Marine microorganisms
Definition of Marine microorganisms:
Marine microorganisms comprise the microscopic cellular organisms that occur in seawater, marine sediments, biofilms and on or within marine organisms. They include bacteria, archaea and a great diversity of microscopic eukaryotes. Viruses are acellular, but are generally included in marine microbiology because of their abundance and ecological importance.
This is the common definition for Marine microorganisms, other definitions can be discussed in the article
|
Notes
Marine microorganisms do not form a single taxonomic group. The term covers organisms from several fundamentally different branches of the tree of life. Cellular microorganisms are commonly classified as Bacteria, Archaea and Eukaryota. Viruses are acellular and are therefore shown separately in Fig. 1.
Bacteria and archaea are collectively referred to as Prokaryotes because their cells lack a membrane-bound nucleus. Bacteria include photosynthetic cyanobacteria as well as many heterotrophic and chemotrophic groups. Archaea are evolutionarily distinct from bacteria. Their cell membranes contain distinctive lipids, while their DNA replication, transcription and translation machinery has several features more similar to that of eukaryotes than to that of bacteria. Methanogenesis—the biological production of methane—is found only among archaea, although most archaea are not methanogens.
Eukaryotic microorganisms have cells containing a nucleus and membrane-bound organelles. They include microalgae, heterotrophic and mixotrophic protists, microscopic fungi, microscopic animals and microscopic life stages of larger animals. The commonly used term protists is a convenient collective name for diverse, predominantly unicellular eukaryotes, but they do not constitute a single evolutionary lineage.
Fig. 1 shows several major eukaryotic lineages that contain important marine microorganisms. The well-supported SAR lineage comprises Stramenopiles, Alveolates and Rhizarians and includes diatoms, dinoflagellates, ciliates, foraminifera and radiolarians. Haptista includes the haptophytes, among which are the coccolithophores. Cryptista includes cryptophytes and related flagellates. Archaeplastida includes green and red microalgae.
Fungi, animals and their closest unicellular relatives belong to Opisthokonta. They are shown together in Fig. 1 because of this evolutionary relationship, not because fungi are animals. Choanoflagellates are unicellular opisthokonts closely related to animals but are not themselves animals.
Telonemia comprises small heterotrophic flagellates occurring in marine and freshwater environments. Phylogenomic analyses generally place Telonemia as the closest known relative of SAR, together forming the grouping TSAR. However, the deeper relationships of TSAR, Haptista and several other major eukaryotic lineages are not yet fully resolved. The deep evolutionary position of Cryptista is also uncertain; it is often recovered close to Archaeplastida but is shown separately in Fig. 1.[1][2][3]
Fig. 1 is a simplified orientation to the principal groups commonly referred to as marine microorganisms, not a complete phylogenetic tree. More information about these organisms, their feeding modes and their relationships in marine food webs is given in the article Marine Plankton.
Related articles
- Marine Plankton
- Nutrient conversion in the marine environment
- Measurements of biodiversity
- Plankton bloom
- Microbial loop
References
- ↑ Adl, S.M., Bass, D., Lane, C.E., Lukeš, J., Schoch, C.L., Smirnov, A., Agatha, S., Berney, C., Brown, M.W., Burki, F., Cárdenas, P., Čepička, I., Chistyakova, L., Del Campo, J., Dunthorn, M., Edvardsen, B., Eglit, Y., Guillou, L., Hampl, V., Heiss, A.A., Hoppenrath, M., James, T.Y., Karnkowska, A., Karpov, S., Kim, E., Kolisko, M., Kudryavtsev, A., Lahr, D.J.G., Lara, E., Le Gall, L., Lynn, D.H., Mann, D.G., Massana, R., Mitchell, E.A.D., Morrow, C., Park, J.S., Pawlowski, J.W., Powell, M.J., Richter, D.J., Rueckert, S., Shadwick, L., Shimano, S., Spiegel, F.W., Torruella, G., Youssef, N., Zlatogursky, V. and Zhang, Q. 2019. Revisions to the classification, nomenclature, and diversity of eukaryotes. Journal of Eukaryotic Microbiology 66: 4–119
- ↑ Burki, F., Roger, A.J., Brown, M.W. and Simpson, A.G.B. 2020. The new tree of eukaryotes. Trends in Ecology & Evolution 35: 43–55
- ↑ Strassert, J.F.H., Jamy, M., Mylnikov, A.P., Tikhonenkov, D.V. and Burki, F. 2019. New phylogenomic analysis of the enigmatic phylum Telonemia further resolves the eukaryote tree of life. Molecular Biology and Evolution 36: 757–765
