Nature as an ally in the fight against drug resistant superbugs

Featured Scientist: Juan Canchola (he/him/his) Bachelor of Science (Anticipated: Spring 2021), School of Biological Sciences, Illinois State University

Two pictures of Juan. One is a picture of him shaking hands with another man, as if he had just received a scholarship or award. The other is a picture of him in the lab. He is filling a balloon with a gas.
Juan at the Illinois State University 6th annual Charles Morris STEM Social (left) and adding a chemical to a reaction flask in the lab (right).

Birthplace: Bloomington, Illinois

My Research: I work in the Mills Medicinal Chemistry research lab, where we study the development of antibiotics from natural products. Natural products are chemicals that occur in nature. Our goal is to create an antibiotic that can be used to fight against antibiotic-resistant bacteria.

Research Goals: I’m very interested in infectious diseases and in Medicinal Chemistry. I would like to continue in research involving both of these fields.

Career Goals: I’d really like to continue research in a M.D/Ph.D. program, but my ultimate goal is to be a dedicated scientist who contributes to the fight against infectious diseases. 

Hobbies: In my free time, I love to work out, play with my dog, and binge watch cooking shows and anime. 

Favorite Thing About Science: I really like science because it is an essential and enjoyable field of study. Science has been society’s number one tool to fight off dangers like disease and illness, but it is also very interesting to study and enjoyable to practice. 

Organism of Study:  We studied and synthesized Anaephene A and B, which are two natural products that can be used to make antibiotics. Anaephene A and B were isolated from a marine cyanobacteria (Hormoscilla sp., Oscillatoriales) by a team of marine biologists off the coast of Guam.

Two images. One has the chemical structure of Anaephene A and Anaephene B. The other has a picture of grey marine cyanobacteria.
The two natural products that we synthesized, Anaephene A and B (left). The marine cyanobacteria (Hormoscilla sp., Oscillatoriales) from which the natural products were isolated (right).

Field of Study:  Medicinal Chemistry

What is Medicinal Chemistry? Medicinal Chemistry is a field of research that uses techniques and knowledge from various fields of chemistry and biology to make medicine. In the research lab I work in, we mainly use organic chemistry and microbiology. Organic chemists study the process of making compounds, while microbiologists study small living organisms, like bacteria. In my work, I use laboratory techniques from both fields to try to make antibiotics out of natural products.

Check Out My Original Paper: “Synthesis of the Cyanobacterial Antibiotics Anaephene A and B” 

A picture of David pipetting chemicals under a fume hood.
 David Kukla looks for his desired chemical after purifying a reaction mixture.

My Team: I work with Dr. Jonathan Mills in his medicinal chemistry research lab. At the time of this research, Dr. Mills had just arrived at Illinois State University and the only members of the lab were me and a fellow undergrad, David L. Kukla. David is now a graduate student in the Mills Lab. Under the guidance of Dr. Mills, I made Anaephene A and David made Anaephene B. Dr. Mills grew the bacteria and tested our compounds against them. Once we had results, a team effort was made to assemble the data in a more organized format. Dr. Mills handled writing and editing for the paper. David and I helped to proofread so that we could become familiar with the process of turning data into a scientific paper.

Research At A Glance: In our study, we made two chemical compounds that were effective at killing antibiotic resistant bacteria. The compounds that we used were Anaephene A and B. These are naturally made by a type of marine cyanobacteria and are considered natural products. They were selected because other researchers had found them to be biologically active against some strains of bacteria. Our goal was to find a way to make these natural products in the laboratory and see if they were effective against antibiotic resistant bacteria. We were able to make Anaephene A and B and tested them against three strains of bacteria. We exposed the bacteria to different levels of Anaephene A and B to find the smallest amount needed to prevent their growth. Both compounds did well against all three strains of bacteria, including a superbug known as Methicillin-resistant Staphylococcus aureus (MRSA). Anaephene B performed better than Anaephene A, but both were very effective against MRSA

