ESTCP Project #1011, Rhizosphere
tubes with sterile caps after adding inoculant.
1. Incubate in the dark at room temperature (25C).
2. Read the MPN tubes on the following schedule:
Weeks of incubation
BH - Negative
3. Microbial growth or a positive reading is indicated by turbidity in the tube(s).
Vortexing the tubes is helpful to discern microbial growth. When positive tubes are
determined, the MPN value can be determined using appropriate MPN tables
Reference: Woomer, P.L. 1994. Most probable number counts. p. 59-79. In R.W. Weaver
(ed.). Methods of soil analysis. Part 2. Microbiological and biochemical properties. SSSA
Book Ser. 5. SSSA, Madison, WI.
See Appendix B.
Note: The MPN determination method appears suitable for adaptation to microtiter plate
Haines, J.R., B.A. Wrenn, E.L. Holder, K.L. Strohmeier, R.T. Herrington, and A.D. Venosa.
1996. Measurement of hydrocarbon-degrading microbial populations by a 96-well plate
most probable number procedure. J. Indust. Microbiol. 16:36-41.
Wrenn, B.A., and A.D. Venosa. 1996. Selective enumeration of aromatic and aliphatic
hydrocarbon degrading bacteria by a most-probable-number procedure. Can. J. Microbiol.
To determine temperature of media after autoclaving, use stick on thermometers. DO NOT