Effect of the Removal of Microbial Communities by Antibiotics on Callosobruchus macultus During Various Life Cycle Stages Open Access

Schlager, Emmalee (Spring 2019)

Permanent URL: https://etd.library.emory.edu/concern/etds/4j03d074h?locale=en


Commensal microbial organisms have a profound impact on their hosts. While the host supplies an environment for the microorganisms to live, the microbes also interact with their host, often assisting them in various ways. Many microbes provide essential functions for their host organisms. One of the ways microbial communities benefit their hosts is by contributing to the nutrition. Callosobruchus maculatus (the bean beetle) is a species of beetle whose larval life cycle occurs within stored legumes. They lack the genes to produce cellulase, which is essential for cellulose digestion. Therefore, bean beetles are likely assisted by their gut microbial community in the digestion of the plant material they consume. In order to test the impact of the microbial communities on the fitness of C. maculatus, antibiotics were added to their environment at various life cycle stages. Extended exposure to antibiotics was hypothesized to alter the gut microbial communities, ultimately having a negative impact on the beetles’ fitness. I found that exposure to antibiotics during early development resulted in fewer beetles emerging from beans. Similarly, treatment of artificial beans with antibiotics throughout the bean showed that continued exposure to antibiotics during the beetles’ larval stages prevented successful emergence. Furthermore, adult beetles with access to liquid antibiotic solutions had significantly lower densities of gut bacteria, but no impact on their overall lifespan was observed. Overall, the presence of antibiotics was shown to have a negative impact on the fitness of the beetles, particularly during larval development.

Table of Contents

Table of Contents


Introduction 1

Methods 8

Results 13

Discussion 21

Conclusion 28

References Cited 30

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