Discipline: Biological Sciences
TyChrisa Whitmire - Claflin University
Co-Author(s): Chandlar Glover, Claflin University, Orangeburg, SC; Randall H. Harris PhD, Claflin University, Orangeburg, SC
An antibiotic treats bacterial infections by inhibiting the growth of or killing bacteria. Antibiotic resistance occurs when the bacterium is no longer sensitive to the antibiotic and often emerges soon after an antibiotic is introduced to the market. Seventy five percent of antibiotics in clinical use are derived from soil bacteria. The purpose of this research is to discover new antibiotics from bacteria in soils recovered from locations on and surrounding Claflin University. Using the USDA web soil survey database, we chose 3 sites on or near Claflin’s campus with a soil composition of Dothan loamy sand or Ailey sand. We collected soil samples from the O and A horizons and recovered bacteria by placing the samples onto brain heart infusion (BHI) medium to encourage growth of the bacteria. We sub-cultured the bacterial isolates based on differences in colony morphology. We assessed the ability of the bacteria to produce an antibiotic that inhibited the growth of another bacterium. After determining which bacteria produced an antibiotic, butanol extracts were prepared from the culture supernatants. The extracts were dried, resuspended in water, and used for a spot diffusion assay. Dothan loamy sand contained 1.87 x 106 bacteria per gram of soil whereas Ailey sand contained 1.51 x 108 bacteria per gram of soil. Dothan loamy sand from site 1 or site 3 has 1.8 times or 5 times as much bacteria per gram of soil in the O horizon than in the A horizon, respectively. Ailey sand from site 2 has 128 times as much bacteria per gram of soil in the A horizon than in the O horizon. Seventy three bacterial isolates were tested against Escherichia coli, Micrococcus luteus, Staphylococcus aureus, S. epidermidis and Salmonella enteritidis. Zones of inhibition were observed for the bacterial isolates against E. coli (2), M. luteus (27), S. aureus (4), and S. epidermidis (2). No zones were observed against S. enteritidis. After conducting the spot diffusion assay, we found that the antibiotic extract from soil isolate 31 was active against S. aureus and Bacillus subtilis. In conclusion, we recovered 35 antibiotic producing bacteria from soil. Future experiments will include making more concentrated antibiotic extracts for the spot diffusion assays and identifying the genus and species of the bacteria.
Funder Acknowledgement(s): This study was supported, in part, by a grant from NSF/HBCU-UP (1332516) awarded to Dr. Angela Peters, Vice Provost for Academic Programs, Claflin University, Orangeburg, SC.
Faculty Advisor: Randall H. Harris, PhD, email@example.com
Role: I decided where to collect soil samples from and carried out the experiments needed to get the results that we have so far.