How the microbiome influences mosquito populations
Meet Assistant Professor Matan Shelomi
November 7, 2020
Around the world, the microorganisms that cause some of our most deadly – and therefore feared – diseases are borne by mosquitoes. The Aedes genus of mosquitoes are known to spread Dengue Fever, Yellow Fever, Chikungunya and Zika viruses. Their cousins, Anopheles mosquitos, carry parasites like those that cause malaria. According to the World Health Organization, Dengue is the most prevalent viral infection transmitted by the Aedes mosquitos with an estimated 96 million symptomatic cases and 40,000 deaths per year (1). However, other microorganisms have a role to play in the lifecycle of the mosquito and their presence or absence in the water the mosquitoes use as nurseries for their young may affect the outcome of those larval mosquitoes.
Matan Shelomi, Ph.D., is an assistant entomology professor at National Taiwan University (NTU) in Taipei. He and his Insect Microbiology Laboratory study how the microbiome influences mosquitoes’ lifecycles and how they can potentially affect behavior across Aedes mosquitoes.
How did you first get interested in science and microbiome research?
Science was my calling for as far as I can remember. I was always enamored with insects and wanted to become an entomologist since learning and memorizing that word in third grade. I never wavered from this dream and eventually achieved it, graduating from Harvard University and then the University of California-Davis with my doctorate in entomology, a postdoc in Germany, and in my current position as an entomology professor at NTU.
My interest in microbes grew out of a realization that everything I loved about insects is found in microbes as well: they have unfathomable diversity and myriad functions and interactions, are misunderstood by most people, and are easy to study without the paperwork associated with vertebrate research. To better study these two major groups of life, I established the Insect Microbiology Laboratory at NTU where I now work. Third grader me would be quite proud.
Can you give a summary of your current project?
My most recent project was called the Stagnant Water Microbiome Project (SWaMP). I studied the microbiota of stagnant water containers, where the Aedes mosquitoes that spread Dengue, Zika, Chikungunya, and Yellow Fever Viruses prefer to lay their eggs. These containers can be anything from an abandoned tire to rainwater collection barrels to gutters to tree hollows. Dengue is endemic in Southern Taiwan, and controlling the containers is one of the most effective ways to control the mosquitoes and prevent disease. Within these containers mosquitoes interact with microbes in several ways. Microbes are the main source of food for the larvae, yet microbes can also be pathogenic.
There are symbiotic microbes, parasitic microbes, and commensal microbes, some of which the larvae retain into adulthood and which can modulate how well it vectors disease pathogens. In addition, different microbes in the water can attract certain mosquitoes. However, the relationships are not well defined. For example, mosquito larvae will not develop well or at all in microbe-free water, but which microbes are present does not seem to matter: even E.coli is enough to restore normal development. By studying the microbes in the waters mosquitoes either lay in or avoid, we hoped to establish causal relationships between a microbe species and a mosquito behavior or function, and possibly develop new vector control tools.
What is a typical day like at your lab?
Much of it is spent reading papers and writing grant applications, including new collaborative projects with other departments at NTU or other potential microbe sources in Taiwan and elsewhere. The collecting of microbe samples and extracting of DNA can all be done in a few [long and labor-intensive] days, but the wait for the sequencing data is considerable and culturing the microbes and mosquitoes in the lab and testing their effects on each other in controlled experiments takes time. My typical day involves mentoring my graduate students and undergraduates on their subprojects under the umbrella of insect-microbe interactions, conducting lectures as part of an insect microbiology course I give, and identifying new field sites for our next collecting trips.
What would you say surprises you about what you’ve found out about mosquito microbiomes through this research?
What surprises me most is how differently mosquitoes and microbes behave in different parts of the world: results from research in Florida or Cambodia are not always the same as those in Panama or Taiwan. The mosquito species that prefer natural containers in one country may only be found in manmade containers in another. That’s quite different from insects like, say, aphids, which have the same primary symbionts no matter where they are in the world. As mosquito symbioses are not obligate, they can take multiple forms and are unpredictable. It is truly impossible to guess what microbes will be found in water or mosquitoes until you look. This variability emphasizes the need for local research to prepare locally appropriate control measurements.
How does your microbiome research impact health and disease? Where do you see this heading in the next five years?
Any research with mosquitoes has a clear public health goal: eradicating vector-borne disease. Mosquitoes are mankind’s most lethal foe, killing more humans through their vectored pathogens than any other animal does, including other humans. Beyond mortality, the morbidity associated with disease as well as the risks for permanent disability, as we saw with Zikainduced microcephaly, are a heavy burden for nations where these diseases are endemic, and that area is increasing as global climate change and human transportation cause the mosquitoes’ ranges to spread ever further. We are currently testing some of the microbes we and our collaborators collected for their abilities to kill larvae.
Our lab is not solely focused on mosquitoes, however. Our newest project, starting this summer, looks at the coconut rhinoceros beetle, Oryctes rhinoceros, which is a pest of palm trees across Southeast Asia and the Pacific. We hope studying its microbes can help us find new targets for pest management.
What are your hobbies?
I am quite fond of travel, having lived and worked in three continents and visited over 78 countries as of 2020. I especially enjoy eating exotic foods. My regular hobby is playing PokémonGO, which is still quite popular here in Taiwan, with trainers of all ages collecting together and even city governments organizing special events for players. It’s the perfect place to catch ‘em all.
What are the major challenges you face in your research with regards to sample collection, nucleic acid isolation and data analysis?
I started the Insect Microbiology Laboratory when I first came to work at NTU. We didn’t have so much as a pipette tip at the time. Everything had to be bought and set up from scratch, but I am pleased to say that everything is now running smoothly. Perhaps the biggest challenge with SWaMP was extracting the DNA from the water samples, which needs to be done as soon as possible after collecting, and keeping the samples cold until then. Finding the best way to collect, preserve, and extract DNA from samples in the field under sterile conditions is a challenge, especially if you are collecting far from the nearest laboratory bench. Samples can sometimes be low in microbes and/or high in contaminants that interfere with DNA extraction, so finding the right nucleic acid extraction protocol is critical.
Which QIAGEN products do you use/have you used in the past and what did you like about the products?
I’ve been using QIAGEN products since graduate school. I used the DNeasy® Blood and Tissue kits to extract microbial DNA from insects then and the DNeasy® PowerWater® kits to process my filtered water samples now, followed by the QIAquick® PCR Purification or DNeasy® PowerClean® Pro Cleanup kits to prepare higher-quality DNA samples. I homogenize my samples using a TissueLyser LT® machine with QIAGEN stainless steel beads, which I made certain to buy when I set up my new lab.
The products are easy to use. Training students to use these products to produce high quality nucleic acids for next generation sequencing is simple. I particularly enjoy the lack of hazardous chemicals such as chloroform or phenol relative to other nucleic acid extraction protocols, as my laboratory does not have a fume hood nor any space for one, so I am limited in the kind of chemicals I can use and appreciate the safety and convenience of the QIAGEN kits.
- World Health Organization (2020) Fact Sheet: Vector-Borne Diseases, https://www.who.int/en/news-room/fact-sheets/detail/vector-borne-diseases