immunity

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Why are pathogens rarely resistant to vaccines?

We have all heard the horrifying tales of incurable bacterial infections due to antibiotic resistance. But why don’t we see pathogens becoming resistant to vaccines? Intuitively, it seems that vaccines, like antibiotics, put selective pressure on pathogens. The selective force should drive the evolution of vaccine resistance, right? David Kennedy and Andrew Read explore this quandary in their recent publication in the Proceedings of the Royal Society.

Historically, when vaccine resistance arises, it takes much longer compared to antibiotic resistance. Vaccines created as early as the 1920s are still effective today while resistance to a new antibiotic can develop within a few years. Because the evolution of vaccine resistance is so rare, vaccines may be a solution to the drug resistance problems we face today. Vaccines reduce the need for antibiotic treatment and also decrease the number of cases and spread of infections. (more…)

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Eaten alive from the inside: predatory bacteria kill pathogenic bacteria from the inside out

When it comes to predators, we naturally think of large, agile, and powerful animals on the prowl. But we often don’t think about the most abundant predators on our planet, predators of the microscopic world. In the depths of the microbial universe, predatory bacteria (those that feast upon other bacteria) have emerged. These bacteria are now ubiquitous in terrestrial and marine environments. Predatory bacteria penetrate the outer membrane of bacterial prey and ingest their prized nutrients, killing the prey. (more…)

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Microbes in costumes trick the immune system

Halloween has finally arrived and everyone around you has been busy working on their costumes in anticipation for this glorious day of tricks and treats. Come Halloween night, you may not even recognize the faces behind the costumes. How would you tell apart friends with a sweet tooth from foes ready for some tricks?

For some bacteria, putting on costumes is an everyday event when it comes to tricking the immune system. The immune system distinguishes the body's own cells from those of invading bacteria and viruses. Since the microbe's outer membrane is usually the first thing the immune system sees, the body takes advantage of molecules found on the outer membrane to generate an immune response. This seems like a wise defense mechanism but microbes have several tricks up their sleeves; they disguise themselves from the immune response by changing molecules on their outer membrane (antigenic variation) or by turning on and off expression of genes encoding for surface molecules (phase variation). (more…)