title: Application of flow cytometry to monitor assimilable organic carbon (AOC) and microbial community changes in water.
abstract: Flow cytometry is an efficient monitoring tool for rapid cell counting, and can be applied to research on water quality and treatment. In this study, a method that employs flow cytometry and a natural microbial inoculum to determine assimilable organic carbon (AOC) was adapted for use with challenging surface waters that have a high organic and particle content, and subsequently applied in a long term river water study. AOC method optimization showed that river water bacteria could pass through a 0.2μm membrane filter, and therefore membrane filtration combined with heat treatment was required for sample sterilization. Preparation of the natural river inoculum with an acceptable yield value could only be achieved when grown using the natural water source, since growth was limited on different types of inorganic minimal media and in natural spring water. The resulting flow cytometry AOC method was reliable and reproducible, and results were comparable to the standard plate count AOC method. Size exclusion chromatography showed that both high and low molecular weight organic matter fractions were utilized by the natural AOC inoculum. Flow cytometry was used to measure both AOC levels and total cell counts in a long term study to monitor the water quality of a river which was used as a drinking water source. The method could distinguish between high nucleic acid (HNA) and low nucleic acid (LNA) groups of bacteria, and HNA bacteria were found to respond faster than LNA bacteria to seasonal changes in nutrients and water temperature.
authors.affiliation: NSERC Chair in Water Treatment, Department of Civil and Environmental Engineering, University of Waterloo, 200 University Avenue West, Waterloo, Ontario N2L 3G1, Canada. Electronic address: a2elhadi@uwaterloo.ca.
authors.forename: Ahmed M
authors.initials: AM
authors.lastname: Elhadidy
authors.affiliation: NSERC Chair in Water Treatment, Department of Civil and Environmental Engineering, University of Waterloo, 200 University Avenue West, Waterloo, Ontario N2L 3G1, Canada.
authors.forename: Michele I
authors.initials: MI
authors.lastname: Van Dyke
authors.affiliation: NSERC Chair in Water Treatment, Department of Civil and Environmental Engineering, University of Waterloo, 200 University Avenue West, Waterloo, Ontario N2L 3G1, Canada.
authors.forename: Sigrid
authors.initials: S
authors.lastname: Peldszus
authors.affiliation: NSERC Chair in Water Treatment, Department of Civil and Environmental Engineering, University of Waterloo, 200 University Avenue West, Waterloo, Ontario N2L 3G1, Canada.
authors.forename: Peter M
authors.initials: PM
authors.lastname: Huck
mesh_terms: D001419:Bacteria / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D001704:Biopolymers / Q000032:analysis; D002244:Carbon / Q000378:metabolism*; D002452:Cell Count / Q000379:methods; D002850:Chromatography, Gel; D004784:Environmental Monitoring / Q000379:methods*; D005374:Filtration; D005434:Flow Cytometry / Q000379:methods* / Q000592:standards; D005453:Fluorescence; D005618:Fresh Water / Q000032:analysis; D064307:Microbiota; D008970:Molecular Weight; D009696:Nucleic Acids / Q000032:analysis; D009864:Ontario; D045483:Rivers / Q000382:microbiology; D012621:Seasons; D013242:Sterilization; D013696:Temperature; D014867:Water / Q000737:chemistry*; D014871:Water Microbiology; D018508:Water Purification / Q000379:methods; D060753:Water Quality
chemical_list: D001704:Biopolymers; D009696:Nucleic Acids; D014867:Water; D002244:Carbon
keywords: Assimilable organic carbon; Biopolymers; Flow cytometer; High nucleic acid bacteria; Low nucleic acid bacteria