• Bacteria

Scanning electron micrograph of E. coli, a gram negative rod that is a normal inhabitant of the human colon.

Bacteria get their own section in this website for their important roles in maintaining human health and in causing human disease. The information given here is slated to bolster understanding of those roles.

Here's the background check on exactly what bacteria are, and what their biology has to do with ours.

• Individual bacteria are too small to be seen without a microscope.
  • they range in size from
  • each one is one single cell.
• The make-up of any bacterial cell is characteristically different than the make up of any one of ours.
  • Bacterial cells are prokaryotes, our cells are eukaryotes. The differences are not just in name, but in chemistry and in structure. That has practical importance because medicine uses those differences as a weapon against bacterial infection.
  • Several antibiotics kill only prokaryotic cells.
• Despite being tiny organisms, and having a different cell architecture, bacteria have all the qualities that enable any kind of being - including us- to be called "alive".
• • They carry on the biochemical reactions of life (metabolism), and can reproduce to produce progeny that are like themselves, all on their own.
  • That makes them different from the even tinier particles called viruses, which are not considered to be - all by themselves- alive at all.
    • Viruses have to get inside a living cell and hijack its biochemical machinery to do such things as reproduce. That fact has everything to do with how viral infections affect us.
    • Even though, in theory, bacteria are single celled living things, in the smudged actuality of life - there are groups of bacteria that are stripped down models, able to reproduce only if they parasitize cells. These obligate cellular parasites turn out to be particularly important in causing some diseases.

There are other microscopic organisms besides bacteria that influence human health. Fungi and protozoa can also exist as single- celled organisms, and as mutli-celled organisms that are too small to be seen without a microscope, as well.

• Bacteria were the first microscopic living things to be found to cause disease. In that sense, they were the first germs ever discovered. Physicians and biologists call microorganisms that can cause illness by the name of "pathogens". However, the vast majority of bacteria are not pathogens.
• Some are called probiotics, because they are actually good for health.
• Others have nothing much to do with human life at all.

In the last century, with the discovery of DNA, RNA and molecular biology, a new classification system camde about - one based on the similarity of the sequences in

That may seem creepy, but it's actually a great thing. Just as the forest animals trim the trees and bury their seeds, and generally advance the health of the forest - so our guys, the little guys that make a layer of microbes on our body surfaces and in our gut, belong there and, generally, add to the health of their habitat - us.

I think that we get grossed out by the thought because somehow we translate the word 'microorganism' into 'germ' or 'parasite'.

• The truth is that just as we live in a much larger world and are a natural part of that landscape, so we provide a world and a landscape for these itty bitty beings.
• The truth is that part of living in the material world involves living in the bacterial world, and more over - providing a berth for bacteria in the human body.

Not everywhere in the human body - but on the external surface and the borderlands between what's outside and what's inside. Those borders are a span of where the external dips in to become internal. The lips "dip" into the mouth and down the throat, and all the way into the stomach that surface supports the life of other beings - tiny beings, naturally. At the other end, the genitals and the anus are covered with the soft skinlike surface that, like the lips, is mucus membrane rather than true skin. The skin of the vulva shades into the mucus membrane over the clitoris and labia and that mucus membrane dips into the vagina- and it is not until the uterus that the body's defenses put up the "keep out- trespassers will be shot dead" sign.

In men, and women, the urethra- the opening of the urinary tract to the outside world, puts up it's barrier right at the gate, the urinary sphincter that gives us control over just when we want to release urine.

When it comes to bacteria, the anus is loaded, and as it dips in -big-time- all the way up through several feet (meter) of large bowel, the bacterial population actually increases. It changes, too- because the strains that live in the bowel are not the same as those on the skin of the opening between the buttocks.

For those of us who have studied the natural world of forests and plains and swamps and such, we can imagine these different areas of the body as being different sorts of natural habitats.

The only way to keep bacteria away from the human body would be to sterilely transfer a baby from inside the womb into a sterile bubble. And, should that be done, the baby would suffer from his isolation from bacteria that are partners with our digestive systems.

Our digestive systems have evolved to work in concert with a heavy load of resident bacteria in our large intestines.

Our skin and throats depend on having a coating of the right sorts of bacteria in the right numbers to be healthy. I'm not sure if they would be jus fine in the "bubble world", maybe they would - because that dependence seems to center on keeping other bacteria in line.

• American Society For Microbiology

Bacteria consist of only a single cell, but don't let their small size and seeming simplicity fool you. [for complete article - click!]

http://www.microbeworld.org/microbes/bacteria/

• University of California Museum of Paleontology

http://www.ucmp.berkeley.edu/bacteria/bacteria.html