Category Archives: symbioses

The start of a slow poop movement?

Well I am not 100% sure I believe all the claims in this but it is fascinating: What Drives a Sloth’s Ritualistic Trek to Poop? | Articles | Smithsonian.  I knew nothing about sloths and their poop until reading this.  The key part of the article to me:

The scientists’ results point to linked mutualisms between the sloths, the algae, and the moths: the sloth climbs down the tree to poop and, because the ground around the tree is littered with poop from previous descents, moth larvae growing in the poop can hitch a ride on the sloth’s back. The moths find shelter and thrive in the fur ecosystem. They also bring nutrients to their new home from the poop they were born in and when they die and decompose. Those nutrients fuel algae growth in the fur, and the algae supplement sloths’ foliage diets with lipids that the scientists speculate could serve as a high-energy snack. Then, when the sloths go down to do their business again, moths hop on their back and the cycle starts over again. 

I think this could be the start of a slow poop movement …

Tweets from Nancy Moran’s talk at #UCDavis on "Two sides of symbiosis" storified

I went to a talk yesterday by Nancy Moran at UC Davis.  Nancy is one of my science heroes.  I have worked on a few projects with her and am just a big fan of her body of work on symbioses.  I have written about her work her on this blog many times before including

Anyway – I live tweeted her talk and then tried to “Storify” those tweets but Storify was not working well.  Thankfully  Surya Saha made a storify which I then edited (with his permission).


Bad Ome-like word of the week: symbiome

Well I got pointed to this paper: Transgenerational Transmission of the Glossina pallidipes Hytrosavirus Depends on the Presence of a Functional Symbiome

And as many might guess – the word “symbiome” did not sit well with me.  Alas, they don’t define it in the paper.  So I can’t really quibble with their definition.  But I did find some other stuff out there that, well, at least helps see how other people are using the word:

I can’t really tell from most of these if “symbiome” can be a useful term or not sometimes.  Certainly the iPhylo example above has potential.  But in general, the word seems awkward at best.  Now – as far as I can tell, nobody is using it in the context of “genomics” so this does not fit in with my “badomics” obsession.  But it still does not make me feel warm and fuzzy so I am going to give it a pseudo-award – the Bad Ome-like word award.

Convoluted title, cool paper in #PLoSGenetics on relative of insect mutualists causing a human infection

Saw this tweet a few minutes ago:

The title of the paper took me a reread or two to understand.  But once I got what they were trying to say I was intrigued.  And so I went to the paper:  PLOS Genetics: A Novel Human-Infection-Derived Bacterium Provides Insights into the Evolutionary Origins of Mutualistic Insect–Bacterial Symbioses.  And it is loaded with interesting tidbits.  First, the first section of the results details the history of the infection in a 71 year old male and his recovery and the isolation and characterization of a new bacterial strain.  Phylogenetic analysis revealed this was a close relative of the Sodalis endosymbionts of insects.

And then comparative genomics revealed a bit more detail about the history of this strain, it’s relatives, and some of the insect endosymbionts.  And plus, it allowed the authors to make some jazzy figures such as

And this and other comparative analyses revealed some interesting findings.  As summarize by the authors

Our results indicate that ancestral relatives of strain HS have served as progenitors for the independent descent of Sodalis-allied endosymbionts found in several insect hosts. Comparative analyses indicate that the gene inventories of the insect endosymbionts were independently derived from a common ancestral template through a combination of irreversible degenerative changes. Our results provide compelling support for the notion that mutualists evolve from pathogenic progenitors. They also elucidate the role of degenerative evolutionary processes in shaping the gene inventories of symbiotic bacteria at a very early stage in these mutualistic associations.

The paper is definitely worth a look.

Dueling microbial diversity talks at #UCDavis on May 2 #symbioses #microbiology

Here is a storification of the dueling microbial diversity talks that happened at UC Davis on Wednesday May 2.[View the story “Dueling microbial diversity talks at #UCDavis” on Storify]

Nice #openaccess review on the ecology of chemosynthetic symbioses from @chicaScientific & Guus Roeselers

Figure 1 from 10.1007/s00253-011-3819-9. Sediment cross section 
exposing the characteristic Y-shaped burrow dug by S. velum. 
Positioning itself at the triple junction of the Y, the bivalve alternates
 between actively pumping oxygenated water from the upper arms of
 the burrow through the mantle cavity and across the gills and 
accessing reduced sulfur compounds diffusing up from the anoxic 
zones below and pumped through a ventral incurrent opening in the 
mantle. Scale bar equals 2.5 cm

