessment of VBNC bacteria in UVC-disinfected drinking and reclaimed water points out treatment deficiencies of UVC and the necessity to develop more effective strategies to eliminate VBNC cells.
- Publication status:
- Published
- Peer review status:
- Peer reviewed
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(Preview, Version of record, pdf, 2.9MB, Terms of use)
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- Publisher copy:
- 10.3389/fmicb.2018.02243
Authors
- Publisher:
- Frontiers Media
- Journal:
- Frontiers in Microbiology More from this journal
- Volume:
- 9
- Issue:
- SEP
- Pages:
- 2243
- Publication date:
- 2018-09-25
- Acceptance date:
- 2018-09-03
- DOI:
- EISSN:
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1664-302X
- ISSN:
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1664-302X
- Pmid:
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30319570
- Language:
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English
- Keywords:
- Pubs id:
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pubs:926228
- UUID:
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uuid:c782cb63-774e-4e43-b915-487f8d50fa4b
- Local pid:
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pubs:926228
- Source identifiers:
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926228
- Deposit date:
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2019-01-09
Terms of use
- Copyright holder:
- Zhang et al
- Copyright date:
- 2018
- Notes:
- © 2018 Zhang, Guo, Yang, Zhang, Ye, Chen, Yu, Huang and Cui. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
- Licence:
- CC Attribution (CC BY)
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