Microbiology: Study of microbesWhat 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 (1632-1723)

• 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 (1822-1895) 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 preventionCleaner 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