Microbiology: Study of microbes What is a microbe? Typically microbes are small and most cannot be seen without the aid of a microscope Microbes are comprised of prokaryotes and eukaryotes Most microbes classified as bacteria, archaea, fungi, protozoa or algae Is a virus a microbe?

Bacteria and Archaea Prokaryotes -- single-celled organisms without nuclei Typically very small Usually have cell walls and membranes Live in many different environments Many bacteria cause disease (pathogenic) Most haploid and reproduce asexually

Fungi -- Molds and Yeasts Eukaryotic organisms either multi- or unicellular, pathogenic or beneficial Many are microscopic Fungi contain cell walls but are not photosynthetic Molds are typically multi- cellular and have sexual and non-sexual reproduction by spores Yeasts are unicellular and reproduce asexually by budding or via sexual spores

Protozoa Eukaryotic single-celled organisms similar to animal cells Most are motile and are classified by means of locomotion (cilia, flagella or pseudopodia) Many species are pathogenic

Algae Unicellular or multi-cellular eukaryotes All are photosynthetic Have cell walls Classification based on cell wall composition and composition of their photosynthetic proteins Large multi-cellular forms include seaweed and kelp Diatoms contain silicates (glassy) in cell walls

Highlights of a History of Microbiology Leeuwenhoek -- the microscope (1670’s) Redi, Needham, Spallanzani and Pasteur -- spontaneous generation debunked Germ theory of disease Koch’s postulates Development of aseptic techniques and vaccination Molecular microbiology

Antoni van Leeuwenhoek ( ) First to view (1674)“animalcules” (protozoa) in drops of water Reported the existence of bacteria in 1676 Spent 50 yrs. observing and reporting on microbes, but didn’t share techniques

The question of spontaneous generation Embraced for 1900 yrs. since the time of Aristotle, at least for small organisms Late 17th century: Francesco Redi demonstrated that maggots appearing “spontaneously” on old meat required the presence of flies

18th century experiments on spontaneous generation: Needham vs. Spallanzani Needham’s experiments used boiled beef gravy and corked vials Microbes grew readily Spontaneous generation supported Spallanzani used boiled infusions and heat-sealed glass vials No microbial growth occurred Spontaneous generation does not occur

Louis Pasteur ( ) Father of Microbiology Disproved spontaneous generation by carefully demonstrating under what conditions microbes appear

Other contributions by Pasteur Demonstrated anaerobic fermentation by both bacteria and yeasts (bacteria produce acid and yeast produce alcohol) Developed pasteurization to prevent spoilage of wine by bacteria Began field of industrial microbiology when he added yeast to sterilized grape juice to make wine Bacterial spoiling of wine led to Germ theory of Disease (1857)

Koch’s postulates drive search for disease causative agents Examined patients blood and identified bacteria associated with different diseases Postulates: (1) Disease agent must be present in every patient and absent in others; (2) Agent is isolated and when introduced into healthy person, causes the disease; (3) Disease agent can be reisolated from experimentalhost

Disease prevention Cleaner is better Nosocomial infections were rampant through mid 19th century Semmelweis demonstrated that hand washing could significantly lesson childbirth-related fatalities in mid-1800’s Lister demonstrated 2/3 reduction in patient death by sterilizing equipment with phenol in early 20th century Florence Nightingale introduced antiseptic techniques into nursing practices in mid 1850’s

Modern microbiology Biochemical basis of life Microbial genetics Recombinant DNA and biotechnology