Human skin populated by veritable zoo of bacteria

[Al-khiyal]

Bacteria commonly found on human skin - Staphylococcus aureus, E. Coli, Proteus mirabilis, and others - blossoms into a full-blown handprint on a culture medium.

WASHINGTON (Reuters) - Researchers on a safari for microbes have found that human skin is populated by a veritable menagerie of bacteria - 182 species - some apparently living there permanently and others just dropping by for a visit.

There's no need for alarm, said microbiologist Dr. Martin Blaser of New York University School of Medicine: the bacteria have been with us for quite a while and some are helpful.

In research published on Monday in the Proceedings of the National Academy of Sciences, Blaser and his colleagues took swabs from the forearms of six healthy people to study the bacterial populations in human skin - our largest organ.

"We identify about 182 species," Blaser said in an interview. "And based on those numbers, we estimate there are probably at least 250 species in the skin."

"In comparison," Blaser added, "a good zoo might have 100 species or 200 species. So we already know that there are as many different species in our skin, just on the forearm, as there are in a good zoo."

Bacteria are single-celled microorganisms believed to have been the first living things on Earth. While some cause disease, bacteria also reside normally in our bodies, for example in the digestive tract, performing useful chores.

"Without good bacteria, the body could not survive," added Dr. Zhan Gao, a scientist in Blaser's lab involved in the study.

The researchers noted that microbes in the body actually outnumber human cells 10-to-1.

"Our microbes are actually, in essence, a part of our body," Blaser said.

"We think that many of the normal organisms are protecting the skin. So that's why I don't think it's a great idea to keep washing all the time because we're basically washing off one of our defense layers," Blaser added.

It has long been known that bacteria reside in the skin, but Blaser and his colleagues used a sophisticated molecular technique based on DNA to conduct a rigorous census.

The inhabitants proved to be more diverse than had been thought, with about 8 percent of the species previously unknown, the researchers found.

Some bacteria seemed to be permanent residents of the skin, with four genera - Staphylococcus, Streptococcus, Propionibacteria and Corynebacteria - accounting for a bit more than half the population. Others were more transient.

In each person, the population of bacteria changed over time although a core set existed for each.

The volunteers included three men and three women, and the findings suggested the two sexes may differ in the bacteria they tote along.

The researchers previously had studied bacteria in the stomach and esophagus. With this research, they found that the insides of the body and the skin had major differences in bacterial populations.

"Microbes have been living in animals probably for a billion years. And the microbes that we have in our body are not accidental. They have evolved with us," Blaser said.

Human skin populated by veritable zoo of bacteria

[Al-khiyal]

Proceedings of the National Academy of Sciences

[Bent_Bladi]

