7

Many gut microbes are pathobionts or opportunistic pathogens — these organisms can be part of the normal gut flora (microbiome) of healthy individuals, but under the right (for them) circumstances (e.g.s: when introduced into the bloodstream by a cut, or due to immunosuppression) they can cause disease.1,2 As for urine, there are many fewer microbes present ...


6

Urine is contaminated with skin bacteria and possibly something excreted from your blood. A very tiny fraction of urine is microbial. Feces is basically a solid mass of undigested food, gut bacteria, and their byproducts. Many gut bacteria in particular have evolved in the conditions the human body produces so many can survive well in human tissue. about 30%...


5

The kidney is essentially a filter which extracts dissolved waste products & water from the blood. It basically allows only molecular-sized things to pass, otherwise it would continually leak blood cells. The digestive tract OTOH is basically a tube. Stuff gets mashed up at one end and ejected at the other. Even fairly large objects can pass through ...


3

I can only speak to what I am familiar with, but I would assume that the large majority of those viruses are bacteriophages. These bacteriophages, or "phages" for short, are viruses that infect bacteria. I should mention that these phages are not human pathogens though. When we go out into the field to discover novel phages, we often go to wastewater ...


3

It's not like a strain of E. coli that may cause disease in immunosuppressed individuals yet is a part of normal microbiota for other people. Well, actually, it is kind of like that. The answer is complicated, but can be boiled down to, virulent serotypes of Neisseria meningitidis infect susceptible populations. For the short answer, just read between the ...


2

I have no idea how practical it would be for your intended application, but people do estimate airborne concentrations of fungi and bacteria by sampling aerosols (i.e., filtering a volume of area to extract dust etc. that can carry the target organisms) and then using quantitative PCR with primers targeted at generic fungal or bacterial DNA sequences to ...


2

I can't think of any pathogenic organisms that are completely resistant to the immune system. Some bacteria that cause chronic diseases (e.g. tuberculosis) are relatively resistant, and a handful of viruses (e.g. spumaviruses) are relatively invisible, but the nature of pathogen transmission would mean that completely resistant organisms would spread through ...


1

A recent Nature article, entitled A new genomic blueprint of the human gut microbiota, contains the following Figure: [Fig. 3 Phylogeny of reference and uncultured human gut bacterial genomes] I don’t know much about bacteria, but, according to their entries in Wikipedia, Actinobacteria, and most Firmicutes are gram-positive and, as these appear to be ...


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