Actinomyces usually exist in nature in the form of spores or hyphae. No matter the quantity or the type, the soil is the richest. According to the determination, each gram of soil can contain tens of thousands or even millions of spores, but it is affected by soil properties, seasons, crop species and other conditions. Generally speaking, there are more fertile soil than thin soil, more farmland soil than forest soil, and more neutral or alkaline soil. Soil environmental factors such as organic matter, moisture, temperature and ventilation also affect its quantity. It is suitable for growing in soil with low water content. However, the activity of thermophilic actinomycetes is limited in manure and compost. Metabolites produced by actinomycetes often produce a special muddy smell in the soil.
In rivers and lakes, the number of actinomycetes is small, mostly micromonospora, actinomycetes and Streptomyces cysts, and there are also a few Streptomyces. Most actinomycetes in the ocean come from soil or feed on algae floating on the sea surface. There are also salt-tolerant actinomycetes in seawater.
There are also a large number of actinomycetes hyphae and spores in the atmosphere, not the original microbial flora, but because there are a large number of actinomycetes on the surface of soil, animals, plants, food and even clothes. Because they are dry-resistant, they often fly into the atmosphere with dust and water droplets by wind.
Actinomycetes often grow on food, especially in dry and warm conditions, which are easy to multiply and make food smell pungent and musty.
There are a large number of actinomycetes in the intestines of healthy animals, especially ruminants. Some of them may be microorganisms that settle in the intestine, and thermophilic actinomycetes in compost may come from this. There are a large number of saprophytic actinomycetes on the surface of animals and plants, and occasionally there are parasitic actinomycetes.
Understanding the distribution of actinomycetes is undoubtedly very important for further developing actinomycetes resources and discovering and screening new antibiotics.
Second, the morphology and structure of actinomycetes
Actinomycetes are single cells, mostly composed of well-branched hyphae, the simplest of which are rod-shaped or with primitive hyphae. The diameter of mycelium is similar to that of coryneform bacteria, about 1 micron. The chemical composition of cell wall also contains cell wall acid and diaminopimelic acid unique to prokaryotes, but it does not contain chitin or cellulose. Gram staining is positive and rarely negative. Many actinomycetes, such as Nocardia actinomycetes, can resist the positive reaction of acid staining. Compared with mycobacterium tuberculosis, the decolorization time is too long to turn negative, which is one of the differences between Nocardia and mycobacterium tuberculosis.
The mycelium cell structure of actinomycetes is basically the same as that of bacteria. According to the shape and function of mycelium, it can be divided into three types: vegetative mycelium, gas filament and spore filament.
(1) vegetative hyphae, also called primary hyphae or primary hyphae, crawl in the culture medium, and their main physiological function is to absorb nutrients, so they are also called matrix hyphae. Vegetative hyphae generally have no septa, and even if there is one, there are few. The diameter is 0.2-0.8 micron, but the length varies greatly, ranging from less than 100 micron to more than 600 micron. Some have no pigment, and some produce different pigments such as yellow, orange, red, purple, blue, green, brown and black. If it is a water-soluble pigment, it can also penetrate into the culture medium to dye the culture medium with the corresponding color. If it is a water-insoluble (or fat-soluble) pigment, the colony ton will show the corresponding color. Therefore, pigment is an important basis for identifying strains.
(2) aerial hyphae are also called secondary hyphae. When the vegetative hyphae develop to a certain period, the hyphae that grow out of the culture medium and extend into the space are aerial hyphae. It is superimposed on the vegetative mycelium, so that it can cover the whole colony surface. Under the optical microscope, it is darker in color and thicker in diameter than vegetative hyphae, about 1- 1.4 micron, and the length is quite different. Straight or curved and branched, some produce pigments.
(3) When the aerial hyphae develop to a certain extent, sporotrichum can differentiate into spores, namely sporotrichum, also known as sporotrichum or reproductive hyphae. The shape of sporophyte and its arrangement on aerial mycelium vary from strain to strain.
