Event Title

Metabolic Diversity in Bacteria Associated with Earthworm Cocoons

Location

CSU Ballroom

Start Date

16-4-2013 10:00 AM

End Date

16-4-2013 12:00 PM

Student's Major

Biological Sciences

Student's College

Science, Engineering and Technology

Mentor's Name

Dorothy Wrigley

Mentor's Department

Biological Sciences

Mentor's College

Science, Engineering and Technology

Description

The cocoons of Eisenia fetida, a common earthworm species, contain diverse populations of symbiotic bacteria. Bacterial species are found in the surrounding soil or are passed directly from the parent earthworm to the offspring. It is important to understand the behavior of these symbionts as they are a vital component in the fitness of Eisenia fetida. To determine metabolic diversity, cocoons were selected and sterilized using ethanol. The contents were then squeezed onto individual Petri dishes containing tryptic soy agar (TSA). These plates were incubated at room temperature in microaerophilic conditions. From these plates, six organisms were selected based on colony morphology and isolated onto their own plates. Oxidase, citrate, and thioglycolate tests were performed on each of these six isolates. Of the six isolates, all but one tested positive for oxidase, and all isolates tested positive for citrate utilization. Five of the six organisms showed strictly aerobic growth, while the sixth showed facultatively anaerobic growth; this was the same organism which was negative for oxidase. From these results, it can be concluded that diversity in metabolic behavior does exist within the simbiont population of Eisenia fetida cocoons. Further tests will be performed to reinforce these results, including gram reactions of the organisms and nitrate tests, which will provide further information on each organism, leading eventually to a better understanding of each organism’s effect on the fitness of Eisenia fetida.

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Apr 16th, 10:00 AM Apr 16th, 12:00 PM

Metabolic Diversity in Bacteria Associated with Earthworm Cocoons

CSU Ballroom

The cocoons of Eisenia fetida, a common earthworm species, contain diverse populations of symbiotic bacteria. Bacterial species are found in the surrounding soil or are passed directly from the parent earthworm to the offspring. It is important to understand the behavior of these symbionts as they are a vital component in the fitness of Eisenia fetida. To determine metabolic diversity, cocoons were selected and sterilized using ethanol. The contents were then squeezed onto individual Petri dishes containing tryptic soy agar (TSA). These plates were incubated at room temperature in microaerophilic conditions. From these plates, six organisms were selected based on colony morphology and isolated onto their own plates. Oxidase, citrate, and thioglycolate tests were performed on each of these six isolates. Of the six isolates, all but one tested positive for oxidase, and all isolates tested positive for citrate utilization. Five of the six organisms showed strictly aerobic growth, while the sixth showed facultatively anaerobic growth; this was the same organism which was negative for oxidase. From these results, it can be concluded that diversity in metabolic behavior does exist within the simbiont population of Eisenia fetida cocoons. Further tests will be performed to reinforce these results, including gram reactions of the organisms and nitrate tests, which will provide further information on each organism, leading eventually to a better understanding of each organism’s effect on the fitness of Eisenia fetida.

Recommended Citation

Balster, Jeremy and Mark Walchuk. "Metabolic Diversity in Bacteria Associated with Earthworm Cocoons." Undergraduate Research Symposium, Mankato, MN, April 16, 2013.
http://cornerstone.lib.mnsu.edu/urs/2013/poster-session-A/3