Who doesn't love protein and fat?

INTRO: from 50,000 feet to angstroms

I've begun this blog about bioenergy research with two articles seemingly unrelated to the field of bioenergy research.  I did this to begin with a 50,000 foot view of the field of bioenergy research and look at its challenges and prospects more broadly.  As a graduate student myself, I know what it's like to spend a lot of time down in the deep dark depths of a problem without coming up for air for some time.  So, it's been refreshing to begin this project looking from 50,000 feet up rather than in its depths.

However, today I'd like to zoom in from 50,000 feet to delve into the depths of bioenergy research with a paper that just came out focused on algal biology.  I don't think I'll get too lost in the depths because this paper does a good job of linking its research to the big problem it's trying to solve.

THE BIG PICTURE: veal algae?

One way to get more biodiesel from algae may be to get each individual algal cell to produce more lipids -- perhaps to even fatten them up like some kind of veal calf.  Indeed, under certain conditions, many algae will store energy as lipids in specific intracellular structures called oil bodies.  Some algae can reach a lipid content of 70% by dry weight.

In a recent paper, appearing in the journal Proteomics, Hoa M. Nguyen and others set out to discover the protein machinery that make up the oil bodies in the hopes that some day this knowledge will translate into a way to fatten up individual microalgae to produce high-yielding biofuel.

Scanning electron micrograph image of the microalgae C. reinhardtii

THE STRATEGY: classic purification with new analysis

 It has been possible to purify oil bodies using classic, established biochemical techniques since the mid-nineties.  However, a detailed profile of all the proteins found in these purified oil bodies has yet to be published.  Nguyen and others decided to grow a mutant strain of the model microalga C. reinhardtii under conditions known to produce oil bodies. They then processed the algae through 7 purification steps to recover pure oil bodies.  They tested these oil bodies and found a relatively pure fraction containing high levels of the lipid triacylglycerol (TAG) as well as a known component of oil bodies (major lipid droplet protein).

Once they knew they had a respectably pure sample, they ran the peptide versions of their proteins through a mass spectrometer and identified the proteins present in their sample.

Summary of Chlamydomonas oil body purification and proteomic analysis. Nile red staining labels oil bodies.  SDS-PAGE stain reveals purification of oil body fraction. Abbreviations: M, protein marker; MLDP, major lipid droplet protein; TLC, thin-layer chromatography; TAG, triacylglycerol; MGDG, monogalactosyldiacylglycerol; DGDG, digalactosyldiacylglycerol; PG, phosphatidylglycerol; PE, phosphatidylethanolamine; PC, phosphatidylcholine. Note: Numbers below the gel lanes correspond to the major steps of oil body purification as indicated in the figure. (From Nguyen et al. 2009)

THE RESULTS: well, what do we have here?

The authors found 330 relatively abundant proteins in their oil body purification. To see the top proteins identified check out table 1 from the paper.

To get further understanding, the authors put these proteins through a series of bioinformatic programs to figure out what their functions might be. As a result, they found that many of the proteins they discovered were involved in metabilism, transport, vesicle trafficking, and redox. Many of the highly abundant proteins are known to be involved in lipid metabolism.

THE ENTICING FUTURE: what to do with this new knowledge

One aspect of this paper I enjoy is that it's a dataset brief, meaning it's very high quality, but preliminary data.  In the end, its findings yield more questions for the field than answers, and also some enticing possibilities.

One such question is, how can we manipulate the proteins found in oil bodies to increase the oil content of algae? To this end, the authors provide an enticing possible answer.  For instance, the authors point out "Oil body-associated lipases could be involved in TAG degradataion processes occurring concurrently to TAG synthesis. Down regulation of such lipases might boost oil accumulation under non-stress conditions".  It would be exciting and promising, indeed to see if knockout of these newly-identified lipases could promote oil body formation.

In the end this paper offers an enticing beginning to a stream of new questions.  What is the role of highly abundant proteins of unknown function found in the oil bodies?  What proteins are found in oil bodies in the context of growing oil bodies vs shrinking oil bodies? Can the proteins found in oil bodies be manipulatied to yield more oily algae?

I look forward to follow the research of these authors and others as they continue the basic biological research into algal oil production processes. Hopefully someday soon, we will have more answers than questions!

REFERENCE:

Nguyen HM et al. "Proteomic profiling of oil bodies isolated from the unicellular green microalga Chlamydomonas reinhardtii: With focus on proteins involved in lipid metabolism" Proteomics (2011) issue 11. PMID 21928291.