The human microbiome (or human microbiota) is the aggregate of microorganisms that reside on the surface and in deep layers of skin, in the saliva and oral mucosa, in the conjunctiva, and in the gastrointestinal tracts. They include bacteria, fungi, and archaea. Some of these organisms perform tasks that are useful for the human host. However, the majority have no known beneficial or harmful effect. Those that are expected to be present, and that under normal circumstances do not cause disease, but instead participate in maintaining health, are deemed members of the normal flora. Though widely known as "microflora", this is, in technical terms, a misnomer, since the word root "flora" pertains to plants, and biota refers to the total collection of organisms in a particular ecosystem. Recently, the more appropriate term "microbiota" is applied, though its use has not eclipsed the entrenched use and recognition of "flora" with regard to bacteria and other microorganisms. Both terms are being used in different literature. Studies in 2009 questioned whether the decline in biota (including microfauna) as a result of human intervention might impede human health^[1]

Bacteria[link]

Populations of microbes (such as bacteria and yeasts) inhabit the skin and mucosa. Their role forms part of normal, healthy human physiology, however if microbe numbers grow beyond their typical ranges (often due to a compromised immune system) or if microbes populate atypical areas of the body (such as through poor hygiene or injury), disease can result.

It is estimated that 500 to 1000 species of bacteria live in the human gut^[2] and a roughly similar number on the skin.^[3][4] Bacterial cells are much smaller than human cells, and there are at least ten times as many bacteria as human cells in the body (approximately 10¹⁴ versus 10¹³).^[5][6] Though members of the flora are found on all surfaces exposed to the environment (on the skin and eyes, in the mouth, nose, small intestine), the vast majority of bacteria live in the large intestine.

Many of the bacteria in the digestive tract, collectively referred to as the gut flora, are able to break down certain nutrients such as carbohydrates that humans otherwise could not digest. The majority of these commensal bacteria are anaerobes, meaning they survive in an environment with no oxygen. Normal flora bacteria can act as opportunistic pathogens at times of lowered immunity.^[7]

Escherichia coli (a.k.a. E. coli) is a bacterium that lives in the colon; it is an extensively studied model organism and probably the best-understood bacterium of all.^[8] Certain mutated strains of these gut bacteria do cause disease; an example is E. coli O157:H7.

A number of types of bacteria, such as Actinomyces viscosus and A. naeslundii, live in the mouth, where they are part of a sticky substance called plaque. If this is not removed by brushing, it hardens into calculus (also called tartar). The same bacteria also secrete acids that dissolve tooth enamel, causing tooth decay.

The vaginal microflora consist mostly of various lactobacillus species. It was long thought that the most common of these species was Lactobacillus acidophilus, but it has later been shown that the most common one is L. iners followed by L. crispatus. Other lactobacilli found in the vagina are L. jensenii, L. delbruekii and L. gasseri. Disturbance of the vaginal flora can lead to bacterial vaginosis.

Archaea[link]

Archaea are present in the human gut, but, in contrast to the enormous variety of bacteria in this organ, the numbers of archaeal species are much more limited.^[9] The dominant group are the methanogens, particularly Methanobrevibacter smithii and Methanosphaera stadtmanae.^[10] However, colonization by methanogens is variable, and only about 50% of humans have easily-detectable populations of these organisms.^[11]

As of 2007, no clear examples of archaeal pathogens are known,^[12][13] although a relationship has been proposed between the presence of some methanogens and human periodontal disease.^[14]

Fungal flora[link]

Fungi, in particular yeasts, are present in the human gut. The best-studied of these are Candida species. This is because of their ability to become pathogenic in immunocompromised hosts.^[15] Yeasts are also present on the skin, particularly Malassezia species, where they consume oils secreted from the sebaceous glands.^[16][17]

Anatomical areas[link]

Skin flora[link]

A study of 20 skin sites on each of 10 healthy humans found 205 identified genera in nineteen bacterial phyla, with most sequences assigned to four phyla: Actinobacteria (51.8%), Firmicutes (24.4%), Proteobacteria (16.5%), and Bacteroidetes (6.3%).^[18]

Conjunctival flora[link]

These are sparse in occurrence, but Gram-positive cocci and Gram-negative rods are present.^[19]

A small number of bacteria are normally present in the conjunctiva. Staphylococcus epidermidis and certain coryneforms such as Propionibacterium acnes are dominant. Staphylococcus aureus, streptococci, Haemophilus sp. and Neisseria sp. sometimes occur. The lachrymal glands continuously secrete, keeping the conjunctiva moist, while intermittent blinking lubricates the conjunctiva and washes away foreign material. Tears contain bactericides such as lysozyme, so that microorganisms have difficulty in surviving the lysozyme and settling on the epithelial surfaces.

Some pathogens able to infect the conjunctiva, such as Neisseria gonorrhoeae and Chlamydia trachomatis are thought to have special processes allowing them to attach to the conjunctival epithelium. Newborn infants are particularly prone to bacterial attachment. Chlamydia and Neisseria may be present in an infected mother and show up on the cervical and vaginal epithelium - in such cases the newborn's eyes may be treated with silver nitrate or antibiotics.

