Microbes make chemicals for odor labeling in a cat

Domestic cats, like many other mammals, use the smelly secretions of anal sacs to mark the territory and communicate with other animals. A new study by the Genome Center at the University of California at Davis has shown that many odorous compounds from a male cat are actually not made by the cat, but by a community of living bacteria in the anal bags. The work is published on September 13 in PLOS ONE.

"Cats use a lot of volatile chemicals for signaling, and they probably do not make them all," said David Coil, project scientist at the Genome Center and author of the paper.

Many species, including cats, dogs, bears, pandas, skunks and hyenas, use secretions from the anal sac as a chemical language. Skunks, of course, also use them as a defense.

The experience grew out of the KittyBiome project at Genome Center by Holly Ganz, a postdoctoral researcher working with Coil and Jonathan Eisen, professor of evolution and ecology at UC Davis College of Biological Sciences. The KittyBiome project has since been created under the name AnimalBiome, a company run by Ganz.

The researchers obtained the anal secretions of a bag of a Bengal male cat, proposed by its owner. They extracted the DNA for sequencing to identify the types of bacteria and also took samples for chemical odor analysis in the laboratory of Professor Cristina Davis of the Department of Mechanical Engineering and aerospace of UC Davis.

Sequencing showed that the microbial community was not very diverse and was dominated by a small number of bacterial genera.

"There are not a lot of players out there," Coil said.

Analyze volatile organic matter

The most abundant bacteria from the screen were grown. Mei Yamaguchi, a postdoctoral researcher at the Davis Laboratory, analyzed the volatile chemicals released by the bacteria.

The Davis lab focuses on the technology to detect and characterize low levels of volatile organic compounds that can be markers of health and disease, from the human flu to citrus greening in trees fruit.

Yamaguchi and Davis were able to detect 67 volatile compounds released by bacterial cultures. Fifty-two of these compounds have also been found directly in the secretions of the anal sac.

The results support the idea that the bacterial community, not the cat itself, produces many of the smells used by the cat to communicate.

Coil and his colleagues want to follow up by watching more cats. If these smells are made by bacteria, why do cats feel different from each other? How do cats acquire bacteria and change over the course of life? Understanding how microbes influence their odor could have broad implications for understanding odor communication in animals.

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