Azotobacter salinestris

Last updated

Azotobacter salinestris
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Bacteria
Phylum: Pseudomonadota
Class: Gammaproteobacteria
Order: Pseudomonadales
Family: Pseudomonadaceae
Genus: Azotobacter
Species:
A. salinestris
Binomial name
Azotobacter salinestris
Page and Shivprasad, 1991 [1]

Azotobacter salinestris [2] is a Gram-negative, nitrogen-fixing bacterium; its specific name, salinestris, comes from the Latin words salinus meaning saline and estris which means "living in". [2] It can be found living in soil or marine habitats as single cells or in chains of six to eight cells. [2] This organism is motile at younger stages, but loses its flagella at older stages. [2] This species is known for its potential use in bioremediation. [3]

Contents

Isolation

William J. Page and Shailaja Shivprasad isolated A. salinestris from saline soils. [2] The colonies used for their study were first taken from air-dried surface soil from Alberta, Canada. [4] The soil was inoculated into a Burk nitrogen-free mineral-salt medium, which contained 1% glucose and 0.25 micrograms of copper(I) chloride per milliliter of solution. [2] The medium was incubated at 30 °C and stored at 4 °C. [2] Colony formation was noted after 2–3 days of incubation. [2] The same soil samples were also used to inoculate slant cultures, which were stored at room temperature. [2] A. salinestris was found to lose viability in the slant cultures when stored at 4 °C. [2] Through these cultures and characterization tests, A. salinestris was found to share many of the general characteristics specific to the species Azotobacter. [2] Originally, A. salinestris colonies were classified as Azotobacter chroococcum , but were later identified as a separate species based on their salt-dependent growth. [5]

Characteristics

Morphology

Azotobacter salinestris is a Gram-negative, rod-shaped organism. [5] This organism's cells are about 2 x 4 μm in size when they are 18 hours old and can grow up to 5 μm in diameter. [2] [3] Older cells can also form cysts. [2] A. salinestris colonies appear to be brown-black in color because they produce water-soluble catechol melanin. [2]

Physiology

The bacteria that performed the most efficient atmospheric nitrogen fixation were from samples grown in 0.05% to 0.10% saline concentration soils. [2] Nitrogen fixation rates were not affected by the presence of oxygen. [2] A. salinestris that grows in soils is a facultative anaerobe. [2] Colonies growing in aquatic habitats were determined to be microaerophilic and very sensitive to the presence of hydrogen peroxide since they do not produce a catalase enzyme. [2]

Metabolism

A. salinestris can use melibiose, galactose, mannitol, sucrose, glucose, and fructose as primary carbon sources. [2] They prefer to use sodium ions as their electron acceptor, but also use rubidium. [2] Strains that do not have access to sodium ions produce acid as a product of the metabolism of their growth-promoting carbon substrate. [2]

Ecology

All known A. salinestris samples were isolated from soils that had a neutral or slightly basic pH. [2] The optimal growth pH of this species is 7.2–7.5. [2] Soils must have at least one millimolar concentration of saline for this organism to grow. [2] Unlike other Azotobacter species, iron was absolutely required for growth. [2] While most Azotobacter species are commonly found in soil, A. salinestris is unique due to being found in soils with high salt content and requiring the presence of iron to grow. [2] These organisms can survive in aerobic and anaerobic conditions. [2] It is dependent on, so can also be found in marine environments. [2]

A. chroococcum is the most common species from Azotobacter to be isolated from soil samples. [2] It is also a close relative to A. salinestris. [2] All growth conditions used to isolate and determine optimum living conditions for A. salinestris were based on the optimal living conditions for A.chroococcum. [2] The defining factor between these two species was the dependence on sodium ions to live. A. salinestris displayed a stronger dependence on sodium to live than A. chroococcum. [2]

Genetics

While Page and Shivprasad are credited with the discovery and characterization of A. salinestris, Eydne and Wachter are credited with the sequencing of the bacterium’s 5S rRNA in 1987. [2]

Although the results were never published, sequencing data placed this bacterial strain in the genus Azotobacter. [2] The bacterium’s DNA has a melting point of 96.68 to 97.08 °C and the GC content was 67.73-67.8%. [2] A separate sequencing of the 16S rRNA sequence, conducted by Moore et al. confirmed that A. salinestris was indeed a separate species of that genus. [2]

