Enumeration and factors influencing the relative abundance of a denitrifier, Pseudomonas sp JR12, entrapped in alginate beads

The relative abundance of the denitrifier, Pseudomonas sp. JR12, was examin ed in an alginate-based entrapment complex under non-sterile, denitrifying conditions. Immuno-labeling of the Pseudomonas inoculant followed by flow c ytometry (FCM) was used for determination of the relative abundance of this bacterium under the various incubation conditions. Additional information on the relative abundance of the inoculant was obtained by a quantitative e nzyme-linked immunosorbent assay (ELISA) and results obtained by FCM and EL ISA were compared. Ambient nitrate levels controlled the successful, long-t erm proliferation of the inoculant. At low ambient nitrate levels, Psc Pseu domonas sp. remained the dominant microorganism during incubation. Higher a mbient nitrate concentrations, attained by either decreasing the inoculum s ize of Pseudomonas sp. or raising inlet nitrate concentrations of the mediu m supplied to the incubation vessels, resulted in a gradual shift toward ot her, nitrite-accumulating denitrifiers. Thus far, most studies on the use o f entrapped microorganisms for bioremediation purposes have been conducted under controlled laboratory conditions. Based on this study, conducted unde r non-sterile laboratory conditions, it is concluded that in-situ bioremedi ation using entrapped target microorganisms is bound to fail without a prop er understanding of the factors that cause the target microorganism to outc ompete undesired microbial invaders. Furthermore, based on the close agreem ent between the two detection methods used, it is concluded that flow cytom etry provides a rapid and accurate tool for the detection of the relative a bundance of immuno-labeled target organisms in heterogeneous microbial popu lations. (C) 2001 Elsevier Science Ltd. All rights reserved.