Spore silk can be divided into straight, wavy and spiral. The spiral structure and length of spiral spore silk are very stable, and the number, density and rotation direction of spiral are the characteristics of species. The helix number is usually 5- 10, ranging from 1 to 20; The rotation direction is mostly counterclockwise, and a few are clockwise. Spore filaments are alternately arranged, clustered or whorled. Spore silk divides more than three spore branches from one point, which is called whorl branch. It has first-class wheels and second-class wheels. The above characteristics can be used as the basis for strain identification.
Spore silk can form spores when it grows to a certain stage under the optical microscope. Spores are spherical, oval, rod-shaped, melon seeds, etc. The surface structure of spores can also be seen under the electron microscope, some are smooth, some have small warts, some have spines (different kinds of spores have spines of different lengths) or hairs (Figure 2-63). The spore surface structure is also an important basis for actinomycetes species identification. The surface structure of spores is also related to the shape and color of sporophytes. Generally, the spores formed by straight or wavy sporophytes have smooth surfaces. The shape and color of spiral sporophyte are also related. Generally, the spores formed by straight or wavy sporophytes have smooth surfaces. The spores formed by spiral sporophytes are smooth, spiny or hairy; White, yellow, light green, grayish yellow and lavender spores are generally smooth, pink spores have only a few thorns, and black spores mostly have thorns and hairs.
Because spores contain different pigments, the mature spore pile also presents a specific color, which is relatively stable under certain conditions, so it is also one of the basis for identifying strains. It should be pointed out that the shape and size of spores can not be used as an important basis for classification and identification. Because even spores differentiated from sporophytes may be different in shape and size.
The development cycle of actinomycetes is a continuous process. Taking Streptomyces as an example, the life history of actinomycetes is summarized as follows: spores germinate under suitable conditions and grow 1-3 germ tubes; The bud tube is elongated and branches grow, and more and more branches form vegetative hyphae; When the vegetative hyphae develop to a certain stage, they grow into aerial hyphae to the outer space of the culture medium; The aerial hyphae develop to a certain extent and form sporophytes on them; Spore filaments form spores in some way. Only in this way can we survive and develop.
Three. Characteristics of Actinomyces and Colonies
Actinomycete community is composed of mycelium. Generally round, flat or with many folds, under the optical microscope, there are radial hyphae around the colony. The general characteristics are between mold and bacteria, which can be divided into two categories due to different species:
One is a colony formed by a large number of branched aerial hyphae and strains. The colony of Streptomyces is the representative of a type. Streptomyces hyphae are fine, grow slowly, have many branches and are intertwined with each other, so the colonies formed are dense in texture, and the surface is dense velvet or solid, dry and wrinkled, and the colonies are small and do not spread; Vegetative hyphae grow in the culture medium, so the colony is closely combined with the culture medium, and it is not easy to be stirred up or broken after being stirred up: before aerial hyphae differentiate into sporophytes, young colonies are very similar to bacterial colonies, smooth or tangled. Sometimes aerial hyphae are concentric rings, and typical actinomycetes colonies are flocculent, powdery or granular only after sporophytes produce a large number of spores and cover the whole colony surface. Some kinds of spores contain pigments, which make the surface or back of colonies have different colors.
Another kind of colony is formed by a strain that does not produce a large amount of mycelium, such as the colony of Actinomyces Nocardia, which has poor adhesion and a powdery structure and can be broken with a needle.
If actinomycetes are inoculated in liquid culture medium, they can form punctate or membranous colonies on the liquid surface of the bottle wall, or settle at the bottom of the bottle without turbid culture medium. If cultured in shake flask, spherical particles composed of short mycelium will often be formed.
Fourth, the propagation mode of actinomycetes
Actinomycetes propagate mainly through the formation of asexual spores, or by using bacteria as fission fragments.
When actinomycetes grow to a certain stage, some aerial hyphae form sporophytes, and when the sporophytes mature, they differentiate into many spores, which are called conidia. Spores can be produced in the following ways.
