Behind the paper: Modifying bacteria metabolism to increase susceptibility to antibiotics

In this ‘behind the paper’ post, Hansol Im explains how the drive to test a hypothesis, collaboration and team work led them to find that blocking metabolism enhances antibiotic susceptibility of Streptococcus pneumoniae. 

My name is Hansol Im, and I am a postdoctoral fellow in the Department of Microbiology at the University of Alabama at Birmingham. My primary research project during my postdoctoral fellowship has been investigating Streptococcus pneumoniae physiology and adaptation during disease. Since our laboratory has demonstrated that Streptococcus pneumoniae varies its gene expression profile in an anatomical site-specific manner, I was interested in finding key factors that determine bacterial behavior during disease in these different anatomical sites.

I believe that information on specific bacterial behavior during the course of disease can provide potential therapeutic targets like our recent paper in PLOS Biology has done. In this work, we describe that targeting the energy metabolism of pathogens can have a great potential as a novel therapeutic strategy. We evaluated the importance of NAD(H) metabolism in Streptococcus pneumoniae using genetic mutations affecting growth, redox balance, virulence, and antibiotic susceptibility. While investigating, we observed that an impaired NAD(H) pathway made Streptococcus pneumoniae vulnerable to antibiotic stresses. Our next question was whether pharmacochemicals could induce similar outcomes. This led us to investigate if fomepizole, an FDA-approved alcohol dehydrogenase inhibitor that is typically used to treat methanol poisoning, could be our answer. We observed that fomepizole manipulated bacterial NAD(H) metabolism and increased antibiotic susceptibility. In a follow-up study using a mouse model, we successfully confirmed that targeting NAD(H) metabolism in Streptococcus pneumoniae using fomepizole has great potential to treat antibiotic-resistant bacterial infections. 

Image credit

Hansol Im, CC BY 4.0

This project was initially conceptualized in 2020 with my supervisor, Dr. Orihuela. At the beginning of the pandemic, most of the work was delayed and minimal progress was made. The idea and experimental plans were just saved on my computer for over six months. I truly believed that this project could have potential, so it was frustrating when I could not pursue it. I also knew that this publication could play a major role in finding a job once my fellowship ended. Fortunately, I could finally start working on this project in 2021. I trained my first technician and tested my hypothesis that blocking of Streptococcus pneumoniae metabolism has great therapeutic potential, starting from in vitro bacterial culture assays and ending with the animal treatment model. After we decided to research this project, every day was quite busy. Since our campus was closed for around three months because of the SARS-CoV-2 pandemic, I had to carefully plan out each experiment to make sure our time and resources were used wisely. In addition, I worked on three different projects simultaneously, and this project was not the top priority initially because it was not included in our grant proposal. However, I wanted to prove my hypothesis and believed it could have great potential for therapeutic purposes. After I started to observe the strong correlation between Streptococcus pneumoniae metabolism and its influence on antibiotic resistance, we decided to focus on this project with more intention.

In between other studies, I started to test energy metabolism and its influence on bacterial physiology. As soon as other studies finished, I organized my findings into individual figures and focused all my energy on this project to discover mechanisms and pharmacological approaches for the complete storyline. I cannot forget when we first saw that fomepizole could work as an energy metabolism inhibitor. At that moment, we had a hard time finding a pharmacological agent which can support our hypothesis by inhibiting the energy metabolism. When I first found the potential of fomepizole as strong inhibitor for Streptococcus pneumoniae energy metabolism, that was the most fantastic moment during the study.

On the other hand, our success did not always come easily. We faced many challenges, such as failing to construct the mutants in the beginning. The solution to overcome this was communicating with other members in my lab and working together. My lab colleague troubleshooted the problem with me and helped me generate the mutants that we came to use. Since most genes are involved in essential fermentation processes, the initial yield of the mutants was poor. The ultimate fix for the problem ended up simply being to do it again. We increased the concentration of target DNA fragment and tested different bacterial concentrations to optimize our process and finally got several mutated colonies.

Although I was aware of the importance of collaboration and teamwork, I was reminded of its power. I deeply appreciate the experience and partnership during the study and how much that has made me a better scientist. Collaboration has always been an important part of research for me. However, when you have a project that you design and put so much effort into seeing it succeed, you can forget that it is okay to ask for help from those around you. I am fortunate to have a lab full of scientists with varying areas of expertise that are always happy to lend a hand.

Overall, our study described targeting energy metabolism as a novel antimicrobial strategy for the current worsening problem in antibiotic-resistant pathogen infections. Personally, I want to emphasize that collaboration and teamwork can make your science not only move more efficiently, but also enhance the quality of your results. I believe that without the support and assistance from my lab mates, this project would not be what it is today. Whether I need someone to bounce ideas off or assist directly with an experiment, they are always there to support me. This type of environment is where science can truly flourish and produce meaningful results.

About the author

Hansol Im is a postdoc in Carlos J Orihula’s lab. 0000-0002-0629-7461