Actinomycetes: Characteristics Overview

Actinomycetes: Introduction and Characteristics

• Actinomycetes are prokaryotic, unicellular organisms with a gram-positive cell wall.
• Their morphology resembles fungi, but they are more closely related to bacteria.
•  Classification: Domain: Bacteria; Phylum: Actinobacteria; Class: Actinobacteria; Order: Actinomycetales; Family: Actinomycetaceae
• Size: Typically 1-2 µm in diameter.
• Shape: Primarily rod-shaped, often with filamentous and branched structures.
• Cell wall: Contains muramic acid and mycolic acid.
• Metabolism: Mostly aerobic, but some species are anaerobic or facultative anaerobes.
• Growth rate: Slower than bacteria and fungi, hence called "slow growers."
•  Genetic composition: Possessing a G+C content of 60-78%.
• Habitat: Abundant in soil (10⁰-10¹⁰ g) and marine environments.
• Motility: Usually non-motile, non-encapsulated, and non-acid-fast.
• Optimal growth pH: Alkaline pH.

Industrial and Economic Importance of Actinomycetes

• Actinomycetes play crucial roles in various industries.
• Bioremediation: Digest complex carbohydrates (chitin, cellulose, etc.) and degrade toxic compounds in the environment. They can survive high temperatures (50°C) critical for composting.
•  Industrial use: Produce enzymes with diverse applications, lipase (detergents, pharmaceuticals), cellulases (animal feed), catalase (detergents), amylase (food, textiles, paper), and chitinase (biochemical industries).

Biomedical Use of Actinomycetes

• Produce important antibiotics like amphotericin, neomycin, novobiocin, chloramphenicol, tetracycline, erythromycin.
• Used to target bacterial ribosomes (tetracycline, erythromycin) and cure respiratory infections.
• Vancomycin is effective against bacterial cell walls (e.g., Streptococcus aureus).
• Rifampicin targets bacterial RNA polymerase, useful for tuberculosis and leprosy treatment.
• Adriamycin treats cancer.
• Rapamycin assists in organ transplantation.
• Amphotericin primarily affects fungal membranes.
• Many antibiotics are derived from Actinomycetes.

Actinomycetes in Plant Growth Regulation

• Actinomycetes in soil produce phytohormones, extracellular enzymes, and bioactive compounds.
• The compounds promoted plant growth and protect plants against pathogens and pests.
• E.g. indole-3-acetic acid, siderophores, and phosphate solubilizers.

Use as Agroactive Compounds

• Present extensively in the rhizosphere aiding plant growth.
• Protect roots from pathogenic fungi by preventing biocorrosion.
• Examples like Frankia promote root nodule formation and nitrogen fixation.

Use as Biopesticides

• Control insects like Musca domestica and Culex quinquefasciatus, especially in their larval/pupal stage to kill about 90%.
• Produce diverse hydrolyzing enzymes that are also environmentally friendly.

Role of Actinomycetes in Soil

• Decomposition of complex polymers, soil organic matter cycle.
• Inhibition of plant pathogens, soil buffering, major role in crop production.
• Degradation of high molecular weight compounds (e.g., hydrocarbons) in polluted environments.
• Crucial for compost formation and humus development,
• Improve nutrient availability, support soil health through stability and formation of humus.
• Collaboration with other soil microorganisms in nutrient cycling.

Biological Nitrogen Fixation by Actinomycetes

• Play crucial role in the nitrogen cycle via transforming nitrogen into various forms.

Explore the fascinating world of actinomycetes, unique prokaryotic organisms that bridge the gap between bacteria and fungi. This quiz delves into their classification, morphology, metabolism, and ecological significance, highlighting their crucial roles in both nature and industry. Perfect for students and enthusiasts in microbiology and related fields.