Bacteria do it better

The Economist hath written an interesting article about a recent discovery from a lab here in OSU. The Giovanonni lab studies marine bacteria. Cool enough right? Well, it gets even cooler - with PARASITES!!!

The main bacterium they study, Pelagibacter ubique (pelagi = ocean, bacter = bacteria, ubique = everywhere (ubiquitous), is the most popular member of a larger group of bacteria called SAR11. I can give you all the statistics or you can believe that it's given scientific name is true and that there are more of them than anything else in the ocean. Anyways, a funny thing some people noticed since this bacterial group was described, was that there didn't seem to be any bacteriophages (bacterio = bacteria, phage = to consume) associated with it...

From BIOS Oceanic Microbial Observatory

You may think, Well they are quite small for bacteria so maybe they just avoid encountering phages or Maybe being incredibly minute makes P. ubique hard to infect? But no no no, there are so many of them out there and there are others of similar size with plenty of phages that eat away at them...

Well, rest easy folks, they found them! Now we know it's not that SAR11 has magic anti-infection powers. It's just that no one has found them until now. These researchers did an ingenious study, the methods of which are concisely explained in this Economist piece. They used P. ubique and found it does indeed have phages - and since their are lots of P. ubique (and their SAR11 cousins) out there, there are lots of their phages too. How might this work?

Remember the mid-14th century? Under plague conditions, people whose immune systems could not handle infection died in the masses, taking their genes with them. Those with the fortunate cocktail of immune genes would survive the outbreak, have babies, and continue the human race. A very dramatic case of natural selection. Why am I talking about the Black Death? Why, to bring up The Red Queen Hypothesis. This evolutionary theory (RIP Leigh Van Valen) posits that "it takes all the running you can do, to keep in the same place." And so, immunity traits must keep changing and evolving in order for its host to stay one step ahead of parasites and pathogens. Humans recombine genes during sex and make a kid. Way to go for the kid but the parents are still stuck with the same genes they were born with for the rest of their life -> bummer! Bacteria don't play that. They can swap DNA with each other (conjugation) or just absorb it from the environment around them (transformation)! What a wild and crazy world, huh? As you would imagine, this means a community of bacteria can evolve to adapt rapidly to stressful conditions. And that is exactly what this paper suggests. They suggest that rapid* coevolution in the SAR11 group in response to phage predation has helped lead them to successful dominance of the ocean!

It will be very interesting to see what new research comes of this discovery. Being one of the most abundant things out there in the marine landscape, SAR11 plays a huge role in the microbial food web and in regulating geochemical cycles.



* the Nature article also mentioned studies in which they found recombination rates in the SAR11 group were also freakishly high!

Zhao Y et al. Abundant SAR11 viruses in the ocean. 13 Feb 2013. Nature <http://www.nature.com/nature/journal/vaop/ncurrent/full/nature11921.html>

Leaf Miners

If anyone can tell me what critter made these I would appreciate it! The trail is light pink with a shimmer to it :)

I found this suspicious trail on a hike this past weekend. It looks like someone took one of those glittery gel markers and drew all over a leaf! My botanically-inclined companion informed me this is the work of a leaf miner. The term loosely refers to the larvae of any insect that lives within the leaf and eats the cellulose material. That way, the little critters are somewhat protected from predators and any chemical plant defenses that may exist on the outer layers. Pretty sneaky of them...

The Wikipedia page cited a 2009 BBC article mentioning the discovery of a plant from Ecuador that has suspicious leaf miner markings... but not caused by an insect at all! One of the first things we learn in biology class is that chlorophyll allows plants to make energy from the sun and gives them their green color, right? So, if a plant has splotches of white on the leaves, that just decreases the area on which photosynthesis can occur...non bueno right? Not so! These researchers from Germany found those splotches might be doing good in another sense...

Traipsing around the Ecuadorian forest they noticed a plant that sometimes had fully green leaves and sometimes had leaves with white splotches:

"A leaf damaged by mining moths (left) compared to one faking it (right)."

