1. Microbio and Microorganisms Flashcards
What is microbiology
- Organisms that are too small to be seen with the naked eye (bacteria, viruses, single-celled eukaryoted)
- Microorganisms that are visible to the naked eye (fungi, algae)
- Some multi-cellular organisms ( myxobacteria, slime molds)
Why can some microorganisms be multicellular?
They have very little to no differentiation in cells
How can microbiology be defined?
- By techniques
1. Culture media for isolation/growth of orgnisms in pure cultures (growing all the same microbes)
2. Biochemical to study cell components
3. Molecular and genetic techniques - sequencing the genomes
Why is microbiology important?
- Oldest form of life
- Largest mass of living material on earth
- Carry out major processes for biogeochemical cycles
- Can live in places unsuitable for other organisms
- Other life forms require microbes to survive
___% of Humans are made of bacteria
50
What do all microbial cells have in common
- Cytoplasmic membrane (barrier that separates the inside from the outside of a cell)
- Cytoplasm (aqueous mixture of macromolecules, ions and proteins
- Ribosomes (sites of photosynthesis)
- Genetic material (divided into units called genes - 1 gene = 1 protein)
- Chromosome (carries essential genes in function)
- Plasmid (carries non-essential genes)
- Genome: chromosome + plasmid
Chromosome shape in prokaryotes?
circular
Can cells survive without a plasmid?
Yes, depending on the environment
Eukaryotes
- Membrane-bound organelles and nucleus
- Complex internal organization
- Divides by mitosis and meiosis
What are the membrane bound organelles?
- Mitochondria
- Endoplasmic Reticulum
- Golgi Complex
What is a protist and what are the different types?
What it is:
1. Eukaryotes
2. Unicellular or multicellular (but no differentiation between the tissues)
Types:
1. Protozoa - animal-like microorganisms
2. Algae - photosynthetic plant-like microorganisms
3. Slime-molds and water molds - filamentous
What is a fungi and what are the different types
What it is
1. Eukaryotes
2. Unicellular and multi-cellular
3. Filamentous
Types
1. Yeasts - unicellular
2. Molds - filamentous
3. Mushrooms - multi-cellular
Prokaryotes
- No membrane bound nucleus or organelles
- Generally smaller because they don’t have mem. bound organelles
- Simple internal organization
- Divide by binary fission
- Mostly unicellular
What is a nucleoid and where is it found?
- Twisted and balled up nucleus
- In prokaryotes
What is a bacteria?
- Prokaryote
- Genetically diverse
- Diverse metabolism
- Pathogens and non-pathogens
What is an archaea?
- Prokaryote
- Genetically and biochemically distinct from bacteria
- Diverse metabolism
- Never pathogenic
- Live in extreme environments
What is a virus?
- Acellular infectious particles
- Small
- Non-living intracellular parasites
- Lack metabolism - they need to get it from their host (no ribosomes, RNA)
Evolution/Diversity of Microbial Cells
- 3.8-3.9 years ago - First anaerobic life appeared (because there was a lack of oxygen)
- 2 billion years ago - photosynthetic bacteria oxygenated the earth and allowed for the evolution of modern eukaryotic microorganism
- First plants and animals appeared about 0.5 billion years ago
Explain this phylogenetic tree
LUCA: last universal common ancestor (but we don’t know exactly what it is yet though
Archaea and Eukarya are more closely related than Archaea and Bacteria or Eukarya and Bacteria
Classifying organisms based on evolutionary relationships
- Comparing by small subunit (SSU) rRNA genes
- Prokaryotes - 70S ribosomes (16S SSU rRNA)
- Eukaryotes - 80S ribosomes (18S SSU rRNA) - We study ribosomes because they change slowly over time
- It looks at the genetic differences rather than the size differences
Can you look at evolutionary relationships of viruses?
No because they lack ribosomes so we can’t compare them - which is why we don’t know a lot about viruses
Steps in sequencing rRNA genes
PCR!
1. Collection of DNA from a pure culture
2. SSU rRNA is amplified using PCR
3. Gene is now sequenced
4. Sequence is aligned with sequences from other organisms
- Number of differences is used to calculate evolutionary distance
Phylogenetic tree
A graphic representation of the evolutionary distance between organisms
Phylogenetic Tree of Microorganisms
- Based on 16S or 18S ribosomes DNA sequences
- Bacteria, Archaea and Euakrya
- Microorganisms are more genetically diverse than plants and animals
Explain the Molecular Tree of Life
- Red circle is the only macroorganisms
- The rest are microorganisms
- Archaea is more related to Eukarya than it is to Bacteria
- Bottom point is the LUCA
Species Concept
- Species is the fundamental unit of biological diversity
- A group of strains that share certain diagnostic traits, are genetically cohesive and have a unique recent common ancestor
Species concept of Bacteria and Archaea
- They should have most characteristics in common
- Greater than 97% sequence similarity in the 16S rRNA gene (therefore. The other 3% difference is the strains)
- High degree of genome similarity (DNA-DNA hybridization)
What is a strain?
