Parasitic worm manipulating ants into zombie-like behaviour the focus of recent U of L study

trevor.kenney — Fri, 06 Mar 2020 16:48:07 +0000

A new study co-authored by the ��Ѹ��Դ��߿�Ƭ of Lethbridge’s Dr. Cam Goater and graduate student Dr. Brad van Paridon (BSc ’10, PhD ’17) is beginning to unlock the evolution of one of the most captivating and complex parasite life cycles in nature.

Dr. Brad van Paridon holds a vial of infected ants.

In a paper published in this week’s issue of Proceedings of the National Academy of Sciences (PNAS), Goater, van Paridon , Dr. John Gilleard (��Ѹ��Դ��߿�Ƭ of Calgary) and collaborator Dr. Charles Criscione (Texas A&M ��Ѹ��Դ��߿�Ƭ) assess the genetic relationships of a parasitic worm to help explain how they take over the brains of ants, effectively manipulating them into zombies as they seek to complete their life cycle.

PNAS is widely considered one of the top three science journals in the world and Goater is quick to praise van Paridon’s work during his PhD studies as a driver of the latest research findings.

“His focus on integrating approaches in animal ecology, molecular biology and evolutionary theory is really what pushed this paper forward,” says Goater. “It’s a testament to the talent of our graduate students and the high level of research being done in our graduate programs.”

The parasite, known as the lancet liver fluke, Dicrocoelium dendriticum, is one of the most well-known and least understood parasites in nature. It infects ants and causes them to cling to vegetation and wait to be eaten by animals, including cattle and sheep. Consuming the parasite can cause the animals to develop liver diseases that are difficult to diagnose and treat, costing farmers time and money. They are prevalent in the Cypress Hills area of southeastern Alberta and southwestern Saskatchewan.

Infected ants cling to vegetation waiting to be consumed. Photo by Andy Hurly.

“When these ants ingest larvae of the fluke, they crawl to the tops of flowers that are adjacent to their nests,” says Goater, a researcher in the Department of Biological Sciences who has been studying the ants and observing their bizarre behaviour for years. “Once they have settled on a flower, they firmly attach with their mandibles. A few hours later, if not eaten by a grazing mammal, the infected ants detach from the flower and return to their nest. They repeat the same attach/detach sequence the very next day — often on precisely the same flower petal.”

The natural world is ripe with examples of hosts changing their behaviour and even appearance at the bequest of a parasite, but researchers still do not fully understand how parasites cause these alterations or how they evolve.

Their paper, Clonemate cotransmission supports a role for kin selection in a puppeteer parasite, emphasizes that to understand the evolution of this absurd manipulation, it is important to understand how ants are exposed to these parasites, their fate inside an ant, and the genetic relationships between individual parasites. The life cycle starts as a microscopic egg in the dung of a grazing mammal such as a cow or deer before infecting and multiplying in snails and being released in tiny slime balls. Ants love to eat these slime balls but when they do, they become exposed to myriads of minuscule larvae that pass into the ant’s abdomen. Those in the abdomen reside there for the rest of the ant’s life, awaiting ingestion by a cow. One lone larvae, however, heads to the brain where it initiates the zombie-like behaviour — knowing it will die upon ingestion by a grazing mammal. Thus, the parasite in the brain sacrifices its life for its mates that live in the abdomen — a classic case of altruistic behaviour.

“Unlike equivalent stages of similar parasites, there is a very close genetic relationship between the parasite in the brain and those in the abdomen. In fact, they tend to be perfect clones,” says Goater. “This means that in sacrificing itself, the ‘brainworm’ facilitates the movement of close relatives into the next host where they can reproduce.”

The evolutionary explanation for why some animals appear to sacrifice themselves for others is a subject of much debate. The theory of kin selection seeks to explain altruistic behaviour as a mechanism by which individuals can increase the chance of their genes being passed to the next generation by improving chances of survival and reproduction of genetically related family members.

“By demonstrating the close genetic relations between brain- and abdomen-dwelling parasites in manipulated ants, we’ve been able to demonstrate the key role of kin selection in the evolution of this puppet master parasite.”

Research paper examines novel approaches to addressing antibiotic-resistant pathogens

trevor.kenney — Mon, 02 Mar 2020 23:24:01 +0000

��Ѹ��Դ��߿�Ƭ of Lethbridge researchers in the Alberta RNA Research and Training Institute (ARRTI) are making strides in addressing the antibiotic crisis caused by the steady emergence and spread of antibiotic-resistant pathogens.

Dr. HJ Wieden, standing, with student Josh Friesen in the ARRTI lab..

Recent work on the molecular basis of antibiotic action conducted in the research group of Dr. Hans-Joachim Wieden, director of ARRTI, was published in the Proceedings of the National Academy of Sciences of the United States of America (PNAS). This report, published in one of the three most influential scientific journals in the world, is a result of a collaboration with Dr. Scott Blanchard (St. Jude Children’s Research Hospital, and adjunct professor at Weill Cornell Medical College) and Dr. Karissa Sanbonmatsu (Los Alamos National Laboratory).

“Antimicrobial resistance (AMR) continues to be a global health risk and we need new strategies for developing antimicrobials,” says Wieden, a professor in the Department of Chemistry & Biochemistry. “A global action plan on AMR was endorsed at the World Health Assembly in 2015 and even though this is one of the most predictable challenges for medicine worldwide, research focusing on identifying new antibiotics has diminished significantly.”

Wieden and his graduate students, including co-author Dr. Dylan Girodat (PhD ’19), study the bacterial ribosome and the biomolecular factors that regulate its function. The bacterial ribosome is the part of the essential cellular machinery responsible for protein production and therefore a target for more than 50 per cent of the currently used antibiotics.

A closer look at the ribosome.

Wieden says there are two broad approaches to addressing the issue, finding new drugs for known targets or identifying novel targets for known or existing drugs. Their paper, Elongation factor-Tu can repetitively engage aminoacyl-tRNA within the ribosome during the proofreading stage of tRNA selection, examines the EF-Tu protein and how it works with the ribosome during the complicated process of translation.

“By understanding, at the molecular level, how EF-Tu and the ribosome work together, we are convinced it will be possible to identify novel targets for antimicrobials or even a completely novel mode of action,” says Wieden.

The work by Girodat, who recently defended his PhD, has translated into an outstanding professional opportunity as well.

“Not only has Dylan’s work been published in a fantastic journal, he’s secured a postdoctoral position with Dr. Sanbonmatsu at the Los Alamos National Lab in New Mexico,” says Wieden. “This is the kind of success and impact that sets U of L trainees apart.”

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Parasitic worm manipulating ants into zombie-like behaviour the focus of recent U of L study

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Research paper examines novel approaches to addressing antibiotic-resistant pathogens

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