.6. Comparison of common bacterial growth on LBG and SDA
Glycerol stocks of either S. aureus or E. coli were streaked for isolation onto LBG plates and incubated overnight at 37 °C. A single colony
from each plate was picked and streaked onto one half of LBG, SDA,
LBG-CRN, or SDA-CRN plates. Plates were incubated overnight at 37 °C
and subsequently observed for growth. These experiments were
repeated for n = 2 plates of each type streaked with both S. aureus
and E. coli.
2.7. Isolation of an antibiotic-producing fungus using CRN-HCl
Individual fungal colonies were selected from soil samples previously plated on LBG-CRN growth agar, transferred to individual LBG
plates without CRN-HCl, and incubated at room temperature; a total
of greater than 50 fungi of varying morphologies were isolated. Fungal isolates were plated on a medium without CRN-HCl in order to
ensure that subsequent testing with bacteria could be accomplished.
Fungal colonies were tested for antibiotic production when colonies
were 2–3 cm in diameter. Cultures of S. aureus, E. coli, S. cerevisiae,
and R. mucilaginosa to be used as the test target organisms were
diluted to approximately 1 × 104 cfu/mL. Using 25 μL drops, each culture was spotted four times inward from the edge of the plate toward
each fungal colony (termed “the drop-test” method) and plates
were incubated overnight at 37 °C. Plates were subsequently observed for microorganism growth and presence of zones of inhibition indicating antibiotic production by the fungus. Antibiotic
production by an environmental fungal isolate is a representative
of n = 10 replicates.