Prochlorophyta | |
---|---|
Scientific classification | |
Domain: | |
Phylum: | |
Order: | Prochlorales Lewin, 1977 |
Synonyms | |
|
Prochlorophyta is a group of photosynthetic bacteria, an important component of picoplankton. [1] These oligotrophic organisms are abundant in nutrient poor tropical waters and use a unique photosynthetic pigment, divinyl-chlorophyll, to absorb light and acquire energy. [1] [2] [3] Prochlorophyta lack red and blue phycobilin pigments and have stacked thylakoids, making them distinctly different from Cyanobacteria (or Cyanophyta), [2] but some authors consider them as part of the Cyanobacteria, as the group Prochlorales.
This unique group of phytoplankton, with no phycobilin pigments, were initially found in 1975 near the Great Barrier Reef [4] and off the coast of Mexico ( Prochloron ). [5] Prochlorophyta was soon assigned as a new algal sub-class in 1976 by Ralph A. Lewin of the Scripps Institution of Oceanography. [6] [7] Other phytoplankton that lacked phycobilin pigments were later found in freshwater lakes in the Netherlands by Tineke Burger-Wiersma and colleagues [8] and were termed Prochlorothrix (additional reading on Prochlorothrix can be found in a journal article by A.V. Pinevich [9] ). In 1986 Prochlorococcus was found by Sallie W. (Penny) Chisholm and colleagues. [10] Prochlorococcus may be responsible for a significant portion of the global primary production.
Prochlorophytes are very small microbes generally between 0.2 and 2 μm (photosynthetic picoplankton). They morphologically resemble Cyanobacteria (formally known as Blue Green Algae). Members of Prochlorophyta have been found as coccoid (spherical) (Coccus) shaped, as in Prochlorococcus , and as filaments, as in Prochlorothrix.
A photosynthetic pigment is a pigment that is present in chloroplasts or photosynthetic bacteria and captures the light energy necessary for photosynthesis.
An algal bloom or algae bloom is a rapid increase or accumulation in the population of algae in freshwater or marine water systems. It is often recognized by the discoloration in the water from the algae's pigments. The term algae encompasses many types of aquatic photosynthetic organisms, both macroscopic multicellular organisms like seaweed and microscopic unicellular organisms like cyanobacteria. Algal bloom commonly refers to the rapid growth of microscopic unicellular algae, not macroscopic algae. An example of a macroscopic algal bloom is a kelp forest.
Phytoplankton are the autotrophic (self-feeding) components of the plankton community and a key part of ocean and freshwater ecosystems. The name comes from the Greek words φυτόν, meaning 'plant', and πλαγκτός, meaning 'wanderer' or 'drifter'.
Cyanobacteria, also called Cyanobacteriota or Cyanophyta, are a phylum of autotrophic gram-negative bacteria that can obtain biological energy via oxygenic photosynthesis. The name "cyanobacteria" refers to their bluish green (cyan) color, which forms the basis of cyanobacteria's informal common name, blue-green algae, although as prokaryotes they are not scientifically classified as algae.
Prochlorococcus is a genus of very small (0.6 μm) marine cyanobacteria with an unusual pigmentation. These bacteria belong to the photosynthetic picoplankton and are probably the most abundant photosynthetic organism on Earth. Prochlorococcus microbes are among the major primary producers in the ocean, responsible for a large percentage of the photosynthetic production of oxygen. Prochlorococcus strains, called ecotypes, have physiological differences enabling them to exploit different ecological niches. Analysis of the genome sequences of Prochlorococcus strains show that 1,273 genes are common to all strains, and the average genome size is about 2,000 genes. In contrast, eukaryotic algae have over 10,000 genes.
Chlorophyll a is a specific form of chlorophyll used in oxygenic photosynthesis. It absorbs most energy from wavelengths of violet-blue and orange-red light, and it is a poor absorber of green and near-green portions of the spectrum. Chlorophyll does not reflect light but chlorophyll-containing tissues appear green because green light is diffusively reflected by structures like cell walls. This photosynthetic pigment is essential for photosynthesis in eukaryotes, cyanobacteria and prochlorophytes because of its role as primary electron donor in the electron transport chain. Chlorophyll a also transfers resonance energy in the antenna complex, ending in the reaction center where specific chlorophylls P680 and P700 are located.
