Bacteria are single-celled organisms that are essential to human health, both in our environment and inside our own bodies. However, certain bacterial species can make us sick.
Bacteria are single-celled organisms that are essential to human health, both in our environment and inside our own bodies. However, certain bacterial species can make us sick.
When a physician suspects an illness of bacterial origin, they will perform diagnostic tests to identify what bacterial species is causing disease so that a course of treatment can be devised. One of these tests is called the Gram stain, after Hans Christian Gram, who developed the technique in the 1880s. Gram discovered that certain bacterial species, the so-called “Gram-negative” bacteria, shrug off a purple dye he was using to help visualize the microbes under his microscope. Scientists eventually discovered that Gram-negative bacteria resist dye uptake because they are enveloped in what is, essentially, a microbial suit of armor: their vulnerable cell membrane is protected by a layer of tightly packed sugars called the cell wall, and on top of that, a specialized outer membrane.
“One of the main components of the outer membrane is a unique molecule called lipopolysaccharide (LPS), which covers the surface of the cell,” explains Guest, a postdoctoral fellow in Silhavy’s lab and lead author on the review article in Trends. “LPS helps to increase the mechanical strength of the Gram-negative cell envelope and it also forms a surface coating that prevents toxic molecules, including certain antibiotics, from entering the cell.”
Read more at: Princeton University
In Gram-negative bacteria, LPS and phospholipids are manufactured at the inner bacterial membrane and must be delivered across the cell wall to the outer membrane. The manufacture and delivery of LPS to the outer bacterial membrane is carefully balanced against phospholipid levels because imbalances can be lethal to the cell. Princeton University researchers have identified a new bacterial protein that assists in delivering components to the outer membrane of the Gram-negative bacterium Escherichia coli, as they report in recent papers in PNAS and Trends in Microbiology. (Photo Credit: Silhavy Lab, Princeton University)
