Animal Senses and Quorum Sensing

Study Notes

Animal Senses

Elephants can smell water up to 20 km away
Bears can smell a carcass up to 30 km away
Great white sharks can smell blood in the water up to 5 km away and swim towards the source at a speed of 50 kilometers per hour

Quorum sensing is a complex and fascinating communication phenomenon observed primarily in bacterial populations. This process allows individual bacteria to detect and respond to the density of their own kind in a given environment. By releasing and sensing specific chemical signals known as autoinducers, bacteria can effectively gauge how many of their peers are nearby. When the concentration of these signaling molecules reaches a certain threshold, it indicates that a sufficient number of bacteria are present to carry out group behaviors that would be ineffective or even impossible for a solitary bacterium to achieve.

These collective behaviors can include the formation of biofilms, which are structured communities of bacteria adhering to surfaces; the secretion of virulence factors that aid in pathogenesis; and the coordination of activities, such as bioluminescence in some marine bacteria. Essentially, quorum sensing enables bacteria to act in unison, enhancing their survival and adaptability in changing environments. This communication mechanism is not just crucial for bacterial communities but also has implications for various fields, including medicine, where disrupting quorum sensing can be a strategy to combat bacterial infections.

Sensing

Quorum sensing is a process of communication between bacteria
Quorum sensing allows bacteria to sense their population density
This communication uses chemical signals to determine the minimum number of bacteria needed to perform a task
An example is the bacteria Myxococcus xanthus, which forms fruiting bodies when nutrient levels are low

Quorum Sensing in Myxococcus xanthus

Myxococcus xanthus is rod-shaped soil bacteria
When nutrient levels are low, starving cells send a chemical signal to nearby cells
This signal causes the bacteria cells to aggregate together and form a fruiting body
Fruiting bodies are spore-forming structures that enable the bacteria to survive in unfavorable conditions
The size of a fruiting body is approximately 2.5 mm
The diameter of individual bacteria cells is approximately 0.5mm