Microbiology Overview and Taxonomy

Microbiology

• Study of microorganisms: bacteria, viruses, fungi, protozoa, and algae.
• Microorganisms are typically too small to be seen with the naked eye.
• Research focuses on their roles in diseases, environmental processes, and industrial applications.

Three Domains of Taxonomy

• Bacteria:
  • Prokaryotic, single-celled, with peptidoglycan in cell walls.
  • Adaptable to diverse environments (soil, water, human body).
• Archaea:
  • Prokaryotic, single-celled, unique cell walls containing pseudomurein.
  • Thrives in extreme conditions (hot springs, salt lakes).
• Eukarya:
  • Eukaryotic, cells possess a nucleus.
  • Includes animals, plants, fungi, and protists with complex organelles.

Groups of Life

• Bacteria: Single-celled, ubiquitous, prokaryotic.
• Archaea: Prokaryotic, often found in extreme environments.
• Fungi: Eukaryotic, decomposers; includes molds and yeasts.
• Protozoa: Eukaryotic, motile, single-celled, typically aquatic.
• Algae: Eukaryotic, photosynthetic, can be unicellular or multicellular in water.
• Helminths: Multicellular parasitic worms (e.g., tapeworms, roundworms).
• Viruses: Non-living entities made of genetic material and a protein coat; require a host to replicate.

Importance of Microorganisms

• Food Production: Yeast used in bread, beer, and wine making.
• Decomposition: Bacteria and fungi recycle nutrients from dead organic matter.
• Nitrogen Fixation: Certain bacteria convert atmospheric nitrogen for plant use.
• Biotechnology: Bacteria produce important medicines like insulin and antibiotics.
• Digestive Health: Gut bacteria assist in food digestion and vitamin production.

Pathogens

• Microorganisms that can cause diseases.
• Primary Pathogen: Causes disease in healthy hosts (e.g., Mycobacterium tuberculosis).
• Opportunistic Pathogen: Produces disease when host defenses are weakened (e.g., Candida albicans).

Microbes and Their Classifications

• Microbe: A microorganism, such as a bacterium, virus, or fungus.
• Microbiology: Field studying microbes and their interactions with living organisms and environment.
• Major Microorganism Types:
  • Bacteria: Prokaryotic, single-celled.
  • Archaea: Prokaryotic, often extremophiles.
  • Fungi: Can be unicellular or multicellular.
  • Protozoa: Eukaryotic, single-celled, motile.
  • Algae: Eukaryotic, photosynthetic.
  • Viruses: Non-living, host-reliant for replication.

Prokaryotic vs. Eukaryotic Cells

• Prokaryotic Cells:
  • Lack a nucleus and membrane-bound organelles.
  • Typically smaller and simpler.
  • Contain one circular chromosome and divide by binary fission.
• Eukaryotic Cells:
  • Have a nucleus and organelles.
  • Larger and more complex structure.
  • Possess paired chromosomes and divide by mitosis.

Bacteria vs. Archaea

• Bacteria:
  • Contain peptidoglycan in cell walls.
  • Decomposers crucial for nutrient recycling.
  • Some are nitrogen-fixing and photosynthetic.
• Archaea:
  • Cell walls made of pseudomurein.
  • Thrive in extreme environments, non-pathogenic.
• Both are prokaryotic but differ in cell wall composition and habitats.

Endosymbiotic Theory

• Proposes eukaryotic cells evolved from engulfed prokaryotic cells.
• Endosymbionts became organelles like mitochondria and chloroplasts.
• Mitochondria and chloroplasts possess their own DNA resembling prokaryotic cells.

Protista: Algae vs. Protozoa

• Algae:
  • Photosynthetic, produce oxygen, and have cellulose or silica cell walls.
  • Can be unicellular or multicellular.
• Protozoa:
  • Heterotrophic, typically mobile with no cell wall, and unicellular.
• Both are classified under Protista but vary in nutrition and structure.

Viruses

• Small, non-living particles composed of genetic material in a protein coat.
• Must infect host cells to replicate, do not fit into the tree of life, existing outside traditional life classifications.

Significance of DNA

• Carries genetic information essential for all life forms.
• Encodes instructions for protein synthesis, determining traits like eye color and enzyme activity.
• DNA replication ensures heredity across generations.

Protists

• Represent the first eukaryotes, marking the evolutionary transition from prokaryotes.