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Terms Lecture 1Microbio - study of organisms too small to be seen by the naked eye
Techniques used in microbiology
● culture media for isolation and growth of organisms in pure culture
● biochemical study of cell components
● molecular and genetic techniques
Importance of microorganisms
● oldest form of life
● largest mass of living material on earth
● widest habitats of organisms
● carry out major processes for biochemical cycles
● Can live in places unsuitable for other organisms
All cells have
● Cytoplasm - aqueous mixture of macromolecules, ions, and proteins
● cytoplasmic membrane - barrier that separates the inside of the cell from the outside environment
● Ribosomes - site of protein synthesis
Genome - cells full component of genes
Chromosome - genetic element carrying genes essential to cellular function
Plasmid - piece of DNA that carries non-essential genes
ex. antibiotic resistance
Eukaryote characteristics
● membrane bound nucleus
● membrane bound organelles
● complex internal organization
● division by mitosis and meiosis
● generally multicellular
Eukaryotic groups
● Fungi
○ unicellular (yeast)
○ filamentous (molds)
○ multicellular (mushrooms)
● Protists
○ unicellular (sometimes multicellular)
○ no differentiation in tissues
○ ex. protozoa, algae, slime molds
Eukaryote gene sequence
● 18SSU rRNA
● 80s ribosomes
Eukarya
● unicellular/multicellular
● no peptidoglycan
● size- 5-50um
Prokaryote characteristics
, ● no membrane bound nucleus
● no membrane bound organelles
● simple internal structure
● divide by binary fission
● generally unicellular
Prokaryotic groups
● Bacteria
○ unicellular prokaryote
○ cell wall has peptidoglycan
○ contain pathogens and non-pathogens
○ size- 0.3-2um
● Archaea
○ unicellular prokaryote
○ cell wall has no peptidoglycan
○ often live in extreme environments
○ never pathogenic
○ size- 0.3-2um
Prokaryote gene sequence
● 16SSU rRNA
● 70s ribosomes
Viruses
● acellular infectious particles
● extremely small
● obligate intracellular parasites
● lack independent metabolism (no ribosomes/RNA)
● cannot be classified with other microbes
First anaerobic life - 3.8-3.9 billion years ago
First photosynthetic life - oxygenated the earth, 2 billion years ago
● allowed evolution of modern eukaryotic microorganisms
first plants/animals - 0.5 billion years ago
Steps of rRNA sequencing
● DNA is collected from a pure culture
● SSU rRNA gene amplified using polymerase chain reaction gene is sequenced
● Sequence aligned with sequences of other organisms - number of differences used to calculate evolutionary distance
Phylogenetic tree - graphic representation of evolutionary distance between organisms based on 16s or 18s ribosomal DNA
sequences
Characteristics of a species of Bacteria and Archaea should have
● Greater than 97% similarity in 16s rRNA gene
● most characteristics in common h
● igh degree of similarity (DNA + DNA hybridization)
Robert Hooke
● First to describe microbes
● Used two glass lenses to view bread mold
● Beginning of cell theory (all living things are made up of cells)
Antoni van Leeuwenhoek
, ● Built the first microscope that could see cells
● Named bacteria he saw "animalcules"
● First discovery of bacteria
Louis Pasteur
● Developed method of gentle heating to kill unwanted bacteria "pasteurization"
● Performed swan-neck experiments
● Significance of swan-neck experiments
○ sterilized broth in swan necked flasks
○ air microbes + dust settled in bend
○ only contaminated broth if they were tipped into it
○ led to development of aseptic techniques we use today
○ disproved spontaneous generation theory (somehow?)
Robert Koch
● studied anthrax - responsible for epidemics in livestock
● isolated pure cultures from dead animals - Bacillus anthracis
● injected healthy animals with bacterium - animals became ill with same disease
● isolated B.anthracis from test subjects to prove it was identical
● established set of criteria for relating specific microbes to a disease "Koch's postulates"
● also developed agar to isolate cultures
Agar - a polysaccharide from marine algae
● melts 97ºC
● solidifies 43ºC
● not easily digested by bacteria
Methods to isolate pure cultures
1. streak plate technique
● one edge of a plate inoculated with a sample of bacteria
● sample diluted by streaking it across plate (to separate cells)
● plate incubated
● individual cells grow to form colonies
● used to create pure cultures
2. spread plate technique
● Sample diluted
● spread over solid medium surface use spreading rod
3. pour plate technique
● Diluted sample mixed with agar (~45ºC)
● poured into empty petri dishes
● Colonies form in and on plate
Colony - a mass of cells that (ideally) arose from one single cell
Standard plate count - spread and pour plates allow you to calculate the concentration of bacteria in a population (bacterial titre)
titre = (# of colonies)/(volume plated x dilution)
expressed in cfu/ml
(cfu=colony forming unit)
countable plate has between 30 + 300 colonies
● if more than one countable plate we take an averag
Lecture 2
Light microscopy - Compound (2 lenses) light microscope uses visible light to illuminate cells
● resolution limited to ~0.2um
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