A microbial universe in the soil and gut of a beetle – Northern Arizona University


researcher Javier Ceja Navarro has been a science communicator since childhood.

“I have a younger brother, and for him I was the encyclopedia,” said Ceja-Navarro, a professor of microbiology in the Department of Biological Sciences and the Center for Ecosystem Science and Society at Northern Arizona University. “He would ask me how things work. As all worked,” says Ceja-Navarro with a laugh. “‘I must study!’ I thought so I could give him answers.”

So Ceja-Navarro went to the small library in his town of Tuxpan, Nayarit, Mexico, read books, and came back ready to explain to his brother the answers he had found.

Ceja-Navarro was also an avid artist as a child—a skill he has further cultivated as part of his science communication practice. By the time he entered high school, Ceja-Navarro knew he wanted to be close to science. At the age of 15 he received a scholarship to enter clinical analysis in high school, where he spent most of his time collecting all kinds of human specimens to test for diseases.

“A lot of the diseases we’ve seen in my area are caused by protists, and I thought, where are they coming from?” Protists, a diverse group of single-celled microorganisms found in terrestrial and aquatic ecosystems, include some notorious ones pathogens: Giardia lambliaa common intestinal parasite, and plasmodium, a large group of protists that cause the disease malaria in humans. “And wow, then I saw protists in the ground,” said Ceja-Navarro. Intrigued, he learned to isolate them in the lab.

Ceja-Navarro also credits his mother with helping him talk to laypeople about his research.

“My mother was always very curious and read the books I read,” said Ceja-Navarro, a first-generation chemical engineering student with a PhD in biotechnology from the Centro de Investigacion y de Estudios Avanzados del IPN in Mexico City. When he was preparing for his Ph.D. Defense, he practiced his speaking for his mother. “‘No, no, no,'” he recalls her words. “‘Explain it to me in a way I can understand.'” So he practiced and explained again.

When he joined Lawrence Berkeley National Laboratory in Northern California as a postdoctoral researcher studying the insect gut microbiome, Ceja-Navarro noticed that in his new department — where soil was the main research topic — “everyone was talking about soil bacteria.” But he didn’t hear many questions about these protists, which he’d had in mind since his days as a clinical analysis technician. “I thought: where are the protists when protists eat pretty much everyone else?”

Expanding this conversation inspired Ceja-Navarro to study soil microbial food webs and the often complex relationships between microbes and the visible world. One relationship Navarro continues to unravel is how microbes in insect guts allow certain insects to be “bioreactors.”

For example the coffee beetle, Hypothenemus hampei, can consume lethal amounts of caffeine when chewing through its diet of coffee berries. Ceja-Navarro theorized that the beetle received help from its associated microbes, and by sequencing its gut microbiome, he narrowed the list of suspects to a few bacteria, including Pseudomonas fulva. When he fed the beetle an antibiotic that killed all the bacteria in its gut, Ceja-Navarro saw that the beetle could no longer digest caffeine or reproduce. When he added again S. fulva In the bowels of the bug, his coffee-absorbing superpower returned.

“We have shown that we can systematically study the environment represented by the beautiful guts of this beetle,” he said. Such discoveries could have major implications for crop management, epidemiology, and even energy solutions.

But Ceja-Navarro says this is just one example of the holistic research approach he brings to NAU. He sees great potential in studying the microbiome as a complex system that, like other food webs, is governed by apex predators—often protists. And as one of the leaders of a new $3 million Department of Energy project, Ceja-Navarro and his colleagues at NAU and Lawrence Livermore National Laboratory will study who eats who in the soil and how that chain affects critical biogeochemical processes like carbon and nitrogen cycle. “I want to get everyone excited about all members of the soil microbiome so that we all take a holistic systems perspective,” said Ceja-Navarro.

For him, this enthusiasm begins with mentoring students. “I want to share my curiosity about our world with students and get them to think about the little aspects of the world that we don’t usually think about.”

He also wants to help more Latinos pursue science majors and careers.

“When I came to the Berkeley Lab, I didn’t see many Latinos working in the lab,” Ceja-Navarro said. So he joined an outreach program Science at Calin which university scholars visit local libraries and schools to host scientific talks in Spanish. In northern Arizona, he also hopes to share his scholarship with Latino students and communities off campus.

“As a Latino, I see it as my responsibility to share this enthusiasm for science with other Latinos. My hope is to ‘hear’ more Latinos speaking Spanish in the lab as well.”

For Ceja-Navarro, it’s not just about educational and career opportunities, it’s about empowering science itself when it comes to stimulating interest in science among students of all backgrounds. In its comprehensive grasp of what science can accomplish, the field of microbial ecology is an essential way to bring more people to the lab bench to meaningfully solve the myriad of mysteries contained within a microbiome.

“A microbiome is a universe full of stars,” said Ceja-Navarro. “It’s that complex. Imagine being able to study each of these stars – think of all the things we could discover! Everyone is there waiting for us to be curious.”


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