Targeting tumors with bacterial magnets.


Breaking down the microbiology world one bite at a time

Targeting tumors with bacterial magnets.

What do you associate with the word, “magnet?” Perhaps you think about various magnets hanging on your fridge, or maybe you picture the stereotypical red U-shaped magnet that cartoon characters love to use. Compasses might also cross your mind. What if you learn that bacteria relate to magnets? Scientists have researched aquatic microorganisms called magnetotactic bacteria (MTB) that function similarly to compasses — sensing and reacting to Earth’s magnetic field. As such, MTB survive on little oxygen (aka microaerobic environments), typically thriving in oxic-anoxic transition zones.  These transition zones describe oases in freshwater sediments with vertical chemical gradients (think diffusion), which comprise reduced iron and sulfide plus oxygen (think redox reactions). Thus, MTB use their magnetic, chainlike organelles — called magnetosomes — to sense, then locate, the best place with a suitable oxygen concentration. Simply put, MTB go where the geomagnetic field lines take them.

Sounds interesting, but how does that help anyone or anything?. Scientists have originally used inorganic magnetic nanoparticles (MNPs) — tiny iron oxide objects. They remain small enough to permeate cells, while offering some compatibility with other biological structures (e.g., cell membranes). This has prompted the potential to shrink cancerous tumors. Think about it: you’ve got something virtually invisible that can enter cells, so what happens if you load it with drugs that attack tumors? Scientists have tried exactly that, however they soon stumbled upon a few roadblocks. First, the nanoparticles only penetrate cells so much — limiting drug delivery’s precision and accuracy. Then, that dosage ends up in some places more than others or fails to make it to their target completely; thus reducing or ruining their initial purpose. Simply put, these nanoparticles lack direction — rendering them useless for their intended goal.

Hence, MTB potentially rectify these issues, because scientists may manipulate MTB’s magnetism to lead them directly toward a tumor — cancer-fighting drugs in tow — thanks to their self-propulsion. Plus MTB can naturally produce these particles. Such particles also convert electromagnetic energy into heat. Scientists apply this heat to tumors until their cells apoptose (undergo cell death). Increased heat causes proteins to denature/unfold — leading to dysfunction and ultimately apoptosis. Think about bubble wrap — the sheet representing a tumor, each bubble a cell. Each popped bubble or cell deflates. Eventually, you pop nearly every bubble, flattening the sheet. A popped bubble corresponds to a cell [within the tumor] apoptosing, while the flatter sheet indicates a shrunken tumor. 

Programmed cell death: evidence in the empty white spaces.
Ltumanovskaya V. Nagibin, CC BY-SA 4.0 <;, via Wikimedia Commons 

The above techniques prove very specific. Specificity allows scientists to better treat cancer because it minimizes negative side effects from traditional treatment that harms surrounding, healthy cells while administering the proper drug concentration at the right place [within the body]. MTB promise so much for medicine, yet still possess drawbacks. 

  1. Scientists require a lot more magnetotactic bacteria (MTB) to mass-deliver sufficient drugs for cancer patients.

Alongside that, scientists must tweak how MTB’s magnetism works through their organelles, magnetosomes — also in mass quantity. This means modifying the proteins that make up magnetosomes (many of which scientists have yet to understand). Remember, magnetism drives this treatment so ensuring that MTB propel themselves to the right place remains top priority!

  1.  MTB must travel through the bloodstream — which offers some resistance and may limit motility.

Consider this: you need to meet someone a block away, easy enough if your pathway remains clear. But, what if a crowd forms? You would have to push past many people to break through — if you can manage that. A similar situation applies to MTB: the bloodstream may block or dampen its effect on the tumor. 

  1. Scientists and medical professionals will likely utilize multiple treatment methods to attack a tumor, including MTB.

Everyone has different bodies so one person may respond differently than another with the same cocktail treatment. Additionally, MTB might respond differently in tandem with other treatments/therapies. Scientists must determine the optimal concoction between MTB, traditional chemotherapy and radiation, and any other party involved.

Overall, magnetotactic bacteria (MTB) give scientists plenty to work with. MTB’s self-propulsion alongside Earth’s magnetic fields offers control, precision, and accuracy when targeting cancer at a newfound level. Scientists still have much to learn, yet the future brims with awe-inspiring possibility. Because just as a compass points northward, magnetotactic bacteria point towards a brighter future — all using similar mechanisms.

Link to the original post: M. L. Fdez-Gubieda, J. Alonso, A. García-Prieto, A. García-Arribas, L. Fernández Barquín, and A. Muela , “Magnetotactic bacteria for cancer therapy”, Journal of Applied Physics 128, 070902 (2020)

Featured image: Image by Pexels from Pixabay