Name: actinobacteria: soil bacteria and cheese
Uploaded: 2025-06-06T07:56:35.000Z
Duration: 1 min 30 s
Channel: JoVE

Actinobakterien sind eine vielfältige Gruppe von grampositiven Bakterien, darunter Coryneform-Bakterien, Propionsäurebakterien, Mykobakterien und Actinomyceten, und zeichnen sich durch ihren hohen G+C-DNA-Gehalt aus. Die Coryneform-Bakterien sind aerobe, unbewegliche Stäbchen mit unregelmäßigen, keulenförmigen oder V-förmigen Anordnungen aufgrund der Schnappteilung. Zu den Hauptarten gehören die pathogenen Corynebacterium, Diphtheriae, und Arthrobacter – eine Gattung von Bodenbakterien, die in der Lage sind, zwischen Stäbchen- und Kokkenformen zu wechseln. Propionsäurebakterien wie Propionibacterium, sind Anaerobier, die Milchsäure fermentieren und dabei Kohlendioxid und Propionsäure produzieren. Mykobakterien kommen häufig in Böden vor; die meisten sind harmlos, aber einige, wie Mycobacterium tuberculosis, sind bedeutende Krankheitserreger für den Menschen. Mycobacterium tuberculosis ist eine langsam wachsende Art, aber die Gattung Mycobacterium umfasst auch schnell wachsende Arten wie Mycobacterium smegmatis. Zu ihren einzigartigen Eigenschaften gehören Mykolsäuren in ihren Zellwänden und die Fähigkeit, sich zu verzweigen oder filamentös zu wachsen. Actinomyceten sind filamentöse und aerobe Bakterien, die Myzelien und austrocknungsresistente Sporen bilden. Eine vielfältige Gattung, Streptomyces, ist bekannt für ihre Antibiotikaproduktion.

