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Heliobacteria are a unique subset of prokaryotic bacteria that process light for energy. Distinguishable from other phototrophic bacteria, they utilize a unique photosynthetic pigment, bacteriochlorophyll g and are the only known Gram-positive phototroph. They are a key player in symbiotic nitrogen fixation alongside plants, and use a type I reaction center like green-sulfur bacteria.
Purple bacteria or purple photosynthetic bacteria are Gram-negative proteobacteria that are phototrophic, capable of producing their own food via photosynthesis. They are pigmented with bacteriochlorophyll a or b, together with various carotenoids, which give them colours ranging between purple, red, brown, and orange. They may be divided into two groups – purple sulfur bacteria and purple non-sulfur bacteria. Purple bacteria are anoxygenic phototrophs widely spread in nature, but especially in aquatic environments, where there are anoxic conditions that favor the synthesis of their pigments.
In taxonomy, Ruegeria is a genus of the Rhodobacteraceae. This genus was formerly known as the marine Agrobacterium before they were reclassified in 1998. It bears in fact the name of Hans-Jürgen Rüger, a German microbiologist, for his contribution to the taxonomy of marine species of Agrobacterium.
In taxonomy, Roseobacter is a genus of the Rhodobacteraceae. The Roseobacter clade falls within the {alpha}-3 subclass of the class Alphaproteobacteria. The first strain descriptions appeared in 1991 which described members Roseobacterlitoralis and Roseobacterdenitrificans, both pink-pigmented bacteriochlorophyll a-producing strains isolated from marine algae. The role members of the Roseobacter lineage play in marine biogeochemical cycles and climate change cannot be overestimated. Roseobacters make up 25% of coastal marine bacteria and members of this lineage process a significant portion of the total carbon in the marine environment. Roseobacter clade plays an important role in global carbon and sulphur cycles. It can also degrade aromatic compounds, uptake trace metal, and form symbiotic relationship. In term of its application, Roseobacter clade produces bioactive compounds, has been used widely in aquaculture and quorum sensing.
Aerobic anoxygenic phototrophic bacteria (AAPBs) are Alphaproteobacteria and Gammaproteobacteria that are obligate aerobes that capture energy from light by anoxygenic photosynthesis. Anoxygenic photosynthesis is the phototrophic process where light energy is captured and stored as ATP. The production of oxygen is non-existent and, therefore, water is not used as an electron donor. They are widely distributed marine bacteria that may constitute over 10% of the open ocean microbial community. They can be particularly abundant in oligotrophic conditions where they were found to be 24% of the community. Aerobic anoxygenic phototrophic bacteria are photoheterotrophic (phototroph) microbes that exist in a variety of aquatic environments. Most are obligately aerobic, meaning they require oxygen to grow. One aspect of these bacteria is that they, unlike other similar bacteria, are unable to utilize BChl (bacteriochlorophyll) for anaerobic growth. The only photosynthetic pigment that exists in AAPB is BChl-a. Anaerobic phototrophic bacteria, on the contrary, can contain numerous species of photosynthetic pigments like bacteriochlorophyll-a. These bacteria can be isolated using carotenoid presence and medias containing organic compounds. Predation, as well as the availability of phosphorus and light, have been shown to be important factors that influence AAPB growth in their natural environments. AAPBs are thought to play an important role in carbon cycling by relying on organic matter substrates and acting as sinks for dissolved organic carbon. There is still a knowledge gap in research areas regarding the abundance and genetic diversity of AAPB, as well as the environmental variables that regulate these two properties.
Rhodovulum sulfidophilum is a gram-negative purple nonsulfur bacteria. The cells are rod-shaped, and range in size from 0.6 to 0.9 μm wide and 0.9 to 2.0 μm long, and have a polar flagella. These cells reproduce asexually by binary fission. This bacterium can grow anaerobically when light is present, or aerobically (chemoheterotrophic) under dark conditions. It contains the photosynthetic pigments bacteriochlorophyll a and of carotenoids.
Chlorobaculum tepidum, previously known as Chlorobium tepidum, is an anaerobic, thermophilic green sulfur bacteria first isolated from New Zealand. Its cells are gram-negative and non-motile rods of variable length. They contain chlorosomes and bacteriochlorophyll a and c.