Coagulation and division form concentrated spores. The process is that the protoplasm in the spore wall surrounds the nuclear material, and gradually condenses into a series of small fragments with the same volume or similar size from top to bottom, and then the small fragments contract, and a new spore wall is generated outside each fragment, which becomes a round or oval spore. When the spores mature, the sporophyte wall breaks and the spores are released (Figure 2-65). Most actinomycetes form spores in this way, such as Streptomyces spores. Now some people have raised objections to some methods.
The diaphragm divides to form diaphragm spores. The process is that when the single-celled sporophyte grows to a certain stage, it first produces a diaphragm in it, and then ruptures at the diaphragm to form spores, which are called diaphragm spores, also called mesospores or pollen spores (Figure 2-66). Generally cylindrical or rod-shaped, the volume is basically equal and the size is similar, about 0.7-0.8× 1-2.5 microns. This is how Nocardia forms spores.
Some actinomycetes first form sporangia on mycelium, and spores are formed in sporangia. When the sporangium matures, it ruptures and releases a large number of sporangium spores. Sporangia can be formed on aerial hyphae, vegetative hyphae or both. Actinomyces and ascomycetes need to form spores in some way. Sporangium can be coiled by sporophyte, and some are expanded by the top of sporangium stalk. The formation process of sporangium spores is shown in Figure 2-67.
The spore formation of most species of Micromonosporaceae is through uniaxial branching on the vegetative line, and special branches with straight and short length (5- 10 micron) are regenerated from the base. The branches can be further branched, and a spherical, oval or rectangular spore is formed at the top of each branch, which is clustered together, much like a bunch of grapes (Figure 2-68).
Some actinomycetes occasionally produce thick-walled spores.
Actinomycete spores have good dry resistance, but not high temperature resistance. When 10- 15 was treated at 60-65℃, they lost their vitality.
Actinomycetes can also form mother bacteria from the broken fragments of hyphae, which are common in liquid culture medium. Actinomycetes proliferate in this way when industrial fermentation produces antibiotics. If the culture is left standing, a bacterial membrane is usually formed on the surface of the culture, and spores can also be produced on the membrane.
Verb (abbreviation for verb) Actinomyces Physiology
Except for a few autotrophic strains such as autotrophic Streptomyces, most of them are heterotrophic. The nutritional requirements of heterotrophic bacteria vary greatly, some can use simple compounds, while others need complex organic compounds. They can use different carbohydrates. They can use different carbohydrates, including sugar, lakes, powdered organic acids, cellulose, hemicellulose and so on as energy sources. The best carbon sources are glucose, maltose, dextrin, starch and glycerol, followed by sucrose, xylose, raffinose, alcohol and organic acids. Among the organic acids, acetic acid, lactic acid, citric acid, succinic acid and malic acid are easy to use, while oxalic acid, tartaric acid and hippuric acid are difficult to use. Some actinomycetes can also use chitin, hydrocarbons, tannins and even rubber.
In terms of nitrogen nutrition, protein, peptone and some amino acids are the most suitable, and nitrate? Followed by ammonium salts and vitamins. Except Nocardia, most actinomycetes can use cold protein and liquefied gelatin.
Like other organisms, the growth of actinomycetes generally needs potassium, magnesium, iron, copper and calcium, among which magnesium and potassium have significant effects on mycelium growth and antibiotic production. The mineral nutrients required for the production of various antibiotics are not exactly the same. For example, when Streptomyces fradiae produces neomycin, Zn is necessary, while Mg, Fe, Cu, Al and Mn are ineffective. Co is an essential element for actinomycetes to produce vitamin B 12. When the culture medium contains 1 or 2ppm of Co, the vitamin yield in streptomyces griseus can be increased by 3 times, and if the content of Co in the culture medium is as high as 20-50ppm, it will have toxic effects. In addition, Co can also promote spore formation.
Most actinomycetes are aerobic bacteria, and only some species are trace aerobic bacteria and anaerobic bacteria. Therefore, in the process of producing antibiotics by industrial fermentation, sufficient ventilation must be ensured; Temperature will also affect the growth of actinomycetes. The optimum growth temperature of most actinomycetes is 23-37℃, while that of thermophilic actinomycetes is 50-65℃, and many strains still grow well below 20-23℃. Actinomycete mycelium has stronger anti-drying ability than bacterial vegetative body, and many strains can survive for about one and a half years in CaCl2 _ 2 and H2SO4 dryers.
