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Actinobacteria
 
 
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Actinobacteria or actinomycetes are a group of Gram-positive
Gram-positive

Gram-positive Bacteria are those that are stained dark blue or violet by Gram staining. This is in contrast to Gram-negative bacteria, which cannot retain the crystal violet stain, instead taking up the counterstain and appearing red or pink....
 bacteria with high G+C ratio.

include some of the most common soil life
Soil life

Soil life or soil biota is a collective term for all the organisms living within the soil....
, playing an important role in decomposition of organic materials, such as cellulose
Cellulose

File:Cellulose Sessel.svgCellulose is an organic compound with the chemical formula , a polysaccharide consisting of a linear chain of several hundred to over ten thousand ? linked D-glucose units....
 and chitin
Chitin

Chitin n is a long-chain polymer of a N-acetylglucosamine, a derivative of glucose, and is found in many places throughout the natural world....
 and thereby playing a vital part in organic matter turnover and carbon cycle
Carbon cycle

The carbon cycle is the biogeochemical cycle by which carbon is exchanged among the biosphere, pedosphere, geosphere, hydrosphere, and Earth's atmosphere of the Earth....
. This replenishes the supply of nutrients in the soil and is an important part of humus
Humus

Humus is degraded organic material in soil, which causes some soil layers to be dark brown or black.In soil science, humus refers to any organic matter that has reached a point of stability, where it will break down no further and might, if conditions do not change, remain essentially as it is for centuries, if not millennia....
 formation.






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Actinobacteria or actinomycetes are a group of Gram-positive
Gram-positive

Gram-positive Bacteria are those that are stained dark blue or violet by Gram staining. This is in contrast to Gram-negative bacteria, which cannot retain the crystal violet stain, instead taking up the counterstain and appearing red or pink....
 bacteria with high G+C ratio.

Characteristics

They include some of the most common soil life
Soil life

Soil life or soil biota is a collective term for all the organisms living within the soil....
, playing an important role in decomposition of organic materials, such as cellulose
Cellulose

File:Cellulose Sessel.svgCellulose is an organic compound with the chemical formula , a polysaccharide consisting of a linear chain of several hundred to over ten thousand ? linked D-glucose units....
 and chitin
Chitin

Chitin n is a long-chain polymer of a N-acetylglucosamine, a derivative of glucose, and is found in many places throughout the natural world....
 and thereby playing a vital part in organic matter turnover and carbon cycle
Carbon cycle

The carbon cycle is the biogeochemical cycle by which carbon is exchanged among the biosphere, pedosphere, geosphere, hydrosphere, and Earth's atmosphere of the Earth....
. This replenishes the supply of nutrients in the soil and is an important part of humus
Humus

Humus is degraded organic material in soil, which causes some soil layers to be dark brown or black.In soil science, humus refers to any organic matter that has reached a point of stability, where it will break down no further and might, if conditions do not change, remain essentially as it is for centuries, if not millennia....
 formation. Other Actinobacteria inhabit plants and animals, including a few pathogen
Pathogen

A pathogen , infectious agent, or germ, is a biological agent that causes disease or illness to its Host .There are several substrates and pathways whereby pathogens can invade a host; the principal pathways have different episodic time frames, but soil contamination has the longest or most persistent potential for harboring...
s, such as Mycobacterium
Mycobacterium

Mycobacterium is a genus of Actinobacteria, given its own family, the Mycobacteriaceae. The genus includes pathogens known to cause serious diseases in mammals, including tuberculosis and leprosy....
, Corynebacterium
Corynebacterium

Corynebacterium is a genus of Gram-positive, aerobic or Facultative anaerobic organism, non-motile, non-sporulated, rod-shaped actinobacteria. Most do not cause disease, but are part of normal human skin Flora ....
, Nocardia
Nocardia

Nocardia is a genus of weakly-staining Gram-positive, catalase, rod-shaped bacteria. It has total 85 species. Some species are non pathogenic; some species are pathogenic ....
, Rhodococcus
Rhodococcus

Rhodococcus is a genus of aerobic, non-sporulating, non-motile gram-positive bacteria closely related to Mycobacteria and Corynebacteria . While a few species are pathogenic, most are benign and have been found to thrive in a broad range of environments, including soil, water, and eukaryotic cells....
 and a few species of Streptomyces
Streptomyces

Streptomyces is the largest genus of Actinobacteria and the type genus of the family Streptomycetaceae. Over 500 species of Streptomyces bacteria have been described....
.

