Genome-Wide CRISPR Screening: Putting Death on Hold

We share this planet with approximately 8.7 million species of plants and animals. Within such a diverse environment, it’s only natural that many complex relationships have developed among different species. Some relationships are mutually beneficial, some are parasitic—and some are lethal.

Genome wide - crisper screening to help with toxic compounds to humans

Natural toxins and venoms are biologically active compounds produced by normal metabolic processes in an organism but are harmful to other organisms. Typically, toxins are encountered passively or ingested by the affected organisms, and have a specific mode of action and binding site within a cell. In contrast, venoms are introduced directly into the victim through a specialized delivery mechanism, and they may consist of a mixture of compounds that affect a range of cell types and tissues (1). Both types of poisons are produced for predation, defense, or to offer a competitive advantage (1).

Continue reading “Genome-Wide CRISPR Screening: Putting Death on Hold”

A Tale of Two Toxins: the mechanisms of cell death in Clostridium difficile infections

When someone is admitted to a hospital for an illness, the hope is that medical care and treatment will help them them feel better. However, nosocomial infections—infections acquired in a health-care setting—are becoming more prevalent and are associated with an increased mortality rate worldwide. This is largely due to the misuse of antibiotics, allowing some bacteria to become resistant. Furthermore, when an antibiotic wipes out the “good” bacteria that comprise the human microbiome, it leaves a patient vulnerable to opportunistic infections that take advantage of disruptions to the gut microbiota.

One such bacteria, Clostridium difficile, is of growing concern world-wide since it is resistant to many different antibiotics. When a patient is treated with an antibiotic, C. difficile can thrive in the intestinal tract without other bacteria populating the gut. C. difficile infection is the leading cause of antibiotic-associated diarrhea. While symptoms can be mild, aggressive infection can lead to pseudomembranous colitis—a severe inflammation of the colon which can be life-threatening.

C. difficile causes disease by releasing two large toxins, TcdA and TcdB. Understanding the role these toxins play in colonic disease is important for treatment strategies. However, most published research data only report the effects of the toxins independently. A 2016 study demonstrated a method of comparing the toxins side-by-side using the same time points and cell assays to investigate the role each toxin plays in the cell death that leads to disease of the colon. Continue reading “A Tale of Two Toxins: the mechanisms of cell death in Clostridium difficile infections”

Exploiting Bacterial Toxins for Good (Making Lemonade from Lemons?)

Bacterial exotoxins are scary things. The names of the big three: Tetanus, Anthrax and Botulinum, are sufficient to evoke fear and conjure up images of agony, paralysis, mass hysteria, and permanently frozen Hollywood faces. The worst toxin stories are hard to forget. I can still remember the gruesome textbook case studies that accompanied my bacteriology college lectures. There were the home-canning-gone-horribly-awry botulism stories, the historical examples of agonizing tetanus poisonings, and the less lethal but still nasty cases of fast-acting staph toxins delivered to unsuspecting airline passengers in re-heated meals (avoid the ham sandwiches!). It’s all coming flooding back to me.

So, a healthy respect for bacterial toxins is not a bad thing. The worst ones are highly potent and lethal, others may be less potent but are still capable of delivering effects from temporary misery to long-lasting debilitation. But it’s not all bad news. As any microbiology student knows, studies of bacterial toxins have led to some of the most significant advances in the history of medicine–the most well-known example being the development of vaccines based on denatured, inactive forms of toxins. Tetanus and diphtheria are the classic examples where knowledge of the properties of the toxin itself proved to be the key to developing treatment strategies. Continue reading “Exploiting Bacterial Toxins for Good (Making Lemonade from Lemons?)”