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KMID : 0364820150510040355
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Korean Journal of Microbiology
2015 Volume.51 No. 4 p.355 ~ p.363
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Growth kinetics and chlorine resistance of heterotrophic bacteria isolated from young biofilms formed on a model drinking water distribution system
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Park Se-Keun
Kim Yeong-Kwan
Oh Young-Sook
Choi Sung-Chan
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Abstract
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The present work quantified the growth of young biofilm in a model distribution system that was fed with chlorinated drinking water at a hydraulic retention time of 2 h. Bacterial biofilms grew on the surface of polyvinyl chloride (PVC) slides at a specific growth rate of 0.14 ± 0.09 day?1 for total bacteria and 0.16 ± 0.08 day?1 for heterotrophic bacteria, reaching 3.1 × 10⁴ cells/㎠ and 6.6 × 10³ CFU/㎠ after 10 days, respectively. The specific growth rates of biofilm-forming bacteria were found to be much higher than those of bulk-phase bacteria, suggesting that biofilm bacteria account for a major part of the bacterial production in this model system. Biofilm isolates exhibited characteristic kinetic properties, as determined by μmax and KS values using the Monod model, in a defined growth medium containing various amounts of acetate. The lowest μmax value was observed in bacterial species belonging to the genus Methylobacterium, and their slow growth seemed to confer high resistance to chlorine treatment (0.5 mg/L for 10 min). KS values (inversely related to substrate affinity) of Sphingomonas were two orders of magnitude lower for acetate carbon than those of other isolates. The Sphingomonas isolates may have obligate-oligotrophic characteristics, since the lower KS values allow them to thrive under nutrient-deficient conditions. These results provide a better understanding and control of multi-species bacterial biofilms that develop within days in a drinking water distribution system.
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KEYWORD
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Methylobacterium, Sphingomonas, biofilm, chlorine resistance, drinking water, growth kinetics
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