introduction to bacteriology

Question 1

what are the 3 domains of life?

Answer 1

bacteria

archaea

eukarya

Question 2

when did prokaryotes come to be? eukaryotes

Answer 2

prokaryotes
around 4-3.5 billion years ago

eukaryotes
around 2-1.5 billion years ago

Question 3

what’s unique about archaea (in comparison to bacteria)?

Answer 3

can live in extreme environments

don’t cause human diseases (they are not pathogenic)

Question 4

what are prokaryotes?

Answer 4

the smallest, simplest, and most abundant cells on Earth

includes bacteria and archaea

lacks a nucleus and other complex organelles
— they have no membrane bound organelles

Question 5

describe the 4 phases of growth bacteria undergo

Answer 5

LAG
- cellular activity
—- cells increase in size, but no cell division

LOGARITHMIC GROWTH
- cell divides by binary fission and doubles in numbers after each generation time
- high metabolic activity because DNA, RNA, cell wall components, and other substances necessary for growth are generated by division
- appears like a steep incline

STATIONARY
- population growth starts to decline because of depletion of available nutrients and accumulation of waste products
—- increased competition for nutrients and cells become less metabolically active
—- in this phase, spore forming bacteria produces endospores and pathogenic bacteria produce virulence factors that help them survive harsh conditions and cause disease
- appears like a plateau on the graph, no overall population growth

DEATH
- as nutrients become less available and waste increases, number of dying cells rises
- as dying cells lyse, they spill their contents into the environment, making these nutrients available to other bacteria
- appears as a sharp decline

Question 6

what are endospores?

Answer 6

type of spore that is formed within a vegetative or mother cell. the vegetative cell is mainly referred to as a sporangium.

they are highly resistant to heat, desiccation, radiation, chemicals, and some disinfectants

ensures the survival of a bacteria during harsh environmental conditions e.g. overpopulation, nutrient deficiency, or unfavorable climatic conditions

Question 7

what are virulence factors?

Answer 7

bacteria-associated molecules that are required for a bacterium to cause disease while infecting eukaryotic hosts such as humans

Question 8

what is generation time aka doubling time?

Answer 8

time it takes for one generation to divide into daughter cells

varies for species - some grow fast (e.g. DT = 10 minutes) or slow (e.g. DT = 24 hours)

Question 9

what are the 3 types of bacterial shapes?

Answer 9

bacillus
- rod shaped

coccus
- spherical

spirillum
- spiral-shaped or curved

Question 10

what is bacillus?

Answer 10

bacteria that are rod shaped

Question 11

what is coccus?

Answer 11

bacteria that are spherical

Question 12

what is spirillum?

Answer 12

bacteria that are spiral-shaped or curved

Question 13

what are obligate aerobes?

Answer 13

requires oxygen for growth

Question 14

what are obligate anaerobes?

Answer 14

oxygen is toxic for growth

Question 15

what are facultative anaerobes?

Answer 15

can use oxygen if present, but can also growth without oxygen

Question 16

what are aerotolerant anaerobes?

Answer 16

don’t use oxygen – but oxygen isn’t toxic!

Question 17

what are microaerophiles?

Answer 17

grows best with low levels of oxygen

Question 18

in order, what’s the taxonomic ranks for classifying bacteria

Answer 18

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domain

kingdom

phylum

class

order

family

genus – should be capitalized

species – should be italicized

strain (diversity within species!)

Question 19

among bacterial species, what’s notorious for their diversity? how diverse is this specie?

Answer 19

E COLI

only 60% of it is identical to other E coli

(humans 99.5% identical with each other!)

Question 20

why is there diversity within bacterial species?

Answer 20

due to bacteria’ short life cycle, high reproduction rate, and ability to adapt to environmental changes

Question 21

who developed the staining technique?

Answer 21

Hans Christian Gram

Question 22

what are the staining colours of the 2 major types of bacteria?

Answer 22

gram+
—- purple (bc more dense with peptidoglycan)

gram -
—- pink (bc less dense with peptidoglycan)

Question 23

what happens when gram staining is conducted on mycobacteria? why?

Answer 23

appears neutral - neither positive nor negative

due to thick, waxy cell wall that resists destaining/decolourization with the acid and alcohols used in gram staining – ability called acid fast and is found in mycobacteria

Question 24

what is acid-fast?