Papers in the Biological Sciences


Date of this Version



Applied and Environmental Microbiology, Sept. 1999, p. 4181–4188 Vol. 65, No. 9


Copyright © 1999, American Society for Microbiology. All Rights Reserved.


Municipal effluent is the largest reservoir of human enteric bacteria. Its public health significance, however,

depends upon the physiological status of the wastewater bacterial community. A novel immunofluorescence

assay was developed and used to examine the bacterial growth state during wastewater disinfection. Quantitative

levels of three highly conserved cytosolic proteins (DnaK, Dps, and Fis) were determined by using

enterobacterium-specific antibody fluorochrome-coupled probes. Enterobacterial Fis homologs were abundant

in growing cells and nearly undetectable in stationary-phase cells. In contrast, enterobacterial Dps homologs

were abundant in stationary-phase cells but virtually undetectable in growing cells. The range of variation in

the abundance of both proteins was at least 100-fold as determined by Western blotting and immunofluorescence

analysis. Enterobacterial DnaK homologs were nearly invariant with growth state, enabling their use as

permeabilization controls. The cellular growth states of individual enterobacteria in wastewater samples were

determined by measurement of Fis, Dps, and DnaK abundance (protein profiling). Intermediate levels of Fis

and Dps were evident and occurred in response to physiological transitions. The results indicate that chlorination

failed to kill coliforms but rather elicited nutrient starvation and a reversible nonculturable state. These

studies suggest that the current standard procedures for wastewater analysis which rely on detection of

culturable cells likely underestimate fecal coliform content.

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