Importance

A. salinestris was the first prokaryote to show Na+/succinic acid efflux. [4] It can tolerate up to 5% glyphosate, which is a pesticide used to kill weeds that compete with crops. [6] Because the species is a common nitrogen fixer, it is important to the agricultural industry for the species to be able to survive in the presence of such a common pesticide. [6] It can degrade endosulfan, which is an insecticide that is highly hazardous to human, mammal, and fish health. [3] Endosulfan use was banned in 2012 by the United States, following a precedent established by New Zealand and the European Union. [7] The decision to ban endosulfan use came after a study that showed the health risks to humans and wildlife were much higher than expected. [8] [9] It is similar to dichlorodiphenyltrichloroethane, causes birth defects, and is an estrogen analog. [8] Therefore, the ability of A. salinestris to break down endosulfan is important for bioremediation to the environments where the substance was used. [3]

See also

Related Research Articles

<span class="mw-page-title-main">Bioremediation</span> Process used to treat contaminated media such as water and soil

Bioremediation broadly refers to any process wherein a biological system, living or dead, is employed for removing environmental pollutants from air, water, soil, flue gasses, industrial effluents etc., in natural or artificial settings. The natural ability of organisms to adsorb, accumulate, and degrade common and emerging pollutants has attracted the use of biological resources in treatment of contaminated environment. In comparison to conventional physicochemical treatment methods bioremediation may offer considerable advantages as it aims to be sustainable, eco-friendly, cheap, and scalable. Most bioremediation is inadvertent, involving native organisms. Research on bioremediation is heavily focused on stimulating the process by inoculation of a polluted site with organisms or supplying nutrients to promote the growth. In principle, bioremediation could be used to reduce the impact of byproducts created from anthropogenic activities, such as industrialization and agricultural processes. Bioremediation could prove less expensive and more sustainable than other remediation alternatives.

<span class="mw-page-title-main">Bacteriological water analysis</span>

Bacteriological water analysis is a method of analysing water to estimate the numbers of bacteria present and, if needed, to find out what sort of bacteria they are. It represents one aspect of water quality. It is a microbiological analytical procedure which uses samples of water and from these samples determines the concentration of bacteria. It is then possible to draw inferences about the suitability of the water for use from these concentrations. This process is used, for example, to routinely confirm that water is safe for human consumption or that bathing and recreational waters are safe to use.

Diazotrophs are bacteria and archaea that fix gaseous nitrogen in the atmosphere into a more usable form such as ammonia.

<i>Azotobacter</i> Genus of bacteria

Azotobacter is a genus of usually motile, oval or spherical bacteria that form thick-walled cysts and may produce large quantities of capsular slime. They are aerobic, free-living soil microbes that play an important role in the nitrogen cycle in nature, binding atmospheric nitrogen, which is inaccessible to plants, and releasing it in the form of ammonium ions into the soil. In addition to being a model organism for studying diazotrophs, it is used by humans for the production of biofertilizers, food additives, and some biopolymers. The first representative of the genus, Azotobacter chroococcum, was discovered and described in 1901 by Dutch microbiologist and botanist Martinus Beijerinck. Azotobacter species are Gram-negative bacteria found in neutral and alkaline soils, in water, and in association with some plants.

Azotobacter vinelandii is Gram-negative diazotroph that can fix nitrogen while grown aerobically. These bacteria are easily cultured and grown.

<span class="mw-page-title-main">Soil conservation</span> Preservation of soil nutrients

Soil conservation is the prevention of loss of the topmost layer of the soil from erosion or prevention of reduced fertility caused by over usage, acidification, salinization or other chemical soil contamination.

<span class="mw-page-title-main">Atrazine</span> Herbicide

Atrazine is a chlorinated herbicide of the triazine class. It is used to prevent pre-emergence broadleaf weeds in crops such as maize (corn), soybean and sugarcane and on turf, such as golf courses and residential lawns. Atrazine's primary manufacturer is Syngenta and it is one of the most widely used herbicides in the United States, Canadian, and Australian agriculture. Its use was banned in the European Union in 2004, when the EU found groundwater levels exceeding the limits set by regulators, and Syngenta could not show that this could be prevented nor that these levels were safe.

