Monera and Bacterial Cell Structure

Monera: General Introduction

• Monera is a kingdom classifying prokaryotic organisms (those lacking a nucleus or membrane-bound organelles).
• Its two major groups are bacteria and cyanobacteria (blue-green algae).
• Bacteria are unicellular, microscopic, and ubiquitous.

Bacterial Cell Structure

• Bacteria possess a simple structure compared to eukaryotic cells.
• Cell Wall: Provides shape and protection, composed of peptidoglycan.
• Cell Membrane: Regulates substance movement in and out of the cell.
• Cytoplasm: Gel-like, containing enzymes, ribosomes, and genetic material.
• Nucleoid: Region containing circular DNA, without a nuclear membrane.
• Plasmids: Small, circular DNA carrying extra genes like antibiotic resistance.
• Flagella: Whip-like structures facilitating movement.
• Pili: Hair-like structures for attachment and conjugation (genetic material transfer).
• Capsule: Slimy outer layer for protection and adhesion.

Mode of Nutrition in Bacteria

• Bacteria are classified by nutrition: autotrophic and heterotrophic.
• Autotrophic bacteria synthesize their own food.
  • Photoautotrophs use sunlight for energy (e.g., cyanobacteria).
  • Chemoautotrophs use inorganic chemicals for energy (e.g., nitrifying bacteria).
• Heterotrophic bacteria depend on organic matter for food.
  • Saprophytes feed on dead organic matter.
  • Parasites feed on living hosts.
• Symbiotic bacteria live in mutualistic relationships (e.g., nitrogen-fixing bacteria in legume roots).

Bacterial Growth

• Bacteria reproduce asexually through binary fission (one cell divides into two identical cells).
• Bacterial growth occurs in four phases:
  • Lag Phase: Adaptation to the environment.
  • Log Phase: Exponential growth.
  • Stationary Phase: Growth rate equals death rate.
  • Death Phase: Nutrients deplete, cells die.

Cyanobacteria (Blue-Green Algae)

• Cyanobacteria are photosynthetic bacteria producing oxygen.
• Their structure is similar to bacteria but contains chlorophyll-a and phycobilins for photosynthesis.
• Some have specialized cells called heterocysts for nitrogen fixation.
• Cyanobacteria are photoautotrophic and are environmentally important.
• They contribute to oxygen production and fix atmospheric nitrogen, enriching soil fertility.
• They form symbiotic relationships, such as with fungi to form lichens.

Virus: General Introduction

• Viruses are non-living, infectious agents replicating inside a host cell.
• They are obligate intracellular parasites, requiring a host to reproduce.
• Viruses infect bacteria, plants, and animals.

Structure of a Virus

• A virus consists of:
  • Genetic Material: DNA or RNA, single or double-stranded.
  • Capsid: Protein coat protecting the genetic material.
  • Envelope: Lipid membrane surrounding the capsid in some viruses, derived from the host cell.
  • Spikes: Glycoproteins on the surface that aid in host cell attachment.

Importance of Viruses

• Viruses have negative and positive impacts.
• Negative: Cause diseases in humans (HIV, influenza), animals, and plants.
• Positive: Used in gene therapy to deliver genes and bacteriophages are used in biotechnology and medicine.
• They play a role in controlling bacterial populations in nature.

Bacteriophage

• A bacteriophage is a virus infecting bacteria.
• It includes:
  • Head: Contains DNA or RNA.
  • Tail: Injects genetic material into the host cell.
• Bacteriophages are essential in research, for example, in the Hershey-Chase experiment proving DNA is the genetic material.
• They have potential use in treating antibiotic-resistant bacterial infections.

Impacts of Biotechnology in Microbiology

• Biotechnology has many applications in microbiology:
  • Genetic Engineering: Modifying microorganisms to produce insulin, vaccines, and enzymes.
  • Bioremediation: Using bacteria to clean up oil spills and toxic waste.
  • Agriculture: Developing genetically modified, pest and disease-resistant crops.
  • Medicine: Producing antibiotics, vaccines, and monoclonal antibodies.
• Ethical Issues include:
  • Risk of creating harmful pathogens.
  • Concerns about genetically modified organisms (GMOs) in the environment.
  • Intellectual property rights over genetically engineered organisms.