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Chapter 1 Notes - Introduction to Microbiology
General Micro (MICRO 305)
Clemson University
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Chapter 1: Microbial Life: Origin and Discovery
Microbe: is a living organisms – dust is not a microbe. Must be alive! Size ranges form millimeters to 0 micrometers. Some can consist of a single cell or hundreds of thousands of cells Must be able to reproduce its own cell kind
All microbes have different shapes, sizes, and are good or bad.
1: What is a Microbe: Exceptions: 1. Supersize microbial cells – are very large in the amount of cells they have. Some microbes are not tiny. 2. Microbial communities – bacteria can be single cell or can have communities where they make a biofilm kind of surface. Can be single microbe cells or microbe communities. Another challenge for research because of these exceptions of having communities. 3. Viruses Because of these exceptions, microbe definition has contradictions. As long as it is ALIVE and can reproduce, it is a microbe.
Eukaryotes: have mitochondria, nucleus, and membrane Algae and pats, fungi, animals, and protists Prokaryotes: only the cell and the DNA is in the cytosol, does not have a specific organelles. Bacteria and Archaea
Most information we know about microbes comes from the genome and the DNA of each microorganism. When we started to extract DNA, then we could create the genome.
Genome is the only thing we have to study the features of the microorganism.
1: History of Microbes Microbes have shaped human culture because of alcohol, bread, yogurt, etc. Some are good microbes, but most are bad microbes to destroy monuments or make us sick.
Examples of Impact: 1. 14th century Bubonic plague caused by Yersinia pesitis. 2. 19th century tuberculosis caused by mycobacterium tuberculosis 3. Today – AIDS & HIV, ebolla, zika virus
War changed history the most with the impact of microbes. It helped to improve our lives because of the advancements of modern medicine. Soldiers were the first target of the microbes. First recognized by Florence Nightingale – founded the polar area chart of mortality data during Crimean War. Her findings helped to improve health care and army practice to save soldiers.
Robert Hooke – built the first compound microscope and used it to observe mold. His findings changed the world of microbiology. He coined the term “cell”.
Antonie can Leeuwenhoek – built single lens magnifiers, with a sample holder and focus adjustment. Observed first single celled microbes and called them “small animals”. Spontaneous Generation : theory that living creatures could arise without parents. Redi = showed that maggots in decaying meat where the offspring of flies. Spalanzani = showed that a sealed flask of meat broth sterilized by boiled failed to grow microbes.
1: These tell us that microbes exist in the food that we have, and sterilization causes them to go away. Pasteur = discovered the microbial basis of fermentation – showed that after boiling, the content remained free of microbial growth despite access to air. Germ Theory of Disease = many diseases are caused by microbes. Koch = founder of the scientific method of microbiology. Applied his methods to a number of lethal diseases around the world. Worked with anthrax and discovered the chain of infection or transmission of the disease, and that there is a relationship between the two. In order to prove all of his theories, he needed to have tools, and have something to hold them and grow them in. He needed a pure culture. Hesse = solid medium using agar Petri = double dish container
Used these 2 things to grow and store bacteria
Koch’s Rules
- Microbes is always present in the diseased host, but absent in the healthy hosts.
- Microbes are grown in pure culture – and no other microbes are present
- When you introduce a pure microbe into a healthy host, the individual becomes sick.
- Same microbe is re-isolated from the now sick individual.
After culture, they put it in a healthy (animal) host, and see if the specific pathogen can make the new host sick. Then the now sick host is re isolated to see if it is the same E coli. Use the 4 steps to determine if a specific pathogen is the main reason why someone is getting sick or it is the main problem
- Microbial species are hard to define – overcome by devising working definitions of microbial species (95% similarity of DNA sequence)
Haeckel = microbes are neither plants or animals – 3rd kind of life called Monera Copeland = divided Monera into 2 groups – eukaryotes & prokaryotes Whittaker = added fungi as a 5th kingdom of eukaryotic microbes
The 5 kingdom system was modified by Margulis = proposed that eukaryotic organelles evolved by symbiosis from prokaryotic cells engulfed by preeukaryotes
Implied a polyphyletic ancestry instead of a monophyletic ancestry.
Woese = discovered prokaryotes that live in hot springs & produce methane. rRNA = 2 subunits Called them Archaea Replaced the 5 kingdoms with 3 domains = bacteria, Archaea and Eukarya.
1: Cell Biology & DNA Revolution More than 99% of microbes today were discovered after 1900. Advanced revealed fundamental structure and function of cell membranes and proteins. Also led to the discovery of DNA & RNA sturcutures, and help to model genetic programs of model organisms. Also helped to produce “genetic engineering”
Helped to make the electron microscope = RUSKA – revealed the internal structure of cells Helped to make ultracentrifuge = SVEDBERG – helped to enable separation of subcellular parts
Griffith – transformation of bacteria Avery – DNA Franklin – DNA = double helix
Very hard to classify microbes because we do not have the sensitive tools to do this. Bacteria and viruses transform quickly because they have genetic mutation, so the structure of the microbes can change.
Call the DNA recombinant.
PCR = polymerase chain reaction. Can extract an enzyme to amplify DNA and help to determine cell structure. Most drugs and medicines we have uses this technique. Without PCR we are not able to study any genomic structures.
Chapter 1 Notes - Introduction to Microbiology
Course: General Micro (MICRO 305)
University: Clemson University
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