<span class="mw-page-title-main">Mycoremediation</span> Process of using fungi to degrade or sequester contaminants in the environment

Mycoremediation is a form of bioremediation in which fungi-based remediation methods are used to decontaminate the environment. Fungi have been proven to be a cheap, effective and environmentally sound way for removing a wide array of contaminants from damaged environments or wastewater. These contaminants include heavy metals, organic pollutants, textile dyes, leather tanning chemicals and wastewater, petroleum fuels, polycyclic aromatic hydrocarbons, pharmaceuticals and personal care products, pesticides and herbicides in land, fresh water, and marine environments.

<span class="mw-page-title-main">Endosulfan</span> Chemical compound

Endosulfan is an off-patent organochlorine insecticide and acaricide that is being phased out globally. It became a highly controversial agrichemical due to its acute toxicity, potential for bioaccumulation, and role as an endocrine disruptor. Because of its threats to human health and the environment, a global ban on the manufacture and use of endosulfan was negotiated under the Stockholm Convention in April 2011. The ban has taken effect in mid-2012, with certain uses exempted for five additional years. More than 80 countries, including the European Union, Australia, New Zealand, several West African nations, the United States, Brazil, and Canada had already banned it or announced phase-outs by the time the Stockholm Convention ban was agreed upon. It is still used extensively in India and China despite laws against its use. It is also used in a few other countries. It is produced by the Israeli firm Makhteshim Agan and several manufacturers in India and China. On 13.05.2011, the India Supreme Court ordered a ban on the production and sale of endosulfan in India, pending further notice.

<span class="mw-page-title-main">Soil biology</span>

Soil biology is the study of microbial and faunal activity and ecology in soil. Soil life, soil biota, soil fauna, or edaphon is a collective term that encompasses all organisms that spend a significant portion of their life cycle within a soil profile, or at the soil-litter interface. These organisms include earthworms, nematodes, protozoa, fungi, bacteria, different arthropods, as well as some reptiles, and species of burrowing mammals like gophers, moles and prairie dogs. Soil biology plays a vital role in determining many soil characteristics. The decomposition of organic matter by soil organisms has an immense influence on soil fertility, plant growth, soil structure, and carbon storage. As a relatively new science, much remains unknown about soil biology and its effect on soil ecosystems.

<span class="mw-page-title-main">Streaking (microbiology)</span> Method for isolation of bacterial strains

In microbiology, streaking is a technique used to isolate a pure strain from a single species of microorganism, often bacteria. Samples can then be taken from the resulting colonies and a microbiological culture can be grown on a new plate so that the organism can be identified, studied, or tested.

Paracoccus denitrificans, is a coccoid bacterium known for its nitrate reducing properties, its ability to replicate under conditions of hypergravity and for being a relative of the eukaryotic mitochondrion.

<i>Pseudomonas stutzeri</i> Species of bacterium

Pseudomonas stutzeri is a Gram-negative soil bacterium that is motile, has a single polar flagellum, and is classified as bacillus, or rod-shaped. While this bacterium was first isolated from human spinal fluid, it has since been found in many different environments due to its various characteristics and metabolic capabilities. P. stutzeri is an opportunistic pathogen in clinical settings, although infections are rare. Based on 16S rRNA analysis, this bacterium has been placed in the P. stutzeri group, to which it lends its name.

Soil biodiversity refers to the relationship of soil to biodiversity and to aspects of the soil that can be managed in relative to biodiversity. Soil biodiversity relates to some catchment management considerations.

<span class="mw-page-title-main">Environmental impact of pesticides</span> Environmental effect

The environmental effects of pesticides describe the broad series of consequences of using pesticides. The unintended consequences of pesticides is one of the main drivers of the negative impact of modern industrial agriculture on the environment. Pesticides, because they are toxic chemicals meant to kill pest species, can affect non-target species, such as plants, animals and humans. Over 98% of sprayed insecticides and 95% of herbicides reach a destination other than their target species, because they are sprayed or spread across entire agricultural fields. Other agrochemicals, such as fertilizers, can also have negative effects on the environment.

<span class="mw-page-title-main">Agricultural pollution</span> Type of pollution caused by agriculture

Agricultural pollution refers to biotic and abiotic byproducts of farming practices that result in contamination or degradation of the environment and surrounding ecosystems, and/or cause injury to humans and their economic interests. The pollution may come from a variety of sources, ranging from point source water pollution to more diffuse, landscape-level causes, also known as non-point source pollution and air pollution. Once in the environment these pollutants can have both direct effects in surrounding ecosystems, i.e. killing local wildlife or contaminating drinking water, and downstream effects such as dead zones caused by agricultural runoff is concentrated in large water bodies.