For those who do not know, I got my first taste of microbiology research when I was an undergrad at Harvard and I did my senior/honors research project in the lab of Colleen Cavanaugh. Colleen studied (and in fact still studies) symbioses between invertebrates and chemosynthetic bacteria. The bacteria basically allow these invertebrates to function like plants in many ways. Some of these invertebrates (like the giant tube worms in hydrothermal vents) have lost their mouths and digestive systems and basically live by bringing in high energy chemicals for their symbionts which then make sugars, vitamins, amino acids and other goodies for the host.
Anyway – I am still very interested in these symbioses and have published a few papers on the topic here and there. All that lead in is to simply point everyone out there to a nice new Open Access review paper by Guus Roeselers and Irene Newton: On the evolutionary ecology of symbioses between chemosynthetic bacteria and bivalves. When I first saw the reference in the “Applied Microbiology and Biotechnology” journal I was worried I would not have access to it, but I clicked on the link and discovered it was published using Springer’s version of Open Access. Yippee.  The article is worth a look. Roeselers, G., & Newton, I. (2012). On the evolutionary ecology of symbioses between chemosynthetic bacteria and bivalves Applied Microbiology and Biotechnology, 94 (1), 1-10 DOI: 10.1007/s00253-011-3819-9

Hydrogen as a fuel? No this is not about cars, this is about animals and their symbionts in the deep sea As many of you know, I generally avoid writing about non open access publications here.  But occasionally I make exceptions.  And I am making one today.  There is a wicked cool paper out in Nature today.  Entitled “Hydrogen is an energy source for hydrothermal vent symbioses” comes from Nicole Dubilier, Jillian Petersen and others.  It is about my favorite ecosystem(s) on the planet – hydrothermal vents.  I became interested in these vents in 1989 when I met Colleen Cavanaugh who at the time was a Junior Fellow at Harvard.  She told me about her work on bacteria that live inside tubeworms, clams and other creatures in the deep sea that are key to the lives of these animals.  The bacteria are chemosynthetic (i.e., they use the energy of chemicals to drive carbon fixation).  The animals have either no digestive systems or very degenerate ones and the bacteria function much like chloroplasts do for plants.  The bacteria basically make everything for their hosts while the hosts collect energy (chemicals in this case) and oxygen and CO2 for the microbes.

After hearing Colleen tell me about her work on these symbioses and how at the time nobody knew much about the symbionts, I joined her new lab at Harvard (she was just appointed as a junior professor) and worked in her lab in my Senior year and after graduating (and ended up publishing my first paper on symbionts of a clam Solemya velum).  I have been captivated by symbioses ever since.  So much so that many years later I worked with Colleen, Irene Netwon, Tanya Woyke, Dongying Wu and others to sequence and analyze the first genome of any of the chemosynthetic symbiotic bacteria.

Anyway – enough about me.  Prior to this new work, all of the symbioses in the deep sea had been found to involve either H2S (or related S compounds) or methane as energy sources.  What is completely fascinating about the new work is that they show here that H2 can also serve as an energy source for chemosynthetic symbioses.  From the abstract:

The discovery of deep-sea hydrothermal vents in 1977 revolutionized our understanding of the energy sources that fuel primary productivity on Earth. Hydrothermal vent ecosystems are dominated by animals that live in symbiosis with chemosynthetic bacteria. So far, only two energy sources have been shown to power chemosynthetic symbioses: reduced sulphur compounds and methane. Using metagenome sequencing, single-gene fluorescence in situ hybridization, immunohistochemistry, shipboard incubations and in situ mass spectrometry, we show here that the symbionts of the hydrothermal vent mussel Bathymodiolus from the Mid-Atlantic Ridge use hydrogen to power primary production. In addition, we show that the symbionts of Bathymodiolus mussels from Pacific vents have hupL, the key gene for hydrogen oxidation. Furthermore, the symbionts of other vent animals such as the tubeworm Riftia pachyptila and the shrimp Rimicaris exoculata also have hupL. We propose that the ability to use hydrogen as an energy source is widespread in hydrothermal vent symbioses, particularly at sites where hydrogen is abundant.

I am personally hoping that the authors post PDFs of the paper somewhere for everyone to read.  I will post a link if they do.

