Exploring the stomachs of tropical carnivorous plants

Thibaut Goldsborough
Tuesday 6 August 2019

I’ve just finished my first 5-week Laidlaw project in Singapore and Indonesia to study a tropical carnivorous pitcher plant called Nepenthes. These plants, found throughout South-East Asia have the extraordinary ability to trap, kill and digest insects. My study focused on three Nepenthes species, N. ampullaria, N. rafflesiana and N. gracilis which can be found in the incredibly pristine National Parks of Singapore. During the whole length of my project, I was accompanied by Dr Kadeem Gilbert, a Nepenthes researcher from the University of Harvard who helped me study these plants in the wild. Our research focused on the microbial communities that live within the digestive fluid and help the plants digest their prey.

Nepenthes rafflesiana, a plant that eats insects.

One of the most remarkable observations we made in the field was the extremely acidic pH found in some, but not all of the carnivorous pitchers. We recorded pH as low as pH 1.5 which is almost as acidic as battery acid. This extreme environment puts a lot of selective pressure on the bacterial communities that live within, and we studied these communities by looking at their DNA. We collected over a hundred Nepenthes digestive fluid samples, filtered the bacteria and then went through the lengthy process of isolating and purifying the bacterial DNA in a laboratory in the National University of Singapore (NUS). I had the opportunity of practicing some leadership skills in the lab as I had three PhD and Masters students working with me trying to investigate the research question that I had come up with.

Hundreds of ants being digested by Nepenthes rafflesiana

A large part of my research was spent in the field, as before taking bacterial samples I made sure to take as much data I could on the properties of the digestive fluid that I was collecting. This included the measurement of pH, oxygen, carbon dioxide, nitrite, nitrate, nitrous oxide, ammonium, phosphate and peroxide concentrations that can be controlled by the plants and affect the bacterial communities. One of the bacterial community that our team is focusing on is denitrifying bacteria. These bacteria have the ability remove Nitrogen from the soils and bodies of water and can drastically reduce plant growth. It was noticed that these bacteria, although widespread, may be absent from Nepenthes pitcher fluid. Our team is the first trying to investigate how Nepenthes may be inhibiting the growth of these parasitic bacteria without affecting the growth of other beneficial bacteria. This research is very exciting as it explores an entirely novel question in Nepenthes biology and might result in potentially useful applications in agriculture.

In the field, collecting fluid samples of a rare Nepenthes hybrid.

During the last 10 days of my research we went to the island of Sulawesi in Indonesia where we were looking for more populations of Nepenthes species that have never been studied in the wild. Our team made many remarkable discoveries in the montane rainforests of Sulawesi that were previously unexplored by botanists. These discoveries included a new population of N. maxima, a beautiful Nepenthes that is only found on the island of Sulawesi as well as a potential new species of the extremely rare Paphiopedilum orchid. This whole expedition was very successful, and was a great opportunity for me to practice my leadership skills. The end of this first project leaves me extremely excited and impatient to start the second half of my project next summer where I will analyse the DNA that I purified using cutting edge DNA technologies.

I wish to thank the Laidlaw Scholars team and Lord Laidlaw himself for making this project possible.









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