Actinobacteria are well known as secondary metabolite
Secondary metabolite

Secondary metabolites are organic compounds that are not directly involved in the normal cell growth, Biological development or reproduction of organisms....
 producers and hence of high pharmacological and commercial interest. In 1940 Selman Waksman
Selman Waksman

Selman Abraham Waksman was an United States of America Biochemistry and Microbiology whose research into organic substances—largely into organisms that live in soil—and their decomposition promoted the discovery of Streptomycin, and several other antibiotics....
 discovered that the soil bacteria
Bacteria

The Bacteria are a large group of unicellular microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals....
 he was studying made actinomycin
Actinomycin

The actinomycins are a class of polypeptide antibiotics isolated from soil bacteria of the genus Streptomyces, of which the most significant is actinomycin D....
, a discovery which granted him a Nobel Prize
Nobel Prize

The Nobel Prize , established in the 1895 will of Swedish chemist Alfred Nobel; it was first awarded in Nobel Prize in Physics, Nobel Prize in Chemistry, Nobel Prize in Physiology or Medicine, Nobel Prize in Literature, and Nobel Peace Prize in 1901....
. Since then hundreds of naturally occurring antibiotics have been discovered in these terrestrial microorganism
Microorganism

A microorganism or microbe is an organism that is microscopic . The study of microorganisms is called microbiology, a subject that began with Anton van Leeuwenhoek's discovery of microorganisms in 1675, using a microscope of his own design....
s, especially from the genus Streptomyces
Streptomyces

Streptomyces is the largest genus of Actinobacteria and the type genus of the family Streptomycetaceae. Over 500 species of Streptomyces bacteria have been described....
.

Some Actinobacteria form branching filaments, which somewhat resemble the mycelia
Mycelium

Mycelium is the Vegetative reproduction part of a fungus, consisting of a mass of branching, thread-like hyphae. The mass of hyphae is sometimes called shiro, especially within the Fairy rings fungi....
 of the unrelated fungi
Fungus

A fungus is a Eukaryote organism that is a member of the Kingdom Fungi . The fungi are a monophyletic group, also called the Eumycota , that is phylogeny distinct from the morphologically similar slime molds and water molds ....
, among which they were originally classified under the older name Actinomycetes. Most members are aerobic
Aerobic organism

An aerobic organism or aerobe is an organism that can survive and grow in an oxygenated environment....
, but a few, such as Actinomyces israelii, can grow under anaerobic conditions. Unlike the Firmicutes
Firmicutes

The Firmicutes are a division of bacterium, most of which have Gram-positive cell wall structure. A few, the Mollicutes or mycoplasmas, lack cell walls altogether and so do not respond to Gram staining, but still lack the second membrane found in other Gram-negative forms....
, the other main group of Gram-positive bacteria, they have DNA with a high GC-content
GC-content

GC-content , in molecular biology, is the percentage of nitrogenous bases on a DNA molecule which are either guanine or cytosine . This may refer to a specific fragment of DNA or RNA, or that of the Genome....
 and some Actinomycetes species produce external spore
Spore

In biology, a spore is a reproduction structure that is adapted for biological dispersal and surviving for extended periods of time in unfavorable conditions....
s.

Some types of Actinobacteria are responsible for the peculiar odor emanating from the soil after rain, mainly on warmer climates.

Genera

Most Actinobacteria of medical or economic significance are in subclass Actinobacteridae
Actinobacteridae

Actinobacteridae is a subclass of bacteria, in the class of Actinobacteria ....
, order Actinomycetales
Actinomycetales

Actinomycetales is an Scientific classification of Actinobacteria. They are very diverse and contain a variety of subdivisions as well as yet unclassified isolates....
. While many of these cause disease in humans, Streptomyces
Streptomyces

Streptomyces is the largest genus of Actinobacteria and the type genus of the family Streptomycetaceae. Over 500 species of Streptomyces bacteria have been described....
 is notable as a source of antibiotics. Examples of organisms in this order include:

  • Suborder Actinomycineae
    Actinomycineae

    Actinomycineae is a suborder of the order Actinomycetales that contains the medically important genus Actinomyces....
    • Family Actinomycetaceae
      Actinomycetaceae

      Actinomycetaceae is a family of bacteria in the order Actinomycetales that contains the medically important genus Actinomyces....
      • Actinomyces
        Actinomyces

        Actinomyces is a genus of the actinobacteria class of bacteria. They are all Gram-positive and can be either Anaerobic organism or Facultative anaerobic organism ....
    • Family Propionibacteriaceae
      Propionibacteriaceae