They also noticed that the fully green leaves seemed to be infected by leaf miners more often than the splotchy one. A hypothesis was born. They hypothesized that plants 'faking' leaf miner infestations would have less damage from actual leaf miners (in this case it was a type of moth) because insects prefer to lay their larvae in uninfected leaves (duh, more food and no damage). They did some experiments with green leaves, splotchy leaves, and hand-painted splotchy leaves (they used white-out!) and found that moths indeed preferred to infect fully green leaves. (By the way, they did tests to see if the chemicals in the white-out affected moth behavior and it didn't.)

This is the official scientific paper but if you just want a cursory look the BBC article does a good job casually pinning down the main points. So, that's how a quick internet search on the pretty pink  leaf trail ended up being a blog post! Pretty cool huh? If enough of these plants start faking it I wonder if the moths will wise up and start using more non-visual cues to assess infection...


Soltau, Ulf, Stefan Dötterl, and Sigrid Liede-Schumann. "Leaf variegation in Caladium steudneriifolium (Araceae): a case of mimicry?." Evolutionary Ecology23.4 (2009): 503-512.

Bats and viruses, a continuing love affair

Bats continue to be an intriguing player in the field of wildlife disease. Beside the fact that they carry disease pathogens, they can carry human disease pathogens - and crazy fatal ones to boot! Most of us don't have to worry about this, but if you are a horse rancher in Australia  or a pig farmer in Malaysia or Singapore - be careful! Two of the most deadly and thus fascinating human diseases (in my opinion) to erupt in recent years have taken hold in these areas. Hendra and Nipah viruses are current examples of what disease researchers call spillover events. In short, this refers to the 'fuzziness' of the boundaries separating humans, domesticated animals, and wildlife. As our worlds come into more contact with each other, it makes sense that we all start swapping pathogens and start getting new diseases from them.

The tricky thing is, you can't just say, 'Oh this animal has no visible disease symptoms, I'll be safe, my contact with it won't result in me catching anything bad." We are becoming more aware that some pathogens, while living just fine in one type of animal , can inflict surprisingly detrimental harm as soon as it "spills over" into a new animal host. It's like seeing the mild-mannered Dr. Jekyll turn into a violent, inflammatory Mr. Hyde! The term researchers use for the animal host that physically tolerates and harbors the pathogen is reservoir species. A lake reservoir holds water much like a reservoir host stores (and transmits) the pathogen.
When the pathogen is transmitted to a new/different host, i.e. a host who has never encountered this pathogen in its evolutionary history, its body can basically flip out and go bananas. The new host will likely get sick from having this foreign invader and in the most dire scenario, might even die from it. The cascade of these events are varied and dependent on A LOT of things. Many people spend their whole research careers trying to tease apart this puzzle so I won't try to here. But what is it about bats that make them so special? There are plenty of ideas: http://cmr.asm.org/content/19/3/531.abstract, http://onlinelibrary.wiley.com/doi/10.1111/zph.12000/abstract (from my labmate, Paul Bradley). Bats hang out in large groups, are highly social, eat a variety of plant/animal/bug material, can fly (!), all the while being warm-blooded mammals like us! It will be interesting to see what comes of this line of disease research...

For now, you can read more on:
- this Wikipedia page [http://en.wikipedia.org/wiki/Henipavirus]
- this CDC website [http://www.cdc.gov/ncidod/dvrd/spb/mnpages/dispages/nipah.htm]
 - this Nature piece from 2006 [http://www.nature.com/nrmicro/journal/v4/n1/abs/nrmicro1323.html]


UPDATE Feb-16-2013:
I just found out a group of researchers have evidence pinpointing bats as being the reservoir host for the Ebola virus in Bangladesh [http://www.sciencedaily.com/releases/2013/01/130116163819.htm]

And this just came in the recent issue of Nature: Bats as disease reservoirs. Let me know if you are interested in this article :)