The physiological characteristics of actinomycetes are complex, so we can only briefly introduce them here. Understanding the above characteristics is undoubtedly very important for further exerting its economic benefits and finding and developing actinomycetes resources.
Six, the representative genus of actinomycetes
(1) There are more than 65,438+0,000 species of Streptomyces, including many different species and varieties. Their hyphae are developed, hyphae are branched, there is no diaphragm, the diameter is about 0.4- 1 micron, the length is different, and they are multinucleate. Mycelia can be divided into vegetative hyphae, aerial hyphae and sporotrichum, which form conidia in turn. The morphology of sporangium and spore varies from species to species, which is one of the main distinguishing characteristics of Streptomyces species.
Although some Streptomyces can also be found in fresh water and ocean, it mainly grows in soil with low water content and good ventilation. Because the antibiotics produced by many Streptomyces have great economic value and medical significance, people have done a lot of research work on this kind of actinomycetes. Studies have shown that antibiotics are mainly produced by actinomycetes, 90% of which are produced by Streptomyces. The famous common antibiotics that can effectively control rice sheath blight, such as streptomycin, oxytetracycline, bleomycin and mitomycin, antifungal nystatin, kanamycin and validamycin, are all secondary metabolites of Streptomyces. Some Streptomyces can produce more than one antibiotic, which are chemically unrelated to each other. However, different species found in many different parts of the world may produce the same antibiotics; Changing the nutrition of Streptomyces may lead to the change of antibiotic properties. These bacteria are generally resistant to their own antibiotics, but may be sensitive to antibiotics produced by other Streptomyces. Although Streptomyces producing antibiotics has been extensively studied in the past, little is known about the ecological relationship of these organisms, which should be strengthened in the future. In addition, many infectious diseases can not be properly inhibited by existing antibiotics or produce drug-resistant strains, so we must continue to look for and screen new antibiotics.
There are many kinds of Streptomyces, more than 50% of which can produce antibiotics. According to the climate, the color of mycelium (the color of spore pile) of Beijing Institute of Microbiology, Chinese Academy of Sciences; According to the characteristics of matrix mycelium such as color, soluble pigment, sporophyte shape, spore shape and surface structure, Streptomyces is divided into 14 species groups, and each species group includes many different species.
(2) Nocardia, also known as protoactinomycetes, forms a typical mycelium on the culture medium, which bends or does not bend violently like a tree root and has long mycelium. The characteristic of this genus is that within 0/5 hour to 4 days of culture/kloc-0, hyphae produce septa, and all branched hyphae suddenly break and grow into rod-shaped or spherical bodies or branched rod-shaped bodies (Figure 2-69). Each stem has at least one nucleus, which can be replicated to form a new multinucleated mycelium. Most species of this genus have no aerial hyphae, but only vegetative hyphae, which form spores by transverse division. A few species cover the surface of vegetative hyphae with a very thin layer of aerial hyphae-fruiting bodies or sporophytes. Spore silk is straight, and some species are hooked or spiral with diaphragm. Spores are divided by diaphragm, and the spores are rod-shaped, cylindrical, truncated at both ends or oval.
Colonies are diverse in appearance and structure, generally smaller than Streptomyces colonies, with uneven and wrinkled surfaces, dense and dry, easily broken, or dough; Some kinds of colonies are smooth or convex, dull or shiny, and have been soaked in water.
This genus is mostly aerobic saprophytic bacteria, and a few are anaerobic parasitic bacteria. It can assimilate various carbohydrates, and some can use hydrocarbons, cellulose and so on.
Nocardia is mainly distributed in soil. It has been reported that 100 can produce more than 30 kinds of antibiotics. Such as rifamycin with special effects on mycobacterium tuberculosis and mycobacterium leprae, mitomycin with special effects on bacteria causing plants, protozoa and viruses, and ristomycin with special effects on gram-positive bacteria. In addition, Nocardia is used to decompose nitrile compounds in petroleum dewaxing, hydrocarbon fermentation and sewage treatment.
