Immunity system complexity: bacterial spears (Introduction)

by David Turell , Thursday, January 18, 2024, 18:25 (100 days ago) @ David Turell

Just as bacteria spear opponents, they spear our cells:

https://www.sciencenews.org/article/disease-microbes-inject-proteins-cells

"Swallow the wrong microbe, and you might end up in the hospital with a needle or two in your arm — and plenty of itty-bitty bacterial needles poking at you from the inside. That’s because many bacteria that make us sick use microscopic, syringelike structures to inject our cells with proteins that wreak havoc from the inside. Now, researchers have shown how these microbes load their nanoscale needles with proteins.

"Tracking individual proteins as they jittered around inside living bacteria revealed the microbes use a shuttle bus–like system to load their syringes: shuttle proteins travel random paths within the microbes’ interiors, grabbing cargo destined for injection as they go and dropping it off at the syringes, scientists report January 3 in Nature Microbiology. Knowing how these bacterial needles work could help scientists learn how to disrupt them — or commandeer them for medical applications, like using bacterial needles to inject cancer cells with targeted drugs while leaving healthy tissue unscathed.

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"Under the microscope, the syringelike structures, called a type-III secretion system, look like hollow needles just wide enough for a single unfolded protein to slither through, Diepold says. A microbe’s entire surface might be covered in such needles, giving the bacterium the look of a sinister little pincushion. Scientists know the protein structure of these nanoscale needles quite well. But “we don’t know the basic question of how they recruit whatever is injected,” he says.

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"This type of secretion system, one of a handful of different types of needles bacteria have at their disposal, is widespread across different species of bacteria, Diepold says, so they’re good targets for new types of antibacterial drugs.

"They’re also promising tools for medicine and biotech, Hughes says. But as much as they look like medical syringes, bacterial syringes work differently — and scientists still don’t know exactly how bacteria push proteins through their needles. It’s also unclear how the proteins that load up the needles recognize their targets. “We want to understand the riddle of how these systems work,” Diepold says. “We want to understand which solutions evolution came up with to allow bacteria to infect us.”

Comment: this is like the spikes viruses use. It will be interesting to learn how the 'syringes' work.