Lecture 1: What is Microbiology? Flashcards
What is Microbiology?
What is Microbiology?
Study of organisms too small to be seen with the naked eye
(bacteria, viruses, single-celled eukaryotes, fungi, algae)
the 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 ______ to survive
microbes!
all cells have what things in common?
cytoplasmic membrane
cytoplasm (contains macromolecules, ions, proteins)
ribosomes (site of protein synthesis)
______:
membrane bound nucleus
membrane bound organelles
complex internal organization
divides by mitosis/meiosis
eukaryotes
what are the two major groups of eukaryotic microbes?
protists (unicellular or multi-cellular without differentiation into tissues)
fungi
what are the four types of protists?
protozoa (animal-like
microorganisms)
algae (photosynthetic plant-like microorganisms)
slime molds and water molds (filamentous)
what are the three forms of fungi?
yeasts- unicellular
molds- filamentous
mushrooms- multi-cellular
_________:
No membrane bound nucleus or organelles
Generally smaller (approx 1 µm diameter)
Simple internal structure
Divide by binary fission
Most are unicellular (if they’re multicellular, they’re not differentiated)
prokaryotes
what is advantageous about prokaryotes not having compartmentalization?
they’re smaller- so they’re super efficient!
what are the two major groups of prokaryotic microbes?
bacteria and archaea
_______:
Genetically diverse
Extremely diverse metabolic styles
Includes both pathogens and non-pathogens
bacteria
true/false: bacteria can change from a non-pathogen to a pathogen easily and fast
true! they change often and very quickly- think about the amount of division taking place (mutations)
_______:
Genetically and biochemically distinct from bacteria
Also have diverse metabolism
Never pathogenic
Most famous for living in extreme environments
Archaea
true/false: archaea are eukaryotes with some sort of adaptation
false! they’re often prokaryotes with some sort of adaptation
________:
Acellular infectious particles
Extremely small
Obligate intracellular parasites
Lack independent metabolism
* No ribosomes
* No ribosomal RNA
* Cannot be classified with other microbes
viruses
because viruses don’t have _____ they defy normal classifications schemes (how we compare/contrast other organisms)
ribosomal RNA
First anaerobic life appeared between
3.8 and 3.9 billion years ago
Photosynthetic bacteria oxygenated the Earth about 2 billion years ago
(Allowed the evolution of modern _______)
First plants and animals appeared about 0.5 billion years ago
eukaryotic microorganisms
how do we classify organisms based on evolutionary relationships?
by comparing small subunit (SSU) rRNA genes
_____: have 70S ribosomes,
16S SSU rRNA <- what’s compared!
prokaryotes
there are TWO protein subunits and they are NOT _____
additive
prokaryotes have 2 ribosomal subunits: ___S and ____S
30S and 50S, NOT additive (like a shoebox)
_____: have 80S ribosomes,
18S SSU rRNA <- what’s compared!
eukaryotes
eukaryotes have 2 ribosomal subunits: ___S and ____S
40S and 60S
rRNA genes change ___ over time, we look at differences to identify/compare things that have evolved
slowly
sequencing rRNA genes:
Step 1:
DNA is collected from a _____ culture
Step 2:
The SSU rRNA gene is amplified using the polymerase chain
reaction (PCR)
Step 3:
The gene is sequenced
Step 4:
Sequence is aligned with sequences from other organisms
pure
______– a technique used to synthesize many identical copies of a short sequence
of DNA
PCR
when sequencing rRNA genes- the number of ______ is used to calculate evolutionary distance
differences
________ – A graphic representation of the evolutionary distance
between organisms
Phylogenetic tree
the Tree of Life is a…
Phylogenetic tree based on 16S or 18S ribosomal DNA sequences
what three groups can all organisms be assigned to within the Tree of Life?
Bacteria, Archaea, Eukarya
the 3 distinct domains of life
Microorganisms are far more genetically diverse than plants and
animals, why?
they’re so simple that they can make more changes, they evolve faster and have more mutations
what is a species?
