- characteristics
- Types of phototrophic or photosynthetic bacteria
- -Photrophs
- Sulfur red bacteria of the family
- Sulfur red bacteria of the Family
- Green sulfurous bacteria of the Family
- Non-sulfurous filamentous green bacteria of the Family
- Non-sulfurous red bacteria of the Family
- Family unsulfurized red bacteria
- Family unsulfurized red bacteria
- Other genera of anoxygenic bacteria
- -Oxygenic photosynthetic
- References
The phototrophic are microorganisms that obtain chemical energy using sunlight (light energy). They are divided into photoautotrophs and photoheterotrophs according to the carbon source they use.
Photoautotrophs are those that use sunlight as a source of energy and use CO2 as the main source of carbon. While photoheterotrophs also use light as an energy source, but they use organic compounds as a carbon source.
Filaments of Cyanobacteria Genus Lyngbya (Oxygenic Photosynthetic-type Bacteria)
These bacteria play a fundamental role in microbial ecology, especially in the biogeochemical cycles of sulfur and carbon, making the most of the different forms in which these elements are found in nature.
In addition to the above classification they are also divided into oxygenic phototrophs and anoxygenic phototrophs. Cyanobacteria are known as oxygenic phototrophs, while anoxygenic ones include red and green bacteria (sulfurous and non-sulfurous).
Sulfuroes are generally photolithoautotrophic, although some can grow photoorganoheterotrophic, but still require small amounts of H 2 S, while non-sulfurous are photoheterotrophic.
On the other hand, most sulfurous bacteria are anaerobic, although oxygen is not toxic to them, they just don't use it.
In the case of non-sulfur bacteria, they are generally facultative aerobes, depending on the conditions, that is, if there is light and anaerobiosis, the process to be carried out will be photosynthesis, but if there is aerobiosis they will do aerobic respiration, regardless of whether there is light or not.
It is important to note that the compound that captures photons of light in these bacteria is called bacteriochlorophyll.
characteristics
The different types of photosynthetic bacteria are widely distributed in aquatic ecosystems, but also in terrestrial ecosystems with extreme conditions such as hypersaline, acidic, alkaline and hydrothermal vents, among others.
These microorganisms have been little studied, due to some drawbacks, such as the difficulty in obtaining and preserving pure cultures. However, various techniques have now been developed for this purpose. Among them is the Pour plate technique.
Types of phototrophic or photosynthetic bacteria
-Photrophs
Anoxygenic phototrophic bacteria are a very diverse group of microorganisms with photosynthetic capacity, which inhabit anaerobic zones (without oxygen) of aquatic systems mostly, with exposure to sunlight.
The following families belong to this group of microorganisms: Chlorobiaceae (sulphurous greens), Chloroflexaceae (non-sulphurous green), Rhodospirillaceae (non-sulphurous red), Ectothiorhodospiraceae and Chromatiaceae (both sulphurous red).
Sulfur red bacteria of the family
They are strictly anaerobic, therefore they use sulfur-derived compounds such as Na 2 S, S, thiosulfate, sulfide, molecular hydrogen or simple low molecular weight organic compounds as electron donors.
They can have various morphologies, including: spiral (Thiospirillum), bacilli (Chromatium), ovoid or vibrioid (Thiopedia); they are arranged in space as individual cells or in pairs, and are motile due to flagella, sliding, or gas vacuoles.
Some of its species contain bacteriochlorophyll a and others b. They may also have carotenoid pigments of the spiriloxanthine, okenone, and rhodopinal series. These have the function of protection against photo-oxidation.
Additionally, they have the ability to accumulate sulfur intracellularly.
Sulfur red bacteria of the Family
These are unable to store sulfur intracellularly as do those of the Chromatiaceae Family. Their morphology is in the form of Vibrios, they are arranged in an isolated way in space and they are mobile.
These bacteria are important for their participation in the carbon and sulfur cycle, and also for serving as food for various aquatic organisms.
Green sulfurous bacteria of the Family
They are a group of microorganisms that carry out anoxygenic photosynthesis that inhabit areas rich in sulfur and anaerobic in lakes.
They are photolithoautotrophic and obligate anaerobic, most are immobile, but some can move due to the presence of flagella.
While others contain gas vesicles that allow you to adjust the appropriate depth in the lakes (areas without oxygen) and also obtain the necessary amount of light and H 2 S.
The immobile ones live in the bottoms of the lakes, specifically in the muddy muds rich in sulfur.
The reason why they can live at great depths is thanks to chlorosomes, which allow them to grow at lower light intensity than red bacteria, and also because of their ability to withstand high concentrations of sulfur with ease.