(3) Actinomycetes are mostly pathogenic bacteria, only vegetative hyphae, with a diameter of less than 65438 0 microns and a diaphragm, which can be broken into a "V" shape or a "Y" shape. There are no aerial hyphae and no spores. Generally anaerobic bacteria or facultative anaerobic bacteria. Actinomyces bovis, which causes swelling of bovine jaws, is a typical representative of this genus. The other is actinomycetes evansi, which is parasitic on human body and can cause tumors in the posterior jaw and lung infection. Their growth needs rich nutrition, and serum or heart and brain juice are usually added to the culture medium.
(4) Micromonospora hypha is slender, with a diameter of 0.3-06 microns, without diaphragm and fracture. The hypha invades the culture medium and does not form aerial hypha. There are only many branches and petioles on the mycelium, and a spore is attached to the top.
Colonies are much smaller than Streptomyces, generally 2-3 mm, generally orange-yellow, but also dark brown, black and blue; The surface of the colony is covered with a thin layer of spores. This kind of bacteria is usually aerobically saprophytic and can utilize various nitride carbohydrates. Most of them are distributed in soil or lake bottom soil, and there are also a lot of compost manure. There are about 30 species in this genus, which also produces more antibiotics. For example, gentamicin is produced by Micromonospora fuciformis and Micromonospora echinosporus, and some of them can produce more than 30 kinds of antibiotics such as rifamycin and halomycin. At present, it is considered that this genus has great potential to produce antibiotics, and some species have accumulated vitamin B 12, which should be paid attention to.
(5) The main feature of Alternaria is that it can form cysts and spores. Its formation process is shown in Figure 2-67. Sometimes it can also form spiral spore filaments, which divide into conidia after maturity. The vegetative thallus of this genus has many branches and few transverse septa, with a diameter of 0.5- 1.2 micron. The aerial hyphae are clustered, dispersed or concentrically arranged. There are more than 15 species in this genus, many of which have attracted attention because they can produce broad-spectrum antibiotics. Polymycin produced by Neurospora can inhibit gram-positive bacteria, gram-negative bacteria, viruses, etc., and also inhibit tumors. The green pigment produced by Alternaria viridis has effects on bacteria, mold and yeast. Amphotericin produced by Alternaria Siberia has certain curative effect on tumors.
(6) Actinomycetes usually grow on underwater leaves. Generally, there are or few aerial hyphae; Vegetative hyphae are more or less branched, with or without septa, with a diameter of about 0.2-2.6 microns; It is spread by sporangium spores. Sporangium is formed on vegetative hyphae or sporangium. The stalk of sporangium is straight or branched, and the top of each branch forms one to several sporangium. Sporangium spores are usually slightly angular, with one or several illuminants or several terminal flagella, which can move, which is the most special feature of the genus.
It depends on the professional literature. I will give you some English information and search according to the content in this information.
1. Marine Actinomycetes: Prospects, Challenges and Future Directions.
Bullat, Stachje, Wardac, Goodfellow M. (These are all authorities of marine actinomycetes, hehe) School of Biological Sciences, University of Kent, Canterbury, Kent CT27NJ,
The United Kingdom. A.T.Bull@kent.ac
In this paper, we evaluate the current situation of biological research.
Biotechnology of marine actinomycetes. Topics covered include
Abundance, diversity, novelty and biogeographic distribution of marine life
Actinomycetes, ecosystem function, biological exploration, and a new research method.
Exploration on the classification space of actinomycetes. Future ocean agenda
Based on the above considerations, it is suggested to study actinomycetes.
problem
PMID: 1597 1359
2. Environmental microorganisms. July 2005; 7(7): 1039-48.
Diversity of culturable marine actinomycetes in tropical Pacific sediments.
Jensen PR，Gontang E，Mafnas C，Mincer TJ，Fenical W .
