ACTINOMYCETES.pptx

Bacteria-ACTINOMYCETES.

Details on actinomycetes in this PPT. For video visit Microbial Concepts on You Tube.

1. ACTINOMYCETES Microbial Concepts

2. Actinomycetes Actinomycetes belong to the group of prokaryotic, Gram-positive bacteria those are having a filamentous structure . Its filamentous structure resembles the fungal mycelium, which consists of a highly dense and  filamentous  network. Due to the filamentous structure of actinomycetes, it is also termed as  thread  or  ray bacteria . The cell wall and the internal structure of the actinomycetes are similar to the group of bacteria. Thus, actinomycetes refer to the filamentous actinobacteria that serve as a  connecting link  between the bacteria and fungi and shows resemblance with both. They include members like Mycobacterium, C orynebacterium, Streptomyces, and Actinomyces. The diameter of an actinomycete cell is much smaller (1-2 µm) than the branched fungi (ranges between 5 µm-10 µm). biologyreader.com DON’T GET CONFUSE WITH FUNGI

3. They are the  true bacteria  (not fungus) P laced in the kingdom “Bacteria” and a class “ Actinobacteria ”. They are ubiquitous in nature (commonly found in soil). T hey are also very common in marine habitat and considered as a treasure house of  secondary metabolites . Actinomycetes behave like  decomposers , which carry out the degradation of organic compounds like chitin, complex sugars, hemicellulose etc. Its filamentous forms are predominantly aerobic, while a few are anaerobic. They can produce a filamentous, dense, branched and raised colony over the substrate like fungi. The filamentous forms of actinomycetes are aerobic and they may produce spore singly or in chains. Its colony appears as a pigmented powdery mass due to the formation of aerial spores.

4. Classification : Domain : Bacteria Phylum : Actinobacteria Class : Actinobacteria Order : Actinomycetales Family : Actinomycetaceae Characteristics Actinomycetes share the following physicochemical properties: Actinomycetes usually have  1-2 µm  diameter. They generally possess a rod shape with a filamentous or branched structure. The filaments contain  mumaric acid . 4.Most of the species are  aerobic , while a few are anaerobes to facultative aerobes. 5.Cell wall and internal structures are similar to bacteria. The cell wall of actinomycetes consists of  mycolic acid . 6. The growth or reproduction of actinomycetes is slower than the bacteria and fungi. Hence, actinomycetes are sometimes called as “ Slow growers ”. 7.They are having  60-78%  of G+C content. 8.Actinomycetes are most abundant in  soil  (10 6 -10 8 g) and  marine habitat . 9.The majority of species are usually non-motile, non-capsulated and non-acid fast. 10. They show optimum growth at  alkaline pH . 11. Colony is hard to pick from media plate and you may actinomycetes plate has earthy odor/ smell. Science source

5. Image source: Science Photo Library Image source: bacdive.dsmz.de

6. Life Cycle of Actinomycetes Their life cycle includes the following stages: Germination : The spores of actinomycetes remain dispersed in the environment as a “ Free spore ”. Free spore remains dormant until the stage of germination. When the spores get favourable conditions, they start the germination process by forming a germ tube. Vegetative growth : The germ tube promotes vegetative growth, which eventually gives rise to the substrate and aerial hyphae. First, a germ tube will produce a primary mycelium, i.e.  substrate hyphae  that grow within the media. After the growth of primary mycelium, a secondary mycelium, i.e.  aerial hyphae  forms above the substratum. Coiling : During unfavourable conditions, the aerial hyphae turn into a  spiral shape . Septation : At this stage, a  septum  forms between the vegetative hyphae. Spore maturation : A septum within the vegetative hyphae maturates and forms a  chain of spores . Thus, the spores originate via fragmentation or swelling of the hyphae. 6.Release of spore : During unfavourable conditions, the spores detach from the vegetative hyphae and remain free in the environment.

