As the Earth continues its journey around the sun, plants and animals in the northern hemisphere prepare for the onset of autumn in September and the coming winter. Humans rely on calendars to tell us the seasons, but other creatures use changes in the weather and amount of sunlight to signal that winter is approaching. For example, long-lived trees often retain their leaves until the days get shorter, even if an early snowstorm signals the arrival of winter.
Plants and animals have complex proteins and sophisticated memories that allow them to decide when to prepare for cold weather. Bacteria and other microorganisms are also vulnerable to winter cold, so we need to prepare for harsher weather. However, because microorganisms have simple ecology and short lifespans, it is difficult to detect seasonal changes.
Some microorganisms can sense sunlight hours. A group of these microorganisms known as cyanobacteria can predict the beginning and end of your day. Cyanobacteria use three Kai proteins called KaiA, KaiB, and KaiC to track time by sensing the light and dark times of the day. photoperiod. A team of researchers at Vanderbilt University wanted to test whether cyanobacteria’s ability to sense photoperiods could also allow them to sense seasonal changes.
The scientists grew cyanobacterial cells on a nutrient-filled dish for eight days under varying photoperiods. Some cells grow in summer-like days with 16 hours of daylight, others grow in winter-like days with 8 hours of daylight, and some cells grow in winter-like days with 12 hours of mid-day light. The scientists took cells from each photoperiod condition and placed half of them in a bucket of ice at 32°F (0°C). The halves are placed in a closed, temperature-controlled chamber. incubator at 86°F (30°C) for 2 hours. Cells were then returned to the dish at 86°F (30°C) and left to grow for 5 days.
The scientists calculated the survival rate in each photoperiod condition by comparing the number of cells that could grow from an ice bucket and an incubator. They reasoned that if cells could recognize that shorter days meant winter was coming, they might become more tolerant of the cold and fewer would die in ice buckets. Scientists found that cyanobacterial cells grown under short photoperiods were two to three times better at surviving at freezing temperatures than cells grown under longer photoperiods.
The researchers also wanted to investigate whether the cold tolerance of cells grown in short photoperiods was due to a sense of photoperiod. So they removed the Kai protein from the cells and repeated the experiment. These cells had the same survival rate of approximately 35% regardless of the length of the photoperiod in which they were grown. By comparison, cells containing the Kai protein had a 75% survival rate when grown under winter photoperiods and 25% survival when grown under summer photoperiod conditions. The scientists concluded that these cyanobacteria sense the days getting shorter and respond by preparing for the colder weather.
Next, the scientists wanted to understand how cells prepare for cold weather. They knew that some cells can change the composition of fat in their cell walls to maintain their physical structure when the temperature drops. By chemically extracting the fats present inside the cells using chloroform, methanol, and water, the researchers investigated whether the same changes in cell wall fats occur in cyanobacteria grown under winter photoperiods. was tested. They measured the amount of different fats in the cells using a device called a mass spectrometer. Through this analysis, the scientists demonstrated that cyanobacteria grown under shorter photoperiods also increased the amount of fat in their cell walls that made them more cold resistant.
The researchers concluded that because cyanobacteria can sense seasonal changes, this ability probably evolved long ago and may be active in other microorganisms as well. The research team hopes that by studying cyanobacteria and their ability to sense photoperiods, scientists can learn more about how ancient organisms felt the seasons. Researchers say that because algae sense photoperiods and can threaten aquatic habitat during algal blooms, researchers are trying to understand the relationship between photoperiods and how algae adapt to the seasons. By understanding this, he suggested, it may be possible to control algal blooms and protect aquatic habitats.
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Source: sciworthy.com
