Researching Parasites and Living Symbiotically



Dr. Haili Zhang and Dr. Fengguang Guo

Almost any scientist who doubles as a parent knows that sometimes laboratory work takes a back seat to your kiddos in the car seat. For couples who both work in research, one person tends to sacrifice more, resulting in a sort of parasitism of one career by the other.

However, for Dr. Haili Zhang, an assistant research scientist, and Dr. Fengguang Guo, a research associate, both in the Texas
A&M College of Veterinary Medicine & Biomedical Sciences’ (CVM) Department of Veterinary Pathobiology (VTPB), their relationship resembles a symbiosis that benefits each other, their research, and their children.

Zhang and Guo grew up in China’s Inner Mongolia region and met at Inner Mongolia University for Nationalities.

“We were studying plant protection,” Guo said, “basically, the study of plant parasites.”

Like the plants they studied, their affinity for each other grew where it was planted: they studied together, they graduated together, and before they knew it, they were planning their lives.

“I think we were actually studying on our first date,” said Zhang, smiling as she reminisced about their early years.


Learning and growing together is exactly where they wanted to be, and 20 years later, they still share that sentiment.


Although they still study parasites, they made the jump to human-animal parasites eight years ago when they started working with Dr. Guan Zhu, professor and principal investigator in the VTPB department. Zhang had just completed her doctorate in genetics at the Chinese Academy of Sciences, and Guo was preparing to start his doctorate in veterinary microbiology.

Surprisingly, the jump from plant to people parasites was not as grandiose as their move from the East to the West. The group of parasites they study, called apicomplexans, share many similarities to plants in terms of molecular structure and biochemistry. For instance, both plants and apicomplexan parasites have a plastid, a structure that makes and stores chemicals important for metabolism (apicoplast in apicomplexans) or photosynthesis (chloroplasts in plants).

Molecules unique to the parasite, and not the host, serve as the perfect avenue for developing drugs to combat parasites. Unfortunately, not every apicomplexan has such an easy target as an apicoplast, such as the organism Zhang and Guo study, Cryptosporidium parvum (C. parvum).

C. parvum – a single-celled, eukaryotic parasite belonging to the group Apicomplexa — infects the digestive system, causing severe diarrheal disease or Cryptosporidiosis (which tends to be especially severe in developing countries and for the immunocompromised, such as young children, the elderly, and AIDS patients). C. parvum is especially tricky because it is resistant to common disinfectants such as bleach and chlorine; thus, even treated water may harbor the parasite. As a result, about 748,000 cases can be attributed to the apicomplexan a year in the U.S. alone.

To target disease-causing parasites like C. parvum, Zhang and Guo study pathways important to the parasite’s biochemistry, such as enzymes involved in parasite metabolism. Normally, enzymes make excellent drug targets because without them, essential reactions cannot occur like those involved in energy metabolism. The problem is that many of the enzymes in a parasite’s metabolism are similar to their counterparts in humans, so it becomes critical to identify drugs that act more on the parasite’s enzyme rather than the host’s.




Using a method called drug screening, Zhang and Guo simultaneously test many drugs with similar chemical properties that target specific parasite enzymes. Through this process, they find the best match, the drug compound that will inhibit the most parasite growth and be the least toxic to the host cell.

Studying parasites is hardly romantic, and there’s hardly any romance shared between the couple, from what an observer can tell. During the day, they are hard at work at their separate stations—Guo, hunched over his bench, pipetting and separating samples into tiny, plastic tubes, and Zhang, on the other side of the room, eyes glued to a microscope as she counts the parasites left after her drug treatment.

No one would guess that these two meticulous researchers share a private life. Yet, come five o’clock, they leave together hand-in-hand.

“They work very hard, and they work well together,” Zhu said. “I can always count on them.”

Collectively, they publish two to three papers a year, sometimes individually and sometimes together; yet, daily productivity is difficult to maintain if the daycare is closed or a child is sick. On days like this, they alternate between their roles as parent and as scientist — Zhang takes the morning shift with the kids, while Guo is busy at the bench; they reconvene for lunch and swap.

Jumping between roles never diminishes their role as spouse, however; they believe sacrificing for their kids is necessary, but sacrificing for each other’s career is not an option. From books to bench, they continue to be each other’s support in a field that is
physically and mentally demanding.

“We are fortunate to be in the same molecular biology laboratory with similar research interests and technical abilities; we understand each other’s projects and can help each other with some of the experiments, if need be,” said the couple.

But at the end of the day, they happily trade pipettes and petri dishes for baby dolls and toy cars, which is the secret to balancing their roles as scientists and parents, according to Zhang.

“You have to adjust yourself to where you are and enjoy the moment, whether we are at work or at home,” she said, adding that as soon as they see their children’s smiling faces, it’s hard to think of anything else.

The walls of Zhang and Guo’s shared office are adorned with pictures created by their children

Once the kids are asleep, the couple might seek each other’s help in solving a problem in their research. They share a basic knowledge of each other’s projects, but not too much detail which keeps the work theirs, an important consideration when working so closely together.


“I feel like I have my own thing and he has his,” Zhang said.

Despite their obvious passion for science, there’s no pressure for their kids to be scientists.

“That’s not our decision,” said Guo, as they hold their little ones on the couch. “We just want them to have the best education and want them to be happy.”

For now, that’s drawing for Lucy, age 6, and everything cars for Lucas, age 4.

Zhang and Guo proudly display Lucy’s crayon ponies and princesses in their office, adding a splash of color to the gray walls and brightening their work-time moods.

If deadlines call for weekend experiments, Lucy can be found working on her next masterpiece with her markers spread out across
her mother’s desk. Lucas’ artistry is more narrowly focused, as he draws the same car again and again; he prefers a good story, either read to him or memorized and “read” by himself. His favorite books are, you guessed it, about cars.

For some couples, sharing a life-long career with their spouse is not appealing.

“I could never work with my husband,” admits Mary Yu, a doctoral candidate in Zhu’s lab who works with the couple. “I need my own
space and I like that my husband and I have different interests and specialties.”

But Zhang and Guo are grateful to share the scientific passion and culture that is difficult to relate to if one of them were a nonscientist. They are excited about what they might discover together, and their constant presence in the laboratory is a good reminder that their careers are a part of their life, and not the other way around.

Because, after all, what’s the point of discovery if you have no one to share it with?


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Contact Information: Megan Palsa, Executive Director of Communications, Media & Public Relations, Texas A&M College of Veterinary Medicine & Biomedical Science;; 979-862-4216; 979-421-3121 (cell)

This story originally appeared in the Spring 2018 edition of CVM Today magazine.