Graduation Year


Document Type




Degree Name

Master of Science (M.S.)

Degree Granting Department

Biology (Cell Biology, Microbiology, Molecular Biology)

Major Professor

Lindsey N. Shaw, Ph.D.

Committee Member

Prahathees Eswara, Ph.D.

Committee Member

Larry Dishaw, Ph.D.


Cinnamaldehyde, Secondary Metabolites


There is a vital need to find new clinical treatment options to combat ESKAPE pathogen infections. Nature has thus far been the most fruitful at providing antimicrobial compounds, which have been derived from a plethora of sources. Ranging from plants to microbial communities, these organisms create chemical compounds that are used as defense mechanisms against invasive or encroaching organisms and confer the producers with competitive advantages. In this study, cinnamaldehyde was investigated as a botanical approach to finding active antimicrobial compounds that inhibit the ESKAPE pathogens. Here, we show that all the ESKAPE pathogens are inhibited by cinnamaldehyde concentrations between 105 µg/mL and 630 µg/mL. To test biofilm eradication capabilities of cinnamaldehyde, we show that at the MIC, there is <50% biofilm recovery for E. faecium, K. pneumoniae, A. baumannii, P. aeruginosa, and E. cloacae. Adaptive mutation assays showed that A. baumannii and S. aureus did not gain resistance to cinnamaldehyde after repeated exposure in comparison to known drug controls. On a biological level, microbial means of inhibiting the ESKAPE pathogens by use of secondary metabolite production was explored as well. In this study, bacteria were isolated and characterized from marine sediment samples collected from the Gulf of Mexico, Hawaii, and Antarctica, and their secondary metabolites tested for growth inhibition against the ESKAPE pathogens. Of the 286 isolates tested, 22 had metabolites inhibiting the growth of S. aureus, E. faecium or both, whilst an additional organism produced metabolites that inhibited K. pneumoniae, E. cloacae as well as both Gram-positive species. From a microbial ecology perspective, following DNA sequencing of the 16S-23S rRNA genes from our microbial collection, 102 were found to be Proteobacteria, 100 were Firmicutes, whilst 47 were from the phylum Actinobacteria. Surprisingly, four were considered to-date uncultured, and therefore are a potential goldmine for novel metabolites and potential future antibiotics. Collectively, compounds derived from botanical and microbial sources can be harnessed for the discovery and development of potential future antibiotics.

Included in

Microbiology Commons