Accessory pigments are light-absorbing compounds, found in photosynthetic organisms, that work in conjunction with chlorophyll a. They include other forms of this pigment, such as chlorophyll b in green algal and vascular ("higher") plant antennae, while other algae may contain chlorophyll c or d. In addition, there are many non-chlorophyll accessory pigments, such as carotenoids or phycobiliproteins, which also absorb light and transfer that light energy to photosystem chlorophyll. Some of these accessory pigments, in particular the carotenoids, also serve to absorb and dissipate excess light energy, or work as antioxidants. The large, physically associated group of chlorophylls and other accessory pigments is sometimes referred to as a pigment bed.
Photosynthetic picoplankton or picophytoplankton is the fraction of the photosynthetic phytoplankton of cell sizes between 0.2 and 2 μm. It is especially important in the central oligotrophic regions of the world oceans that have very low concentration of nutrients.
Synechococcus is a unicellular cyanobacterium that is very widespread in the marine environment. Its size varies from 0.8 to 1.5 μm. The photosynthetic coccoid cells are preferentially found in well–lit surface waters where it can be very abundant. Many freshwater species of Synechococcus have also been described.
Picocystis is a monotypic genus of green algae, the sole species is Picocystis salinarum. It is placed within its own class, Picocystophyceae in the division Chlorophyta.
Picoeukaryotes are picoplanktonic eukaryotic organisms 3.0 μm or less in size. They are distributed throughout the world's marine and freshwater ecosystems and constitute a significant contribution to autotrophic communities. Though the SI prefix pico- might imply an organism smaller than atomic size, the term was likely used to avoid confusion with existing size classifications of plankton.
Bacterioplankton refers to the bacterial component of the plankton that drifts in the water column. The name comes from the Ancient Greek word πλανκτος, meaning "wanderer" or "drifter", and bacterium, a Latin term coined in the 19th century by Christian Gottfried Ehrenberg. They are found in both seawater and freshwater.
Pediastrum duplex is a species of fresh water green algae in the genus Pediastrum. It is the type species of the genus Pediastrum.
Prochloron is a genus of unicellular oxygenic photosynthetic prokaryotes commonly found as an extracellular symbiont on coral reefs, particularly in didemnid ascidians. Part of the phylum cyanobacteria, it was theorized that Prochloron is a predecessor of the photosynthetic components, chloroplasts, found in photosynthetic eukaryotic cells. However this theory is largely refuted by phylogenetic studies which indicate Prochloron is not on the same line of descent that lead to chloroplast-containing algae and land plants.
Akashiwo sanguinea is a species of marine dinoflagellates well known for forming blooms that result in red tides. The organism is unarmored (naked). Therefore, it lacks a thick cellulose wall, the theca, common in other genera of dinoflagellates. Reproduction of the phytoplankton species is primarily asexual.
Anthony William Derek Larkum is a British plant scientist and academic based in Sydney. He is professor emeritus of plant sciences at the University of Sydney and adjunct professor at the University of Technology Sydney (UTS).
William Li is a Canadian biological oceanographer who did research on marine picoplankton, marine macroecology, ocean surveys of plankton from measurements of flow cytometry, and detection of multi-annual ecological change in marine phytoplankton.
Marine primary production is the chemical synthesis in the ocean of organic compounds from atmospheric or dissolved carbon dioxide. It principally occurs through the process of photosynthesis, which uses light as its source of energy, but it also occurs through chemosynthesis, which uses the oxidation or reduction of inorganic chemical compounds as its source of energy. Almost all life on Earth relies directly or indirectly on primary production. The organisms responsible for primary production are called primary producers or autotrophs.
Greta Albrecht Fryxell was a marine scientist known for her work on the biology and taxonomy of diatoms. In 1996, she was elected a fellow of the American Association for the Advancement of Science.
Linda Karen Medlin is a molecular biologist known for her work on diatoms. She is an elected member of the Norwegian Academy of Science and Letters.