MILWAUKEE — Glowing bacteria in the tiny Hawaiian bobtail squid may shed new light on the role bacteria play in the human body to synchronize daily tasks such as sleeping and eating, and keeping the immune system healthy, research at the University of Wisconsin-Madison suggests.

Circadian rhythms in humans and animals — responsible for sleep cycles and other physiological and metabolic functions — have long been thought to be regulated mostly by exposure to light and darkness. The rhythms are important because disrupting the body’s internal clock by traveling to a different time zone, or by working a night shift, can contribute to sleep and immune system disorders, or conditions like seasonal affective disorder.

If there’s a connection between circadian rhythm and bacteria in the human gut, it would provide further evidence of the need to be careful with antibiotics that kill bacteria which may be important to maintaining a healthy immune system.