Nitrogen Fixed for Termites

3d image of green spiraled bacteria with white spots

Biological Strategy

Bacteria

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Capture, Absorb, or Filter Chemical Entities

Living systems often require chemical elements and chemical compounds, including complex sugars, proteins, and odor-making compounds, to perform critical activities. These compounds exist in various states–solid, liquid, and gas–and are ubiquitous in soil, water, and air. This requires that living systems not only have ways to capture, absorb, or filter them, but also ways to differentiate among them, selecting those that are valuable or harmful. For example, mangrove trees live with their roots in salty water and sediments. Various mangrove species have different strategies for removing salt from the water they take in so that their tissues can use the fresh water.

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Capture, Absorb, or Filter Gases

Oxygen, carbon dioxide, and nitrogen are all gases of particular importance to living systems. Living systems obtain these gases from water and air by trapping them, absorbing them across surfaces, or filtering them. Gases are low in density and viscosity, and when dissolved in liquids, are very low in concentration–so extracting them requires specialized strategies. As a result, living systems use the properties of gases, liquids, and solids to assist in capture, absorption, and filtering. For example, fish gills have many filaments to create a large surface area to maximize how many blood vessels come in close contact with oxygen dissolved in the water.

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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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Spirochete bacteria found in the hindgut of termites fix atmospheric nitrogen for termite nutrition via nitrogenase enzymes.

“Our results reveal a new dimension to the metabolic diversity within the Spirochaetes and now extend to 6 (of 18) the number of phyla within the domain Bacteria that contain N2-fixing representatives (11, 25). They also reveal a role for spirochetes in termite nitrogen nutrition. Two observations suggest that N2 fixation by spirochetes is important to termite nitrogen economy. First, spirochetes are unusually abundant in termite guts, accounting for as much as 50% of all prokaryotes (26). Second, many of the spirochete NifHs characterized in this study were identical or nearly identical to NifH clones obtained from a variety of termites, including NiMs known to be expressed in termite guts (Fig. 2), suggesting a spirochete origin for the latter…Our results also reveal a heretofore unrecognized role for free-living spirochetes in global N cycling.” (Lilburn et al. 2001:2497)

Last Updated March 23, 2018

References

Journal article

Nitrogen fixation by symbiotic and free-living spirochetes

Science, 292(5526): 2495-2498 | 29/06/2001 | Lilburn TG; Kim KS; Ostrom NE; Byzek KR; Leadbetter JR; Breznak JA

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