One of the more fascinating topics in biology/medicine today. This article offers a nice overview:
That bacteria can cause disease is no revelation. But the diseases in question are. Often, they are not acute infections of the sort 20th-century medicine has been so good at dealing with (and which have coloured doctors’ views of bacteria in ways that have made medical science slow to appreciate the richness and relevance of people’s microbial ecosystems). They are, rather, the chronic illnesses that are now, at least in the rich world, the main focus of medical attention. For, from obesity and diabetes, via heart disease, asthma and multiple sclerosis, to neurological conditions such as autism, the microbiome seems to play a crucial role.
One way to think of the microbiome is as an additional human organ, albeit a rather peculiar one. It weighs as much as many organs (about a kilogram, or a bit more than two pounds). And although it is not a distinct structure in the way that a heart or a liver is distinct, an organ does not have to have form and shape to be real. The immune system, for example, consists of cells scattered all around the body but it has the salient feature of an organ, namely that it is an organised system of cells.
The microbiome, too, is organised. Biology recognises about 100 large groups of bacteria, known as phyla, that each have a different repertoire of biochemical capabilities. Human microbiomes are dominated by just four of these phyla: the Actinobacteria, Bacteroidetes, Firmicutes and Proteobacteria. Clearly, living inside a human being is a specialised existence that is appropriate only to certain types of bug.
We just learned about this is Biology a few weeks ago. Very cool stuff. Especially when you consider that these "foreign" organisms are just as important to our own bodies as our own cells are. They play such a big role in our biology, i'm surprised i havn't heard about this earlier.
Love this kind of stuff. For as much as people are impressed by the enormity of space and the forces at work, I'm fascinated by the forces at work in the human body on a cellular level. So many things working in perfect unison to make the simplest things possible- I feel this area in particular has a lot of potential.
Aren't the mitochondria in our cells originally a foreign species with there own unique genome?
Originally Posted by AfroThunder396
That's the theory. Chloroplasts in plant cells too.
Both have their own DNA and membranes, we assume they were originally free-floating prokaryotes.
To add to AfroThunder's post, mitochondria are passed along in the mother's ovum as discrete units, which means it's separate from the 23 chromosomes you get from each parent. Once cell division commences, the mitochondria are simply passed along in every cell.