Water Channels Prevent Cellular Rupture

microscopic image of yellow bacteria and red blood cells

Biological Strategy

Staphylococcus

AskNature Team

Image: National Institute of Allergy and Infectious Diseases (NIAID)_NIH / Flickr / Public Domain - No restrictions

Modify Pressure

For many living systems, modifying pressure provides extra strength. For others, it provides ways to move air. To use pressure effectively requires a reliable source of pressure, as well as mechanisms to create and release the pressure as needed. Often, modifications in pressure within a living system are created by water, although air can also be a source. An example of a water-facilitated pressure system is wilted leaves that use hydrostatic pressure to stiffen. They do so by bringing solutes (such as salts) into their cells, which causes them to draw in water.

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Sense Touch and Mechanical Forces in a Living System

Perceiving touch enables living systems to detect other living systems around them and environmental conditions, such as air movement, water currents, and temperature. This ability can help them sense danger as well as opportunity, as when a Venus flytrap’s hairs sense the presence of an insect to eat. Sometimes, a living system senses touch or mechanical forces at a coarse scale; other times, at a sensitive scale that detects very subtle differences. For example, a human elbow is not nearly as sensitive to textures as human fingertips. Fingertips have dermal ridges and many nerve endings that increase sensitivity, enabling them to explore the environment in detailed ways. Elbows don’t need to sense at that level of detail.

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Bacteria

Domain Bacteria (“small staff”): L. acidophilus, Staphylococcus

From inside of our own bodies to the deepest parts of the ocean, bacteria have adapted to almost every possible environment. All bacteria are unicellular, microscopic, and lack a membrane-bound nucleus and organelles, and come in three basic shapes: spherical (cocci), rod (bacilli), and spiral (spirilla). Some strains can be deadly, like Staphylococcus aureus (MRSA) while others, like Lactobacillus acidophilus, found in our intestinal microbiome, keep us healthy. Cyanobacteria, also known as blue green algae, caused the Great Oxidation Event 2.4 billion years ago, producing Earth’s first oxygenated atmosphere.

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Proteins embedded in the membranes of Staphylococcus aureus bacteria open up to form relief channels in response to extreme internal water pressure.

Certain conditions, such as exposure to a sudden downpour, can cause the influx of large amounts of water into a living cell. Like an overfilled balloon, the cell will rupture and die if it’s not able to relieve the pressure. Many bacteria have evolved pressure-sensitive relief channels that allow water to flow out of the cell in response to increased pressure on the cell membrane. Under these extreme conditions, Staphylococcus aureus bacteria produce a compound made up of four proteins. As the pressure on the membrane increases nearly to the breaking point, the proteins arrange themselves into a pore allowing water and dissolved material to exit the cell.

Last Updated August 23, 2016

References

Journal article

Mesophyll conductance with a twist

Plant, Cell & Environment | 04/07/2014 | DANNY THOLEN, GILBERT ÉTHIER, BERNARD GENTY

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Reference

Journal article

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