Julie Theriot, Associate Professor of Biochemistry and of Microbiology and Immunology at Stanford, discusses the different types of microorganisms present in the human body and their functions, the distinction between disease-causing and benign or helpful microorganisms, and the interactions between human cells and both harmful and helpful microorganisms.
Dr. Pizzo opens the section by recommending Ghost Map by Steven Johnston. It's a good read.
All organisms have parasites on them, and she opens with a joke about fleas having their own parasites.
About 10% of our cells have human DNA, the rest are bacterial, fungal or protozoa. Human 10 to the 13th, bacterial cells are ten times more. Humans are more or less a thriving ecosystem. The bacterial cells are much smaller, being 1/100th to 1/1,000th the size of human cells. Naturally the highest concentration is in the lower intestine. These bacteria are our friends (remember, bacteria is simply a name). Disease causing bacteria are rare relative to the overall number of bacteria in the world.
Though we are accustomed to thinking of the world as being inhabited by large beings, the reality is that most of the world is inhabited by microscopic, unicellular beings. Many of these are eukaryotic cells (that carry their own DNA inside them).
Prokaryotic cells are typically small and morphologically simple. They do not carry their DNA in an enclosed package within the cell (eurkayotic cells do) instead they carry it in their cytoplasm along with their ribosomes and other cellular parts. They greatly outnumber the eukaryotic cells. They include bacteria and archaea. Eukaryotic cells tend to be more complex and are capable of being much larger.
All cells have similar elements, in particular ribosomes. Ribosomes are responsible for taking the information from the messenger RNA and converting it into proteins that can then carry out the activities of the cell. You can compare and contrast the ribosomes to see how organisms relate to each other.
Norm Pace, Indiana University, did a study measuring ribosomal RNA established that all of these cells are derived from a common ancestor.
Dr. Pizzo opens the section by recommending Ghost Map by Steven Johnston. It's a good read.
All organisms have parasites on them, and she opens with a joke about fleas having their own parasites.
About 10% of our cells have human DNA, the rest are bacterial, fungal or protozoa. Human 10 to the 13th, bacterial cells are ten times more. Humans are more or less a thriving ecosystem. The bacterial cells are much smaller, being 1/100th to 1/1,000th the size of human cells. Naturally the highest concentration is in the lower intestine. These bacteria are our friends (remember, bacteria is simply a name). Disease causing bacteria are rare relative to the overall number of bacteria in the world.
Though we are accustomed to thinking of the world as being inhabited by large beings, the reality is that most of the world is inhabited by microscopic, unicellular beings. Many of these are eukaryotic cells (that carry their own DNA inside them).
Prokaryotic cells are typically small and morphologically simple. They do not carry their DNA in an enclosed package within the cell (eurkayotic cells do) instead they carry it in their cytoplasm along with their ribosomes and other cellular parts. They greatly outnumber the eukaryotic cells. They include bacteria and archaea. Eukaryotic cells tend to be more complex and are capable of being much larger.
All cells have similar elements, in particular ribosomes. Ribosomes are responsible for taking the information from the messenger RNA and converting it into proteins that can then carry out the activities of the cell. You can compare and contrast the ribosomes to see how organisms relate to each other.
Norm Pace, Indiana University, did a study measuring ribosomal RNA established that all of these cells are derived from a common ancestor.
Short lines suggest more commonality. Longer lines diverge more.
Photosynthesis resulted from a captured bacterium that transformed into a chloroplast. Much of life works along these lines as different cellular organisms combine in mutually beneficial ways.
LUCA was a population of cells. Possibly there was a period of time when there were many cells in big 'ole groups that exchanged material left and right. But eventually a cell decided to keep its DNA for itself (the Darwinian threshold - beneficial mutations are kept in house). Evolution had been occurring, DNA, PCR, ribosomes, but all were shared in common. Bad bacteria and viruses (bits of DNA that may have emerged later on) are kind of the bad guys from this group; grew up interacting and taking from other cells, got selfish and decided to take without giving back. From this beginning the other cells then had to wall themselves off and team up in mutually beneficial relationships (think early immune system). And so it goes from there.
Interestingly, many of the bacteria in us remain a mystery because they can't yet be grown in a culture dish outside the body, so our ability to study them is limited.
Different types of bacteria thrive on different types of food. This is one of the reasons why changing your diet can be awkward. And some research suggests that the type of bacteria in your gut may also influence how likely you are to gain excessive weight.
Mucus is wonderful. It protects your GI, traps bacteria and keeps things running smoothly.
