Creative Minds: Giving Bacteria Needles to Fight Intestinal Disease

Cammie Lesser

Cammie Lesser

For Salmonella and many other disease-causing bacteria that find their way into our bodies, infection begins with a poke. That’s because these bad bugs are equipped with a needle-like protein filament that punctures the outer membrane of human cells and then, like a syringe, injects dozens of toxic proteins that help them replicate.

Cammie Lesser at Massachusetts General Hospital and Harvard Medical School, Cambridge, and her colleagues are now on a mission to bioengineer strains of bacteria that don’t cause disease to make these same syringes, called type III secretion systems. The goal is to use such “good” bacteria to deliver therapeutic molecules, rather than toxins, to human cells. Their first target is the gastrointestinal tract, where they hope to knock out hard-to-beat bacterial infections or to relieve the chronic inflammation that comes with inflammatory bowel disease (IBD).

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Snapshots of Life: Biological Bubble Machine

plasma membrane vesicles

Credit: Chi Zhao, David Busch, Connor Vershel, Jeanne Stachowiak, University of Texas at Austin

As kids, most of us got a bang out of blowing soap bubbles and watching them float around. Biologists have learned that some of our cells do that too. On the right, you can see two cells (greenish yellow) in the process of forming bubbles, or plasma membrane vesicles (PMVs). During this blebbing process, a cell’s membrane temporarily disassociates from its underlying cytoskeleton, forming a tiny pouch that, over the course of about 30 minutes, is “inflated” with a mix of proteins and lipids from inside the cell. After the PMVs are fully filled, these bubble-like structures are pinched off and released, like those that you see in the background. Certain cells constantly release PMVs, along with other types of vesicles, and may use those to communicate with other cells throughout the body.

This particular image, an entrant in the Biophysical Society’s 2017 Art of Science Image Contest, was produced by researchers working in the NIH-supported lab of Jeanne Stachowiak at the University of Texas at Austin. Stachowiak’s group is among the first to explore the potential of PMVs as specialized drug-delivery systems to target cancer and other disorders [1].

Until recently, most efforts to exploit vesicles for therapeutic uses have employed synthetic versions of a different type of vesicle, called an exosome. But Stachowiak and others have realized that PMVs come with certain built-in advantages. A major one is that a patient’s own cells could in theory serve as the production facility.

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Nanoparticles Create Spirals in the Lungs

Image of black spirals

Caption: Snapshot of changes that occur (black) when surfactant molecules are stressed by carbon nanoparticles. For the less spectacular “before” image, click the “Continue reading” link.
Source: Prajnaparamita Dhar, Department of Chemical Engineering, University of Kansas, Lawrence

These eye-catching spirals may resemble a trendy print from Diane von Furstenberg’s Spring Collection, but they’re actually a close-up of lung surfactant—a lipid-protein film that coats the inside of the air sacs in the lungs, making it easier to breathe. Made using fluorescence microscopy techniques, this image shows what happens to the surfactant (black) when it interacts with carbon nanoparticles.

Scientists found that carbon nanoparticles rearrange the surfactant molecules from kidney bean shaped clusters into solid spirals. Since carbon nanoparticles may be effective drug delivery vehicles, it’s important to know how these molecules alter the surfactant—and whether these changes are harmful.

The verdict is still out on whether disrupting the surfactant triggers breathing problems, but we can still be mesmerized by the image. Continue reading