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Advancing research into evolution
Stefan Ruhl takes a saliva sample from Kwizera, a gorilla at the Buffalo Zoo who had received anesthesia before undergoing a physical examination. Photo: DOUGLAS LEVERE
The most striking thing about gorillas’ teeth, says Stefan Ruhl, is their similarity to human teeth.
“They are bigger, but the morphology is surprisingly similar,” Ruhl says. “The animals have a different diet, and their facial expressions are so different, so you would expect the teeth to look different. But most of the teeth look really similar.”
Ruhl, assistant professor in the departments of Oral Biology and Microbiology and Immunology, visited the Buffalo Zoo on Dec. 1 to obtain saliva, blood and dental plaque samples from Kwizera, a 200-plus-pound female gorilla undergoing a physical examination before heading to the Memphis Zoo for breeding. The specimens will advance his research into evolution—into how the types of bacteria living inside the oral cavity of primates differ from the types living inside humans, and why.
Ruhl explains that certain strains of oral streptococci bind to sialic acid, a sugar decorating many salivary glycoproteins. It is known that, while there is an almost 99 percent overall homology in the genome between gorillas and humans, the sialic acids in great apes differ from those in humans. Ruhl hypothesizes that the streptococci living in the oral cavity of these primates will differ from those living in people’s mouths as well. Such distinctions in sialic acid and bacteria biology could be important for better understanding the human-bacteria relationship and associated changes that happened during their co-evolution.
If Ruhl’s conjecture holds true, it would help demonstrate that bacteria rely, for survival, on the presence of sialic acids and other counter-receptors to which they attach. Scientists then could manufacture products, such as mouth rinses, that contained synthetic sugars to which harmful bacteria could bind before adhering to organic molecules in the oral cavity.
Kwizera, known as “Bumpy,” was Ruhl’s fourth gorilla. In summer 2009, he took samples from three others at the zoo who, like Bumpy, had received anesthesia to immobilize them before undergoing medical tests. He worked with each animal for about five minutes, using a scaler to remove plaque, of which he found surprisingly little—Ruhl theorizes this is due to a “natural” diet without the sweets or soft drinks that cause so much decay in humans. He reports that the best saliva specimens actually came from a keeper who collected them while playing with the gorillas.
Next up for Ruhl: More apes. To further his research project, a collaboration with scientists at the University of California-San Diego, Ruhl is working to gain access to chimpanzees as well.
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