History of Microbiology

The First Golden Age of Microbiology

• Joseph Lister introduced antiseptic surgical methods using carbolic acid, greatly reducing surgical infections and validating germ theory.
• Agostino Bassi demonstrated in 1835 that a fungus caused a silkworm disease, the first evidence of a microorganism causing animal disease, supporting germ theory.
• Ignaz Semmelweis found that handwashing with chlorinated lime decreased puerperal fever in maternity wards, highlighting hygiene's importance in disease prevention.
• Robert Koch formulated Koch’s postulates to link specific microbes to diseases, identifying causative agents of anthrax, tuberculosis, and cholera.

Koch’s Postulates

• Postulate 1: Microorganisms should be present in abundance in diseased organisms, absent in healthy ones.
• Postulate 2: They must be isolated and grown in pure culture.
• Postulate 3: Introduced microbes should cause disease in a healthy host.
• Postulate 4: The microorganism must be re-isolated from the experimental host and match the original causative agent.

Edward Jenner's Contribution

• In 1796, Edward Jenner developed the first vaccination using cowpox material to immunize against smallpox, laying the groundwork for immunology.

The Second Golden Age of Microbiology

• Paul Ehrlich pioneered chemotherapy, discovering Salvarsan, arsenic-based and effective against syphilis, marking a key advancement in antimicrobial treatment.
• Alexander Fleming discovered penicillin in 1928 from mold Penicillium notatum, transforming bacterial infection treatment and leading to new antibiotic developments.

Bacteriology and Significant Discoveries

• Bacteriology began with van Leeuwenhoek's examination of tooth scrapings, revealing pathogenic bacteria's roles in health and disease.
• Thiomargarita namibiensis, discovered by Heide Schulz in 1997, is a notable bacterium visible to the naked eye, thriving in African mud and processing hydrogen sulfide.

Evolution of Molecular Genetics

• George W. Beadle and Edward L. Tatum established the connection between genes and enzymes in the 1940s, linking genetics to biochemical processes.
• Oswald Avery and colleagues identified DNA as hereditary material, crucial for genetics.
• Joshua Lederberg and Edward L. Tatum explored bacterial conjugation, shedding light on genetic material exchange in bacteria.
• James Watson and Francis Crick proposed the DNA double helix model, explaining replication mechanisms.
• François Jacob and Jacques Monod discovered messenger RNA (mRNA) and gene regulation in bacteria, enhancing protein synthesis understanding.

Microbial Applications in Human Welfare

• Sewage treatment utilizes microbes to recycle water, converting organic materials into by-products that aid environmental sustainability.
• Bioremediation emerged in 1988, employing microbes to clean pollutants, with bacteria using hazardous substances as energy sources and breaking down toxins.
• Microbes in bioremediation can be native or genetically modified, with Pseudomonas and Bacillus species commonly used, including Bacillus enzymes in detergents.

Insect Pest Control through Microorganisms

• Entomopathogenic fungi (e.g., Beauveria bassiana) are used in integrated pest management to control insect populations while reducing chemical pesticide reliance.
• Beneficial nematodes (e.g., Steinernema) target soil insects, releasing symbiotic bacteria that produce toxins to kill pests.

Emerging Infectious Diseases (EIDs)

• Factors leading to EIDs include the evolution of existing organisms and the global spread of diseases due to modern transportation.
• Ecological changes increase human exposure to new infectious agents (e.g., deforestation linked to Venezuelan hemorrhagic virus).
• Notable EIDs include Zika virus (associated with birth defects), Ebola (high mortality hemorrhagic fever), SARS and MERS coronaviruses (severe respiratory illnesses), and COVID-19 (global pandemic caused by SARS-CoV-2).