Center for Marine Biotechnology and Biomedicine, Scripps Institute
Oceanography, University of California, San Diego, La Jolla, CA 92093-0204,
America. pjensen@ucsd.edu
Actinomycetes are selectively isolated and cultured by using various culture media.
Technology of 275 marine samples collected from around Guam. In ...
A total of 6425 actinomycetes colonies were observed, including 983 (15%).
Representing the range of morphological diversity observed from each sample,
It was obtained in pure culture. Most strains isolated (58%)
The seawater needed for growth shows a high degree of marine adaptability. this
The recovered dominant actinomycetes (568 strains) belong to marine actinomycetes.
Marine taxon' Halospora', a new genus of Micromonosporaceae. A
The formal description of this taxon has been accepted for publication.
Al. , 2005) and includes the revision of the genus name of Halobacterium.
Members of two main new branches related to Streptomyces. , tentative
Known as MAR2 and MAR3, they are cultivated and seem to represent new genera.
Streptomycetaceae. There are five new types of marine life, including two.
In thermomonosporaceae, it seems to represent a new taxon and obtain
Culturally. These results support the existence of classification diversity.
There are different actinomycetes populations living in the ocean.
environment These bacteria can be easily cultured in low nutrient medium.
Represents undeveloped resources for drug discovery.
PMID: 1594630 1[ under postgraduate study]
3. Natural production. March 2005; 68(3):349-53.
Chinikomycins A and B: Isolation, Structure Identification and Biological Activity
New antibiotics from marine Streptomyces. Isolate M045.
Li F, muskie RP, Qin S, Satler I, Fiebig HH, Maier A, Zeeck A, Laatsch H.
Department of organic and biomolecular chemistry, University of G? ttingen,
No.2, Taman Street, D-37077, Gottingen, Germany.
When we screened the bioactive components of marine Streptomyces, we found two new species.
Antitumor antibiotics named chinikomycins A (2a) and B (2b)
It was isolated with chiral A (1) and its structure was clarified by the following method.
A detailed explanation of their spectra. Chinikomycins A (2a) and B (2b) are
64-pABA-2 type chlorine-containing aromatic chiral derivatives
Unusual para-orientation of side chains. They show anti-tumor effect.
Activity against different human cancer cell lines, but in
Antivirus, antibacterial and phytotoxicity tests.
PMID: 15787434
4. Dependent on culture and independent of cultural diversity.
Obligate marine actinomycetes halospora
Tracy J. Mincer? William Finical and Paul Zhan Sen *
Center for Marine Biotechnology and Biomedicine, Scripps Institution of Oceanography, University of California, San Diego, La Jolla, California, 92093-0204.
Received 65438 on 6 April 2005/accepted on 4 July 2005. Halobacteria is the first specialized marine genus of Actinomycetes, and it is the main source of bioactive secondary metabolites. Although there are global, tropical or subtropical distributions in marine sediments, only two species of halospores have been cultivated so far, indicating that the diversity at the species level is limited. In order to further explore the diversity and distribution of Halospora, the phylogenetic diversity of more than 350 strains isolated from sediments collected around the Bahamas was studied, including those cultivated by new enrichment methods. A culture-independent method, which uses halophyte-specific semi-nested PCR technology, is used to detect halophyte from environmental DNA and estimate its diversity. Generally speaking, 16S rRNA gene
The sequence diversity of the cultured strains is consistent with that detected in the environmental clone library. Despite extensive efforts, no new species diversity was detected, and 97% of 105 strains detected by restriction fragment length polymorphism belonged to a systematic type (Streptococcus arenaria). New intraspecific diversity
Including a rich new uncultured systematics, and a new in-depth record 1, 100 m was established for this genus. The errors introduced by PCR, mainly from Taq polymerase, significantly increase the sequence diversity of clone library, which will lead to
Overestimation of the overall diversity. An environmental DNA extraction method specifically for vegetative cells provides evidence of the growth of active actinomycetes in marine sediments, and shows that most sediment samples mainly contain halospores, and their concentration can not be detected in marine sediments.
Environmental clone library. The challenges related to direct sequence-based detection of spore-forming microorganisms in environmental samples are discussed.