Author: Rachel Jarmy

Algal Ancestor Shows How Deadly Pathogens Proliferate

Long ago, when life on our planet was in its infancy, a group of small single-celled algae floating in the vast prehistoric ocean swam freely by beating whip-like tails, or flagella. Now, over 800 million years later, these organisms have evolved into parasites called Apicomplexa, but are better known as the parasites that cause Malaria and Toxoplasmosis—serious diseases that infect millions of people every year, particularly in the developing world.

Now their algal past in the ocean may be the key to stopping the spread of these diseases, and is explored in the recent PLOS Biology article by Francia et al, and also in the accompanying synopsis by Stephanie Huang.

 

 

Parasite cell division depends on a fiber that once anchored the basal body of the flagellum in the algal ancestor. Here, you see the fiber (green), centrosomes (red), parasite daughter cells (blue), and nucleus (grey). The micrograph on the right depicts two Toxoplasma gondii parasites in division.
doi:10.1371/journal.pbio.1001445.g001

Professor Boris Striepen and colleagues from the University of Georgia explain in this paper how an important structure inside these parasitic cells, which evolved from the algal ancestor millions of years ago, allows the cells to replicate and spread inside their hosts. Their research may lead to new therapies to halt these deadly pathogens before they cause disease.

In their study, the researchers demonstrate that during the process of replication, and spreading the infection throughout the body, the parasite cell loads genetic material into its daughter cells via a strand of fiber that connects the two. By altering the genes for the components of this fiber in the laboratory, the researchers discovered that they could prevent parasite replication, rendering the parasite essentially harmless.

“These altered parasites can initially infect cells, but once we turn off the fiber genes, they cannot create new daughter cells and spread,” said Maria Francia, lead author of the study. “Since it cannot replicate, the parasite eventually dies without causing serious harm.”

This replication fiber appears to have evolved from the flagellum that enabled ancient algae to swim.

“This was a surprising finding,” said Boris Striepen. “These parasites no longer use flagella to swim, but they have apparently now repurposed this machinery to organize the assembly of an invasive cell”.

A blood smear showing red blood cells and two crescent- or sausage-shaped malaria parasites. Image from The Centers of Disease Control and Prevention as part of the United States Department of Health and Human Services.

The findings of this new research are also the topic of an accompanying PLOS Biology synopsis, by Stephanie Huang, which highlights the importance of the research with regards to the current difficulties in treating malaria and toxoplasmosis. First, the parasites are eukaryotic and thus more similar to human cells than bacterial pathogens, making it difficult to find treatments that kill the parasite without harming human host cells. Second, the parasite cells reside within human host cells for much of their life cycle, evading detection by the host’s immune system.

“It is extremely important to understand the evolution of different organisms, but especially the evolution of pathogens,” Striepen says. “The analysis of their evolution produces important opportunities to develop treatments, but it also helps us understand the basic structures of the pathogens that we must fight.”

 

Maria E. Francia,, Carly N. Jordan,, Jay D. Patel,, Lilach Sheiner,, Jessica L. Demerly,, Justin D. Fellows,, Jessica Cruz de Leon,, Naomi S. Morrissette,, Jean-François Dubremetz,, & Boris Striepen (2012). Cell Division in Apicomplexan Parasites Is Organized by a Homolog of the Striated Rootlet Fiber of Algal Flagella PLOS Biology : 10.1371/journal.pbio.1001444

Category: Biology, Infectious disease, PLOS Biology | 4 Comments

Tracking Coverage of the Radar Tracked Bees

In a recently published PLOS Biology Research Article, by Prof Lars Chittka and colleagues, (and an accompanying Synopsis), the authors revealed how bumblebees quickly find the shortest route to feed from numerous flowers. In this PLOS Biologue post, we take a look at some of the media interest in this article.

Image: Dr Stephan Wolf

The Telegraph

Environment Correspondent Louise Gray summarises the study, and how it could help farmers identify the best ways to grow crops to ensure faster pollination.  “The results showed that the bees would try a number of different routes to a flower and between plants in order to work out the quickest way to and from a food source. Within hours or even minutes, the apparently random ‘flight of the bumblebee’ is an efficient and learned route.”

The Huffington Post

The online newspaper goes into further detail of the methods used by Prof Chittka and his team, including arrangements of the flowers in the wild, and the average  amount of time the bees took to learn the fastest route.  “Scientists tracking the flight of the bumblebee have been astonished by the power of the insects’ tiny brains. Let loose to find their way among five artificial flowers in a one kilometre-wide field, the bees quickly learned which routes were the most efficient.”

BBC Radio Four’s Material World

In this episode of the weekly radio programme, Quentin Cooper interviews the lead author about the study and the high tech methods used by the team;  “We glued little radar antennae on the backs of bees when they left the hive” explains Prof Chittka. “They don’t necessarily like being manhandled and having an antenna on their back, but we’re stronger.”

Image: Dr Stephan Wolf

Scientific American

Associate Editor Katherine Harmon explains the differences between the cognitive behaviour of these bees compared to larger brained animals. “Although this navigation seems to be a no-brainer for the bees, we humans needed mathematical algorithms to analyze and understand the elegance of their behavior.”

Wired

Virginia Morrell from ScienceNow looks at the study from a mathematical perspective, by homing in on the well known ‘traveling salesman’ problem.  “Bumblebees foraging in flowers for nectar are like salesmen traveling between towns: Both seek the optimal route to minimize their travel costs. Mathematicians call this the ‘traveling salesman problem,’ in which scientists try to calculate the shortest possible route given a theoretical arrangement of cities.”

And here is a snippet of the reaction from Twitter users following the recent PLOS Biology publication from the Chittka Lab, showing how bumblebees quickly find the shortest route to feed from a selection of flowers.


Category: Biology, Environment, PLOS Biology, Uncategorized | Leave a comment