Apr 15, 2012
It’s lunchtime. Your friend wants to meet for sandwiches at DeCafé, but you politely decline because you ate a salad several months ago and haven’t been hungry since. Instead, you decide to spread nude outside, Harkness style, soaking up the sun’s rays. You’ve been doing this every day and are quite con- tent with your seemingly anorexic lifestyle.
Meet Elysia chlorotica, our sunbathing sea-slug relative 500 million years removed. It spends its larva-hood feeding on plankton and marine animalcules and soon matures into an elegant wingèd sea-slug. The slug then becomes fit for Fairkid; it eats an exclusive diet of hair-thin algae, consuming it by meticulously sucking out the contents of each cell.
This gentle slurping keeps the algal cells’ light-harvesting chloro- plasts intact. The brown slugs stably incorporate the chloroplasts into their gut cells until they resemble a vomit-green undulating blanket. This is an incredible blanket though, because the slugs are able to harness the power of the chloroplasts to create food from CO2, water, and light. Now with their new intra-cellular inhabitants, mature green slugs spend most of their time swimming near the water’s surface basking in the sun.
What’s even more spectacular about these slugs is that they steal genes from the alga’s DNA in order to make this whole system work. The slugs make proteins and chlorophyll with the stolen plant genes to help perpetuate the photosynthesis for months on end. This is an example of horizontal gene transfer, when an organism incorporates genetic material from another organism aside from its parents.
Would you consider the slug a free-loader? Well consider this: While the slugs gain a temporary free food voucher, the genes of the alga have hitched a ride in the slug’s genome. The lucky alga thereby ensures that its genetic material will continue to exist even if it never reproduces. This is a profound case where the question can be posed: Which organism is benefitting the most from this arrangement?
Wreaking havoc on the body after entering the bloodstream by way of the penetrating proboscis of a mosquito, malaria is the fifth most prolific killer in the world, with a threatening proficiency for adaptation. One species of the pathogen that causes malaria, Plasmodium vivax, showcases this proficiency with a unique adaption that scientists think may be a first.
New research out of the Hebrew University of Jerusalem suggests that the species P. Vivax has evolved the ability to acquire human genes through a process called horizontal gene transfer. If true, this is the first instance of human genes being transferred to an organism of a different species.
Why would P. vivax want our genes? Horizontal gene transfer is an adaption that these pathogens utilize to evade our immune system. Integrating our genes into P. vivax’s genome, the pathogen adjusts its internal response pathways in order to “fool” our immune system. Alas, our defense cells may see them, but won’t treat them as a threat, vastly increasing the pathogen’s chances of survival.
What is significant about the implications of this research is that while horizontal gene transfer happens all the time in unicellular organisms without a nucleus (called prokaryotes), it has never been documented between humans and another organism with a nucleus like P. vivax (called eukaryotes). Such an advantageous adaption may lead P. vivax to become the deadliest and most widespread species of the genus Plasmodium.