Direct estimation of biomass on different pipe material coupons using a specific DNA-Probe

摘要

A variety of approaches to quantify the biofilm without disruption due to detachmenthave been developed over the years. One basic approach is the combination of advancedmicroscopy with molecular staining. However many stains (4′,6-diamino-2-phenylindole(DAPI), acridine orange or live-dead stains) can be non-specific when corrosionproducts, precipitates, and pipe material are present. In addition, some pipe materialscause high background when using epifluorescent microscopy. The new refinementdiscussed in this presentation used fluorescence spectroscopy to obtain the spectra fromfour common distribution system pipe materials: PVC, cast iron, "concrete" lined castiron, and galvanized iron. The emission maximum for all four materials was between500 and 550 nm, but emissions radically decreased around 575-600 nm. A molecularprobe, BO-PRO3 was identified which has an emission intensity maximum at 599nm (farred), with emission intensity 200 times greater when it is bound to DNA. The BO-PRO3has greatly reduced non-specific staining and background problems. In the preliminaryexperiment, using diluted waste water, a significant linear relationship was foundbetween stained surface area/total area ratio and fixed biomass measurements fromheterotrophic plate counts (HPC) on R2A medium and total direct count (TDC). Inaddition, the biomass on different pipe material coupons from pilot distribution systemswas also correlated to the stained surface area fraction and HPC.