Actenomycetes

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ACTINOMYCETES: : 

ACTINOMYCETES:

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Actinomycetes Actinomycetes are filamentous bacteria. Their morphology resembles that of the filamentous fungi; however, the filaments of actinomycetes consist of prokaryotic cells. Some actinomycetes resemble molds by forming externally carried asexual spores for reproduction. Filamentous, High G + C content, Gram-positive (63 – 78% GC)

ACTINOMYCETES MORPHOLOGY : 

ACTINOMYCETES MORPHOLOGY Have filamentous growth, like fungi On substrate, grow on and in it Thallus -- tissuelike mass, grown in culture Mycelium -- tangled mass of hyphae, found in nature

ACTINOMYCETES MORPHOLOGY : 

ACTINOMYCETES MORPHOLOGY

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An actinomycete colony growing on agar - note the subterranean and aerial hyphae…. ACTINOMYCETES MORPHOLOGY

ACTINOMYCETES REPRODUCTION : 

Actinomycetes (and fungi) reproduce via spores Hyphal growth is followed by fragmentation and release of spores Conidia –spores produced asexually on aerial filaments called sporophores Shape and arrangement of sporophores help identification of actinomycete taxa ACTINOMYCETES REPRODUCTION

ACTINOMYCETES REPRODUCTION : 

ACTINOMYCETES REPRODUCTION formation of cross-walls in the multinucleate sporophores. followed by separation of the individual cells directly into spores.

Various types of spore-bearing structures : 

Various types of spore-bearing structures

Fig. 11.19 : 

Fig. 11.19 Conidia of Streptomyces ACTINOMYCETES REPRODUCTION

ACTINOMYCETES:Ecology : 

ACTINOMYCETES:Ecology

ACTINOMYCETES ECOLOGY : 

ACTINOMYCETES ECOLOGY Predominantly soil bacteria Good at degrading recalcitrant compounds such as chitin & cellulose Often active at higher pH (contrast to fungi who may dominate at lower pH) Give soil the “earthy” smell

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Genus Frankia – --large genus that all form nodules on certain non-legume trees --fixes nitrogen from the air and converts into forms useable by plant host --involved in “tripartite” relationship with plant and mycorrhizal fungus. ACTINOMYCETES ECOLOGY

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ACTINOMYCETES ECOLOGY Frankia nodules on Ceanothus roots

ACTINOMYCETES:antibiotics : 

ACTINOMYCETES:antibiotics

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• Most important genus is Streptomyces - over 500 described species! • Produce many important antibiotics, including Streptomycin - originally from S. griseus. ACTINOMYCETES ANTIBIOTICS

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Other antibiotics produced by Streptomyces spp: Antibiotic: affects: Spectinomycin M. tuberculosis, N. gonorrhea Neomycin Broad spectrum, topical Tetracyclines Broad spectrum, Chlamydias, Rickettsias etc. Nystatin Fungi, esp. Candida Erythromycin Gram + Bacteria and Legionella Chloramphenicol Broad spectrum, typhoid fever ACTINOMYCETES ANTIBIOTICS

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ACTINOMYCETES ANTIBIOTICS Inability of a test organism to grow in the presence of Streptomyces suggests antibiotic production by the latter

Fig. 04.18 : 

Fig. 04.18 Secondary metabolites are produced at the end of the growth phase and during stationary phase…. ACTINOMYCETES ANTIBIOTICS

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