      Propionibacteriaceae is a family of gram positive bacteria found in dairy products or in the intestinal tracts of animals and living in the pores of humans....
      • Propionibacterium
        Propionibacterium acnes

        Propionibacterium acnes is a relatively slow growing, typically aerotolerant anaerobic gram positive bacterium that is linked to the skin condition acne vulgaris; it can also cause chronic blepharitis and endophthalmitis, the latter particularly following intraocular surgery....
    • Family Frankiaceae
      • Frankia
        Frankia

        Frankia is a genus of nitrogen fixing filamentous bacteria that live in symbiosis with actinorhizal plants, similar to Rhizobia. Bacteria of this genus form root nodules....
    • Family Micrococcaceae
      Micrococcaceae

      The family Micrococcaceae includes bacterial genera of Gram positive cocci that inhabit the air and skin such as Micrococcus luteus....
      • Arthrobacter
        Arthrobacter

        Arthrobacter is a genus of bacterium that is commonly found in soil. All species in this genus are Gram-positive obligate aerobes that are bacterial shapes during exponential growth and bacterial shape in their Stationary phase ....
      • Micrococcus
        Micrococcus

        Micrococcus is a genus of bacteria in the Micrococcaceae family . Micrococcus occurs in a wide range of environments, including water, dust, and soil....
    • Family Micromonosporaceae
      Micromonosporaceae

      Micromonosporaceae is a family of bacterium of the order Actinomycetales. They are gram-positive, spore-forming soil organisms that form a true mycelium....
      • Micromonospora
        Micromonospora

        Micromonospora is a genus of bacterium of the family Micromonosporaceae. They are gram-positive, spore-forming, generally aerobic organism, and form a branched mycelium; they occur as saprotrophic forms in soil and water....
    • Family Streptomycetaceae
      Streptomycetaceae

      Streptomycetaceae is a family of Actinobacteria, including the important genus Streptomyces, which was the original source of most antibiotics....
      • Streptomyces
        Streptomyces

        Streptomyces is the largest genus of Actinobacteria and the type genus of the family Streptomycetaceae. Over 500 species of Streptomyces bacteria have been described....


  • Suborder Corynebacterineae
    Corynebacterineae

    Corynebacterineae is a suborder of the Actinomycetales, and includes most of the acid-fast bacteria. It is a high G+C gram positive bacteria. It causes Tuberculosis and leprosy....
    • Family Mycobacteriaceae
      • Mycobacterium
        Mycobacterium

        Mycobacterium is a genus of Actinobacteria, given its own family, the Mycobacteriaceae. The genus includes pathogens known to cause serious diseases in mammals, including tuberculosis and leprosy....
    • Family Corynebacteriaceae
      • Corynebacterium
        Corynebacterium

        Corynebacterium is a genus of Gram-positive, aerobic or Facultative anaerobic organism, non-motile, non-sporulated, rod-shaped actinobacteria. Most do not cause disease, but are part of normal human skin Flora ....
    • Family Nocardiaceae
      Nocardiaceae

      The Nocardiaceae are a Family of Aerobic organism, non-fastidious, High-GC content bacteria, Gram-positive actinomycetes that are commonly found in soil and water....
      • Nocardia
        Nocardia

        Nocardia is a genus of weakly-staining Gram-positive, catalase, rod-shaped bacteria. It has total 85 species. Some species are non pathogenic; some species are pathogenic ....


Of those Actinobacteria not in Actinomycetales, Gardnerella
Gardnerella

'Gardnerella' is a genus of gram-positive Aerobic organism bacteria of which 'Gardnerella vaginalis' is the only species.Once classified as a species of Haemophilus, G....
 is one of the most researched. Classification of Gardnerella is controversial, and MeSH
Mesh

Mesh consists of semi-permeable barrier made of connected strands of metal, fiber, or other flexible/ductile material. Mesh is similar to spider web or Net in that it has many attached or woven strands....
 catalogues it as both a gram-positive
Gram-positive

Gram-positive Bacteria are those that are stained dark blue or violet by Gram staining. This is in contrast to Gram-negative bacteria, which cannot retain the crystal violet stain, instead taking up the counterstain and appearing red or pink....
 and gram-negative
Gram-negative

Gram-negative bacteria are those bacteria that do not retain crystal violet dye in the Gram staining protocol. In a Gram stain test, a counterstain is added after the crystal violet, coloring all Gram-negative bacteria with a red or pink color....
 organism.

Genomes of 44 different strains of Actinobacteria from different genera are either already sequenced or underway right now.

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