I note – there is also a very accessible News and Views written about this paper.  The News and Views is written by Victoria Orphan and Tori Hoehler and is entitled “Hydrogen for dinner.”  I particularly like the last paragraph:

Petersen and colleagues’ work exemplifies the technology-driven revolution that is occur- ring in the biological sciences. The continuous development of ever more powerful and spe- cific molecular tools allows taxonomic identity and gene content to be linked to metabolic potential and activity, and to be visualized in context. As these techniques converge with new instrumentation that allows the in situ characterization of physicochemical parameters — even in environments as remote and extreme as hydrothermal vents — biologists are freed from their reliance on model organisms in artificial surroundings. Now, more than ever, our understanding of biology can be placed in the correct environmental and ecological context, enabling the discovery of previously unknown activities that support life. 

Petersen JM, Zielinski FU, Pape T, Seifert R, Moraru C, Amann R, Hourdez S, Girguis PR, Wankel SD, Barbe V, Pelletier E, Fink D, Borowski C, Bach W, & Dubilier N (2011). Hydrogen is an energy source for hydrothermal vent symbioses. Nature, 476 (7359), 176-80 PMID: 21833083

Selfish DNA, symbionts and parasites – some quick links

I was at a committee meeting yesterday for a great PhD student here at UC Davis, Michael Hornsby and the topic of selfish DNA came up.  After his meeting we sat down and looked for some new papers and review papers on the topic.  I just thought it might be of value to share some of these here:

We also discussed briefly the evolution of mutualists and parasites and here are a few papers that came up:

If anyone knows of any other good recent papers or blog posts about selfish DNA or mutualists vs. parasites please post them here.  Thanks

Why endosymbionts rule – see #PLoS Genetics paper on origin of an alternative genetic code

Way way way cool new paper in PLoS Genetics from Nancy Moran’s lab. The paper (Origin of an Alternative Genetic Code in the Extremely Small and GC–Rich Genome of a Bacterial Symbiont). The paper discusses the use of genome sequencing and proteomics (as well as a variety of bioinformatic analyses) of a bacterial symbiont (Hodgkinia) of cicadas.

And for those not in the know, this is an Open Access paper using a broad Creative Commons license (since it is in a PLoS journal) so anyone can reuse material from it as long as the source is cited. This image to the left is from their paper so I am citing the source here: McCutcheon JP, McDonald BR, Moran NA (2009) Origin of an Alternative Genetic Code in the Extremely Small and GC–Rich Genome of a Bacterial Symbiont. PLoS Genet 5(7): e1000565. doi:10.1371/journal.pgen.1000565

The study has some interesting things including:

  • the genome of the symbiont has a much higher GC content than other small bacterial genomes for which the sequence is available
  • the symbiont is member of the alpha proteobacterial group, which is somewhat unusual since most other insect endosymbionts that have been studied are from the gamma proteobacterial group and/or the bacteroidetes clade
  • the UGA codon in this species is used to encode tryptophan and not as a stop codon

Taken together these things are very interesting since other species that have been found to have the UGA codon reassigned to code for an amino acid all have low genomic GC content. This correlation led people to conclude that the codon reassignment was directly related to the low GC content. However, the authors suggest here that the UGA reassignment in many species might be due to the genome reduction (loss of genes) seen in endosymbionts and not to low GC content.

Anyway the paper is worth a read …

McCutcheon, J., McDonald, B., & Moran, N. (2009). Origin of an Alternative Genetic Code in the Extremely Small and GC–Rich Genome of a Bacterial Symbiont PLoS Genetics, 5 (7) DOI: 10.1371/journal.pgen.1000565

Aphid-bacterial symbiosis in more detail, and in the New York Times

Nice little bit in the New York Times tomorrow about aphids and their symbionts. Henry Fountain writes (Observatory – How Tiny Insects, With a Little Help, Survive on Plant Sap – about a new article by Angela Douglas, one of the true pioneers of endosymbiont research. In her study she dissects in fine scale detail which essential amino acids are missing from the aphid sap only diet and which ones are made by the symbionts. Interestingly, the research apparently shows that the aphids may have figured out how to make methionine by themselves. I say apparently since I have been unable to track down the paper which I assume is coming out soon.

I should note, in one of the symbioses like this that I have studied with Nancy Moran we found that there were two symbionts contributing to the nutrition of the host. We found that one of the symbionts was likely making amino acids for the host (an insect called the glassy winged sharpshooter which eats only xylem sap) and the other symbiont was likley making vitamins. Nancy showed later with John McCutcheon that the symbiont that was making vitamins also was predicted to be making methionine for the host. So it seems possible there might be a missing symbiont in the aphid study? Although it would be cool if the aphid has figured out how to make an amino acid most animals are not able to make.

Hat tip to Max Lambert for pointing this out.