*feeling nauseous* i could've done well w/out the picture
~~~

[Al-khiyal]

Humans may lose battle with bacteria, medicinal chemist's research shows

April 24, 2008 -- It may not be an ideal topic for polite conversation, but human beings are swarming with bacteria: even the average healthy adult plays host to about 100 trillion microscopic organisms. Infection takes place when the bacteria get out of hand.

Now, a University of Kansas researcher has penned a history of the struggle between man and bacteria — and warns that humankind someday may lose its advantage.

In the March 28 issue of the American Chemical Society’s Journal of Natural Products, Lester A. Mitscher, a University Distinguished Professor of Medicinal Chemistry, calls for the development of more potent antibiotics necessary for humanity to manage drug-resistant breeds of microbes.

“Antibiotics are essentially selective poisons that kill bacteria and that do not kill us,” Mitscher said.

In his article, “Coevolution: Mankind and Microbes,” Mitscher chronicles the advent of antibiotics in the 20th century. Sulfonamides, the first anti-infectives, were introduced the mid-1930s. Penicillin — “the first true antibiotic” — was employed widely during World War II. In the decades since, dozens of important antibiotics have been developed and marketed around the world.

“These were called ‘miracle drugs,’ ” said Mitscher. “Unfortunately, that had a downside. They were so relatively safe and so effective that we became careless in their use and in our personal habits. That has caused much of the resistance phenomenon we have today.”

Microbial resistance to these drugs has been an ever-increasing problem because of the speedy reproduction and evolution of microorganisms.

“Bacteria that survive the initial onslaught of antibiotics then are increasingly resistant to them,” said Mitscher. “The sensitive proportion of the bacterial population dies, but then the survivors multiply quickly — and they are less sensitive to antibiotics. The sensitivity goes all the way from requiring a longer course of therapy or a higher dose, to being totally unaffected by the antibiotic.”

Humans have overused antibiotics in areas such as agriculture, worsening the dilemma of highly resistant bacteria.

“People are surprised to learn that almost half of all the antibiotics produced in the world are used in animal husbandry,” said Mitscher. “I’m not referring to using antibiotics for curing infections of animals — what I mean is use of antibiotics in relatively small doses as an animal-feed supplement. Animals then grow quicker to a marketable size, and this is seen as a universal good. The difficulty is that use of antibiotics in that setting is an invitation towards resistance. Unfortunately, humans get infected with resistant strains that were generated in animals in this manner.”

These days, with so-called “super-bugs” like Methacillin-resistant Staphylococcus aureus (MRSA) making news, resistance is becoming a major public health problem.

“Resistance that started in a hospital setting quickly spread into the community, and now resistance is essentially all around us,” Mitscher said. “That does not mean to say we’re all going to die in agony in the immediate future. But this is an important phenomenon that needs to be addressed more carefully than we have in the past.”

Part of the solution is to use antibiotics sparingly for industrial, agricultural and medical purposes. When an antibiotic is called for to treat an infection the best one should be used with appropriate intensity.

Mitscher said that drug corporations must develop antibiotics with the potential not only to kill microbes but also to inhibit their ability to mutate. These new drugs would be made more effective still if they enlisted the body’s own immune system to battle infections.

Alas, because of the economics of the drug industry, Mitscher said such “triple treat” antibiotics might be a long time coming.

“The pace of antibiotic discovery has fallen off, partly because the intensive research on them has lead to increasingly diminishing returns,” said Mitscher. “Pharmaceutical firms have, for a variety of commercial reasons, de-emphasized antibiotic research in recent decades.”

Mitscher adapted his article from a July 2007 speech in Portland, Maine, accepting the American Society of Pharmacognosy’s Norman R. Farnsworth Research Achievement Award, the highest award the society bestows.

A color-enhanced scanning electron micrograph
showing Salmonella typhimurium (red)
invading cultured human cells

[Bent_Bladi]

that's really scary... imagine if we don't figure something out

[Al-khiyal]

Bacteria thrive in inner elbow; no harm done

May 23, 2008 -- The crook of your elbow is not just a plain patch of skin. It is a piece of highly coveted real estate, a special ecosystem, a bountiful home to no fewer than six tribes of bacteria. Even after you have washed the skin clean, there are still one million bacteria in every square centimeter.

But panic not. These are not bad bacteria. They are what biologists call commensals, creatures that eat at the same table with people to everyone's mutual benefit. Though they were not invited to enjoy board and lodging in the skin of your inner elbow, they are giving something of value in return. They are helping to moisturize the skin by processing the raw fats it produces, says Dr. Julia Segre of the National Human Genome Research Institute.

Segre and colleagues report their discovery of the six tribes in a paper being published online on Friday in Genome Research. The research is part of the human microbiome project, microbiome meaning the entourage of all microbes that live in people.

The project is an ambitious government-financed endeavor to catalog the typical bacterial colonies that inhabit each niche in the human ecosystem.

The project is in its early stages but has already established that the bacteria in the human microbiome collectively possess at least 100 times as many genes as the mere 20,000 or so in the human genome.

Since humans depend on their microbiome for various essential services, including digestion, a person should really be considered a superorganism, microbiologists assert, consisting of his or her own cells and those of all the commensal bacteria. The bacterial cells also outnumber human cells by 10 to 1, meaning that if cells could vote, people would be a minority in their own body.

Segre reckons that there are at least 20 different niches for bacteria, and maybe many more, on the human skin, each with a characteristic set of favored commensals. The types of bacteria she found in the inner elbow are quite different from those that another researcher identified a few inches away, on the inner forearm. But each of the five people Segre sampled harbored much the same set of bacteria, suggesting that this set is specialized for the precise conditions of nutrients and moisture that prevail in the human elbow.

Microbiologists believe that humans and their commensal bacteria are continually adapting to one another genetically. The precision of this mutual accommodation is indicated by the presence of particular species of bacteria in different niches on the human body, as Segre has found with denizens of the elbow.

Other researchers have found that most gut bacteria belong to just 2 of the 70 known tribes of bacteria. The gut bacteria perform vital services like breaking down complex sugars in the diet and converting hydrogen, a byproduct of bacterial fermentation, to methane.

The nature of the gut tribes is heavily influenced by diet, according to a research team led by Dr. Ruth Ley and Dr. Jeffrey Gordon of the Washington University School of Medicine in St. Louis. With the help of colleagues at the San Diego and St. Louis Zoos, Ley and Gordon scanned the gut microbes in the feces of people and 59 other species of mammal, including meat eaters, plant eaters and omnivores. Each of the three groups has a distinctive set of bacteria, they report Friday in Science, with the gut flora of people grouping with other omnivores.

Despite the vast changes that people have made to their diet through cooking and agriculture, their gut bacteria "don't dramatically depart in composition from those of other omnivorous primates," Gordon said.

This new view of people as superorganisms has emerged from the cheap methods of decoding DNA that are now available. Previously it was hard to study bacteria without growing them up into large colonies. But most bacteria are difficult to culture, so microbiologists could see only a small fraction of those present. Analyzing the total DNA in a microbial community sidesteps this problem and samples the genes of all bacterial species that are present.

The goals of the human microbiome project include analyzing the normal makeup of bacterial species in each niche on the human body. "The focus in microbiology has been on pathogenic bacteria, but we are trying to identify the commensal bacteria so that we can begin to understand what proteins they make and how they contribute to our health," Segre said.

Another goal is to understand how pathogenic bacteria manage to usurp power from the tribes of beneficial commensals in the skin or gut, causing disease.

The lifetime of an individual bacterium in the human superorganism may be short, since millions are shed each day from the skin or gut. But the colonies may survive for a long time, cloning themselves briskly to replace members that are sacrificed. Just where these colonies come from and how long they last is not yet known. Dr. David Relman of Stanford University has tracked the gut flora of infants and finds their first colonists come from their mother. But after a few weeks, the babies acquired distinctive individual sets of bacteria, all except a pair of twins who had the same set. Relman said he was now trying to ascertain if the first colonists remain with an individual for many years.

Taking a broad spectrum antibiotic presumably wreaks devastation on one's companion microbiome. If the microbiome is essential to survival, it is perhaps surprising that the drugs do not make more people ill. Relman said that perhaps there were subtle long-term consequences that had not yet been identified. Much the same set of bacteria recolonize the gut after a course of antibiotics, he said, suggesting that the makeup of the colony is important and that the body has ways of reconstituting it as before.