It’s a Bacteria Thing: Bacterial Inhibition Of Chytrid Fungus
Location
Lobby in front of Auditorium
Department
Biology
Abstract
The amphibian chytrid fungus, Batrachochytrium dendrobatidis (Bd), was discovered in 1998 as the cause of Chytridiomycosis, which has led to devastating declines in amphibian species. Chytridiomycosis causes an osmotic imbalance and electrolyte depletion by disrupting normal functions of the outer keratin layer of the amphibian skin. The life cycle of the amphibian chytrid fungus begins in the water as a free-swimming zoospore, that penetrates the skin and encysts. The zoospore morphs into sporangia in the encysted stage. The sporangia matures and produces more zoospores, which are released from the surface of the amphibian’s skin. However, the fungal lifecycle is suggested to be halted by bacterial flora on an amphibian’s skin that may secrete antifungal compounds. Like humans, amphibians have naturally occurring bacterial flora on their skin, however amphibians can also acquire additional bacteria from the soil. It is suggested that some amphibian populations are protected from Bd by the bacteria on their skin. Bacillus is a naturally occurring soil bacteria that can be transferred onto amphibian skin. The bacterial genus Bacillus is known to have antifungal effects on the chytrid fungus, but not on a species level. In order to test the antifungal properties of compounds secreted by Bacillus bacteria, Bacillus megaterium and Bacillus subtilis were cultured in BHI broth for 24-36 hours. The culture was then centrifuged, and the bacteria were filtered out using 0.45- and 0.22-micron filters, resulting in conditioned media that contains compounds secreted by the bacteria. Sterile dry paper disks were placed in conditioned media for 15 seconds before being placed on plates with 2-10 day old Bd fungus at room temperature. The plates were left at room temperature for 8-10 days before zones of inhibition were measured. Preliminary results show that both Bacillus megaterium and Bacillus subtilis have inhibition effects against Bd. This suggests that these specific species of Bacillus secrete antifungal compounds which inhibit the amphibian chytrid fungus. From the treated media, antifungal compounds will be extracted and purified. The effects of these compounds will then be tested on the chytrid fungus to see which compound has the strongest inhibitory effect on the chytrid fungus. Overall, this study may explain why some amphibians are protected from Bd infection and why some geographic regions lack Bd in the environment where Bacillus species are concentrated.
It’s a Bacteria Thing: Bacterial Inhibition Of Chytrid Fungus
Lobby in front of Auditorium
The amphibian chytrid fungus, Batrachochytrium dendrobatidis (Bd), was discovered in 1998 as the cause of Chytridiomycosis, which has led to devastating declines in amphibian species. Chytridiomycosis causes an osmotic imbalance and electrolyte depletion by disrupting normal functions of the outer keratin layer of the amphibian skin. The life cycle of the amphibian chytrid fungus begins in the water as a free-swimming zoospore, that penetrates the skin and encysts. The zoospore morphs into sporangia in the encysted stage. The sporangia matures and produces more zoospores, which are released from the surface of the amphibian’s skin. However, the fungal lifecycle is suggested to be halted by bacterial flora on an amphibian’s skin that may secrete antifungal compounds. Like humans, amphibians have naturally occurring bacterial flora on their skin, however amphibians can also acquire additional bacteria from the soil. It is suggested that some amphibian populations are protected from Bd by the bacteria on their skin. Bacillus is a naturally occurring soil bacteria that can be transferred onto amphibian skin. The bacterial genus Bacillus is known to have antifungal effects on the chytrid fungus, but not on a species level. In order to test the antifungal properties of compounds secreted by Bacillus bacteria, Bacillus megaterium and Bacillus subtilis were cultured in BHI broth for 24-36 hours. The culture was then centrifuged, and the bacteria were filtered out using 0.45- and 0.22-micron filters, resulting in conditioned media that contains compounds secreted by the bacteria. Sterile dry paper disks were placed in conditioned media for 15 seconds before being placed on plates with 2-10 day old Bd fungus at room temperature. The plates were left at room temperature for 8-10 days before zones of inhibition were measured. Preliminary results show that both Bacillus megaterium and Bacillus subtilis have inhibition effects against Bd. This suggests that these specific species of Bacillus secrete antifungal compounds which inhibit the amphibian chytrid fungus. From the treated media, antifungal compounds will be extracted and purified. The effects of these compounds will then be tested on the chytrid fungus to see which compound has the strongest inhibitory effect on the chytrid fungus. Overall, this study may explain why some amphibians are protected from Bd infection and why some geographic regions lack Bd in the environment where Bacillus species are concentrated.
Comments
Emily Booms is the faculty sponsor of this poster.