Famous Microbiologists and Their Contributions

Microbiology Pioneers

• Antonie van Leeuwenhoek, known as the "Father of Microbiology", made lenses and microscopes as a hobby and was one of the first to document bacteria, red blood cells, spermatozoa, muscle fibers, and crystals.
• Robert Hooke, an English scientist, discovered microorganisms using a microscope and coined the term "cell".
• Edward Jenner, known as the "Father of Immunology", developed the concept of vaccines and created the first vaccine against smallpox.

Golden Age of Microbiology (1857-1910)

• Louis Pasteur, a French scientist, developed the germ theory and conducted vaccination experiments against fowl cholera, anthrax, and rabies.
• Pasteurization, a heating process to kill microorganisms, was named after him.
• He also discovered microbial fermentation and developed liquid media for pathogenic bacteria growth.

Robert Koch

• Robert Koch, a German scientist, discovered the causative agents of tuberculosis, cholera, and anthrax.
• He developed the bacterial culture method using agar on glass plates and invented Koch's postulates to identify disease-causing bacteria.

Bacterial Structure and Function

• Bacteria are ubiquitous in nature, constituting normal flora on body surfaces and in the GI tract, and are involved in mutualism/symbiosis.
• The bacterial cell envelope consists of a cell wall and phospholipid membrane.
• Peptidoglycan/murein is unique to bacterial cell walls.
• Gram-positive bacteria have a thicker peptidoglycan/murein layer, while Gram-negative bacteria have a thinner layer and an outer phospholipid membrane with porins.

Exceptions and Variations

• Genus Mycoplasma lacks a cell wall.
• Genus Corynebacterium, Mycobacterium, Nocardia, and Rhodococcus (CMNR group) have a complex cell wall with a mycolic acid layer (mycomembrane).
• Phylum Chlamydiae lacks peptidoglycan and has an outer membrane with lipopolysaccharides (LPS).

Surface Structures

• Capsules are firmly attached to the cell wall and composed of polysaccharides or polypeptides.
• Slime layers are loosely attached to the cell wall and composed of polysaccharides.
• Biofilms are extracellular matrices of polysaccharides that allow bacteria to function together.

Cytoplasmic Structures

• Cytoplasm consists of water, proteins, carbohydrates, lipids, and inorganic ions.
• Nuclear material is organized into a single, long, tightly coiled, circular DNA molecule (nucleoid).
• Plasmids are extrachromosomal DNA that can provide advantages like antimicrobial resistance and virulence factors.
• Inclusions are storage granules that store polysaccharides, phosphorus, and sulfur.
• Ribosomes are smaller and less dense than in eukaryotic cells, composed of 30S and 50S subunits.