bacteria
Some ‘Hospital-Acquired’ Infections Traced to Patient’s Own Microbiome
Posted on by Dr. Francis Collins
Caption: New computational tool determines whether a gut microbe is the source of a hospital-acquired bloodstream infection
Credit: Fiona Tamburini, Stanford University, Palo Alto, CA
While being cared for in the hospital, a disturbingly large number of people develop potentially life-threatening bloodstream infections. It’s been thought that most of the blame lies with microbes lurking on medical equipment, health-care professionals, or other patients and visitors. And certainly that is often true. But now an NIH-funded team has discovered that a significant fraction of these “hospital-acquired” infections may actually stem from a quite different source: the patient’s own body.
In a study of 30 bone-marrow transplant patients suffering from bloodstream infections, researchers used a newly developed computational tool called StrainSifter to match microbial DNA from close to one-third of the infections to bugs already living in the patients’ large intestines [1]. In contrast, the researchers found little DNA evidence to support the notion that such microbes were being passed around among patients.
A Microbial Work of Art
Posted on by Dr. Francis Collins
Credit: Scott Chimileski, Sylvie Laborde, Nicholas Lyons, Roberto Kolter, Harvard Medical School, Boston
Bacteria are single-celled organisms that are too small to see in detail without the aid of a microscope. So you might not think that zooming in on a batch of bacteria would provide the inspiration for a museum-worthy sculpture.
But, in fact, that’s exactly what you see in the image. Researchers grew in a lab dish Bacillus licheniformis, a usually benign bacterium from the soil that produces an enzyme used in laundry detergent. The bacteria self-organized into a sand dollar-like pattern to form a cohesive structure called a biofilm. The researchers then took a 3D scan of the living bacterial colony in the lab and used it to print this stainless steel sculpture at 12 times the dime-sized biofilm.
A Bacterium Reaches Out and Grabs Some New DNA
Posted on by Dr. Francis Collins
Credit: Dalia Lab, Indiana University, Bloomington
If you like comic book heroes, you’ll love this action-packed video of a microbe with a superpower reminiscent of a miniature Spiderman. Here, for the first time ever, scientists have captured in real-time—and in very cool detail—the important mechanism of horizontal gene transfer in bacteria.
Specifically, you see Vibrio cholerae, the water-dwelling bacterium that causes cholera, stretching out a hair-like appendage called a pilus (green) to snag a free snippet of DNA (red). After grabbing the DNA, V. cholerae swiftly retracts the pilus, threading the DNA fragment through a pore on the cell surface for stitching into its genome.
A Lean, Mean DNA Packaging Machine
Posted on by Dr. Francis Collins
Credit: Victor Padilla-Sanchez, The Catholic University of America, Washington, D.C.
All plants and animals are susceptible to viral infections. But did you know that’s also true for bacteria? They get nailed by viruses called bacteriophages, and there are thousands of them in nature including this one that resembles a lunar lander: bacteriophage T4 (left panel). It’s a popular model organism that researchers have studied for nearly a century, helping them over the years to learn more about biochemistry, genetics, and molecular biology [1].
The bacteriophage T4 infects the bacterium Escherichia coli, which normally inhabits the gastrointestinal tract of humans. T4’s invasion starts by touching down on the bacterial cell wall and injecting viral DNA through its tube-like tail (purple) into the cell. A DNA “packaging machine” (middle and right panels) between the bacteriophage’s “head” and “tail” (green, yellow, blue spikes) keeps the double-stranded DNA (middle panel, red) at the ready. All the vivid colors you see in the images help to distinguish between the various proteins or protein subunits that make up the intricate structure of the bacteriophage and its DNA packaging machine.
Powerful Antibiotics Found in Dirt
Posted on by Dr. Francis Collins
Caption: Researchers found a new class of antibiotics in a collection of about 2,000 soil samples.
Credit: Sean Brady, The Rockefeller University, New York City
Many of us think of soil as lifeless dirt. But, in fact, soil is teeming with a rich array of life: microbial life. And some of those tiny, dirt-dwelling microorganisms—bacteria that produce antibiotic compounds that are highly toxic to other bacteria—may provide us with valuable leads for developing the new drugs we so urgently need to fight antibiotic-resistant infections.
Recently, NIH-funded researchers discovered a new class of antibiotics, called malacidins, by analyzing the DNA of the bacteria living in more than 2,000 soil samples, including many sent by citizen scientists living all across the United States [1]. While more work is needed before malacidins can be tried in humans, the compounds successfully killed several types of multidrug-resistant bacteria in laboratory tests. Most impressive was the ability of malacadins to wipe out methicillin-resistant Staphylococcus aureus (MRSA) skin infections in rats. Often referred to as a “super bug,” MRSA threatens the lives of tens of thousands of Americans each year [2].
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