Phylogenetic species concept:
“A group of strains that share certain diagnostic traits, are genetically cohesive and have a unique recent common ancestor”
In practice, species of ____ and ______ should have:
Most (but not all) characteristics in common
Greater than 97% sequence similarity in the 16S rRNA gene
High degree of genome similarity
* DNA-DNA hybridization
(2 DNA strands from different organisms should anneal)
Bacteria and Archaea
microbiologists use _____ classification
hierarchical, groups of organisms are placed in successively larger groups (species, genus, phylum typically used)
5 rules for classification and nomenclature:
- Names are latinized
- Italicized or underlined
- Genus capitalized, epithet (species) is not
- Genus name may be abbreviated the second time it’s used: E. coli
- Trivial names can be used, but do not follow these rules
_______:
The first to describe eukaryotic microbes
Used a compound microscope – uses 2 lenses
to magnify the image
Allowed magnification up to 30x
Used it to observe:
* Cells in cork
* Bread mold filaments – 1st microbe
* Beginning of cell theory – all living things are composed of cells
Robert Hooke
_______:
Built microscopes that magnified specimen by 50-300x
Observed single celled microorganisms – called them “animalcules”
First discovery of bacteria (prokaryotic cells!)
Antoni van Leeuwenhoek
________:
Studied wine and beer production
Yeasts convert sugar to alcohol in the absence of oxygen
Fermentation– “La vie sans air”
Bacteria can sour wine by converting alcohols to acid
Louis Pasteur
Louis Pasteur developed a method of gentle heating to kill unwanted bacteria:
Pasteurization
Pasteur tested Spontaneous Generation of cells-
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
Led to the development of methods for controlling the growth of
microorganisms (aseptic technique)
proved that cells CANNOT derive spontaneously, disproved the Spontaneous Generation theory
______:
Studied anthrax– responsible for epidemics in livestock
He isolated bacteria from the carcass of a diseased animal –
Bacillus anthracis
Injected healthy animals with the bacterium
Animals became ill with anthrax
Re-isolated B. anthracis from the test subjects and showed that it was identical
Robert Koch
Robert Koch established a set of criteria for relating a specific microbe to a
disease, they were called what?
Koch’s postulates
Koch realized that ___ media provided a simple way to obtain pure cultures
solid
Koch’s solid media was:
Broth medium solidified with agar
* Polysaccharide derived from _____
* Melts at ~ 97°C and polymerizes (solidifies) at ~ _____
* Cannot be degraded by most microorganisms
* Typical ______ = nutrient broth medium + 1.5% agar
marine algae
43°C
Petri plate
nutrient agar contains:
______ (organic digest)- 5 g/L
______ (nutrience for bacteria)- 3 g/L
______ (ion gradience)- 5 g/L
______ (seaweed polysaccharide)- 15 g/L
then brought up to 1L with distilled water
Peptone
Beef extract
NaCl
Agar
The _______ technique:
* One edge of a plate is inoculated with a
concentrated sample of bacteria
- Sample is diluted by streaking it across the
surface of the plate
(To deposit individual cells on the plate) - Plate is incubated
- Individual cells grow to form colonies
streak plate
______ – a mass of cells that (ideally) arose from
one single cell
* Can be used to create a pure culture
Colony
The ______ and ________ Techniques:
Sample is diluted before plating
Diluted sample can be spread over the surface of the plate with a sterile spreader
(Separate cells grow into colonies on the surface
of the plate)
Or can be mixed with molten agar (~ 45°C)
Colonies form embedded inside the plate
Spread Plate and Pour Plate
Standard Plate Count:
Spread and pour plates allow you to calculate the concentration of
bacteria in a population (bacterial titre)
What is the formula?
titre= (# of colonies)/(volume)(dilution)
expressed in cfu/mL
cfu= colony forming unit
through what range do we consider something a countable plate?
30-300 colonies
under 30= not statistically sig.
over 300= inaccurate counts
calculate titre and average all countable plates
