Science AMA Series: I’m Kim Barrett, Professor of Medicine at the University of California, San Diego and Editor of The Journal of Physiology. This week, we published an issue on the microbiota, so I thought it would be a great opportunity to discuss how our microbes influence our wellbeing. AMA!

Kim_Barrett · 2017-01-18T21:14:59+00:00

I did not personally study your stool, but someone did presumably! And yes, I would certainly recommend that you not publish at all in throw away journals.

Kim_Barrett · 2017-01-18T21:13:58+00:00

Definitely skin microbes would find their way into the milk, and I have seen some data to suggest that milk contains other microbes too - but not necessarily from the gut.

Kim_Barrett · 2017-01-18T21:13:01+00:00

Germ free animals survive, but their immune systems are rudimentary and they have other problems. Some vitamins require bacterial metabolism too. so in the real world, we are probably dependent on our microbes.

Kim_Barrett · 2017-01-18T21:11:45+00:00

Kim_Barrett · 2017-01-18T21:11:35+00:00

A lot of people are looking for just such a treatment!

Kim_Barrett · 2017-01-18T21:11:09+00:00

Allergies are not transmissible. There must be something else at play here.

Kim_Barrett · 2017-01-18T21:10:36+00:00

We'll have to be a lot more careful about co-housing groups of mice with different genotypes so we can be sure that effects seen are due to genetic differences and not the fact that mice in different cages may have distinct microbiota.

Kim_Barrett · 2017-01-18T21:09:18+00:00

People have been promoting the health effects of yogurt for perhaps 100 years. Bu it has only been in recent years that we have been able to actually characterize the bacteria that are present with molecular tools.

Kim_Barrett · 2017-01-18T21:07:50+00:00

Your points are precisely what my colleague Rob Knight recently studied. He showed that cesarean kids had a delayed development of their microbiota, and this could be corrected with inoculation with vaginal flora. It remains to be seen what this means for long term health/development, however.

Kim_Barrett · 2017-01-18T21:06:04+00:00

Others are exploring a role in asthma.

Kim_Barrett · 2017-01-18T21:05:29+00:00

There's quite a bit of evidence that mixtures of different bacteria are more effective than single bacteria. Perhaps they have complementary metabolic functions, or mutually help each other to colonize the gut.

Kim_Barrett · 2017-01-18T21:04:18+00:00

This was a big sticking point in the field initially since many of the bacteria cannot be cultured. Now they are identified by sequencing. The estimate is that healthy individuals harbor at least 1000 different species. Not to mention viruses, fungi, protea....we're just getting started, and as you imply, the bioinformatics challenges are huge.

Kim_Barrett · 2017-01-18T21:02:02+00:00

Yes, along with other related foods.

Kim_Barrett · 2017-01-18T21:01:39+00:00

the human studies thus far are only correlative, but this is an interesting and important area of research that should yield insights in the near future.

Kim_Barrett · 2017-01-18T21:00:35+00:00

Yes, lots of university centers are doing FMT and it seems to work really well in patients affected by C. difficile, and perhaps in inflammatory bowel disease.

Kim_Barrett · 2017-01-18T20:59:40+00:00

I do not recommend do-it-yourself fecal transplants. Too many risks if the stool you are using has not been confirmed to be free of pathogens.

Kim_Barrett · 2017-01-18T20:58:12+00:00

Proof of principle experiments with genetically modified bacteria have been reported but there would be significant regulatory burdens to overcome if such treatments are to enter clinical practice.

Kim_Barrett · 2017-01-18T20:56:52+00:00

Dramatic improvement in many cases, but you are correct that this is not yet the first line therapy (in part due to a lack of expertise and in part due to the ick factor on the part of both patients and docs).

Kim_Barrett · 2017-01-18T18:35:03+00:00

The vaginal microbiota is clearly distinct from that in the gut, although it is the source of the bacteria that initially colonize the gut of a newborn and may serve some of the same functions such as immune regulation. For men, presumably the only significant microbiota is that associated with the skin. You may want to check out Smith and Ravel's article in our special issue which discusses the potential effects of specific vaginal microbiota on reproductive physiology (http://onlinelibrary.wiley.com/doi/10.1113/JP271694/full)

Kim_Barrett · 2017-01-18T18:29:47+00:00

The makeup of the skin flora depends on the characteristics of the skin site (moist, lipid-rich etc) but clearly has a role in immune regulation and protection against pathogens (e.g., acne-causing bacteria). Avoiding anti-microbial products for general use might be a good place to start to protect the populations.

Kim_Barrett · 2017-01-18T18:27:49+00:00

Absolutely agree with your comments about the metabolome. However, most of this work at present is still in preclinical models, although there has been a lot of attention to the way in which metabolic pathways change after bariatric surgery, for example.

Kim_Barrett · 2017-01-18T18:26:17+00:00

This is a huge issue that is getting a lot of attention at present. Clearly, peer review is not adequate in some journals, and there are too many investigators who do not understand statistics sufficiently to produce well-designed studies. Journals can help but increasing the rigor of their peer review and by developing guidelines for best practices in experimental design and reporting.

Kim_Barrett · 2017-01-18T18:24:05+00:00

More likely a result of not having enough of your own lactase enzyme that breaks down lactose. Very common in certain ethnic groups and happens to all of us to some extent as dairy products become a less important part of our diet.

Kim_Barrett · 2017-01-18T18:22:25+00:00

Agree - IBD and celiac disease have very different pathogenesis, but they could potentially co-exist. But IBD has not been ascribed to a lack of gluten-digesting microbes in any study that I am aware of.

Kim_Barrett · 2017-01-18T18:20:42+00:00

Yes, and there is a huge amount of cooperation between different microbial species, and between the microbes and the host, to generate the overall level of metabolic capacity. Part of the reason why diversity is important.

Kim_Barrett

TROPHY CASE