Microbes Aggregate Sediment

closer view of a stromatolite rocks with algae layers in clear waters with sand below in the sunlight

Biological Strategy

Cyanobacteria

AskNature Team

Image: Paul Morris / Flickr / CC BY - Creative Commons Attribution alone

Capture, Absorb, or Filter Solids

Some living systems must secure solid particles such as sediment, usually to keep the particles from hindering their health or activity. The most common way in which they do this is through filtering. To be effective, a filtering system must be appropriate to the sizes of solid particles to be captured and must capture only what is needed. It must also be effective in the appropriate media–air, water, or sometimes solids like soil. An example is mangroves, which are trees that grow along ocean coasts. Their root system slows down and settles sediment out of the water, building up soil to support the mangrove ecosystem.

Search this Function

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.

Search this Living System

Cyanobacteria grow large layered clumps of rock and algae, called stromatolites, by trapping sediment in mucus and filaments.

Image: C. Eeckhout /

“Half dead, half alive, stromatolites represent a partnership between microorganisms and rock. The spongy coating is made of cyanobacterial filaments that secrete a sticky mucus. Grains of sediment get trapped in the mucus and stick together to form a crust of rock. As the filaments grow longer, they trap more sediment and add a new layer to the exterior. What’s left on the inside is dead zone.” (Monastersky 1998:74)

Last Updated September 14, 2016

References

Magazine article

AskNature