The Science of The Superorganism: Host-Microbiota Specificity, Again

What determines the constituents and abundance of microbes in a host? 

A critical question emerging in the science of the Superorganism (our genes + microbial symbionts) is how exactly does the microbial symbiont community inside us assemble? Is it random? Do we just acquire the bacteria that are around us when we're born? Does our diet affect which bacteria thrive in our guts? Do our genes interact with the admixture of microbes in the environment to select for specific ones that confer beneficial traits?

Numerous studies show the influence of diet on the assemblage of the microbial community. But emerging studies in the past year, which have received less attention, indicate the host selects for specific species of bacteria as well. Here are three highlight stories:

1. Hawlena et al (2012) show that in fleas and ticks, the composition of the microbial symbiont community is not determined by their vertebrate host (rodents) or environment, but by their arthropod host. Specifically, ticks have different communities of microbes than fleas, and species of ticks share more similar microbial communities than species of fleas. Other factors such as rodent host did not matter as much.

2. Salem et al (2012) show in firebugs that the "fitness of symbiont deprived bugs could be completely restored by re-infection with the original microbiota, while reciprocal cross-infections of microbial communities across both pyrrhocorid species only partically rescued fitness, demonstrating a high degree of host-symbiont specificity" In particular, survivorship decreases and nymphal development time to adulthood increases in aposymbiotic and cross-infected species, but not control or re-inoculated species. Even mating frequency is reduced. This study has a really beautiful set of functional data.

3. Engel and Moran (2013) describe a specific and stable microbial community of honey bees, suggesting long-term coevolution between bee-specific bacteria and bees.

If anyone has any important studies to highlight on this topic, please let me know so I can post them.

Note: we also found species-specific microbiotas that changed in constituents and abundance in parallel with the speciation events of their Nasonia wasp hosts. Related blog posts on this work:

• The story behind Speciation by Symbiosis (April 26, 2012)
• Is the microbiome part of the organism or the environment? (May 11, 2012)
• Is the microbiota species specific? (June 23, 2012)
• ASM's Small Things Considered Spotlights Our Article (August 16, 2012)

Neil Degrasse Tyson | Video from Vanderbilt Lecture

Scientists and educators do not frequently achieve celebrity status. But shouldn't they? Shouldn't we live in a society where we have more science rock stars like Neil Tyson or the late Carl Sagan. Part of the decline of scientific literacy in America is due to the fact that scientists are not made more visible to the public, that politics trumps facts and smart policy, and that scientists are not valued equally to sports stars or media celebrities.

The media needs to buy into this concept so that science advances as fast as fashion and special effects in our culture. 

Last night, Neil Degrasse Tyson visited Vanderbilt. His visit inspired these brief remarks shared above. I recorded a few snippets of his opening remarks and views on science education. 

Dr. Neil Degrasse Tyson, an American astrophysicist and science communicator, discusses his arrival to Nashville, his talk, twitter, and his books in a very humorous way.

Tyson discusses the difficulties in advancing science education in America, the consequences it has on society, one way in which the fall of American science education can be reversed, and his responsibilities to educating the public, not congress.

Tyson discusses the decreasing trend line of American scientific literacy, the forces that want to change the science curriculum, and the national imperative in science literacy that his new show, COSMOS, will bring to Fox watchers.