Bacteria, those single-celled microscopic critters that inhabit our world and much of our bodies, are still full of surprises after more than four centuries of study under microscopes, 200 years of assault by antiseptics and more than 80 years of antibiotics.
Humans and most living things play host to many bacteria that perform vital body functions, such as digesting food, balancing energy intake and regulating the immune system.
Most of the focus has been on helpful microbes found in the gut, lungs and other internal organs. But a July report from researchers at the National Institutes of Health looked at the protective role of bacteria that live in skin.
Working with mice bred to have no naturally occurring bacteria in the gut or the skin, the team colonized their skin with one type of skin bacteria. Researchers observed the mice were able to produce a cell-signaling molecule needed to protect them from many other skin infections.
Later, the researchers infected two groups of mice -- those that had been colonized with good bacteria as well as those that hadn't -- with a parasite. Mice that had the bacteria were able to mount an effective immune response; those lacking it were not.
The team also tested whether adding good bacteria to the gut of mice rather than the skin made any difference to immune response in the skin. It did not seem to change how skin tissue reacted, suggesting that beneficial microbes have unique roles within each part of the body.
The researchers say it may be that some skin disorders tied to stress and immune reactions, such as eczema and psoriasis, make be linked to some imbalance between beneficial microbes and harmful bacteria. They'll need to do more studies to prove a connection.
The NIH report was published in the journal Science.
Researchers have also gained better understanding about how to assault bacteria.
Although chlorine bleach has been used as a disinfectant for more than 200 years, scientists figured out how the bleach kills bacteria only a few years ago.
University of Michigan researchers made that progress while studying a protein that tends to protect cells under stress from high temperature. They saw that bleach and high temperatures have similar effects on proteins that are essential for bacteria to grow, causing them to lose structure and form clumps, ultimately killing the germs.
The findings, published in the journal Cell in late 2008, also helped build understanding of how the human immune system fights off infections.
One of our weapons against germs is a form of hypochlorite, the same active ingredient found in bleach. But hypochlorite also attacks human cells and is a major source of the damage caused by chronic inflammation.
More recently, researchers at the University of California at Irvine used micro transistors to track how proteins found in human tears work to destroy dangerous bacteria.
Dr. Alexander Fleming, before discovering penicillin in 1928, determined that tears contain the proteins he named lysozymes. Although it was clear the proteins destroyed dangerous bacteria much larger than themselves, scientists had been stumped as to just how they did it.
The UC-Irvine team found a way to attach micro transistors -- 25 times smaller than circuits found in laptops or smart phones -- to individual lysozymes before turning them loose on bacteria.
Writing in the journal Science in January, the researchers said the tiny microphones allowed them to eavesdrop on the proteins as they latched onto bacterial cell walls and chomped through them like ears of corn.
The scientists hope to eventually use the same technology to track other molecules important to health, such as those associated with the earliest stages of cancer.