4.

Question 1

When did the first anaerobic life appear?

Answer 1

between 3.8 and 3.9 billion years ago

Question 2

When did the first plants and animals appear?

Answer 2

about 0.5 billion years ago

Question 3

how do we classify organisms based on evolutionary relationships ?

Answer 3

• compare small subunit (SSU) rRNA genes
• examines genetic differences rather than morphological differences
• rRNA genes change slowly over time
• prokaryotes
• eukaryotes

Question 4

Prokaryotes

Answer 4

• 70S ribosomes

- 16S SSU rRNA

Question 5

Eukaryotes

Answer 5

• 80S ribosomes

- 18S SSU rRNA

Question 6

Basic steps involved in sequencing rRNA genes

Answer 6

step1: DNA is collected from a pure culture
step 2: the SSU rRNA gene is amplified using the polymerase chain reaction (PCR)
step 3: the gene is sequences
step 4: sequence is aligned with sequences from other organisms
(number of differences is used to calculate evolutionary distance)

Question 7

basic steps in easier terms for sequencing rRNA genes

Answer 7

1. isolate DNA from each organisms
2. make copies of rRNA gene by PCR
3. sequence DNA
4. analyze sequence
5. generate phylogenetic tree

Question 8

phylogenetic tree

Answer 8

a graphic representation of the evolutionary distance between organisms

Question 9

what is the phylogenetic tree based on ?

Answer 9

16S or 18S DNA sequences

Question 10

all organisms can be grouped into 3 distinct domains of life:

Answer 10

bacteria,
archaea,
and eukarya

Question 11

microorganisms are far more genetically diverse then….

Answer 11

plants and animals

Question 12

what is a fundamental unit of biological diversity?

Answer 12

the species

Question 13

phylogenetic species concept

Answer 13

a group of strains that share certain diagnostic traits, are genetically cohesive and have a unique recent common ancestor

Question 14

when did photosynthetic bacteria oxygenate the earth?

Answer 14

about 2 billion years ago

-allowed the evolution of modern eukaryotic microorganisms

Question 15

species

Answer 15

represented by one or more strains

a grouped of similar but not genetically identical cells

Question 16

species of bacteria and archaea should have…

Answer 16

• most but not all characteristics in common
• greater that 97% sequence similarity in the 16S rRNA gene
• high degree of genome similarity
  * DNA-DNA hybridization
  * in the very near future: whole genome sequences?

Question 17

microbiologists use hierarchical classification

Answer 17

groups of organisms are places in successively larger groups

in practice:species, genus and phylum are commonly used

Question 18

naming binomial species

Answer 18

1. names are latinized
2. italicized or underline
3. genus capitalized, epithet is not
4. genus name may be abbreviated the second time its used. ex:E. coli
5. trivial names can be used, but do not follow these rules

Genus-capitalized
specific epithet-not capitalized
strains can be identified by symbols after the species name
ex. E. coli K12

Question 19

robert hooke (1635-1703)

Answer 19

-first to describe 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
beggining of cell theory- all living things are
composed of cells

Question 20

Antoni van leeuwenhoek (1632-1723)

Answer 20

• built microscopes that magnified specimen by 50-300x
• observed single celled microorganisms-called them animalcules
• first discovery of bacteria

Question 21

louis pasteur (1822-1895)

Answer 21

• 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
• developed a method of gentle heating to kill unwanted bacteria- pasteurization

Question 22

pasteurization

Answer 22

subject to a process of partial sterilization, especially one involving heat treatment or irradiation, thus making the product safe for consumption and improving its keeping quality

Question 23

pasteur and spontaneous generation

Answer 23

• prepared meat infusions inside a 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)

Question 24

broth medium

Answer 24

a) non-sterile liquid poured into flask
- neck of flask drawn out in flame
- liquid sterilized by extensive heating (stem forced out open end)
b) liquid cooled slowly (dust and microorganisms trapped in bend)
- liquid remains sterile indefinitely
c) flask tipped such that microorganism-laden dust contacts sterile liquid (in a short time)
- the liquid putredies

Question 25

Robert Koch (1843-1910)

Answer 25

- 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 - established a set of criteria for relating a specific microbe to a disease * koch's postulates

Question 26

Kochs postulates:

Answer 26

1. the suspected pathogen must be present in all cases of the disease and absent from healthy animals 2. the suspected pathogen must be frown in pure culture 3. cells from a pure culture of the suspected pathogen must cause disease in a healthy animal 4. the suspected pathogen must be reisolated and shown to be the same as the original

Question 27

koch realized that solid media provided a simple way to obtain ...

Answer 27

pure cultures

Question 28

broth medium solidified with agar

Answer 28

- polysaccharide derived from marine algae - melts at ~97 degrees C and polymerizes (solidifies) at ~43 degrees C - cannot be degraded by most microorganisms - typical Petri plate=nutrient broth medium +1.5% agar

Question 29

nutrient agar

Answer 29

``` peptone 5g/l beef extract 3 NaCl 5 Agar 15 Bring up to 1 litre with dH20 ```

Question 30

isolating pure cultures: | the streak plate technique

Answer 30

- 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

Question 31

Colony

Answer 31

a mass of cells that ideally arose from one single cell | -can be used to create a pure culture

Question 32

spread plate and pour plate

Answer 32

- 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 and the surface of the place - or can be mixed with molten agar (~45 degrees C) - colonies form embedded inside the plate

Question 33

spread plate

Answer 33

- sample is pipetted onto surface of agar plate (0.1 ml or less) - sample is spread evenly over surface of agar using sterile glass spreader - typical spread-plate results

Question 34

countable plates

Answer 34

we normally count plates with between 30-300 colonies 300-colonies grow into each other - inaccurate counts -when we have more than on countable plate -calculate titre from each and take the average

Question 35

strain

Answer 35

genetically identical groups of cells

Question 36

genus

Answer 36

last name

Question 37

standard plate count

Answer 37

-spread and pour plates allow you to calculate the concentration of bacteria in a population (bacterial titre) titre= #colonies/(volume*dilution) titre is expressed in cfu/ml cfu=colony forming unit

Question 38

species

Answer 38

first name

Question 39

biogenesis

Answer 39

living gives rise to living things

Question 40

sponteous generation

Answer 40

living cells can come from non-living matter