7. Classification Actinomycetes have seven families, based on the hyphal and reproductive structures. Streptomycetaceae : Members of this family consist of non-segmented hyphae and 5-50 conidial spores per chain of aerial hyphae. Examples:  Streptomyces ,  Microdlobaspone  and   Sporoctilhya . Nocardiaceae : Members of this family possess typical non-segmented hyphae. Examples:  Nocardia ,  Pseudonocardia . Micromonosporaceae : Members of this family possess typical non-segmented conidia that generally exist singly, in pairs or in chains. Examples:  Micromonospora ,  Thermonospora ,  Thermoactinomycetes ,  Actinobifida . Actinoplanaceae : Members of this family have sporangiospores and hyphae (0.2-2.0 µm wide). Examples:  Streptosporangium ,  Actinoplanes ,  Plasmobispora  and  Dactylosporangium . Dermatophilaceae : Members of this family possess hyphae that undergo fragmentation to give rise to a large number of motile structures. Examples:  Geodermatophilus . Frankiaceae : Members of this family are strictly associated with the roots of a non-leguminous plant and help in nitrogen fixation by forming root nodules. Example:  Frankia . Actinomycetaceae : The members of this family do not contain true mycelium and are facultative anaerobes. Examples:  Actinomyces .

8. Image source: Research gate Type of spore-bearing structure in streptomycetes Essaid Ait Barka ,  Parul Vatsa , Lisa Sanchez, Nathalie Gaveau -Vaillant, Cedric Jacquard, Hans-Peter Klenk , Christophe Clément,  Yder Ouhdouch , Gilles P. van Wezel Image source: mmbr.asm.org Taxonomy, Physiology, and Natural Products of  Actinobacteria

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10. Economic Importance Use in Bioremediation Actinomycetes digest complex carbohydrates like chitin, cellulose, hemicellulose etc. It also helps in the  degradation  of toxic compounds from the environment. Thus, it plays an essential role in the bioremediation of organic compounds. Actinomycetes can survive in a harsh environment like high temperature up to 50 degrees Celsius that is crucial for the  composting  process. Use in Regulating Plant growth Actinomycetes inhabit the soil and produce phytohormones, extracellular enzymes and bioactive compounds. These compounds promote direct plant growth and protect against phytopathogens and pests by producing indole 3-acetic acid , siderophore and solubilize phosphate.

11. Biomedical Use Members of actinomycetes can produce many of the best-known antibiotics like Amphotericin, Neomycin, Novobiocin, Chloramphenicol, Tetracycline etc. Tetracycline  and  E rythromycin  etc. target bacterial ribosomes and cures respiratory infections. Vancomycin  mainly attacks the bacterial cell wall of pathogenic bacteria ( Streptococcus aureus ). Rifampicin  targets bacterial RNAP (RNA-Polymerase) and cures tuberculosis and leprosy. Adriamycin  treats cancer. Amphotericin  attacks fungal membranes and shows a few side effects. Rapamycin  enables organ transplant. Industrial Use Actinomycetes produce several enzymes, which show a wide range of applications in different fields like: Lipase  in detergent and pharmaceuticals industries. Cellulases  in the animal feed industry. Catalase  in the detergent industry. Amylase  in food, textile and paper industries. Chitinase  in biochemical industries.

12. Use as Agro -active compounds Actinomycetes produce agro -active compounds as they are extensively present in the rhizospheric zone of the plant. Thus, they can actively colonize themselves with the plant roots and protect the plant from pathogenic fungi and other phytopathogens. Frankia is an example of actinomycetes, which acts as a “ Symbiont ” that promote root nodule formation and thereby in nitrogen fixation. Prevents Biocorrosion. Actinomycetes produce secondary metabolites, which act as  AMSs  (Antimicrobial substances). These antimicrobial substances attack pathogenic and phytopathogenic microorganisms, which can cause biocorrosion. Use as Biopesticide Actinomycetes are also used as a biopesticide that attacks insects like  Musca domestica ,  Culex quinquefasciatus  etc. It kills 90% of insects at their larval and pupal stage.

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