Who Eats What? Classifying Microbial Populations Based on Diurnal Profiles of rRNA Levels


Identifying the relationships between various bacterial populations and the substrates they consume is central to the understanding of population dynamics and to the development of process control in activated sludge. However, linking a heterotrophic population to its activity in situ is difficult because ribosomal RNA (rRNA) techniques, while allowing the rapid identification of populations, provide little information about their heterotrophic activity. Activated sludge models describe biodegradation kinetics by classifying substrates into two types: readily and slowly degradable substrates. Assuming that bacterial populations specialize in degrading one type of substrate, their growth rate should be affected differently if the COD loading rate varies diurnally as for a municipal activated sludge system. Modeling results suggested that the growth rates of populations consuming readily degradable substrates vary according to variations in COD loading rate. On the other hand, the growth rates of populations consuming slowly degradable substrates do not change despite the variation in COD loading rate. Since the cellular rRNA level is positively correlated with the growth rate, we hypothesized that the rRNA levels of some populations in municipal activated sludge should increase throughout the day, while they should stay constant for other populations. This hypothesis was verified by monitoring the rRNA level of Acinetobacter (a model population consuming readily degradable substrates) and Gordonia (a model population consuming slowly degradable substrates) in the mixed liquor of a full-scale municipal activated sludge reactor for three weeks.


Civil, Architectural and Environmental Engineering

Keywords and Phrases

Bacteria; Biodegradation; Process control; Sewage sludge; Substrates; Population dynamics; RNA; ribosome RNA; bacterial RNA; organic compound; oxygen; activated sludge; bacterium; biological treatment; microorganism; wastewater; Acinetobacter; bacterial growth; bacterial metabolism; bacterium identification; biological monitoring; cell level; chemical oxygen demand; circadian rhythm; classification; conference paper; continuous stirred tank reactor; controlled study; correlation analysis; heterotrophy; mathematical model; microbial population dynamics; nonhuman; population model; sequence analysis; waste water treatment plant; article; bioreactor; genetics; metabolism; microbiology; oligonucleotide probe; sewage; Bioreactors; Oligonucleotide Probes; Organic Chemicals; Bacterial; Ribosomal; Support; Non-U.S. Gov't; U.S. Gov't; Non-P.H.S.; Waste Disposal; Fluid; Bacteria (microorganisms)

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Article - Conference proceedings

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© 2002 IWA Publishing, All rights reserved.

Publication Date

01 Feb 2002

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