refrigeration and was thus avoided (Sinsabaugh and Linkins, 1989; Sinsabaugh et al.,

1991). Biostatic agents were not used in this study as their functions differ among

samples and have been found to repress the activity of some enzymes (Sinsabaugh et al.,

1991).

 Four enzymes were investigated utilizing the following substrates: MUF-P-D

glucoside (Sigma M3633), MUF-cellobioside (Sigma M6018), MUF-phosphate (Sigma

M8168) and L-leucine amidomethylcoumarin (Sigma L2145). These substrates were

used for the determination of P-glucosidase, cellobiohydrolase, phosphatase, and leucine

aminopeptidase activities, respectively.

 Enzyme substrate solutions were prepared in 10 mM Tris-HCl, pH 8.5 in varying

concentration ranges. Buffered conditions stabilize the pH dependent intensity of the

fluorescent product (Chr6st and Krambeck, 1986). Enzyme assays were performed using

a Cytofluor 600TM (Perseptive Biosystems, Inc. Framingham, MA) automated

spectrofluorometer at with KineticalcTM software at 360 nm excitation and 460 nm

emission. Samples were analyzed in Corning 48-well microplates. 360 pL Tris-HCI

pH 8.5 was added to each sample well followed by 400 [tL soil suspension and 40 [tL of

the enzyme substrate. Triplicate replicates of each suspension were used.

 The spectrofluorimeter was set to 250 C, to shake for 3 sec before each reading,

and for end-point analysis. Sensitivity was set at 95, which refers to the sensitivity of the

fluorimeter with a maximum value of 100. The plate was inserted and the initial (Ti)

fluorescence was recorded. A reading was performed every 10 minutes for the duration

of the incubation. A similar detailed spectrofluorimeter method used 1 minute intervals