Topic 2: Bacteria

Question 1

Spherical

Answer 1

• spherical or round
• COCCUS
  -found in various habitats, including soil, water and human body

Question 2

Rod-shaped

Answer 2

• e. coli
• BACILLUS
• commonly found in soil, water, and the human intestine
• use gliding motility
• • cells joined together in a smooth, unbranched filament, trichomes)
• can also grow in branching filaments (hyphae) (clump= mycelia)

Question 3

Comma shaped

Answer 3

• curved
• VIBRIO

Question 4

Spiral-shaped

Answer 4

• bizarre shapes, like telephone cords
• move like corkscrews, rotating clockwise or counterclockwise to go forward or back
• works well in aquatic environments, will find them

Question 5

Variable

Answer 5

• cant quite identify as having one shape
• called pleiomorphic, multiple shapes

Question 6

Why can decreasing cell size be an advantage for bacteria?

Answer 6

a higher surface to volume ratio means a greater rate of nutrient/waste exchange, higher metabolic rate, faster growth rate and evolution

Question 7

Bacteria that are exceptions to the typical size

Answer 7

Thiomargarita namibiensis
Epulopiscium fishelsoni

-both can reach close to a millimeter in length
- advantage of being big, can store more things, inclusion bodies

Question 8

Things in bacterial cytoplasm (11)

Answer 8

DNA nucleoid
Chromosome-packaging proteins
Enzymes involved in synthesis of DNA, RNA
Regulatory factors
Ribosomes
Plasmid(s)
Enzymes involved in breaking down substrates
Inclusion bodies
Gas vesicles
Magnetosomes
Cytoskeletal structures

Question 9

DNA Storage

Answer 9

Nucleoid
- largest region in cell
- no membrane surrounds it
- house chromosomes and DNA replication machinery
-uses several mechanisms to reduce space

Question 10

Inclusion Bodies

Answer 10

accumulations of carbon, nitrogen, sulfur or phosphorus storage compounds
- sulfur globules: store sulfur for energy
- polyhydroxybutyrate (PHB): carbon storage compound

Question 11

Gas vesicles

Answer 11

Used for buoyancy control

Question 12

Carboxysomes

Answer 12

location of carbon fixation reactions (using RuBisCO enzyme)

Question 13

Magnetosomes

Answer 13

associated with direction-finding

Question 14

Topoisomerase

Answer 14

modify structure of DNA to enable “super
coiling”

Question 15

Bacterial Cytoskeleton

Answer 15

• keeps everything in right place
• proteins involved in cell wall synthesis (cell division):
  *MreB: defines cell shape
  *FtsZ: forms ring for cell division
• proteins involved in moving internal items
  *Par homologues: separate newly replicated chromosomes

Question 16

Cell envelope

Answer 16

all layers surrounding the cytoplasm of cells
- cytoplasmic membrane
- cell wall
- outer membrane if present

Question 17

Cell membrane

Answer 17

GENERAL
- All cells have a cytoplasmic membrane
- Separates the interior of the cell from the external environment
STRUCTURE
- Usually composed of a phospholipid bilayer with embedded proteins
- Hydrophobic core
- Hydrophilic surfaces interact with either the external environment or the cytoplasm
- Chemically variable due to changes in fatty acid groups attached to a glycerol backbone
- Connected by ester linkages
- May have sterol-like molecules called “hopanoids” in it to help with stability across temperature ranges
OTHER
- capture energy
- holding sensory systems

Question 18

Cell Wall

Answer 18

• give cells their shape
• protect them from osmotic lysis/ mechanical forces
• structure: matrix of crosslinked strands of peptidoglycan subunits
• peptidoglycan subunits:
• N-acetylmuramic acid (NAM)
• N-acetylglucosamine (NAG)
• short peptide chain

Peptides and peptide crosslinks vary by species

Question 19

Peptide crosslinks features

Answer 19

• NAM connects to NAM
• Unusual D-isomers of amino acids in the crosslinks
• Diaminopimelic acid (DAP) in Escherichia coli
• Pentaglycine interbridges within Staphylococcus aureus

Question 20

Formation of bacteria cell walls

Answer 20

• Bactoprenol transports pentapeptide precursors
• Transglycosylation attaches NAG to NAM
• Transpeptidation connects peptide chains

Question 21

Gram+ Bacteria

Answer 21

• thick outer layer of peptidoglycan
• variable width periplasmic space
• negatively charged teichoic acids in the peptidoglycan

Question 22

Gram- bacteria

Answer 22

• very thin layer of peptidoglycan
• periplasmic space of varying width
• outer membrane composed of lipopolysaccharide (LPS)

Question 23

Gram Stain

Answer 23

Crystal violet stains cells
Iodine traps the colour
Alcohol decolourization shrinks large pores in Gram-positive cells and locks crystal violet stain in
Alcohol strips away some outer membrane lipids in Gram-negative cells
Safranin stains Gram-negative cells pink

Question 24

Outer Membrane

Answer 24

LPS in Gram-negative outer membrane
- O (outer) side chain of polysaccharides can vary
- Changed by the microbe to evade host immune responses
- Must be careful when treating Gram-negative infections because outer membrane may cloak components that elicit a strong immune response (e.g., Lipid A)

Question 25

Facilitated diffusion

Answer 25

involves a protein associated with the cytoplasmic membrane enabling a substrate or solute to pass down its concentration gradient into the cell, doesn't require ATP

Question 26

co-transport

Answer 26

2 types Symport: brings something of low concentration in with something of high concentration Antiport: something with high concentration inside the cell, bring in something with low concentration outside the cell, no ATP required

Question 27

active transport

Answer 27

uses ATP transports solutes into cell against concentration gradient using energy from ATP

Question 28

How do antibiotics target bacteria?

Answer 28

B-lactam inhibits FtsI transpeptidation, interrupting covalent linkages between neighboring peptide chains (in the bacteria, stops cell wall formation)

Question 29

What is some bacteria's response to antibiotics, how is that resolved?

Answer 29

- some bacteria produce b-lactamase, interfere with the lactam ring, destroys the b-lactam, so resistant to antibiotic - resolved by adding clavulanic acid (isn't antibiotic itself), interferes with and occupies b-lactamase, so b lactam can do its job

Question 30

Flagella

Answer 30

- spiral, hollow, semi-rigid filaments extending from the cell surface - locations and number vary across species - three pieces: filament of flagellin proteins, hook protein, basal body - energy comes from proton motive forces

Question 31

Motility of flagella

Answer 31

- Polar flagella: propel forward or backward depending on spin direction - Amphitrichous: propel one way or another depending on which flagellum spins - Peritrichous: one direction of rotation moves forward, a change in direction induces a tumble

Question 32

Chemotaxis

Answer 32

-run and tumble - either towards chemical attractants or away from repellents

Question 33

Gliding motility

Answer 33

smooth sliding over a surface

Question 34

Twitching motility

Answer 34

slow, jerky process using pili that extend, attach to, and pull along a surface

Question 35

Pili

Answer 35

- fibers of pilin protein, possess other protein on their tips for sticking - extend outward from cell, allow attachment and twitching motiliy

Question 36

Stalks

Answer 36

- A “holdfast” of polysaccharides is used to attach an organism to a surface - Provide extra surface area for nutrient absorption

Question 37

Capsules

Answer 37

Thick layer of polysaccharides surrounding some cells: adhesion (e.g., biofilms), defense against host immunity, protection against desiccation

Question 38

Surface arrays (S-layers)

Answer 38

- Crystalline array of interlocking proteins - Protects cell against predation or infection with bacteriophages - Found in Gram-positive and Gram-negative cells