Posts tagged: bacterial cell

Photodynamic Therapy– Is Selective Damage Really that Selective?

Why doesn’t photodynamic therapy (PDT) cause any noticeable damage to human tissue? After all, the reaction causes damage to the bacterial membrane, and human cells have membranes as well.

This was a topic that really grabbed my attention when I first learned about photodynamic therapy.   How is it possible that with the creation of highly reactive molecules are we only limiting cellular destruction to bacterial cells? Although there may be a few different answers to this question, the primary solution is that we are not. Don’t be afraid and swear off photodynamic therapy right away, here me out first. Photodynamic therapy is primarily used as a treatment option for cancers. This treatment is used on cancerous tumours formed in esophageal cancer, lung cancer, skin cancer, as well as many different types. The photosensitizer is accumulated in the tumour either by direct injection or utilizing mutations of the cancerous cells that concentrate the photosensitizer inside the cell. After light is applied, the tumour cells are damaged, but the healthy cells are not greatly harmed. Why? One trait of a cancerous growth is the mutation of certain DNA repair enzymes. (Have a look at this Wikipedia article to give you a small background on DNA repair enzymes) These repair enzymes are responsible for fixing oxidative damage problems caused by free radicals. Scientific researchers, knowing this small fact about most cancerous tumour cells, use PDT and reactive oxygen species to their advantage. A healthy human cell can take some free radical “abuse”, but a tumour cell can only take so much until the cell dies. This fact, coupled with selective photosensitizer accumulation within tumour cells, makes PDT an excellent treatment option in some forms of cancer.

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Antibiotic Resistance: How A Global Health Problem Develops

The public sphere has been pumped full of information about how unnecessary use of antibiotics contributes to the development of resistant bacterial strains. Just take a look at this news article suggesting that more than 25 million pounds of antibiotics are given to livestock every year. However, what is less often explained is how this works at the molecular level. How does bacteria develop antibiotic resistance?

The World Health Organization has called antibiotic resistance one of the greatest global health concerns to date.

Before answering that question it is important to understand how bacterial cells work. Bacterial cells look and work differently than say a cell from our body. They have a genetic code (within DNA) but some of that code floats freely within the cell in circular structures called plasmids. One of the particularities of bacterial cells is their ability to pass plasmids amongst each other (plasmid transfer), allowing them to share traits on an extremely rapid scale. Furthermore, one bacterium can divide into two cells without the need for sexual reproduction between two parent cells.

Like us, bacteria survive on chemical based processes, which allow them to grow and replicate. Protein molecules are essential to these processes. They allow for three things:

  • Destroy/change other molecules
  • Form physical structures and barriers
  • Help build new molecules

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