Introduction to Microbiology

• Microbiology is the science (logos) of small (micro) life (bios).
• Microbiology is the study of microscopic living organisms.
• Microorganisms have a diameter of 1 mm or less.
• Louis Pasteur (1822-1895) was the French chemist who gave the name "microbiology".
• Microbiology was the last of the three major biology divisions to develop, with the other being botany and zoology.
• Microorganisms are diverse in structure, function, habitat, and application and are also called microbes.
• Microbes are indispensable to life on Earth.
• Microbes are responsible for some of the deadliest human diseases and form the basis of many industrial processes.
• The lecture discusses the definition/scope of microbiology, its importance, and how our knowledge of it has grown.

Major Fields of Pure Science (Microbiology)

• Bacteriology: Study of bacteria
• Mycology: Study of fungi, which are achlorophyllous, heterotrophic, eukaryotic organisms with rigid cell walls containing chitin/cellulose.
• Protozoology: Study of protozoans, which are animal-like single-celled eukaryotic organisms.
• Virology: Study of viruses and viral diseases
• Algology/Phycology: Study of micro- and macroalgae
• Parasitology: Study of parasitism and parasites, including pathogenic protozoa, helminths, and certain insects.
• Microbial Ecology: Study of the interrelationship between microbes and the environment.
• Microbial Morphology: Study of the detailed structure of microorganisms.
• Microbial Physiology: Study of the metabolism of microbes at the cellular and molecular levels.
• Microbial Genetics and Molecular Biology: Study of genetic material, structure, function, and biochemical reactions of microbial cells involved in metabolism and growth.

Why Microbiology is Important

• Microorganisms influence human life in both beneficial and detrimental ways.
• Microbes serve as raw ingredients for food production like bread, cheese, yogurt, alcohol, and wine.
• Microbes are required for producing antibiotics like penicillin, streptomycin, and chloromycetin.
• Vaccines, vitamins, and enzymes all rely on microorganisms in their production.
• The stability of the biosphere via C, N, and S cycles is maintained by microorganisms.
• Microbes are a nutrient source for all ectotrophic food chains and webs.
• Bioremediation, a branch of biotechnology, uses microbes to degrade pollutants, industrial toxic wastes, and household garbage.
• A common edible mushroom contains a protein, lectin, that stops cancer cell multiplication (Enoki mushroom).
• An endophytic fungus, Taxomyces andreanae, is used to produce Taxol, an antitumor diterpenoid from the bark of the Pacific yew (Taxus brevifolia).

10 Major Field of Applied Microbiology

• Industrial Microbiology: Focuses on the industrial use of microbes to produce alcohol, beverages, vitamins, enzymes, antibiotics, and drugs.
• Agricultural Microbiology: Studies the relationship between microbes and crops, controls plant diseases, and improves yield.
• Food Microbiology: Deals with microorganisms and food, focusing on food processing, spoilage, foodborne disease, and prevention.
• Dairy Microbiology: Concentrates on the production and quality control of dairy products.
• Aquatic Microbiology: Explores microorganisms found in freshwater, estuarine, and marine environments.
• Air Microbiology: Studies the role of aerospora in food contamination, spoilage, and the spread of plant and animal diseases via air.
• Exomicrobiology: Explores microbial life in outer space.
• Medical Microbiology: Focuses on the identification of disease-causing agents, diagnostic procedures, and preventative measures.
• Public Health Microbiology: Monitors, controls, and prevents the spread of diseases within communities.
• Biotechnology: Uses scientific manipulation of living organisms at the molecular and genetic level, to produce beneficial products.

Spontaneous Generation

• Spontaneous Generation is an archaic theory describing living organisms developing from non-living matter.
• Throughout history, people believed animals could originate from non-living sources, (ex. frogs from falling rain, fleas from dust, mice from sweaty underwear and flies from decaying meat).
• Spontaneous generation is also known as Abiogenesis.

How Our Knowledge of Microbiology Has Grown

• A. v. Leeuwenhoek is the Father of Microbiology.
• Leeuwenhoek was the first to observe, experiment, and describe animalcules (bacteria and protozoa).
• Leeuwenhoek constructed over 250 small, powerful microscopes, capable of magnifying objects 50-300 times.
• Leeuwenhoek described his findings in "Arcana Naturae ope et Beneficio Exquisite Simorum Microscopiorum Detecta" (4 volumes).
• F. Redi is referred to as the “Founder of Experimental Biology" and "Father of Modern Parasitology.”
• Redi proved that maggots were the offspring of flies, not spontaneously generated from a "vital source" in meat.
• C. Darwin is considered to be the Father of Evolution. Darwin's Theory of Natural Selection showed diseases may be biological, not magic.
• L. Pasteur is considered the Father of Modern Microbiology.
• Pasteur demonstrated that infectious diseases are caused by microbes (pathogens)
• L. Pasteur carried out experiments that lead to the acceptance of biogenesis,
• Biogenesis is the idea that life arises only from already existing life.
• J. Tyndall, an English physicist, observed that Penicillium sp. inhibited bacterial growth.
• Tyndall discovered that fungi growing in meat and vegetable infusions killed bacteria by excluding oxygen.
• Tyndall discovered highly resistant bacterial structures called endospores in Hay Infusion.
• Tyndallization is a process that can kill endospores.
• Tyndallization involves steaming/boiling a product at 100°C for 20-45 minutes for 3 successive days with an overnight resting period.
• Dr. Alexander Fleming, a Scottish physician, discovered penicillin in 1928 when he observed fungi limiting bacterial growth in his petri dish.
• J. Lister is the father of Antiseptic Surgery.
• Lister found that wound infections were due to microbes.
• Lister developed the Lister's Antiseptic System by adapting germ theory to surgery using phenol on surgical dressings/in the operating theatre.
• Lister introduced "aseptic techniques," which made surgery safe.
• Germ Theory states that specific microorganisms cause diseases.
• R. Koch is the founder of modern bacteriology
• Koch discovered Mycobacterium tuberculosis on March 24, 1882.
• Koch introduced solid culture media using gelatin as a solidifying agent.
• Gelatin is not an ideal solidifying agent, as the protein is digested by many bacteria via gelatinase, and melts above 25°C.

