Respiratory Mycoplasmas

Published on September 30, 2015   32 min

Other Talks in the Series: Respiratory Infection

0:00
It's a pleasure for me to talk to you today about respiratory mycoplasmas. My name's Stephen Gillespie. I'm the Sir James Black Professor of Medicine at the University of St. Andrews.
0:12
In this talk, I'm going to describe these elusive, interesting, but enigmatic organisms. I first of all will give you a definition of what a mycoplasma is, and then a quick overview of the human mycoplasmas that are a challenge to clinicians. I'm going to focus most of this talk on two important respiratory pathogens, mycoplasma pneumoniae and mycoplasma amphoriforme. Then I'll speak a little bit about the future of mycoplasma research, and hopefully come to some conclusions.
0:45
Mycoplasmas and related organisms are ubiquitous in nature, and such organisms are found widely in humans, animals, and plants. We don't think much about them as clinicians because they're very difficult to diagnose because of their slow growth. Their small cells were the first to have a whole genome sequenced and indeed the first organism to be synthesized synthetically. So they're very small bacteria and the smallest capable of extracellular existence. Their genome is also small, ranging from 0.5 of a megabit to 2.2. They closely adhere to cells, and they lack a typical bacterial cell wall. They have no peptidoglycan. They have an interesting evolutionary past. Mycoplasmas are thought to have evolved from gram positive bacteria, probably clostridia, through reductive evolution. Both pathogens and commensals are found in human samples. And it can be often challenging to differentiate whether the organisms are acting as commensals or pathogens.
1:50
The small genome size of a mycoplasma means it has to depend on the host for many of its metabolic factors. It has very few genes for the biosynthesis of cofactors, nucleic acids, and metabolic precursors. Indeed they do not synthesize their own amino acids and their fatty acids. All mycoplasmas require cholesterol for membrane function, except, of course, the acula plasmas, which in general are not human pathogens. They use glucose as a carbon source or arginine, they are facultative anaerobes, and their optimal growth temperature is 37 degrees Celsius. A major challenge of these fastidious requirements is that they do not grow on normal laboratory media. This means that they fall out of the normal diagnostic pathway and are often unrecognized by bacteriologists.
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Respiratory Mycoplasmas

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