Quantitative proteomic analyses of Staphylococcus aureus treated with punicalagin, a natural antibiotic from pomegranate that disrupts iron homeostasis and induces SOS

Authors: Cooper, Bret; ISALM, NAZRUL - University Of Maryland; XU, YENFENG - Northwest Agricultural & Forestry University; Beard, Hunter; Garrett, Wesley; GU, GANYU - Virginia Tech; Nou, Xiangwu

Submitted to: Proteomics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/1/2018
Publication Date: 3/12/2018
Publication URL: http://handle.nal.usda.gov/10113/6471010
Citation: Cooper, B., Isalm, N., Xu, Y., Beard, H.S., Garrett, W.M., Gu, G., Nou, X. 2018. Quantitative proteomic analyses of Staphylococcus aureus treated with punicalagin, a natural antibiotic from pomegranate that disrupts iron homeostasis and induces SOS. Proteomics. 18:1700461. https://doi.org/10.1002/pmic.201700461.
DOI: https://doi.org/10.1002/pmic.201700461

Interpretive Summary: Staphylococcus aureus, a bacterial, food-borne pathogen of humans, can contaminate raw fruits and vegetables. To help protect people and the food supply, scientists are searching for natural chemicals that serve as antibiotics. Pomegranates are a promising source of natural antibiotics. Pomegranates produce a chemical called punicalagin that is known to reduce bacterial growth, but it’s mechanism of action on the biochemistry of bacteria is not well known. To get a broader understanding of the inhibitory effect of punicalagin on S. aureus, we used mass spectrometry, an analytical method of detection, to measure the proteins in S. aureus after exposure to punicalagin. Nearly half of the bacterial proteins were measured. Punicalagin treatment altered the accumulation of proteins and enzymes needed for iron acquisition and energy production, and it induced the bacterial cells into an emergency survival response. Punicalagin treatment was found to be different than EDTA and ciprofloxacin, other chemicals that also affect iron acquisition and induce emergency survival responses. These results show that punicalagin severely affects bacterial growth and that the biochemical activity of punicalagin on S. aureus may disrupt iron acquisition. These results will be useful to scientists at private companies, universities, and government laboratories who research antibiotics with the goal to protect people and to improve the safety of the food supply.

Technical Abstract: Staphylococcus aureus, a bacterial, food-borne pathogen of humans, can contaminate raw fruits and vegetables. While physical and chemical methods are available to control S. aureus, scientists are searching for inhibitory phytochemicals from plants. One promising compound from pomegranate is punicalagin, a natural antibiotic. To get a broader understanding of the inhibitory effect of punicalagin on S. aureus growth, we used high-throughput mass spectrometry and quantitative isobaric labeling to investigate the proteome of S. aureus after exposure to a sub-inhibitory dose of punicalagin. Nearly half of the proteins encoded by the small genome were interrogated, and nearly half of those exhibited significant changes in accumulation. Punicalagin treatment altered the accumulation of proteins and enzymes needed for iron acquisition and downstream metabolic pathways for glycolysis, citric acid cycling, protein biosynthesis, and purine and pyrimidine biosynthesis. Punicalagin treatment also appeared to induce an SOS cellular response. Transcriptional comparison of marker genes showed that punicalagin-induced iron-sequestration and SOS responses were different than those produced by EDTA and ciprofloxacin. These results show that punicalagin adversely altered the proteome to severely affect bacterial growth and that the biochemical activity of punicalagin on S. aureus may disrupt iron homeostasis and induce SOS.