Microbial Biotechnology (408 AMB)

Microbial Biotechnology (408 AMB)

• Microbial biotechnology applies scientific and engineering principles to raw materials using microorganisms or microbial substances for commercial products and services.
• The United Nations Convention on Biological Diversity defines biotechnology as any technological application that uses biological systems or living organisms to make or modify products or processes for specific use.
• Biotechnology involves using living organisms or substances from organisms to:
  • modify or make new products or processes
  • improve plants or animals
  • develop microorganisms for specific uses
• Biotechnology uses scientific and engineering principles applied to raw materials using biological agents to create commercial products.
• Raw materials include organic and inorganic materials.
• Biological agents include microorganisms, microbial products, animal cells, and plant cells.
• Biotechnology disciplines include:
  • Red Biotechnology (Medical)
  • Green Biotechnology (Agriculture)
  • White Biotechnology (Industrial)
  • Blue Biotechnology (Marine)

Microbial Products Classification

• Microbial products are categorized into 6 industrial sectors:
  • Chemical sector (enzymes, polysaccharides, organic solvents, organic acids)
  • Pharmaceutical and health sector (antibiotics, therapeutic enzymes, vaccines, antibodies, human hormones, biosensors, gene therapy)
  • Energy sector (ethanol, methane biogas)
  • Food sector (baker's yeast, food additives, beverages, single cell protein)
  • Agricultural sector (microbial fertilizers, tissue culture, transfer of nif-gene for nitrogen fixation, increasing milk, meat and egg production, veterinary vaccines, production of animal feed)
  • Environmental sector (removing heavy metals from water, biodegradation of oil, plastics)

Antimicrobial Agents

• Antimicrobial agents are chemical compounds that kill or inhibit the growth or metabolism of microorganisms without significant toxicity to the host.
• Examples of antimicrobial agents include antibacterial drugs, antiviral agents, antifungal agents, and antiparasitic drugs.
• Antibiotics are secondary metabolites produced by some microorganisms that kill or inhibit other microorganisms even at low concentrations.
  • Common antibiotic-producing microorganisms include bacteria, actinomycetes, and fungi.

Classification of Antibiotics

• Antibiotics are classified based on:
  • Antimicrobial spectrum
  • Chemical structure
  • Manner of biosynthesis
  • Producer strain
  • Mode of action

Antimicrobial Spectrum

• The antimicrobial spectrum determines the range of microbial species susceptible to a specific antimicrobial agent.
• Antibiotics can have a broad spectrum (active against a wide range of microorganisms) or narrow spectrum (active against a limited range of microorganisms).
• The spectrum of activity can change with the acquisition of resistance genes.

Antibiotics Mode of Action

• Inhibition of cell wall synthesis is a major mode of action for some antibiotics.
  • Bacteria need to synthesize new peptidoglycan to increase size during binary fission. This involves breaking down existing connections and inserting new monomers while reforming peptide crosslinks.
  • Some antibiotics block the formation of cell walls, causing the cell to break down.
  • Microorganisms like Mycoplasma and Archaea are resistant to some antibiotics because they lack peptidoglycans in their cell walls. Archaea have pseudopeptidoglycans which differ chemically.
• Destruction of the cell membrane is another mechanism. Some antibiotics create pores or channels across the bacterial cell membrane, causing permeabilization, and thereby impairing transport into and out of the cell.
• Inhibition of protein synthesis involves binding to ribosome subunits (30S and 50S), blocking tRNA attachment, misreading mRNA, or interfering with amino acid binding.
• Inhibition of nucleic acid synthesis can halt DNA or RNA replication.
• Competitive inhibition occurs when an antibiotic's structure resembles the enzyme's substrate, blocking the substrate from binding to the active site, thereby inhibiting the synthesis of the product. It can also bind to an allosteric site on the enzyme.
• Bactericidal antibiotics irreversibly kill bacteria by interfering with cell wall formation or cell content.
• Bacteriostatic antibiotics inhibit bacterial growth and reproduction. The cells stop dividing; however, if the antibiotic is removed, these cells start multiplying again.
• Some drugs that are bacteriostatic at lower concentrations can be bactericidal at higher concentrations.

Isolation of Antimicrobial-Producing Microorganisms

• Methods include crowded plate and spot-on-lawn methods.
  • Crowded plate method: isolates antibiotic-producing microorganisms without regard to their sensitivity to the antimicrobial compound; uses serial dilutions for inoculation on plates and observation of inhibition zones around colonies.
  • Spot-on-lawn method: the test microorganism serves as an indicator for antimicrobial activity; serial dilutions of the sample are prepared and spotted on a lawn of the test microorganism. Incubation will reveal areas around spots where no microbial growth occurred.
  • Both have possible disadvantages regarding the selection of organisms and presence of inhibition not directly related to the antibiotic compound being screened.