UV Disinfection
Induces a Vbnc State in <i>Escherichia
coli</i> and <i>Pseudomonas aeruginosa</i>
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Abstract
The occurrence of
a viable but nonculturable (VBNC) state in bacteria
may dramatically underestimate the health risks associated with drinking
water. Therefore, the potential for UV treatment to induce a VBNC
state in <i>Escherichia coli</i> and <i>Pseudomonas
aeruginosa</i> was investigated. UV disinfection effectively
reduced the culturability of <i>E. coli</i> and <i>P. aeruginosa</i>, with the destruction of nucleic acids demonstrated
using <i>gad</i>A long gene fragment qPCR amplification.
Following UV radiation, copy numbers for the high transcriptional
levels of the 16S rRNA gene varied insignificantly in both strains,
confirming results from plate counting assays indicating that VBNC
states were induced in both strains. Furthermore, the virulence genes <i>gadA</i> and <i>oprL</i> remained highly expressed,
suggesting that the VBNC bacteria still displayed pathogenicity. Propidium
monoazide qPCR indicated that cell membranes remained intact even
at a UV dose of 300 mJ/cm<sup>2</sup>. The RT-qPCR results after UV
and chlorine treatments in <i>E. coli</i> were significantly
different (8.41 and 5.59 log units, respectively), further confirming
the induction of VBNC bacteria induced by UV radiation. Finally, resuscitation
was achieved, with <i>E. coli</i> showing greater resuscitation
ability than <i>P. aeruginosa</i>. These results systematically
revealed the potential health risks of UV disinfection and strongly
suggest a combined disinfection strategy