Babies start out without bacteria in the gut but are colonized soon thereafter. The initial acidity level is low in infants.
Photosynthesis resulted from a captured bacterium that transformed into a chloroplast. Much of life works along these lines as different cellular organisms combine in mutually beneficial ways.
LUCA was a population of cells. Possibly there was a period of time when there were many cells in big 'ole groups that exchanged material left and right. But eventually a cell decided to keep its DNA for itself (the Darwinian threshold - beneficial mutations are kept in house). Evolution had been occurring, DNA, PCR, ribosomes, but all were shared in common. Bad bacteria and viruses (bits of DNA that may have emerged later on) are kind of the bad guys from this group; grew up interacting and taking from other cells, got selfish and decided to take without giving back. From this beginning the other cells then had to wall themselves off and team up in mutually beneficial relationships (think early immune system). And so it goes from there.
Interestingly, many of the bacteria in us remain a mystery because they can't yet be grown in a culture dish outside the body, so our ability to study them is limited.
Different types of bacteria thrive on different types of food. This is one of the reasons why changing your diet can be awkward. And some research suggests that the type of bacteria in your gut may also influence how likely you are to gain excessive weight.
Mucus is wonderful. It protects your GI, traps bacteria and keeps things running smoothly.
Babies start out without bacteria in the gut but are colonized soon thereafter. The initial acidity level is low in infants.
Blood Falls
Antibiotics can really throw off your digestive processes. She notes that some studies (the wonderful antibiotic Cipro is mentioned) have shown lingering changes for months. The antibiotics basically wipe out the good and bad bacteria, which can trigger GI problems. Crohn's Disease is more about inflammation and the immune system attacking the gut than anything like this.
Germ free mice. Have a hard time digesting plant matter. Without bacteria they even struggle to take up sugar for energy. The germ free mice actually eat more but weigh less (they have difficulty absorbing their food - and as she noted earlier, bacterial colonies expand when given the type of food they like). In obese mice you have a higher amount of firmicutes relative to bacteroidetes. The same ratio type differences are seen in comparing obese and lean humans (think wasteful metabolism). Curiously the obese folks went on a diet and as they lost weight, the ratios in their gut began to resemble those of skinnier people.
Only one layer of epithelial cells separates the "outside" from the "inside" in both your gut and lungs, which fosters absorption of nutrients, O2, etc., but leaves you vulnerable to infection in these two areas. This is usually where pathogens infect healthy people.
Cholera works by altering the flow of salt and water through the GI tract. The epithelial cells work by uptaking sugar, sodium, water and other nutrients. Cholera reverses that flow, desiccating the cells. Anthrax has a similar style, only it hits the lungs and causes pulmonary edema.
Bacteria can recruit and basically reprogram other cells to do their bidding. Cholera and Listeria are explored as examples.
Most antibiotics are reasonably broad spectrum - targeted antibiotics aren't an easy thing to invest in. Docs would have to know what the patient has, would have to choose a new drug over a proven one, and would have to prescribe a more expensive drug. So there's not a lot of support for it.
Cell mediated immunity - the cell expresses antigens and the immune system comes in and wipes out the cell.
Germ free mice. Have a hard time digesting plant matter. Without bacteria they even struggle to take up sugar for energy. The germ free mice actually eat more but weigh less (they have difficulty absorbing their food - and as she noted earlier, bacterial colonies expand when given the type of food they like). In obese mice you have a higher amount of firmicutes relative to bacteroidetes. The same ratio type differences are seen in comparing obese and lean humans (think wasteful metabolism). Curiously the obese folks went on a diet and as they lost weight, the ratios in their gut began to resemble those of skinnier people.
Only one layer of epithelial cells separates the "outside" from the "inside" in both your gut and lungs, which fosters absorption of nutrients, O2, etc., but leaves you vulnerable to infection in these two areas. This is usually where pathogens infect healthy people.
Cholera works by altering the flow of salt and water through the GI tract. The epithelial cells work by uptaking sugar, sodium, water and other nutrients. Cholera reverses that flow, desiccating the cells. Anthrax has a similar style, only it hits the lungs and causes pulmonary edema.
Bacteria can recruit and basically reprogram other cells to do their bidding. Cholera and Listeria are explored as examples.
Most antibiotics are reasonably broad spectrum - targeted antibiotics aren't an easy thing to invest in. Docs would have to know what the patient has, would have to choose a new drug over a proven one, and would have to prescribe a more expensive drug. So there's not a lot of support for it.
Cell mediated immunity - the cell expresses antigens and the immune system comes in and wipes out the cell.
