Plate Dilution Frequency Assay (PDFA) data for soil samples from for 120 point locations within limestone cedar glades at Stones River National Battlefield near Murfreesboro, Tennessee

This dataset contains data collected within limestone cedar glades at Stones River National Battlefield (STRI) near Murfreesboro, Tennessee. This dataset contains information on soil microbial density (Most Probable Number of heterotrophic, culturable microbes per gram of soil) for soil samples obtained from certain quadrat locations (points) within 12 selected cedar glades. This information was obtained by performing a Plate Dilution Frequency Assay (PDFA) on a series of serial dilutions for each soil sample.For each quadrat location (point), one soil sample was obtained under sterile conditions, using a trowel wiped with methanol and rinsed with distilled water, and was placed into an autoclaved jar with a tight-fitting lid and placed on ice. Soil samples were transported to lab facilities on ice and immediately refrigerated. Within 24 hours after being removed from the field, soil samples were processed for the Plate Dilution Frequency Assay. First, for each soil sample three measurements were taken of gravimetric soil water content using a Mettler Toledo HB43 halogen moisture analyzer (Mettler Toledo, Columbus, OH, USA) and the mean of these three SWC measurements was used to calculate the 10-gram dry-weight equivalent (DWE) for each soil sample. For each soil sample, a 10-gram DWE of fresh soil was added to 90 milliliters of sterile buffer solution in a 125-milliliter plastic bottle to make the first dilution. Bottles were agitated on a wrist-action shaker for 20 minutes, and a 10-milliliter aliquot was taken from each sample using sterilized pipette tips and added to 90 milliliters of sterile buffer solution to make the second dilution. A 1-milliliter aliquot of the second dilution was transferred using a sterile pipette tip to a test tube containing 9.0 milliliters of sterile buffer solution to make the third dilution. The same process was repeated to make the fourth through seventh dilutions, for each soil sample. The six serial dilutions were inoculated onto plastic plates with pre-poured plate-count agar. Agar plates were poured at least 48 hours prior to use, covered, and inspected for contamination prior to use. Starting with the least concentrated dilution and working toward the most concentrated, eight 10-microliter aliquots were used to inoculate eight spots per dilution level onto the agar plates, with spots inoculated directly onto the agar using a sterile pipette tip within circular areas (eight per dilution level) demarcated using a permanent marker on the clear plastic bottom of each agar plate. Plates were immediately covered and incubated at 25 degrees Celcius for seven days (168 hours). After incubation, each plate was visually examined to determine the number of positive responses per dilution level. Any growth of any colony within a circular area was counted as a positive response, regardless of the size or morphology of the colony. Thus, the number of positive responses could range from zero to eight for each dilution level. For each soil sample, the total number of positive responses (the sum of positive responses for the six dilution levels) was compared to a chart derived from Harris and Sommers (1968) to produce an estimate of the most probable number (MPN) of organisms per milliliter of suspension according to Cochran (1950). This same chart also provided 95 percent confidence interval upper and lower bounds on the MPN estimates for each sample. The values contained in the fields of this dataset represent the upper and lower bounds of these 95 percent confidence intervals for MPN. For example, 052512_LB contains the lower bounds of the 95 percent confidence intervals for MPN for soil samples collected on May 25, 2012, and 052512_UB contains the upper bounds of the same confidence intervals. Detailed descriptions of experimental design, field data collection procedures, laboratory procedures, and data analysis are presented in Cartwright (2014).References:Cartwright, J. (2014). Soil ecology of a rock outcrop ecosystem: abiotic stresses, soil respiration, and microbial community profiles in limestone cedar glades. Ph.D. dissertation, Tennessee State University.Cochran, W. (1950). Estimation of Bacterial Densities by Means of the “Most Probable Number.” Biometrics, 6, 105–116.Cofer, M., Walck, J., and Hidayati, S. (2008). Species richness and exotic species invasion in Middle Tennessee cedar glades in relation to abiotic and biotic factors. The Journal of the Torrey Botanical Society, 135(4), 540–553.Harris, R., &amp; Sommers, L. (1968). Plate-dilution frequency technique for assay of microbial ecology. Applied Microbiology, 16(2), 330–334.

Tags: biota, environment, geoscientificinformation, inlandwaters, usgs-55afcfa3e4b09a3b01b51ed4
Organization: Department of the Interior