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Microorganisms have key roles in carbon and nutrient cycling, animal (including human) and plant health, agriculture and the global food web. Microorganisms live in all environments on Earth that are occupied by macroscopic organisms, and they are the sole life forms in other environments, such as the deep subsurface and ‘extreme’ environments.
In the ocean, animal–microbial relationships were historically explored in single host–symbiont systems. However, new explorations into the diversity of marine microorganisms associating with diverse marine animal hosts is moving the field into studies that address interactions between the animal host and a more multi-member microbiome .
Pelagibacter ubique and its relatives may be the most abundant microorganisms in the ocean, and it has been claimed that they are possibly the most abundant bacteria in the world. They make up about 25% of all microbial plankton cells, and in the summer they may account for approximately half the cells present in temperate ocean surface water.
Life originated as marine single-celled prokaryotes (bacteria and archaea) and later evolved into more complex eukaryotes. Eukaryotes are the more developed life forms known as plants, animals, fungi and protists. Protists are the eukaryotes that cannot be classified as plants, fungi or animals. They are mostly single-celled and microscopic.
This process can be entirely abiotic or facilitated by microorganisms, especially iron-oxidizing bacteria. The abiotic processes include the rusting of iron-bearing metals, where Fe 2+ is abiotically oxidized to Fe 3+ in the presence of oxygen, and the reduction of Fe 3+ to Fe 2+ by iron-sulfide minerals.
The pelagic food web, showing the central involvement of marine microorganisms in how the ocean imports nutrients from and then exports them back to the atmosphere and ocean floor. A marine food web is a food web of marine life. At the base of the ocean food web are single-celled algae and other plant-like organisms known as phytoplankton.
Bacteria. In the microbial food web, bacteria play a crucial role in breaking down organic materials and recycling nutrients. They transform DOC into bacterial biomass so that protists and other higher trophic levels can consume it. Additionally, bacteria take part in the nitrogen and carbon cycles, among other biogeochemical cycles. [4] Algae
A schematic showing the cycling of nitrogen within the ocean. The nitrogen cycle in the oceans is mediated by microorganisms, many of which are bacteria, performing multiple conversions such as: nitrogen fixation, denitrification, assimilation, and anaerobic ammonia oxidation . There are many different nitrogen metabolism strategies employed by ...