Roseobacter denitrificans is a species of aerobic pink-pigmented bacteria. It contains Bacteriochlorophyll a. It contains spheroidenone, does not synthesize bacteriochlorophyll anaerobically, but shows aerobic phototrophic activity. Cells are ovoid or rod-shaped and motile by subpolar flagella. R. litoralis does not reduce nitrate, while R. denitrificans does.
Erythrobacter longus is a species of bacteria, the genus' type species. It contains bacteriochlorophyll a. It is motile by means of subpolar flagella. Its type strain is OCh101.
Roseococcus thiosulfatophilus is a species of bacterium, the type species of its genus.
Erythrobacter ramosus is a species of bacterium.
Erythrobacter litoralis is a species of bacterium. E. litoralis strain HTCC2594 was first sequenced in 2009. Erythrobacter litoralis strain DSM 8509 was developed as a comparative genetic model system to investigate the role of visible light in regulation of the general stress response in Alphaproteobacteria. The complete genome sequence of E. litoralis DSM 8509 has been published.
Roseivivax halotolerans is a species of bacteria. It is aerobic and bacteriochlorophyll-containing, first isolated from the epiphytes on the stromatolites of a saline lake located on the west coast of Australia. It is chemoheterotrophic, Gram-negative, motile, rod-shaped and with subpolar flagella. Its type strain is OCh 210T.
Congregibacter litoralis KT71 is a gram-negative Gammaproteobacteria part of the NOR5/OM60 Clade discovered in seawater from Heligoland, an island in the North Sea by H. Eilers from the Max Planck Institute for Microbiology. C. litoralis KT71 is described as a pleomorphic bacterium and has a size of 2 x 0.5 μm. When grown in culture, C. litoralis KT71 has a generation time of 4.5 hours and prefers to grow on complex substrates where the sole carbon source is undefined, though it can utilize some sole carbon sources because they are most likely used by the organism for its central metabolism.
Salinibacter ruber is an extremely halophilic red bacterium, first found in Spain in 2002.
Qipengyuania citrea is a Gram-negative, strictly aerobic, rod-shaped and non-motile bacteria from the genus Qipengyuania which has been isolated from the Bay of Calvi from the Mediterranean Sea near Corsica.
Mary Ann Moran is a distinguished research professor of marine sciences at the University of Georgia in Athens. She studies the role of bacteria in Earth's marine nutrient cycles, and is a leader in the fields of marine sciences and biogeochemistry. Her work is focused on how microbes interact with dissolved organic matter and the impact of microbial diversity on the global carbon and sulfur cycles. By defining the roles of diverse bacteria in the carbon and sulfur cycles, she connects the biogeochemical and organismal approaches in marine science.
Dinoroseobacter shibae is a facultative anaerobic anoxygenic photoheterotroph belonging to the family, Rhodobacteraceae. First isolated from washed cultivated dinoflagellates, they have been reported to have mutualistic as well as pathogenic symbioses with dinoflagellates.
Nitrospinota is a bacterial phylum. Despite only few described species, members of this phylum are major nitrite-oxidizing bacteria in surface waters in oceans. By oxidation of nitrite to nitrate they are important in the process of nitrification in marine environments.
Alison Buchan is the Carolyn Fite Professor at the University of Tennessee. She is known for her work on bacteria in natural environments, especially bacteria within the Roseobacter group. In 2022 she was named as a fellow of the American Academy of Microbiology.
References
- ↑ Shiba, Tsuneo (1991). "Roseobacter litoralis gen. nov., sp. nov., and Roseobacter denitrificans sp. nov., Aerobic Pink-Pigmented Bacteria which Contain Bacteriochlorophyll a". Systematic and Applied Microbiology. 14 (2): 140–145. doi:10.1016/S0723-2020(11)80292-4. ISSN 0723-2020.
- ↑ Nojiri, Akane; Ogita, Shinjiro; Isogai, Yasuhiro; Nishida, Hiromi (2015). "Characterization of giant spheroplasts generated from the aerobic anoxygenic photosynthetic marine bacterium Roseobacter litorali". The Journal of General and Applied Microbiology: 61(2), 44–49. doi: 10.2323/jgam.61.44 .