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Isolating and identifying amoebal species in pine tree bark for Legionella longbeachae co-culture: Implications for preventing Legionnaires’ disease

A postgraduate research opportunity at the University of Otago.

Details

Close date
Sunday, 21 June 2020
Academic background
Sciences, Health Sciences
Host campus
Christchurch
Qualification
Honours
Department
Pathology and Biomedical Science (Christchurch)
Supervisors
Dr Sandy Slow, Professor Steve Chambers, Professor David Murdoch

Overview

Every year, particularly over spring and summer, gardeners are hospitalised with Legionnaires’ disease, an often severe and fatal pneumonia. The cause is infection by Legionella longbeachae, a bacterium that lives in the soil and is also found in composted plant material and potting mix. In both natural and man-made environments, Legionella bacteria are intracellular parasites of free-living amoeba. Humans are “accidental hosts” when lung macrophages become infected following exposure to contaminated materials.

In the environment, following amoebal uptake, Legionella are able to resist the host’s defenses and hijack the cell’s resources so it can replicate, significantly increasing in numbers. It then lyses and kills the amoeba, releasing the bacteria to repeat the cycle anew. Such amplification of L. longbeachae numbers via its amoebal host is likely to be a major contributing factor for the increase in Legionnaires’ disease cases during spring and summer. However the ecology of L. longbeachae and even which amoebal species are important hosts is poorly understood. There is some evidence suggesting pine trees in Australasia and oak trees in Japan are important environmental reservoirs. In addition, we have found L. longbeachae present in the pine bark and sawdust components of commercial potting mix and we have also detected it in the bark of live pine trees. Although limited, such data provides us with a good starting point for investigating the types of amoebal species that could be important hosts; a key requirment for the development of disease prevention strategies.

This project aims to:

  1. Isolate and identify the main amoebal species present in pine tree bark by sequencing the 18S ribosomal gene and comparing against microbial sequence databases;
  2. Develop methods for the continued culture of the isolated pine tree bark amoeba; 3) Test the isolated amoebae’s preference for uptake of L. longbeachae compared to other laboratory cultured bacteria (for example E. coli) in a series of in vitro “eating experiments”.

Preferred student expertise: Microbiology, molecular biology

Further information

This is one of a number of projects on offer for the 2020 intake of BBiomedSc(Hons) at the University of Otago, Christchurch campus.

Dr Sandy Slow’s profile
Professor Steve Chambers' profile
Professor David Murdoch's profile
UOC BBiomedSc(Hons) website
The Infection Group website
Department of Pathology and Biomedical Science website

Contact

Dr Sandy Slow
Tel   +64 3 364 0585
Email   sandy.slow@otago.ac.nz