Introduction & History of Microbiology PDF

Introduction & History of Microbiology Chapters 1 Lecture outline Where microbes come from How disease spreads Significant experiments/people of early microbiology Relatedness of organisms (phylogeny) Organization & naming of organisms Microbiology is a young discipline! mi...

Introduction & History of Microbiology Chapters 1 Lecture outline Where microbes come from How disease spreads Significant experiments/people of early microbiology Relatedness of organisms (phylogeny) Organization & naming of organisms Microbiology is a young discipline! microbiology is not as old as chemistry or physics... why not? did not come into existence until the development of the microscope Anton van Leeuwenhoek described hundreds of living microbes between 1673 – 1723 (called them “little animals”) Christian Ehrenberg coined the term bacteria (meaning “little stick”) in 1838 observing microbes gave rise to questions about where living things, including these “invisible” microorganism came from two camps developed, what were they? parents needed parents not needed Parents needed always & obvious in some organisms as people began looking at living things under the microscope, botanist Matthias Schleiden & zoologist Theodor Schwann put forward the cell theory in late 1830s living things, even big ones, are made of one or more cells all cells come from pre-existing cells (how very first cells came about is still an area of active debate) Parents not needed life came out of non-living material ex: maggots from meat, cadavers or feces ex: rodents from piles of rags or hay what was this idea called? spontaneous generation what evidence showed this wasn’t the case? Francesco Redi (1668) thought maggots did not arise spontaneously; he thought they were baby flies just in a different form & really came from parents Redi’s experiment data allowed us to reject the hypothesis of spontaneous generation Are microbes spontaneously generated? many scientists thought that microorganisms were simple enough to generate from non- living materials ex: boiled broth or beer still showed microbial growth...how? Lazzaro Spallanzani (1768) suggested microorganisms from the air were entering the containers of liquid experiment & data was criticized b/c seals kept “vital force” out of broth Enter Louis Pasteur! (1861) Enter Louis Pasteur! (1861) experiments demonstrated that that microbes can be present in non-living matter solids, liquids & in the air microbial life can be destroyed by heat (sterilization!) microbes are responsible for food spoilage Pasteur’s further research showed that mild heating, rather than boiling, was sufficient to kill undesirable organisms without ruining the taste of the product  pasteurization! this data led scientists to make the connection between microbes & disease (before this, treatment for disease was discovered by trial & error, but the causes of disease were unknown) essentially launched the field of modern microbiology Why do some diseases spread? diseases caused by microbes were commonplace centuries ago as they are today early civilizations unaware of the origin of disease, so humans invented explanations often involved gods or witches, etc. Hippocrates (~460 BCE) suggested disease was part of nature (miasmas) & not supernatural miasma theory  “bad air” diseases were spread by poisonous vapor or foul-smelling air, especially the air emanating from rotting organic matter some diseases are spread this way anthrax, TB, inhalants, COVID-19 but does not cause all disease if miasma true, people could board up their homes or move to escape the bad air, but in reality, they took the disease with them Why do some diseases spread? germ theory living microbes cause & spread disease a person could contain & grow microbes (!!) (1st hypothesized by Anton von Plenciz in 1762 & further advanced by Jakob Henle in 1840, but their ideas were ahead of their time with regards to the scientific technologies needed for validation) Germ theory supported by experimentation Ignatz Semmelweis (1847) handwashing experiment observed higher death rate in women during childbirth tended to by doctors compared to those tended to by midwives hypothesized that doctors transported disease causing agents in “putrid matter” on hands (bacteria not yet widely known) doctors were in contact with cadavers & midwives were not suggested handwashing would decrease number of deaths & it did Germ theory supported by experimentation Joseph Lister (1865) was inspired by Pasteur knew carbolic acid killed bacteria started putting a carbolic acid solution on surgical wounds  the number of infections & deaths greatly reduced his findings proved that organisms cause surgical wound infections he thereby established the principles of antisepsis & aseptic technique (the removal of viable microbes from a particular environment) (sepsis mean decay) Germ theory supported by experimentation Robert Koch (1876) anthrax in mice experiment looked at blood from