The Microbial World Flashcards
What are microorganisms?
- organisms and acellular entities too small to be clearly seen by the unaided eye (some exceptions)
- lack highly differentiated tissues
- often unicellular
- generally less than 1 mm in diameter
What is the difference between prokaryotic and eukaryotic microbial cells?
- prokaryotic cells lack a true membrane-bound nucleus and do not have membrane bound organelles (not absolute)
- eukaryotic cells have a membrane-bound nucleus and membrane bound organelles
- eukaryotes are more complex and are usually larger
How did microbes evolve and become so diverse?
mutation of genetic material -> new genotypes -> advantageous phenotypes -> natural selection
How are bacteria and archaea able to adapt more quickly?
- because they are haploid
- can increase genetic diversity by horizontal gene transfer within the same generation
What are 3 types of horizontal gene transfer and how do they differ?
- transformation: bacteria take up DNA from their environment
- conjugation: one bacterium sends a copy of a plasmid across a protein tube to another bacterium
- transduction: bacterial DNA packed into a virus that can infect another bacterium
In what order did organisms appear on Earth?
- origin of Earth (4.6 bya)
- origin of cellular life (4 bya)
- anoxygenic phototrophic bacteria
- origin of cyanobacteria
- modern eukaryotes (2 bya)
- algal diversity
- shelly invertebrates
- vascular plants
- mammals
- humans
What percentage of Earth’s history had microbial life forms only?
80%
Why are microorganisms important?
- oldest form of life
- most populous and diverse group of organisms
- major fraction of biomass and key reservoir of essential nutrients
- play a major role in recycling essential elements
- some can carry out photosynthesis
- influence all other living things (in a good or bad way)
- excellent tools for study
How do microorganisms affect humans?
- agriculture: help cows digest cellulose
- food: fermentation
- disease
- energy: ferment biofuels
- industry: antibiotics, enzymes
- human microflora: help our immune system and give us essential vitamins
- cycle nutrients: nitrogen
How was the Universal Phylogenetic Tree developed?
- three domain system based on a comparison of the DNA encoding small subunit ribosomal RNA
- divides microorganisms into bacteria, archaea, and eukarya
- isolate DNA from each organism
- make copies of rRNA from PCR
- sequence DNA
- analyze sequence (looking at evolutionary distance)
- generate phylogenetic tree
How are bacteria, archaea, and eukarya related?
- connect at LUCA (last common ancestor)
- archaea come off of the eukarya branch (more closely related DNA wise)
- bacteria: have peptidoglycan, no introns, and no histones
- archaea: no peptidoglycan, have some introns, and have histones
- eukarya: no peptidoglycan, have introns and histones
What is the prokaryotic “species”?
- bacteria and archaea do not reproduce sexually and are therefore not defined as an interbreeding natural population
- a microbial species is a collection of strains that share many stable properties and differ significantly from other groups of strains
What is a microbial strain?
- subset of microbial species
- descendants of a single, pure microbial culture
- one stain is designated as the type strain (permanent example, fully characterized, not necessarily the most representative)
- letter and # combo designates the strain
How are microbes named?
- genus and then species
- developed by Carl Linnaeus
ex: Escherichia coli, Bacillus subtilis, Micrococcus luteus
What did Robert Hooke do?
- coined the term cell
- described the fruiting structures of molds
What did Antony van Leeuwenhook do?
first to observe and accurately describe bacteria
What is the theory of spontaneous generation?
living organisms can develop on nonliving or decomposing matter
ex: dirty clothes produce mice
Who discredited spontaneous generation for large animals?
- Francesco Redi
- meat and fly
Who discredited spontaneous generation for microorganisms?
- Louis Pasteur
- bent flask experiment
What are Koch’s postulates?
- The suspected pathogen must be present in all cases of the disease and absent from healthy animals
- The suspected pathogen must be grown in pure culture
- Cells from a pure culture of the suspected pathogen must cause disease in a healthy animal
- The suspected pathogen must be reisolated and shown to be the same as the original
How is Koch’s 1st postulate carried out in an experiment?
- observe blood/tissue of healthy animal and diseased animal under the microscope
- diseased animal will have suspected pathogen
How is Koch’s 2nd postulate carried out in an experiment?
- streak agar plates with a sample from the diseased animal and a sample from the healthy animal
- healthy animal plate should have no organisms present
- diseased animal plate should have colonies of suspected pathogen
How is Koch’s 3rd postulate carried out in an experiment?
- inoculate healthy animal with cells of suspected pathogen
- animal should become diseased
How is Koch’s 4th postulate carried out in an experiment?
- get blood or tissue sample from newly diseased animal and observe by microscopy
- grow in a laboratory culture
- pure culture must be the same organism as before
What are the other accomplishments of Louis Pasteur?
- demonstrated that microorganisms carried out fermentations
- discoveries led to the development of microbial control methods
- pasteurization
- aseptic technique
- discovered attenuation: live cultures that are weakened strengthen the immune system
- developed vaccines for anthrax, chicken cholera, and rabies
- solidified germ theory of disease
What did Ignaz Semmelweis do?
encouraged handwashing to prevent “childbed fever”
What did Joseph Lister do?
- developed a system of surgery designed to prevent microbes from entering wounds
- his patients had fewer postoperative infections
What did Robert Koch do?
- established relationship between Bacillus anthracis and anthrax
- Mycobacterium tuberculosis and tuberculosis
- Vibrio cholera and cholera
- developed Koch’s postulates to establish the link between a particular microorganism and a disease
What were Koch’s methods and materials?
- obtaining and growing bacteria in pure cultures
- nutrient broth
- nutrient agar (solid at 37 C, bacteria do not eat), idea of Fanny Hessey
- Petri dish (lid larger than base to let in oxygen and make them easy to stack
- streak plating technique to isolate bacterial colonies
What did Edward Jenner do?
- used a vaccination procedure to protect individuals from smallpox
- discovered that people who got cowpox were immune to smallpox
- the word vaccine comes from the word for cow
What did Ferdinand Cohn do?
- discovered bacterial endospores
- classified bacteria based on shape
What did Sergei Winogradsky do?
- discovered numerous interesting metabolic processes such as anaerobic nitrogen fixation
- proposed the concept of chemolithotrophy: microbes can make matter directly out of CO2
What did Alexander Fleming do?
- discovered penicillin
- 1st true antibiotic discovered
What role does genomics play in modern microbiology?
- genomics is the discipline that maps, sequences, analyzes, and compares genomes
- transcriptomics, proteomics, metabolomics, epigenetics, metagenomics, bioinformatics
What did Martinus Beijerink do?
- pioneered the use of enrichment cultures and selective media
- isolated the first pure cultures of many soil and aquatic bacteria
- describes the first virus
- “father of virology”
What are some career fields in microbiology?
- clinical microbiology
- public health
- biological safety
- science outreach
- patent law
- industrial microbiology
- academia
- government
