If raised in different environments they will have different gut microbiota, however there will be a certain predesposition towards allowance/or inhibition of particular types of bacteria. One good reason for the different microbiomes comes from the fact that the number of genes expressed on the bacterial end is much larger than whatever genetic predisposition the human genome may be expressing. Also, the gut microbiome composition is "reversible" or rather could be shifted towards different composition with change in the diet/environment.

Your answer is Epigenetic. In identical twins the structure of genomes is very same but the differences are in Epigenome which is a very high influence of the environment (including Bacteria). In fact, Epigenome tell every gene to when and how much to express. Here is the best reference and an example for you. Good luck

http://www.pbs.org/wgbh/nova/body/epigenetics.html

Thank you Mostafa, so epigenetics is how the environment and genes interact, but i was wondering if our genes specifically affect which bacteria colonies are able to establish in the gut. So if our genes make a particular chemical mileu/ PH levels etc in the gut which attracts certain bacteria to establish.

So part of epigenetics is our microbiome interacting with our genes, but what about our genes controlling for the composition of our microbiome- from the ranges in the external environment.

Is it possible certain genes could make our G.I tract more susceptible to pathological bacteria establishing? Increasing our risk of other infections etc

Yeah., one of the newest and most attractive fields of interdisciplinary sciences are Human-Pathogen genome interaction. The Genomics analysis which is followed by strong stimulation, Bioinformatics and Systems Biology are tools for answering these complicate situations and Pathways such as physiological hosting to any particular bacteria. I love working in this such area and because of this I am working on SiRNA delivery using Nanotechnology for my PhD thesis. You can join me on Linkedin network and I will be honored.

Hi Mostafa, that is definitely an awesome area of research to be in. For so many diseases we say it is genes+environment+epigenetics- the environment influencing gene expression. but what about our genes creating the environment, so a gene associated with multiple sclerosis for example might in fact be influencing gut conditions which allow a pathological species of bacteria to establish which produces epitopes that can trigger myelin autoimmunity. So the gene has nothing to do with the brain and everything to do with modifying the microbiome.

If raised in different environments they will have different gut microbiota, however there will be a certain predesposition towards allowance/or inhibition of particular types of bacteria. One good reason for the different microbiomes comes from the fact that the number of genes expressed on the bacterial end is much larger than whatever genetic predisposition the human genome may be expressing. Also, the gut microbiome composition is "reversible" or rather could be shifted towards different composition with change in the diet/environment.

Agree and as I said, the physiology of getting infected by a particular bacteria created by very complicate genes pathway which is made by very complicate gene network, gene interaction and gene-environment interaction. These complicate network can be simulated with Systems Biology. In other words, every infection we got, made by a very complicated network of genes and effect of environment. Also, as you might know, there are many traits including MS which is not made by only one gene, may be hundred genes making condition to get MS and also an environment (and life style of course). As conclusion, I think we, biologists, must have not reductive view of biological phenomenon like infections or disease. Systems Biology has a better aspect and better solutions and every single gene in our cells are working together in this awesome complicate and unique creature, "WE". :)

Hi Juliet Preston, no doubt gene play role in the host-microbe interaction but change in environment also define the expression and regulation of our genes and thus the host-pathogen interaction. Environment influence this mechanism by two ways i.e. either directly affecting the expression and regulation and secondly by influencing the epigenetics.

Hi,

here are links to papers that indirectly show the impact of environment and genetic background on the composition of the intestinal flora.

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2958200/

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC98167/

Hi, if the truth is like your said. How about the genes' role in the complex network combining by genetic- environment- epigenetics? Which direction is the future medical research work target?

This is really an exciting field and will probably be the area of interest for the next couple of decades. Inflammatory Bowel Diseases are exciting diseases to study for this question as we believe the genome-microbiome interaction to play the key role. It is however interesting to see that monozygotic twins raised in the same environment will not show 100% concordance. In other words there must be more to it then genes, hygiene, diet and general environment.

Exposure to very specific environmental influences will determine whether ill-health or health occurs. So far we have discovered little to explain these differences.

I think IBD is a very interesting area of study because it is going to be the first of many autoimmune diseases with a proven connection to the gut. If IBD is largely a result of the genome-microbiome interaction, which then affects the G.I tract the research is already focused in the right area. It is a bigger leap to connect for example, the joint inflammation in rheumatoid arthritis with the specifics of the patient's microbiome, but i think that will be the next step.

A recent letter in Nature adds nicely to this discussion

http://www.nature.com.wwwproxy0.library.unsw.edu.au/nature/journal/v491/n7422/full/nature11582.html

The authors found significant overlap of host (not microbe) genetic associations between Crohn's and UC in IBD but also with other diseases such as psoriasis. Interestingly they also found that patients with IBD had susceptibility loci that overlapped with mycobacterial infection - a long, contentious and difficult area of research. Now all we need to do is combine host and microbial associations, simple!

"Human Genes Influence Gut Microbial Composition, Study Suggests"

Press release out today, linking a specific gene to the development of gut bacteria

http://www.sciencedaily.com/releases/2013/01/130107082604.htm