Genetically identical cells but different types of species
How do microbiologists classify organisms?
In practice: species, genus and phylum
Taxon: Domain, phylum, class, order, family, genus and species (missing Kingdom)
Rules of binomial species names
- Names are Latinized
- Italicized or underlined
- Genus capitalized, epithet is not
- Genus name may be abbreviated the second time its used
- Trivial names can be used (but don’t follow these rules)
Robert Hooke
- First to describe microbes
- Used a compound microscope - uses 2 lenses to magnify the image (Allowed magnification up to 30x)
- Used it to observed:
1. Cells in cork
2. Bread mold filaments - 1st microbe
3. Beginning of cell theory - all living things are composed of cells
Antoni van Leeuwenhoek
- Built microscopes that magnified specimen by 50-300x
- Observed single-celled microorganisms - and called them animalcules (now known as bacteria)
- He first discovered bacteria
Louis Pasteur
- Studied wine and beer production
- Yeasts convert sugar to alcohol in the absence of oxygen (fermentation)
- Bacteria can sour wine by converting alcohol to acid so he developed “pasteurization” (gentle heating to kill unwanted bacteria)
Pasteurs Meat Infusion Experiment
- Prepared meat infusions inside of long swan-necked flasks
- Boiled the infusion to sterilize it
- As long as the flask remains upright, dust and microbes cannot enter and the infusion remains sterile
How did the Meat infusion experiment influence developmental methods
Led to the development of methods for controlling growth of microorganisms (aseptic technique)
Robert Koch
- Studied anthrax - responsible for disease in livestock
- Isolated bacteria from dead animal (Bacillus anthracis)
- Injected healthy animals with bacterium
- Animals became ill with anthax
- Re-isolated the bacteria from the new ill animals (was identical_
- Created a set of criteria for relating a specific microbe to a disease
how to get Pure Cultures
- Solid media provided a simple way to obtain pure cultures (can be seen better than liquids - gets cloudy)
- Broth medium solidified with agar
- Polysaccharide from algae
- Melts at 97 and solidified at 43
- Can’t be eaten by bacteria (not used as an energy source)
Why can’t we use gelatin for pure cultures?
Bacteria uses it as an energy source (eats it), only some rare bacteria can use agar as an energy source (but not usually studied this way anyways)
What is a typical petri plate?
Nutrient broth medium + 1.5% agar
Nutrient agar ingredients
- Peptone - protein - 5 g/l
- Beef extract - growth factors - 3 g/l
- NaCl - ormolarity - 5 g/l
- Agar - 15 g/l
- dH20 - bring up to 1L
Koch Postulates… describe each step loser
I hope you ate that up
How to isolate pure cultures
- One edge of a plate is streaked with concentrated bacteria
- Sample is diluted by streaking it across the surface of the plate (deposits individual cells on the plate)
- Incubated
- Individual cells grow into colonies
What is a colony?
A mass of cells that arose from a single cell
Spread Plate
- Sample is diluted before plating
- It can be spread over the surface of the plate with a sterile spreader
- Seperate cells grow into colonies on the SURFACE of the plate
- This one is used for counting
Pour Plate
- Sample is mixed with molten agar at 45 degrees
- Colonies form embedded inside the plate
Spread vs Pour Plate benefits
Spread - faster
Pour - good to study bacteria that can’t grow in oxygen
Why does spread plate need a lower volume?
Since it’s on spread on top, it can accept a lower volume
What are spread/pour plates used for
Calculate the concentration of bacteria in a population
How to calculate concentration
titre = # of colonies/(volume)(dilution)
Unit for titre
cfu/ml
CFU stands for?
colony forming unit
Counts that are sig. and not sig.
significant: 30-300
not significant: less than 30, greater than 300
What happens when you have more than 1 countable plate
calculate the titre from each and take the average
Ex) Count = 46 at 10^-4 with 1ml samples, CRU?
46/(0.1)(10^-4) = 4.6 x 10^6