Gut flora[link]

The gut flora is the human flora of microorganisms that normally live in the digestive tract and can perform a number of useful functions for their hosts. The average human body, consisting of about 10¹³ (10,000,000,000,000 or about ten trillion) cells, has about ten times that number of microorganisms in the gut.^{[2][20][21][22]} The metabolic activity performed by these bacteria is equal to that of a virtual organ, leading to gut bacteria being termed a "forgotten" organ.^[23]

Bacteria make up most of the flora in the colon^[24] and 60% of the dry mass of feces.^[21] This fact makes feces an ideal source to test for gut flora for any tests and experiments by extracting the nucleic acid from fecal specimens, and bacterial 16S rRNA gene sequences are generated with bacterial primers. This form of testing is also often preferable to more invasive techniques, such as biopsies. Somewhere between 300^[21] and 1000 different species live in the gut,^[2] with most estimates at about 500.^[22][25] However, it is probable that 99% of the bacteria come from about 30 or 40 species.^[26] Fungi and protozoa also make up a part of the gut flora, but little is known about their activities.

Research suggests that the relationship between gut flora^[27] and humans is not merely commensal (a non-harmful coexistence), but rather is a mutualistic, symbiotic relationship.^[2] Though people can survive with no gut flora,^[22] the microorganisms perform a host of useful functions, such as fermenting unused energy substrates, training the immune system, preventing growth of harmful species,^[21] regulating the development of the gut, producing vitamins for the host (such as biotin and vitamin K), and producing hormones to direct the host to store fats. However, in certain conditions, some species are thought to be capable of causing disease by causing infection or increasing cancer risk for the host.^[21][24]

Some bacteria found in the large intestine of humans:

^[28]

Vaginal flora[link]

Oral cavity[link]

See also[link]

• Microorganism
• Human microbiome project
• Drug resistance

References[link]

Stanley Falkow (2009).

Stanley Falkow, PhD, (born 1934 in Albany, New York) is microbiologist and a professor of microbiology and immunology at Stanford University School of Medicine.^[1] He is sometimes referred to as the father of molecular microbial pathogenesis, which is the study of how infectious microbes and host cells interact to cause disease at the molecular level.^[2] He formulated molecular Koch's postulates, which have guided the study of the microbial determinants of infectious diseases since the late 1980s.^[3] It was while she was at Walter Reed visiting his mentor Lou Baron, that Falkow met Esther Lederberg, one of the leading researchers elucidating the relationship between plasmids and antibiotic resistance. (He would later become her Department Chairman at Stanford in 1981.)^[4][5]

Education and early career[link]

Falkow received his B.S. degree from the University of Maine, graduating cum laude, and went on to earn his Ph.D. from Brown University. Following the completion of his graduate studies, Dr. Falkow went on to become a staff member at the Walter Reed Army Institute of Research (WRAIR) in the Department of Bacterial Immunology where he was eventually named the assistant chief of the department.^[1] Dr. Falkow's early work in the 1960s focused on the genetic mechanisms that enable populations of bacteria to become resistant to antibiotics. He demonstrated that organisms, such as shigella, can possess gene fragments called plasmids that exist apart from the bacterial chromosome and that they carry specialized information for survival. Under selective pressure from antibiotics, one species of bacteria can pass its plasmids to another unidirectionally rather than by mating, thereby preserving its own specialized survival genes.

In 1966, he joined Georgetown University School of Medicine as a professor of microbiology. He later moved to Seattle to become a member of the faculty of the Department of Microbiology and Immunology at the University of Washington School of Medicine. Here he described how meningitis and gonorrhea organisms acquire plasmids to become resistant to penicillin and other antibiotics.

In the 1970s, Falkow shifted his focus to the infection process. During this period, he showed that a life-threatening diarrhea prevalent in many developing countries is caused by a sub-type of E. coli. He also co-authored (with Royston C. Clowes, Stanley N. Cohen, Roy Curtiss III, Naomi Datta and Richard Novick) a proposal for uniform nomenclature for bacterial plasmids.^[6]

In 1981, he was named chairman of the Department of Medical Microbiology at Stanford University School of Medicine, a position he held until 1985. While at Stanford, Falkow encouraged Esther Lederberg to continue directing the Stanford Plasmid Reference Center, an internationally-used registry for plasmids, transposons and insertion sequences.^[7])

Contributions and honors[link]

Among his contributions, Dr. Falkow's adopted the perspective of viewing infection as a process that is ultimately mediated by the host. He discovered that infectious microbes employ genes that are activated only inside host cells. His work carries clinical applications, such as a new vaccine for whooping cough, as well as advancing knowledge in discovery of how cells are penetrated by bacteria.

