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

1. ACTINOMYCE
TES
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, Corynebacterium,
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

3. • They are the true bacteria (not fungus)
• Placed in the kingdom “Bacteria” and a class “Actinobacteria”.
• They are ubiquitous in nature (commonly found in soil).
• They 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:
1.Actinomycetes usually have 1-2 µm diameter.
2.They generally possess a rod shape with a filamentous or branched structure.
3.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 (106-108g) 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:
1.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.
2.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.
3.Coiling: During unfavourable conditions, the aerial hyphae turn into a spiral shape.
4.Septation: At this stage, a septum forms between the vegetative hyphae.
5.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.
1.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.
2.Nocardiaceae: Members of this family possess typical non-segmented hyphae.
Examples: Nocardia, Pseudonocardia.
3.Micromonosporaceae: Members of this family possess typical non-segmented conidia that generally exist
singly, in pairs or in chains. Examples: Micromonospora, Thermonospora, Thermoactinomycetes, Actinobifida.
4.Actinoplanaceae: Members of this family have sporangiospores and hyphae (0.2-2.0 µm wide).
Examples: Streptosporangium, Actinoplanes, Plasmobispora and Dactylosporangium.
5.Dermatophilaceae: Members of this family possess hyphae that undergo fragmentation to give rise to a
large number of motile structures. Examples: Geodermatophilus.
6.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.
7.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

9. www.intechopen.com
www.intechopen.com

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 Erythromycin 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.

13. Thank you for
watching
LIKE
SHARE n
SUBSCRIB
E
www.intechopen.com