Highlights: To see if Anaephene A and B could be used against our strains of bacteria, we conducted Minimum inhibitory concentration assays (MICs). The three bacterial strains that we used were Bacillus cereus (B. cereus), Staphylococcus aureus (S. aureus), and MRSA. We used B. cereus and S. aureus because they are a common cause of infections in humans. We used MRSA because it is an infectious bacterium that is resistant to many antibiotics. We used the MICs to find the minimum amount of Anaephene A and B needed to destroy the bacteria and/or prevent bacterial growth. Compounds that have this effect on bacteria are considered biologically active. A smaller MIC value means that the compound is more potent because less is needed to destroy the bacteria. The purpose of the MIC assay was to confirm that the two natural products were biologically active and to determine if they could be effective against antibiotic resistant bacteria, like MRSA. Our results showed that both compounds were biologically active against the bacterial strains tested. Both of the natural products also succeeded in inhibiting the growth of MRSA at fairly low MICs. Anaephene B, in particular, proved to be highly potent as it displayed an MIC of 8 μg/mL against MRSA and the other two strains of bacteria. As you can see from Table 1, Anaephene A and B were significantly less potent than the positive control, Linezolid. Linezolid is an approved antibiotic that has gone through years of development and optimization. Anaephene A and B, on the other hand, are natural products that have not been modified. The physical structure of these compounds contributes to their biological activity. Investigating the structure of these compounds could help us determine exactly what causes them to have antibiotic properties. 

A table of MIC values for the chemicals tested. Anaephene A has an MIC of 16 micrograms/mL for each bacteria. Anaephene B has an MIC of 8 micrograms/mL for each bacteria. Linezolid has an MIC value of 0.5-1 micrograms/mL for each bacteria.
Table 1. MIC values of Anaephene A, Anaephene B, and Linezolid (a standard synthetic antibiotic).

What My Science Looks Like: To synthesize Anaephene A and B, we had to look at their physical structures. The structure of the compounds helped us to determine the reactions or steps we needed to use to make them (Figure 1).

A chemical reaction that ends with Anaephene A and Anaephene B. The figure highlights the MIC of Anaephene B, 8 microgram/mL against MRSA.
Figure 1. Summary of the main pieces used to make Anaephene A (1) and Anaephene B (2). The more potent compound, Anaephene B (2), is boxed with its reported MIC value. Figure adapted from Kukla et al. 2020.

To make Anaephene A and B, we looked at similar compounds as a reference. We studied the reactions used to make those compounds and used that information as a guide. Through a process of trial and error, we found the arrangement of steps, or the synthetic pathway, that would successfully make Anaephene A (1) and B (2) in 5 steps (Figure 2).

A five step chemical reaction that leads to the precursor that makes both Anaephene A and B.
Figure 2.  The complete synthesis of Anaephene A (1) and Anaephene B (2). This is the synthetic pathway used to make both of the natural products.  Figure adapted from Kukla et al. 2020.

The Big Picture: Many bacteria are evolving resistance to commonly used antibiotics. Bacteria that are resistant to many antibiotics are called superbugs. As superbugs become more and more drug-resistant, the number of antibiotics that can be used against them is decreasing. Since we have a limited number of approved antibiotics, health care professionals are forced to use the same ones over and over again. This is what can lead to antibiotic resistance. Some experts think that if we do not develop more antibiotics soon, common bacterial infections may turn deadly because we will not have the drugs needed to treat them. 

Many of the antibiotics that we use for medicine are made using the same synthetic pathways or they use the same mechanism of action. This means that not only are we running out of antibiotics, but we are also running out of ways to make them. To combat the rise in antibiotic-resistant bacteria, we need to look for new synthetic pathways and mechanisms of action. Most of our successful drugs come from natural products, so nature may be the best place to look for a solution. Biologically active natural products show a lot of potential because they are usually made by an organism to defend against pathogens. Therefore, natural products tend to be harmful for pathogens but not the organism itself.