Soil microbiology is the study of microorganisms in soil, their functions, and how they affect soil properties. It is believed that between two and four billion years ago, the first ancient bacteria and microorganisms came about on Earth's oceans. These bacteria could fix nitrogen, in time multiplied, and as a result released oxygen into the atmosphere. This led to more advanced microorganisms, which are important because they affect soil structure and fertility. Soil microorganisms can be classified as bacteria, actinomycetes, fungi, algae and protozoa. Each of these groups has characteristics that define them and their functions in soil.

Oleispira antarctica is a hydrocarbonoclastic marine bacterium, the type species in its genus. It is psychrophilic, aerobic and Gram-negative, with polar flagellum. Its genome has been sequenced and from this information, it has been recognized as a potentially important organism capable of oil degradation in the deep sea.

<i>Azotobacter chroococcum</i> Species of bacterium

Azotobacter chroococcum is a bacterium that has the ability to fix atmospheric nitrogen. It was discovered by Martinus Beijerinck in 1901, and was the first aerobic, free-living nitrogen fixer discovered. A. chroococcum could be useful for nitrogen fixation in crops as a biofertilizer, fungicide, and nutrient indicator, and in bioremediation.

In microbiology, the term isolation refers to the separation of a strain from a natural, mixed population of living microbes, as present in the environment, for example in water or soil, or from living beings with skin flora, oral flora or gut flora, in order to identify the microbe(s) of interest. Historically, the laboratory techniques of isolation first developed in the field of bacteriology and parasitology, before those in virology during the 20th century.

References

  1. ↑ Parte, A.C. "Azotobacter". LPSN .
  2. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 Page, and Shivprasad. "ITIS Standard Report Page: Azotobacter Salinestris." ITIS Standard Report Page: Azotobacter Salinestris. N.p., 1991. Web. 8 Feb. 2016. <https://www.itis.gov/servlet/SingleRpt/SingleRpt?search_topic=TSN&search_value=959650>
  3. 1 2 3 4 Chennappa, Gurikar; et al. (2014). "Pesticide tolerant Azotobacter isolates from paddy growing areas of northern Karnataka, India". World Journal of Microbiology and Biotechnology. 30 (1): 1–7. doi:10.1007/s11274-013-1412-3. PMID   23813305. S2CID   31936743.
  4. 1 2 Page William J; Shivprasad Shailaja (1991). "Examination of the role of Na+ in the physiology of the Na+-dependent soil bacterium Azotobacter salinestris". Microbiology. 137 (12): 2891–2899. doi: 10.1099/00221287-137-12-2891 .
  5. 1 2 Bergey, D. H.; Brenner, D. J.; Krieg, N. R. & Staley, J. T. (2005). Bergey's manual of systematic bacteriology. Vol. 2. The proteobacteria. Part B. The gammaproteobacteria. New York, NY: Springer.
  6. 1 2 Castillo JM, Casas J, Romero E (2011). "Isolation of an endosulfan degrading bacterium from a coffee farm soil: persistence and inhibitory effect on its biological functions". Sci Total Environ. 412–413: 20–27. Bibcode:2011ScTEn.412...20C. doi:10.1016/j.scitotenv.2011.09.062. PMID   22033355.
  7. ↑ Martin, David S. EPA moves to ban DDT cousin. CNN. June 10, 2010. <http://thechart.blogs.cnn.com/2010/06/10/epa-moves-to-ban-ddt-cousin/>
  8. 1 2 Cone, M. (2010, June 10). Endosulfan to Be Banned, Pesticide Poses "Unacceptable Risks," EPA Says. Retrieved April 27, 2016, from http://www.scientificamerican.com/article/endosulfan-banned-epa/
  9. ↑ Beauvais, S. L.; Silva, M. H. & Powell, S. (2010). "Human health risk assessment of endosulfan. Part III: Occupational handler exposure and risk". Regulatory Toxicology and Pharmacology. 56 (1): 28–37. doi:10.1016/j.yrtph.2009.10.002. PMID   19854234.
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.