Slime Enables Movement

Biological Strategy

Bacteria

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Move in/on Solids

To obtain needed resources or escape predators, some living systems must move on solid substances, some must move within them, and others must do both. Solids vary in their form; they can be soft or porous like leaves, sand, skin, and snow, or hard like rock, ice, or tree bark. Movement can involve a whole living system, such as an ostrich running across the ground or an earthworm burrowing through the soil. It can also involve just part of a living system, such as a mosquito poking its mouthparts into skin. Solids vary in smoothness, stickiness, moisture content, density, etc, each of which presents different challenges. As a result, living systems have adaptations to meet one, and sometimes multiple, challenges. For example, some insects must be able to hold onto both rough and slippery leaf surfaces due to the diversity in their environment.

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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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Nozzles underneath some bacteria eject slime to propel the organism forwards or backwards.

“Gliding motion across surfaces, usually with slime–whether or not by the same scheme–occurs in procaryotic organisms (bacteria and their kin) as well. It’s based on either of two mechanisms. Bacteria are often covered with tiny hairs, pili; retraction of one type (designated IV) through their outer membranes can move them around. Alternatively, they can secrete carbohydrate slime rearward to get a push (Kaiser 2000; Merz and Forest 2002).” (Vogel 2003:450)

Last Updated May 31, 2018

References

Book

Comparative Biomechanics: Life's Physical World, Second Edition

Princeton University Press | 17/06/2013 | Steven Vogel

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Reference

“It has been known for decades that bacteria locomote over surfaces, but the mechanisms that power motility have been unclear. Recent experiments have begun to explain two modes of surface motility. Twitching or social gliding motility is powered by the retraction of type IV pili. Adventurous gliding motility is powered by the rearward secretion of carbohydrate slime. In both cases, cell movement depends on the translocation of enormous volumes of macromolecules through outer membrane pore complexes…Several mechanisms have been proposed to account for gliding motility including treadmill-like motors on the cell surface and secretion of surfactants that draw the cell forward. Recent experiments support another idea: that the gliding of filamentous bacteria — linked chains of dozens to hundreds of cells — is powered by compressive forces arising from the rearward secretion of slime, a polyelectrolyte gel composed of complex carbohydrates.” (Merz et al. 2002:R297)

Journal article

Bacterial surface motility: slime trails, grappling hooks, and nozzles

Current Biology, Vol. 12, R297–R303 | Merz, AJ; Forest, KT

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Reference

Journal article

Bacterial motility: how do pili pull?

Volume 10, Issue 21, Pages R777-R780 | Kaiser, D

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