Genetics and Evolution- Molecular Basis of Inheritance - Types of Operon System in bacteria

Slide 1:

  • Introduction to types of operon system in bacteria
  • Genes and their expressions in bacteria
  • Operon as a regulatory system in bacteria

Slide 2:

  • Definition of operon system
  • Role in gene regulation
  • Types of operon systems in bacteria

Slide 3:

  • Lac operon system
  • Components of lac operon
  • Role of lac operon in lactose metabolism

Slide 4:

  • Inducible operon system
  • Definition and characteristics
  • Examples of inducible operon systems in bacteria

Slide 5:

  • Trp operon system
  • Components of trp operon
  • Role of trp operon in tryptophan synthesis

Slide 6:

  • Repressible operon system
  • Definition and characteristics
  • Examples of repressible operon systems in bacteria

Slide 7:

  • Comparison between inducible and repressible operon systems
  • Regulation mechanisms in each system
  • Examples of genes regulated by each system

Slide 8:

  • Positive control of operon systems
  • Role of positive control in gene expression
  • Examples of positive control in bacteria

Slide 9:

  • Negative control of operon systems
  • Role of negative control in gene expression
  • Examples of negative control in bacteria

Slide 10:

  • Regulation of gene expression in bacteria
  • Importance of operon systems in bacterial physiology
  • Summary of types of operon systems in bacteria

Slide 11:

  • Lac Operon System
    • Consists of three genes: lacZ, lacY, and lacA
    • lacZ encodes β-galactosidase enzyme
    • lacY encodes lactose permease membrane protein
    • lacA encodes transacetylase enzyme

Slide 12:

  • Regulation of Lac Operon
    • Controlled by the lac repressor protein
    • In the absence of lactose, the lac repressor binds to the operator region and inhibits expression
    • In the presence of lactose, inducer molecule allolactose binds to the lac repressor, causing it to be released from the operator

Slide 13:

  • Inducible Operon Systems
    • Require inducer to activate gene expression
    • Examples: Lac operon, Tetracycline resistance operon (tet operon)
    • Inducer binds to repressor protein and prevents it from binding to the operator, allowing gene expression

Slide 14:

  • Trp Operon System
    • Involved in tryptophan synthesis
    • Consists of five genes: trpEDCBA
    • trpE and trpD encode enzymes for tryptophan biosynthesis
    • trpA, trpB, trpC encode enzymes for tryptophan regulation

Slide 15:

  • Regulation of Trp Operon
    • Controlled by the trp repressor protein
    • In the absence of tryptophan, the repressor is inactive and the operon is expressed
    • In the presence of tryptophan, the repressor binds to the operator and blocks gene expression

Slide 16:

  • Repressible Operon Systems
    • Require corepressor to inhibit gene expression
    • Examples: Trp operon, Arginine biosynthesis operon (arg operon)
    • Corepressor binds to repressor protein and activates it, preventing binding to the operator, thereby inhibiting gene expression

Slide 17:

  • Positive Control of Operon Systems
    • Involves activator proteins that enhance gene expression
    • Examples: Catabolite activator protein (CAP) in lac operon, CRP in trp operon
    • Activator proteins bind to specific DNA sequences and stimulate RNA polymerase binding and transcription

Slide 18:

  • Negative Control of Operon Systems
    • Involves repressor proteins that inhibit gene expression
    • Examples: Lac repressor in lac operon, Trp repressor in trp operon
    • Repressor proteins bind to DNA sequences and prevent RNA polymerase binding and transcription

Slide 19:

  • Regulation of Gene Expression in Bacteria
    • Operon systems provide a mechanism for gene regulation
    • Environmental cues and availability of substrates determine the activation or inhibition of operon systems
    • Fine-tuned regulation allows bacteria to adapt to changing conditions

Slide 20:

  • Importance of Operon Systems in Bacterial Physiology
    • Efficient utilization of resources in bacterial metabolism
    • Adaptation to changing external environments
    • Conservation of energy by controlling unnecessary gene expression
    • Maintenance of homeostasis in bacteria

Slide 21:

  • Lac Operon as an example of an inducible operon system
  • Inducible operons are usually turned off until specific conditions activate them
  • In the case of the lac operon, lactose acts as the inducer

Slide 22:

  • Tetracycline Resistance Operon (tet operon) as an example of an inducible operon system
  • The presence of tetracycline induces the expression of genes involved in resistance to the antibiotic
  • Inducer molecules can be natural substances, metabolites, or environmental cues

Slide 23:

  • Trp Operon as an example of a repressible operon system
  • Repressible operons are usually turned on until specific conditions inhibit them
  • In the case of the trp operon, tryptophan acts as the corepressor

Slide 24:

  • Arginine Biosynthesis Operon (arg operon) as an example of a repressible operon system
  • The presence of arginine inhibits the expression of genes involved in arginine biosynthesis
  • Corepressor molecules can be natural substances or end products of metabolic pathways

Slide 25:

  • Comparison between inducible and repressible operon systems
  • Inducible operons are activated by specific conditions, while repressible operons are inhibited by specific conditions
  • Inducible operons typically involve the binding of an inducer to an inactive repressor, while repressible operons involve the binding of a corepressor to an active repressor

Slide 26:

  • Catabolite Activator Protein (CAP) in the lac operon
  • CAP activates gene expression by binding to specific DNA sequences called cAMP response elements (CRE)
  • CAP-cAMP complex enhances the binding of RNA polymerase to the lac operon promoter, increasing transcription efficiency

Slide 27:

  • cAMP Regulation in the lac operon
  • cAMP is synthesized from ATP by the enzyme adenylate cyclase
  • Low glucose levels increase intracellular cAMP levels, leading to enhanced binding of CAP to CRE, and increased lac operon expression

Slide 28:

  • Negative Feedback Regulation in operon systems
  • The end product of a metabolic pathway often acts as a corepressor or an inducer, regulating its own synthesis through negative feedback
  • This regulatory mechanism helps to maintain balanced levels of metabolites and prevent unnecessary overproduction or depletion

Slide 29:

  • Importance of operon systems in bacterial adaptation
  • Operon systems allow bacteria to rapidly respond to changes in their environment and adjust gene expression accordingly
  • This adaptability provides a selective advantage for bacteria in various ecological niches

Slide 30:

  • Summary of types of operon systems in bacteria
  • Inducible operons are activated by specific conditions and involve inducer molecules
  • Repressible operons are inhibited by specific conditions and involve corepressor molecules
  • Positive and negative control mechanisms further regulate gene expression in operon systems