Prokaryotes are one of the most diverse kinds of organisms on Earth, and they make up a large part of the ecosystem.
They play key roles in cycling nutrients through the planet’s ecosystem, including in the carbon cycle (see figure below). Some prokaryotes use photosynthesis to capture energy from sunlight, while others fix atmospheric carbon dioxide into organic compounds that plants can use.
The chemistry of their metabolism is also quite varied, allowing them to thrive in harsh environments as cold as Antarctica and as hot as hydrothermal vents on land or undersea. This diversity makes prokaryotes a vital component of life on earth.
Prokaryotes contribute to plant health through interactions with other species within a community. These interactions may be cooperative, which benefit the species involved, or competitive, in which the two groups compete for resources.
Besides providing a wide range of essential nutrients, prokaryotes also help to protect plants from harmful environmental agents. For example, some plants in the legume family have symbioses with nitrogen-fixing bacteria. These bacteria convert atmospheric nitrogen into ammonia, which plants can incorporate into organic molecules.
These symbiotic relationships are beneficial to both parties, and they are called mutualisms. Other symbiotic relationships involve organisms that live together within a single body, such as those found in the human gut.
Some prokaryotes, especially those that are members of the bacteria domain, have flagella, tail-like structures that help the cell move around. They also have pili, small hair-like structures that assist in cellular attachment and DNA transfer.