bakterien phylum actinobakterien

Bacterial Phylum Actinobacteria

Coryneforme Bakterien sind grampositive, aerobe, unbewegliche St&#228;bchen, die unregelm&#228;&#223;ige, keulenf&#246;rmige oder V-f&#246;rmige Anordnungen aufweisen. Ihre V-Form resultiert aus der sogenannten &#8222;Schnappteilung&#8220;, bei der die innere Zellwandschicht eine Querwand bildet, w&#228;hrend die &#228;u&#223;ere Schicht intakt bleibt, bis sie einseitig aufrei&#223;t, was dazu f&#252;hrt, dass sich die Tochterzellen voneinander abwenden.
Die wichtigsten Gattungen sind Corynebacterium und Arthrobacter. Corynebacterium umfasst vielf&#228;ltige Arten, von Saprophyten bis hin zu Pathogenen wie Corynebacterium diphtheriae. Arthrobacter kommt haupts&#228;chlich im Boden vor und durchl&#228;uft einen Entwicklungszyklus, bei dem zwischen St&#228;bchen- und Kokkenformen gewechselt wird. W&#228;hrend einige coryneforme Bakterien auch kokkoide Zellen entwickeln, zeigt Corynebacterium h&#228;ufig eine keulenf&#246;rmige Struktur, im Gegensatz zu dem weniger stark ausgepr&#228;gten Erscheinungsbild von Arthrobacter.
Arthrobacter-Arten sind &#228;u&#223;erst widerstandsf&#228;hig gegen&#252;ber Austrocknung und N&#228;hrstoffmangel, obwohl sie keine Sporenbildner sind. Sie zeigen eine hohe metabolische Anpassungsf&#228;higkeit und k&#246;nnen Verbindungen wie Herbizide, Koffein, Nikotin und Phenole abbauen, was sie zu wichtigen Akteuren im &#214;kosystem von B&#246;den macht.
Propions&#228;urebakterien (Propionibacterium) wurden erstmals im Emmentaler K&#228;se identifiziert, wo ihre Fermentation CO_2 erzeugt, das die charakteristischen L&#246;cher bildet, sowie Propions&#228;ure, die dem K&#228;se seinen unverwechselbaren Geschmack verleiht. Diese grampositiven Anaerobier fermentieren Milchs&#228;ure, Kohlenhydrate und Polyhydroxyalkohole zu Propions&#228;ure, Essigs&#228;ure und CO_2.
Bei der Herstellung von Emmentaler K&#228;se ist Propionibacterium an der sekund&#228;ren Fermentation beteiligt, indem es das von Streptococcus und Lactobacillus w&#228;hrend der K&#228;sebruchbildung produzierte Laktat verwertet.. Mit dem Abtropfen des Bruchs vermehren sich die Propions&#228;urebakterien und erzeugen CO_2, das sich an Schwachstellen ansammelt und die L&#246;cher im K&#228;se bildet.
Au&#223;erdem produziert das nicht verwandte Bakterium Propionigenium Propionat durch Succinat-Fermentation, was einen anderen, aber energetisch bedeutenden Stoffwechselweg darstellt.
Mykobakterien sind in B&#246;den weit verbreitet und meist harmlos, jedoch sind einige Arten der Gattung Mycobacterium bedeutende Humanpathogene, darunter Mycobacterium tuberculosis, der Erreger der Tuberkulose. Diese st&#228;bchenf&#246;rmigen Bakterien sind s&#228;urefest, da ihre Zellw&#228;nde Mykols&#228;uren enthalten&#8211; komplexe Lipide, die der Zellwand eine wachsartige, hydrophobe Natur verleihen. Aus diesem Grund lassen sie sich mit der Gram-F&#228;rbung schlecht anf&#228;rben und werden stattdessen mit der Ziehl-Neelsen-F&#228;rbung identifiziert, bei der sie roten Farbstoff behalten, w&#228;hrend nicht s&#228;urefeste Bakterien blau erscheinen.
Mykobakterien k&#246;nnen pleomorph auftreten, gelegentlich auch verzweigte Strukturen bilden, entwickeln jedoch im Gegensatz zu Aktinomyzeten keine echten Myzelien. Sie werden in langsam wachsende Arten (z.&#8239;B. M. tuberculosis, M. avium, M. bovis) und schnell wachsende Arten (z.&#8239;B. M. smegmatis, M. chelonae) unterteilt. Langsam wachsende Arten wie M. tuberculosis ben&#246;tigen eine l&#228;ngere Inkubationszeit zur Koloniebildung, wobei die Kolonien aufgrund ihres hohen Lipidgehalts dicht, faltig und hydrophob sind.
Ern&#228;hrungsphysiologisch wachsen Mykobakterien aerob in einfachen Mineralsalzmedien, wobei sie Ammonium als Stickstoffquelle und Glycerin oder Acetat als Kohlenstoffquelle nutzen. M. tuberculosis gedeiht jedoch besser in der Gegenwart von Lipiden und Fetts&#228;uren. Seine Virulenz wird mit strangf&#246;rmigen Aggregaten in Verbindung gebracht, die durch das Glykolipid Cord Factor gebildet werden.
Einige Mykobakterien produzieren Carotinoidpigmente, was zur Identifikation beitr&#228;gt. Sie k&#246;nnen unpigmentiert sein (M. tuberculosis, M. bovis), photochromogen (Pigmentproduktion bei Lichteinwirkung, z.&#8239;B. M. parafortuitum) oder skotochromogen (Pigmentproduktion auch im Dunkeln, z.&#8239;B. M. gordonae). Carotinoide sch&#252;tzen diese Bakterien vermutlich vor oxidativen Sch&#228;den durch Singulett-Sauerstoff.
Aktinomyzeten sind fadenf&#246;rmige, aerobe, grampositive Bakterien, die h&#228;ufig im Boden vorkommen. Viele durchlaufen einen Entwicklungszyklus, bei dem sie austrocknungsresistente Sporen bilden. Ihr Wachstum erfolgt durch Verl&#228;ngerung und Verzweigung von Filamenten, wodurch ein Myzel &#228;hnlich dem von Pilzen entsteht. Wenn N&#228;hrstoffe knapp werden, entwickeln sich Luftmyzelien, die sich zu Sporen differenzieren, um das &#220;berleben und die Verbreitung zu sichern.
Die Gattung Streptomyces mit &#252;ber 500 Arten ist die bedeutendste dieser Gruppe. Die Filamente von Streptomyces, typischerweise 0,5&#8211;1,0 &#956;m im Durchmesser, wachsen an ihren Spitzen und verzweigen sich h&#228;ufig, wodurch ein dichtes Myzel entsteht. Mit der Reifung der Kolonien entstehen aus dem Luftmyzel Sporophoren, die Sporen (Konidien) produzieren. Im Gegensatz zu den Endosporen von Bacillus und Clostridium entstehen Konidien durch Querwandteilung in den Sporophoren.
Die Klassifikation verschiedener Arten basiert auf Variationen in Luftfilamenten und Sporenstrukturen. Konidien und Sporophoren sind h&#228;ufig pigmentiert, was den Kolonien auff&#228;llige Farben verleiht. Die ausgereiften Kolonien sind kompakt, pigmentiert und haben ein staubiges Erscheinungsbild, wodurch Streptomyces-Kolonien auf Agarplatten leicht zu identifizieren sind.