mouse dead of anthrax infection & saw it was full of creatures not found in normal blood took creatures from dead mouse blood & injected into healthy mouse new mouse dies & blood is full of same creatures resulted in the knowledge that living things cause disease (!!) Koch’s postulates a summary of his method for determining if a particular microbe was the cause of a particular disease 1. the causative agent of the disease must be present in all cases of the disease & must be absent from healthy animals 2. the agent of disease can be isolated from the diseased animal & can be cultivated in pure culture (a population of one species of microbes) in the lab 3. the disease can be reproduced by inoculating a portion of pure culture into healthy animals 4. the agent of disease can be reisolated from the infected animal & again cultivated in the lab Koch’s postulates still used today, but there are limitations some pathogens cannot be cultured on media obligate intracellular organisms... some diseases have various causes cancers, diabetes, arthritis, hypertension... chronic diseases can be problematic tuberculosis, Hansen’s disease postulates are not universally applicable viruses, prions This is a micro (see what I did there?) history... many other people played a role in the progression of the discovery of microbes & their role in disease Anton de Bary proved fungus was the cause of the potato blight (& not cold, damp miasma settling over the crops) John Snow discovered the source of cholera in 1849 more on him later Florence Nightingale... more on her later Fanny Hesse suggested using agar to solidify growth media in late 1870’s agar is a powdered seaweed product that she had used to thicken jams & jellies; it dissolves in most liquids & once gelled, it does not liquefy, even in warm incubators Koch first mentioned having used it in an 1884 paper Fanny was one of the 1st Americans to make a contribution to microbiology one by one, the microbes responsible for specific diseases were identified by various scientists methods to kill microbes were being discovered as well Paul Ehrlich discovered arsenic compound treated syphilis in 1910 Alexander Flemming discovered penicillin stopped the growth of Staphylococcus spp. but Koch & Pasteur are considered the 2 greatest figures in medical microbiology Microbes/microbiology... encompasses any sort of organisms that are too small to see unlike botany, for example, where the focus is on a specific set of organisms, microbiology is very diverse bacteria  prokaryotes archaea  prokaryotes fungi  eukaryotes worms  eukaryotes protists  eukaryotes viruses  non-cellular prions  non-cellular Phylogenetic trees if all living things are made of cells, then there will be shared relations phylogenetic trees show relationships between/among organisms very similar to family trees closely related organisms are generally similar to each other 99.99% of all living things are single celled organisms viruses are not on trees b/c much discussion about how they originated & evolve more on this later Modern phylogenetic tree showing 3 domains of life Trees can have varied shapes How do we organize & talk about types of living things? taxonomy! modern taxonomy begun by Linnaeus in 1700s standardized names make for clearer communication Every species gets a name refer to a species using binomial nomenclature (Latin-ish) always genus (capitalized) & specific epithet (not capitalized) always in italics or underlined ex.: Homo sapiens, Bacillus subtilus (handwritten should be underlined) genus can be abbreviated to one letter only if it has already been stated earlier ex.: H. sapiens, B. subtilus (you are expected to use proper scientific notation when referring to specific organisms!) Further rules of nomenclature to refer to any single species (or an unknown species) in a known genus: genus name + “sp.” the “sp.” part is not in italics/underlined ex.: “An unknown Proteus sp.” multiple species in a genus: use “spp.” ex.: “Most Shigella spp. cause disease.” in some cases with prokaryotes, pure cultures of the same species are not identical in all ways but are not distinguishable morphologically, they are called strains identified by numbers, letters or names that follow the specific epithet ex.: E.coli O157 Summary microbiology is relatively new branch of biology; reliant on technology to be studied even though microbes are small, they arise from other, pre-existing cells (cell theory) instead of spontaneously generated microbes can be responsible for disease (germ theory) instead of bad air (miasma theory) & responsible for food spoilage humans can carry, grow & spread microbes some significant people/research supports these claims Redi, Spallanzani, Pasteur, Koch, Semmelweis, Lister, Fanny! all living things are related & relatedness can be diagramed in phylogenetic trees all living things are placed into the taxonomic hierarchy & given a genus & species name; scientific nomenclature rules apply when writing about microbes