Humans as Ecosystems Old Friends Hypothesis
vaginal and nasal cavity is considered part of the body surface
Yes, as is the colon and rest of the GI tract and all areas that normally contain bacteria, exactly as I wrote:
Bacteria and other microbiota are found on all internal and external surfaces of human beings that are exposed to the environment--the skin, eyes, nose, and the entire GI tract from the mouth to the anus--not just the colon.
conclusion: the closed loop cavities such as muscles, organs, blood, etc. in the healthy body do not have bacteria present.
That's correct for healthy individuals. In infected individuals, the bacteria penetrate these areas, such as in the case of an infected wound and sinusitis infection in the normally sterile sinus cavities.
You're not claiming that anyone said that muscles, organs or blood normally contain bacteria in healthy individuals are you?
Organs and cavities that have contact or openings to the outside harbor both beneficial and harmful bacteria.
Correct, and recent science suggests that even "harmful bacteria" may play positive roles in certain limited circumstances (see Valerie Brown on this below) and some microbiota may be effectively neutral (though many of the ones currently regarded as neutral may have beneficial or harmful effects that are simply as yet unknown).
It's also not practical to kill all the bacteria everywhere on and in an adult human. It would require extraordinary bubble-boy type measures. Life-giving air, water and food all contain bacteria. So another conclusion is that while a human could live as a "bubble boy" for years and you can remove the colon from humans without killing them, you cannot remove all the bacteria from a human in a natural environment. To do so using artificial bubble-boy measures would likely produce sub-optimal results anyway, as indicated in the following sources (emphases mine):
Bacterial Bonanza: Microbes Keep Us Alive, Jeffrey Gordon, Director of the Center for Genome Sciences at Washington University in St. Louis
"humans should start thinking of themselves as ecosystems, rather than discrete individuals"Bacteria 'R Us, Valerie Brown
"pathogens and beneficial bacteria are not necessarily mutually exclusive organisms. A microbe’s effects on the human body can depend on conditions. And if you approach the human body as an ecosystem, some researchers are finding, it may be possible to tune that system and prevent many diseases — from acute infections to chronic debilitating conditions — and even to foster mental health, through bacteria."Helminthic therapy (incorrectly referred to as worm therapy): the reason for this siteJaspar Lawrence on
the Old Friends Hypothesis (OFH) (a refinement of
the Hygiene Hypothesis)--the idea that humans evolved to naturally have wider varieties and larger quantities of bacteria, worms and protozoa than what modern humans have and that this contributes to the diseases of civilization. The OFH makes the mistake of ignoring the contributing factor of diet in the development of the diseases of civilization, but I think the OFH likely explains another contributing factor and the OFH and dietary discordance are both part of the larger model of biological discordance.
Hadley C (2004)
Should auld acquaintance be forgot. EMBO Rep 5:1122-1124
"What we're talking about really is
fundamental changes in lifestyle, it's not just the trivial matters of everyday domestic hygiene. It's the fact that we no longer drink water from the stream and we no longer have worms." --Graham Rook, a professor at the Centre for Infectious Diseases and International Health, London, main developer of the OFH
The Gut and Psychology Syndrome, Natasha Campbell-McBrideThere's even a hypothesis that the mitochondria that exist within human cells and that are essential for human life evolved from bacteria:
Evolutionary Origin of Mitochondria
http://www.ruf.rice.edu/~bioslabs/studies/mitochondria/mitorigin.html
The endosymbiotic hypothesis for the origin of mitochondria (and chloroplasts) suggests that mitochondria are descended from specialized bacteria (probably purple nonsulfur bacteria) that somehow survived endocytosis by another species of prokaryote or some other cell type, and became incorporated into the cytoplasm. The ability of symbiont bacteria to conduct cellular respiration in host cells that relied on glycosis and fermentation would have provided a considerable evolutionary advantage. Similarly, host cells with symbiont bacteria capable of photosynthesis would also have an advantage. In both cases, the number of environments in which the cells could survive would have been greatly expanded.
So overall, bacteria and microbiota in general are crucially important for humans.