Bakterien Phylum Actinobakterien

Coryneforme Bakterien sind grampositive, aerobe, unbewegliche St&#228;bchen, die unregelm&#228;&#223;ige, keulenf&#246;rmige oder V-f&#246;rmige ...

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actinobacteria: soil bacteria and cheese

Actinobacteria include several gram-positive bacteria that are common in soil and food production. This group includes coryneform bacteria, propionic acid bacteria, mycobacteria, and actinomycetes. Each group has a different shape, growth pattern, and role.

Coryneform bacteria are aerobic, nonmotile rods that often look irregular, club-shaped, or V-shaped. Their V-shape comes from snapping division. In this process, the inner cell wall forms the cross-wall first, while the outer wall stays intact until it breaks on one side, which bends the daughter cells apart.

The main coryneform genera are Corynebacterium and Arthrobacter. Corynebacterium includes species that range from harmless saprophytes to pathogens such as Corynebacterium diphtheriae. Arthrobacter is found mainly in soil and can switch between rod and coccus forms during its life cycle. It is also very resistant to drying and starvation, even though it does not form spores. Arthrobacter can break down herbicides, caffeine, nicotine, and phenols, so it plays an important role in soil ecosystems.

Propionic acid bacteria, or Propionibacterium, were first found in Swiss cheese. They carry out fermentation that produces carbon dioxide, which forms the holes, and propionic acid, which adds flavor. These gram-positive anaerobes can ferment lactic acid, carbohydrates, and polyhydroxy alcohols to make propionic acid, acetic acid, and CO2. During Swiss cheese making, they take part in secondary fermentation by using lactate made by Streptococcus and Lactobacillus as the curd forms. As the curd drains, the bacteria multiply and release CO2. The gas builds up at weak points and creates the cheese holes. Propionigenium is a different bacterium that also produces propionate, but it does so through succinate fermentation.

Mycobacteria are common soil bacteria, and most are harmless. Some species, however, are major human pathogens, including Mycobacterium tuberculosis, which causes tuberculosis. These rod-shaped bacteria are acid-fast because their cell walls contain mycolic acids, which are complex lipids that make the surface waxy and water repellent. They do not stain well with the Gram stain and instead are identified with the Ziehl-Neelsen acid-fast stain, where they keep the red dye while non-acid-fast cells stain blue.