Koch's Postulates

• The microorganism must be present in every instance of the disease and absent from healthy individuals.
• The microorganism must be capable of being isolated and grown in pure culture.
• When the microorganism is inoculated in a healthy host, the same disease condition must result.
• The same microorganism must be re-isolated from the experimentally infected host.
• Fanne Eilshemius Hesse proposed using agar in culture media.
• Agar has higher melting (96°C) and solidifying (40°C) points than gelatin, and resisted attack by bacteria.
• Julius Richard Petri developed the petri dish for solid culture media.
• Petri dish is a shallow, circular, transparent dish with a flat lid used for solid culture of microorganisms.
• The contributions of Koch, Hesse, and Petri made it possible to isolate pure cultures of microorganisms and stimulated progress in all areas of microbiology.

History of pathogen discovery

• 1876: Koch discovered Bacillus anthracis as the causative agent of Anthrax.
• 1879: Neisser discovered Neisseria gonorrhoeae as the causative agent of Gonorrhoea.
• 1880: Gaffky discovered Salmonella typhi as the causative agent of Typhoid fever.
• 1880: Laveran discovered Plasmodium sp as the causative agent of Malaria.
• 1882: Koch discovered Mycobacterium tuberculosis as the causative agent of Tuberculosis.
• 1883: Koch discovered Vibrio cholerae as the causative agent of Cholera.
• 1883/4: Klebs & Loeffler discovered Corynebacterium diphtheriae as the causative agent of Diphtheria.
• 1885: Nicoaier & Kitasato discovered Clostridium tetani as the causative agent of Tetanus.
• 1886: Fraenkel discovered Streptococcus pneumoniae as the causative agent of Pneumonia (bacterial).
• 1892: Welch & Nuttall discovered Clostridium perfringens as the causative agent of Gas gangrene.
• 1894: Kitasato & Yersin discovered Yersinia pestis as the causative agent of Plague.
• 1896: Van Ermengem discovered Clostridium botulinum as the causative agent of Botulism.
• 1898: Shiga discovered Shigella dysenteriae as the causative agent of Dysentery.
• 1901: Reed discovered Flavivirus as the causative agent of Yellow fever.
• 1905: Schaudinn & Hoffman discovered Treponema pallidum as the causative agent of Syphilis.
• 1906: Bordet & Gengou discovered Bordetella pertussis as the causative agent of Whooping cough.
• 1909: Ricketts discovered Rickettsia rickettsii as the causative agent of Rocky Mountain spotted fever.

Era of Molecular Biology

• Molecular Biology is an independent discipline of Microbiology.
• Molecular Biology studies the composition, structure, and interactions of cellular molecules such as nucleic acids and proteins.
• These carry out the biological processes essential for the cell's functions and maintenance.
• Microorganisms can be used to explore fundamental life processes because they reproduce and grow quickly, they are easily cultured and they grow expiditiously.
• George W. Beadle & Edward L. Tatum were pioneers in Microbial genetics.
• Beadle and Tatum won the noble prize in 1958.
• B and T hypothesized that the synthesis of the compounds essential for cell growth must be under genetic control.
• Beadle and Tatum established that one gene directly produces a single enzyme.
• One gene - One enzyme Theory states that each gene directly produces a single enzyme which then affects an individual step in a metabolic pathway.
• Max Delbruck & Salvador Luria described the genetic nature of viruses in 1943.
• Delbruck and Luria proved gene mutations were truly spontaneous and not directed by the environment.
• Delbruck and Luria used Fluctuation Test - to demonstrate that genetic mutations arise in the absence of selective pressure rather than being a response to it.
• Joshua Lederberg introduced the term “plasmid” to describe non-chromosomal genetic material in bacteria
• Lederberg discovered the “transduction” process by which genetic information is transferred between bacteria using bacteriophages
• James Watson and Francis Crick discovered the molecular structure of DNA in 1953.
• Rosalind Franklin's Photo 51 demonstrated the double-helix structure of deoxyribonucleic acid (DNA)
• 1/3 of nobel prizes have been awarded to researches in the area of microbiology!