In our research, we have made two natural products, Anaephene A and B, which can kill both common bacteria and antibiotic resistant bacteria. Anaephene A and B could potentially aid us in the development of new antibiotics since they were found to be biologically active against the bacterial strains tested. This is only the very beginning and there could still be some unknown drawbacks. For example, we don’t know what effects Anaephene A and B have on the human body. We also don’t know what the mechanism of action is. This is crucial information for antibiotic development, so it is clear that much more work lies ahead. Overall, we have identified natural products that kill antibiotic resistant bacteria and found a way to make them in the laboratory. Much more research is required to determine if these compounds can be developed into antibiotics safe for use in humans, but we’re off to a good start.

Decoding the Language: 

Antibiotic: A substance that kills or prevents the growth of microscopic living organisms, like bacteria. We commonly use antibiotics in medicine to treat bacterial infections.

Antibiotic resistance (drug-resistant): Antibiotic resistance refers to bacteria that have developed the ability to survive the antibiotics that were designed to kill them. Antibiotic resistance is a global issue. As bacteria become increasingly resistant to many antibiotics, the number of antibiotics that can be used for treatment decreases. Scientists fear that in the near future we may completely run out of antibiotics that can be used to fight off bacterial infections. 

Bacillus cereus (B. cereus): B. cereus is a common strain of bacteria that is often found in soil and vegetation and can also be present in foods. It can multiply quickly at room temperature and is a common cause of “food poisoning”, an intestinal illness that can cause nausea and/or vomiting. 

Bacterial strains: Bacterial strains describe subtypes of bacteria that vary in appearance, structure, and function.

Biological activity:  Biological activity is a term used in medicinal chemistry to describe the negative or beneficial effects that a compound has on a living organism. In our case, the compounds negatively affect bacteria, therefore they are biologically active.

Chemical compound: A chemical compound (referred to as just compound in chemistry) is a substance made from two or more elements in a fixed position.

Marine cyanobacteria: Cyanobacteria is a type of bacteria that is capable of photosynthesis, that is, using light to make energy that supports the growth of the bacteria. These types of bacteria are found in biofilms in the ocean. Biofilms are thin, slimy layers or “films” of bacteria that grow over the surface of rocks, plants, and algae, usually underwater.

Mechanism of action: The mechanism of action describes how a chemical performs its actions. In our study, it describes how our compound is able to inhibit the growth of bacteria.

Medicinal Chemistry: A field of chemistry involving the research, design, and development of chemicals that can be used as pharmaceutical drugs.

Methicillin-resistant Staphylococcus aureus (MRSA)MRSA is a strain of bacteria that has developed resistance to several antibiotics. It can cause ‘staph’ infections that are difficult to treat.Minimum inhibitory concentration assays (MICs): MIC is a test that involves diluting a drug several times to find the lowest amount that will prevent visible growth of bacteria.

Natural products: These are chemicals, or substances, that are found in nature or are produced by living organisms.

Pathogen: A bacteria, virus or other microscopic living organism that can cause disease. MRSA is a pathogen because it can cause disease.

Staphylococcus aureus (S. aureus): S. aureus is a common strain of bacteria, frequently found in the upper respiratory tract and on the skin. This strain of bacteria can cause a variety of mild to severe soft tissue infections and pneumonia but is most known for causing skin infections in hospitals.

Superbug: This is a term used for strains of bacteria, viruses, parasites and fungi that are resistant to most of the antibiotics and other medications commonly used to treat the infections they cause. 

Synthesis: The process of manually making a product through the use of chemical reactions. In this research, we synthesized Anaephene A and B.

Synthetic pathway: A synthetic pathway describes the collection of steps, or the path, used to synthesize a product.

Learn More:

Check out the following sources for more information on the Anaephene natural products and on antibiotic resistance:

Original publication on the isolation of the Anaephene natural products

Article from the World Health Organization (WHO) on antibiotic resistance

Article from the Centers for Disease Control (CDC) on antibiotic resistance

Very interesting and relevant information on antibiotic resistance and Covid-19

Synopsis edited by Ian Rines, PhD Candidate (Anticipated: Spring 2023), School of Biological Sciences, Illinois State University and Brooke Proffitt, B.S. 2020, Illinois State University Alumna.

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