Mycobacteria may look pleomorphic and can sometimes form branching shapes, but they do not make true mycelia like actinomycetes. They include slow-growing species such as M. tuberculosis, M. avium, and M. bovis, and fast-growing species such as M. smegmatis and M. chelonae. Slow growers need longer incubation and form tight, wrinkled, hydrophobic colonies because of their high lipid content. They grow aerobically in simple mineral salts media and can use ammonium as a nitrogen source and glycerol or acetate as a carbon source. M. tuberculosis grows better when lipids and fatty acids are present. Its virulence is linked to cord-like cell groups formed by cord factor, a glycolipid.

Some mycobacteria also make carotenoid pigments that help with identification. They may be nonpigmented, photochromogenic and pigment only in light, or scotochromogenic and pigment even in the dark. These carotenoids likely protect the cells from oxidative damage caused by singlet oxygen.

Actinomycetes are filamentous, aerobic, gram-positive bacteria that are commonly found in soil. Many form desiccation-resistant spores during their developmental cycle. Their growth starts with filament elongation and branching, which creates a mycelium that looks like fungal growth. When nutrients are low, aerial hyphae develop and form spores for survival and spread.

Streptomyces is the most important actinomycete genus and includes more than 500 species. Its filaments are usually 0.5 to 1.0 micrometers wide, grow at the tips, and branch often to form a dense mycelium. As colonies mature, aerial filaments called sporophores appear and make spores called conidia. Unlike Bacillus and Clostridium endospores, conidia form by cross-wall division in the sporophores. Species are classified by differences in aerial filaments and spore structures. Mature Streptomyces colonies are compact, pigmented, and dusty, which makes them easy to spot on agar plates.

Actinobacteria: Soil Bacteria and Cheese

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Alveolates are protists with tiny sacs called alveoli beneath the cell membrane. These sacs may help control water balance by limiting how much water moves in and out of the cell. In dinoflagellates, alveoli may also act like armor plates. The three main alveolate groups are ciliates, dinoflagellates, and apicomplexans. Ciliates move with cilia, which are short hair-like structures that can cover the whole cell or appear in rows or tufts. One well-known ciliate is Paramecium, which uses cilia...

diversity of protists iii

Rhizaria: Pseudopods, Tests, and Skeletons

Rhizaria are unicellular protists with threadlike pseudopodia, which are thin cytoplasmic extensions used for movement and feeding. Their amoeboid shape once caused taxonomic confusion, but molecular phylogenetics has since shown where they fit on the evolutionary tree. This group includes Chlorarachniophyta, Radiolaria, and Foraminifera, and each lineage has adapted to a different ecological niche and metabolic strategy. Chlorarachniophyta are unicellular phototrophic protists found in marine...

diversity of protists iv

Amoebozoa: Movement and Life Cycles

Amoebozoa are a diverse group of terrestrial and aquatic protists. They move and feed with lobe-shaped pseudopodia. This feature sets them apart from Rhizaria, which have threadlike pseudopodia. The group includes gymnamoebas, entamoebas, and the plasmodial and cellular slime molds. Phylogenetic evidence also shows that Amoebozoa split from a lineage that later gave rise to fungi and animals. Gymnamoebas are free-living protists that live in water and soil. They move by amoeboid movement,...

key terms and concepts

Learn how Actinobacteria include soil microbes, acid-fast mycobacteria, and Streptomyces, plus the bacteria that create Swiss cheese holes.

Actinobacteria: Soil Bacteria and Cheese | JoVE K12

JoVE Core Microbiology provides an engaging introduction to the microbial world and its influence on health, industry, and the environment. This comprehensive collection covers key concepts such as microbial structure, metabolism, genetics, and ecology. It introduces essential laboratory techniques and microscopy methods through visually engaging animations. Corresponding scientist-in-action videos bridge classroom concepts with real-world research and applications.

microbiology

Actinobacteria: Soil Bacteria and Cheese

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