lecture 2 - taxonomy and structures

Question 1

what structures are the outermost part of bacteria?

Answer 1

the appendages (project from the cell) :
- flagella
- fimbrae
- pili

Question 2

what structure of bacteria are found after the appendages?

Answer 2

the surface and cell wall:
- capsule
- cell wall
- cell membrane

Question 3

what comes after the cell surface on bacteria?

Answer 3

cytoplasm
- chromosome
- plasmids
- ribosomes
- inclusions

Question 4

what are other structures found in bacteria?

Answer 4

endospores

Question 5

what are characteristics of flagella?

Answer 5

• long slender, structures made of protein
• whip like
• enable bacteria to move by rotating like a propeller
• can only be seen using special stains or electron microscopy
• can be single (monotrichous) or multiple, in tufts or around the cell (peritrichous)

Question 6

fimbriae are

Answer 6

• shorter, thinner filaments made of protein, like little fingers not whiplike
• enable bacteria to attach substances

Question 7

pili are

Answer 7

similar to fimbriae in structure and involved in transfer of DNA between bacteria
- look like a channel connecting two organisms to transfer genetic material
- typically hollow

Question 8

characteristics of capsules (inside)

Answer 8

• material that is secreted by bacteria and covers the exterior of the cell
• often polysaccharide
• may be a thick layer; slime coating

Question 9

characteristics of cell wall

Answer 9

• differs from animal cells, or fungi
• a strong layer made of peptidoglycan
• maintains cell shape and integrity
• a principle target for antibiotic action !
• stains using the gram stain
• differs for gram positive vs gram negative organisms

Question 10

peptidoglycan layer (in cell wall)

Answer 10

sugars and proteins with amino acids are linked and laid in a particular way creating a strong lattice

Question 11

gram positive means

Answer 11

• thick peptidoglycan layer
• no outer membrane

Question 12

gram negative means

Answer 12

• has outer membrane
• thin peptidoglycan layer and has another lipid bilayer w LPS on the outside of it
• space between membranes is periplasmic space

Question 13

what are the main differences between gram positive and negative

Answer 13

thickness of peptidoglycan layer and whether there is another cell membrane on the outside of it
- they both have the same lipid bilayer at the bottom of the structure though

Question 14

staining organisms is used for

Answer 14

truly seeing how the organism is arranged and what its cell wall and cell membrane look like
- best when using light microscopy

Question 15

what can you see on an unstained organism? what about when using a “wet prep”?

Answer 15

faint structures or nothing, wet prep can show little movements or shapes of organism

Question 16

what is a simple stain? example?

Answer 16

simple stain doesn’t differentiate organisms from one another except for their shape
- just stains any bacteria on the slide
ex. methylene blue

Question 17

what can complex stains do?

Answer 17

stains that differentiate structures from one another and can be applied at different stages / in between sequences to remove stain
ex. giemsa stains nucleus red and cytoplasm blue

Question 18

who developed the gram stain? what is it?

Answer 18

christian gram in the 19th century
- this technique allows differentiation of many bacteria into 2 groups: gram pos/gram neg
- he found stain could be washed out of some organisms more easily than others

Question 19

what is the method for gram stain? what is needed?

Answer 19

• crystal violet: stains all bacteria dark purple
• iodine: binds to crystal violet and fixes it
• alcohol/acetone (decolourizer): washes out the stain from gram negative bacteria
• safranin: stains the gram negative bacteria pink

Question 20

when is acid fast stain used?

Answer 20

when some bacteria cannot be stained by gram stain because of lipids in the cell walls ex. tuberculosis bacterium

Question 21

what colour will gram positive cells be after staining?

Answer 21

purple

Question 22

what colour will gram negative stains be after staining?

Answer 22

pink

Question 23

what colour are acid fast organisms?

Answer 23

red - sometimes called acid fast bacilli

Question 24

how does acid fast staining work?

Answer 24

1. staining with a strong red stain to “force” the stain into the cell
2. washing out the stain with a mix of acid + alcohol
3. restaining with a blue or green stain

Question 25

what colour are the other organisms in acid fast ?

Answer 25

green or blue, the colour of the counterstain

Question 26

characteristics of the cell membrane are:

Answer 26

- lipid bilayer w proteins - controls the entrance and exit of substances from the cell - contains enzymes involved in cell wall production, cellular metabolism, and production of some extra-cellular materials - in gram negatives, it contains endotoxin

Question 27

characteristic of cytoplasm?

Answer 27

- liquid containing a variety of substances - where metabolism occurs

Question 28

what are ribosomes?

Answer 28

- made of RNA and protein - STRUCTURES WHERE PROTEINS ARE MADE - two subunits. bacterial ribosomes are different from animal or plant cells (euk cells)

Question 29

what are bacterial chromosome?

Answer 29

- made of DNA - a single long circular molecular of DNA - not separated from cytoplasm (no nuclei)

Question 30

bacteria are...

Answer 30

prokaryotic

Question 31

bacterial ribosomes are a great target for what

Answer 31

antibiotics - if you can make bacterial ribosomes nonfunctional, the cell cannot metabolize or go on (good way to kill bacteria)

Question 32

what are plasmids?

Answer 32

- small, circular pieces of DNA - SEPARATE from the chromosome - can be transferred between bacteria

Question 33

what are inclusions?

Answer 33

- granules in the cytoplasm - may act as storage of various substances blanket term for other things in the cytoplasm

Question 34

plasmids may...

Answer 34

- may carry genetic material that will give the organism some kind of advantage, such as antibiotic resistance

Question 35

as a cell replicates and divides into two, the plasmids...

Answer 35

will also divide and replicate the plasmids so that each cell will have copies of those plasmids

Question 36

though plasmids are separate form the chromosome, they may...

Answer 36

integrate into the chromosome

Question 37

another structure made by gram positive organisms is:

Answer 37

endospores

Question 38

what are endospores?

Answer 38

- dormant form of organism that are resilient / environmentally tough that develop in cytoplasm of bacteria

Question 39

endospores can...

Answer 39

remain viable for long periods until the environment becomes favourable again - germinate to form a new cell

Question 40

endospores also do not... and are only formed by...

Answer 40

- also do not grow or divide - only formed by certain genera of bacteria

Question 41

what is bacterial taxonomy?

Answer 41

how bacteria are organized and classified

Question 42

bacterial taxonomy us organized by...

Answer 42

domains - ex. cells lacking nuclei (pro) vs cells with nuclei (euk) kingdoms - animals, protista (parasites), plants, fungi, monera - the prokaryotic organisms

Question 43

how does classification of animals work in bacterial taxonomy?

Answer 43

classification: - kingdom - phylum - class - order - family - genus - species genus and species are used whenever we call a bacterium by its name (used most frequently in clinical practice + family)

Question 44

how are bacteria traditionally (little to no equipment used) classified?

Answer 44

- traditional: size, shape, gram reaction, ability to metabolize sugars, metabolic end products

Question 45

how are bacteria classified using supplements (specialized equipment)?

Answer 45

- comparison of 100-300 characteristics - nucleic acid sequence of ribosomal RNA ex sequencing chromosome or ribosome

Question 46

what does aerobic mean?

Answer 46

(grows in air) - obligate if must have O2

Question 47

if bacteria needs CO2 what term is used there?

Answer 47

capnophilic

Question 48

what does facultative anaerobe mean?

Answer 48

grows in air and can grow without oxygen

Question 49

what does anaerobe mean?

Answer 49

grows without oxygen and most species do not grow well in air as O2 is toxic for them

Question 50

what does microaerophilic mean?

Answer 50

grows in a low concentration of oxygen but not in its absence or in air