They present diverse morphologies, among them: straight bacilli, cocci and vibrios. They are distributed singly or in chains and can be grass green or chocolate brown.
They fix CO 2, via the reverse Krebs cycle. In addition to the genus Chlorobium (Vibrios) there are 2 more genera: Pelodyction (straight bacilli) and Prosthecochloris (Cocoides).
Non-sulfurous filamentous green bacteria of the Family
They are shaped like straight rods and are arranged in filaments. The genus Chloronema has gas vesicles.
They fix CO 2 via the hydroxypropionate. They move by sliding their filaments. In relation to oxygen they are optional.
Most live in lakes or hot springs at temperatures between 45 to 70 ° C, that is, they are thermophilic.
Both Chloroflexus and Chloronema are hybrids, since they have chlorosomes like green bacteria, but their reaction center is the same as that of red bacteria.
Non-sulfurous red bacteria of the Family
They are the most changeable in terms of their metabolism, because although they prefer aquatic environments rich in soluble organic matter, with low concentrations of oxygen and well lit, they can also carry out photosynthesis under anaerobic conditions.
On the other hand, they can also grow chemoheterotrophically in the dark, since they are capable of using a wide repertoire of organic compounds as carbon and / or energy sources.
They are mobile because they have a polar flagellum and are divided by binary fission. These types of bacteria are currently very useful, especially in areas such as biotechnology and medicine.
Its most frequent uses are in processes of bioremediation of contaminated water and soils, in the production of biofertilizers and herbicides, since it has been observed that they produce active substances such as vitamin B12, ubiquinone and 5-aminolevulinic acid, among others.
For the isolation of these bacteria they require special culture media, with 30 days of incubation at room temperature with light and dark cycle ranges of 16/8 respectively, using incandescent lamps (2,200 lux).
Family unsulfurized red bacteria
They are straight, mobile bacilli with a polar flagellum, which divide by binary fission. These bacteria are facultative in terms of oxygen, in aerobiosis they inhibit photosynthesis but in anaerobiosis they do it.
They can also photo-assimilate a wide variety of organic compounds, such as sugars, organic acids, amino acids, alcohols, fatty acids, and aromatic compounds.
Family unsulfurized red bacteria
They have ovoid morphology, are mobile by peritric flagella and are divided by budding. They also have prosteca, that is, extensions of the cytoplasm and the cell wall, whose function is to increase the surface of the microorganism and thus get more food.
It also has exospores (spores that are formed externally).
Other genera of anoxygenic bacteria
Among them are Heliobacteria, Erythrobacter and Chloroacidobacterium.
Heliobacteria fix nitrogen very well and are abundant in tropical soils providing this element. They are essential in some types of crops, for example in rice fields.
Erythrobacter is of little importance.
Chloroacidobacterium closely resembles the photosynthetic apparatus of sulfurous green bacteria with chlorosomes.
-Oxygenic photosynthetic
Cyanobacteria possess chlorophyll, as well as accessory pigments carotenoids and phycobiliproteins.
Pigments involved in photophosphorylation reactions (conversion of light energy to chemical energy) are called reaction center pigments. Surrounding these pigments are pigments called antennae, which act as collectors of light.
In this group are cyanobacteria, which are photoautotrophs. Among the most important are the genus Prochlorococcus, which is the most abundant and smallest photosynthetic organism in the marine world.
On the other hand, there is the genus Synechococcus, abundant in surface waters and, like Prochlorococcus, are part of the marine picoplankton.
References
- Santamaría-Olmedo M, García-Mena J, and Núñez-Cardona M. Isolation and Study of Phototrophic Bacteria of the Chromatiaceae Family that inhabit the Gulf of Mexico. III Meeting, Participation of Women in Science.
- Wikipedia Contributors, "Prosteca," Wikipedia, The Free Encyclopedia, es.wikipedia.org/
- Cottrell MT, Mannino A, Kirchman DL. Aerobic anoxygenic phototrophic bacteria in the Mid-Atlantic Bight and the North Pacific Gyre. Appl Environ Microbiol. 2006; 72 (1): 557-64.
- "Prochlorococcus." Wikipedia, The Free Encyclopedia. 28 Apr 2018, 20:55 UTC. Nov 30, 2018. es.wikipedia.org/
- Synechococcus. »Wikipedia, The Free Encyclopedia. 15 Nov 2018, 12:52 UTC. 30 Nov 2018, 06:16. Taken from es.wikipedia.org
- "Photoautotroph." Wikipedia, The Free Encyclopedia. 18 Aug 2018, 21:45 UTC. Nov 30, 2018. Taken from es.wikipedia.org
- González M, González N. Manual of Medical Microbiology. 2nd edition, Venezuela: Directorate of media and publications of the University of Carabobo; 2011.