Dr. Falkow has published numerous articles, and has served on the editorial boards of several professional publications. In addition, he has received numerous awards for his achievements in science. Some of these include the Bristol-Myers Squibb Award for Distinguished Achievement in Infectious Disease Research,^[8] the Altemeier Medal from the Surgical Infectious Diseases Society of America, the Howard Taylor Ricketts Award Lecture at the University of Chicago, and the Paul Ehrlich and Ludwig Darmstaedter Prize. In 2003, he received the Abbott Lifetime Achievement Award from the American Society for Microbiology and the Selman A. Waksman Award in Microbiology from the National Academy of Sciences.^[9] He received the Robert Koch Award in 2000.^[10]

Dr. Falkow was elected President of the American Society for Microbiology and served from July 1997 through June 1998. He was elected to the Institute of Medicine in 1997 and received the Maxwell Finland Award from the National Foundation of Infectious Diseases in 1999. He also received in 1999 an Honorary Doctor of Science, University of Guelph, Guelph, Ontario and the University of Maine Alumni Career Award. He has received honorary doctorates in Europe and the U.S.

Dr. Falkow is an elected member of the Institute of Medicine, the National Academy of Sciences, and the National Academy of Arts and Sciences. He is also an elected Fellow of the American Association for the Advancement of Science. He was also elected into the UK's Royal Society as a Foreign Member. Dr. Falkow was also nominated twice for a Nobel prize in the category "Medicine".

In September 2008, Dr. Falkow was one of five scientists awarded the prestigious Lasker Award for medical research.^[11]

References[link]

External links[link]

• Who Speaks for the Microbes? - article by Dr. Falkow
• "Host-Pathogen Interaction and Human Disease" online talk by Stanley Falkow

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Sierra Noble
Sierra Noble performing as opening act for Bon Jovi in Winnipeg, MB on his 2010 "Circle" Tour
Background information
Birth name	Sierra Dawn Sky Noble
Born	(1990-02-20) February 20, 1990 (age 22) Ottawa, Ontario, Canada
Genres	Pop, folk, country, roots rock, fiddle, celtic
Occupations	Singer-Songwriter, musician
Instruments	Vocals, fiddle, violin, guitar
Years active	2003–present
Labels	Independent
Associated acts	Norah Jones, Sheryl Crowe, Colbie Caillait, Alison Krauss, Ashley MacIsaac
Website	www.sierranoble.com

Sierra Dawn Sky Noble (born February 20, 1990) is a Canadian singer-songwriter, and fiddle player.

Biography[link]

This section may require cleanup to meet Wikipedia's quality standards. No cleanup reason has been specified. Please help improve this section if you can; the talk page may contain suggestions. (February 2011)

Born in Ottawa, Ontario, Noble is the third and youngest daughter of Sherry Noble (born in Kingston, Ontario) and David Noble (born in Muscatine, Iowa). She moved to Winnipeg, Manitoba in 1990.

Sierra attended École Laura Secord School from pre-school to the grade 4 when she transferred to Wolseley School for grades 5 and 6. She attended and graduated from Gordon Bell High School with the exception of grades 10 and 11 when she attended The University of Winnipeg Collegiate on a full scholarship from the University of Winnipeg president, Lloyd Axworthy.

Sierra Noble began by busking at The Forks in Winnipeg.^[1] At the age of 12, Sierra became the youth ambassador for the Manitoba Campaign to Ban Landmines. In this capacity she began making presentations about the global landmine issue in various schools, universities, and colleges. In 2004 she was selected to be one of two representatives of Canada at the Ban Landmines International Children's Conference.

In 2005, she released an instrumental album of traditional Old Time fiddle music entitled "Spirit of The Strings", produced by Randy Hiebert (guitar player of The Bellamy Brothers), distributed by Arbor Records/EMI Canada.

In December 2008, Sierra released her debut vocal release entitled "Possibilities" on MapleMusic Recordings, produced by Toronto based record producer, Bill Bell. The first single release from the album, "Possibility" (co-written by Noble, Chris Burke-Gaffney, and Keith Macpherson) was on rotation on pop radio and country radio in Canada, with the music video for the song reaching No. 1 on MuchMore and appeared in the Top 20 in CMT (Canada)'s Cross Canada Countdown.

She has received various awards for her humanitarian and volunteer services including the Inaugural Queen’s Golden Jubilee Medal,^[2] the Manitoba Premier’s Volunteer Service Award,^[3] the Manitoba Teacher’s Society Young Humanitarian Award,^[4] and Manitoba Hydro’s Spirit of the Earth Youth Award.

The citation for the Manitoba Teacher’s Society Young Humanitarian read: "Sierra Noble is a Grade 5 student at Wolseley School who has taken it upon herself to help children who have been victims of war. A visit to a War Child exhibit last September inspired her to promote awareness of the landmine issue. She has spoken at a number of schools, collected signatures for a petition to the U.S. president and was heavily involved in Landmines Awareness Week. Sierra works directly with war-affected refugee children at a downtown center called NEEDS. Currently, she is trying to help a Somalian boy get the rest of his family to Canada from Nairobi, Kenya".^[5]

In 2011, she won the 52nd edition of the Viña del Mar International Song Festival with the song Try anything.^[6]

References[link]

Constructs such as ibid., loc. cit. and idem are discouraged by Wikipedia's style guide for footnotes, as they are easily broken. Please improve this article by replacing them with named references (quick guide), or an abbreviated title. (February 2012)

External links[link]

• Official website