Profiling bacterial survival through a water treatment process and subsequent distribution system.
OBJECTIVE
To profile fractions of active bacteria and of bacteria culturable with routine heterotrophic plate count (HPC) methods through a typical water treatment process and subsequent distribution system. In doing so, investigate how water treatment affects both bacterial abundance and diversity, and reveal the identities of active bacteria not detected by traditional HPC culture.


RESULTS
Profiling active fractions was performed by flow cytometric cell sorting of either membrane-intact (BacLight kit) or enzymatically active (carboxyfluorescein diacetate, CFDA) bacteria, followed by eubacterial 16S rDNA-directed PCR and denaturing gradient gel electrophoresis (DGGE). Water treatment significantly reduced active bacterial numbers detected by the BacLight kit and CFDA assay by 2.89 and 2.81 log respectively. Bacterial diversity was also reduced from > 20 DGGE bands in the active fractions of reservoir water to only two bands in the active fractions of finished water. These two bands represented Stenotrophomonas maltophila, initially culturable by HPC, and a Burkholderia-related species. Both species maintained measurable traits of physiological activity in distribution system bulk water but were undetected by HPC.


CONCLUSIONS
Flow cytometric cell sorting with PCR-DGGE, to assess water treatment efficacy, identified active bacteria from a variety of major phylogenetic groups undetected by routine HPC. Following treatment S. maltophila and a Burkholderia-related species retained activity and entered distribution undetected by HPC.


CONCLUSIONS
Methods used here demonstrate how water treatment operators can better monitor water treatment plant efficacy and assess distribution system instability by the detection and identification of active bacteria recalcitrant to routine HPC culture.
Hoefel
D
D
The Cooperative Research Centre for Water Quality and Treatment, Australian Water Quality Centre, SA Water Corporation, Bolivar, SA, Australia.
Monis
P T
PT
Grooby
W L
WL
Andrews
S
S
Saint
C P
CP
D001419:Bacteria / Q000302:isolation & purification*; D044822:Biodiversity; D019117:Burkholderia / Q000302:isolation & purification / Q000502:physiology; D016000:Cluster Analysis; D015169:Colony Count, Microbial / Q000379:methods; D004269:DNA, Bacterial / Q000032:analysis; D004275:DNA, Ribosomal / Q000032:analysis; D004586:Electrophoresis / Q000379:methods; D005434:Flow Cytometry / Q000379:methods; D005452:Fluoresceins; D017404:In Situ Hybridization, Fluorescence / Q000379:methods; D020615:Stenotrophomonas maltophilia / Q000302:isolation & purification / Q000502:physiology; D014871:Water Microbiology; D014881:Water Supply
D004269:DNA, Bacterial; D004275:DNA, Ribosomal; D005452:Fluoresceins; C027780:carboxyfluoresceindiacetate