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14 March 2016

Shedding light on the living world

Using sophisticated imaging techniques, African physicist and TWAS grantee Jeremie Zoueu is helping farmers in his home country of Côte d'Ivoire to develop better defences against crop diseases.

Imagine that we could scan a leaf of rice plant at microscopic scale to detect noxious bacteria at early stages of infection or inspect the inner surface of a red blood cell to spot markers of malaria, simply by using a light beam. The approach would offer farmers and doctors effective means for quick action to improve production or provide medical care.

This is precisely what physicist Jeremie Zoueu, researcher from Côte d'Ivoire, is doing in a field called photonics, the science of generating, controlling, and detecting particles of light called photons. As a recipient of a TWAS research grant in 2009, 2011 and in 2014, Zoueu has used this financial support for the benefit of his country. "I've always been fascinated by the possibility of inspecting things to appreciate how they are made and what's going on inside," Zoueu said during a recent interview. "And imaging techniques offer a powerful tool to understand nature and living organisms."

Zoueu will be in Trieste, Italy, from 18-22 April to join in a TWAS conference called "Research Grants Outstanding Awardees", which will showcase the tremendous results that scientists from the South are obtaining with the Academy's support. The TWAS Research Grants programme is one of the most successful programmes that TWAS offers to scientists from developing countries. Through contributions from the Swedish International Development Cooperation Agency (Sida), the programme is awarding an average of US$1.6 million per year and has assigned more than 2,370 grants from 1986 through 2015. Sida's support began in 1991, a few years after the programme's initial launch. 

While the conference looks to evaluate the programme's past impact, TWAS has recently taken a major step to improve the present and future operation of the programme: For the first time in the Academy's history, it will offer fully digital online applications, for the Research Grants programme in order to speed up the application procedures and make the whole process user-friendly for both applicants and TWAS staff.

Zoueu is a professor in the department of electricity and electronics at the National Polytechnic Institute of Yamoussoukuro (NPIY) in Côte d'Ivoire, where he teaches optics, electronics and spectroscopy and leads a group of 15 young scientists. He is also an associate member of the International Centre for Theoretical Physics (ICTP), based in Trieste, Italy.

The Ivorian physicist is applying photonics and, in general, imaging techniques to biological samples to help find solutions to local problems. He also studies organic materials and applies remote-sensing spectroscopy for Earth analysis. He holds a master in laser engineering and applications from the Galilee Institute and a PhD in the same field from Pierre and Marie Curie University, both in Paris, France.

Within the field of photonics, Zoueu's name is well known in Côte d'Ivoire and beyond. Early in his scientific career, he studied and worked in France, Italy, Germany, Sweden, and in many African countries.

Abroad, he was exposed to mind-opening collaborations and learned from experienced scientists. During those years he also built a network of physicists that is currently carrying out important studies and initiatives.

Theoretical physicists, Zoueu observed, don't have many problems when doing their research: all they need is a pen and a desk. "But I'm an experimental physicist," he explained, "and without costly equipment I cannot produce good results. However, thanks to TWAS's support, I've been able to buy lasers, optical components and detectors to carry out my research."

To be scientifically competitive, he decided to address practical problems related to crop-affecting diseases. Côte d'Ivoire has launched an ambitious programme for agricultural diversification and plans to become West Africa’s leader in rice production. Unfortunately, rice is vulnerable to infections by several noxious organisms. "Rice occupies a prominent place in agriculture and food-security," said Zoueu. "Bacterial wilt and leaf streak, some of the diseases which affect rice production around the world, are quite common and very dangerous even in my country."

To control the damage caused by these diseases, it's important to acquire knowledge about the relationship between the rice plant and pathogenic bacteria, in particular Xanthomonas oryzae. "To tackle this problem, we decided to look for early signs of rice disease on the plant leaves, using imaging spectroscopy (IS)," Zoueu said.
"When light and matter interact after lighting a specimen, they produce a so-called spectrum, a sort of unique zebra-like pattern that describes that sample. By comparing the lines in a spectrum obtained from infected rice with a similar fingerprint obtained from healthy rice we can spot specific markers that tell us we are in the presence of a disease."

Using this technique, the scientists could identify early signs of rice disease, offering farmers a new tool to protect their crops by adopting quick and targeted interventions. In another experiment, they assessed whether rubber plants (Hevea brasiliensis) grown in Côte d'Ivoire show tolerance towards other crops grown in the same field. "It's quite common to grow two different vegetable species in the same field," said Zoueu. "But in the case of rubber, we had observed signs of discomfort when rubber is grown in the presence of other plants. This urged further investigations as rubber takes seven years to mature and late actions could compromise the yield."

Using laser-induced fluorescence spectroscopy, a sophisticated technique that exploits light to trigger fluorescence emission from samples of rubber leaves, Zoueu and colleagues found that cassava and hevea plants are not compatible, as the first turns out to be a heavy stressor to the latter. These techniques offer several advantages, Zoueu pointed out: they avoid using chemicals, can be easily standardized, provide results in little time and are more reliable than analysis carried out by human operators.

"Using imaging techniques, we addressed also malaria, in particular the malaria-causing agent (a parasite called Plasmodium)," added Zoueu. Using 13 different monochromatic sources of light – 13 different wavelengths – they obtained 13 single pictures of the parasite embedded in the red blood cells. "Fingerprints change according to the stage of infection, as each part of the plasmodium and of the blood cell reflect light in its own peculiar way," the scientist explained. Setting up the technique has required three years, but now Zoueu's laboratory is known as one of the best photonics labs in West Africa.

Teaching and tutoring students is equally important. "Each year I accept not more than four to five new students in my lab," he said. "In doing this, I can guarantee that each student receives adequate attention and training. I'm proud to give them what I didn't have when I was a student." Zoueu has an ambitious dream for his future: "I'd really like to train some outstanding students, who might continue what I have started and help make Africa competitive in this field."

Cristina Serra

 

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