diversity and biology of bacteria p2 L8

Question 1

plasmids

Answer 1

circular or linear extrachromosomal DNA

non-essential genes

autonomous replication

selective advantages

can spread antibiotic resistance, genes in general via conjugation

Question 2

flagella

Answer 2

motility

arrangement and number of flagella is characteristic of genus, help classify

using proton motive force to move

Question 3

structure of flagella

Answer 3

long helical filament
connecting hook
basal body as rotor to turn - differences between gram+ve and -ve
hollow structure formed on flagellin = filament

highly antigenic = H-antigen (PAMP), highly strain specific

Question 4

pili and fimbriae

Answer 4

protein spikes that extend from surface
pili are longer
fimbriae are more abundant

Question 5

functions of pili and fimbriae

Answer 5

adhesion using type 1 fimbriae

twitching motility using type 4 pili

DNA transfer using sex pills in conjugation

Question 6

bacterial capsule

Answer 6

amorphous polysaccharide slime tightly bound around cell well

in gram-ve and +ve bacteria
observed under light microscope using specific capsule strains

the presence and composition are strain -specific

Question 7

functions of bacterial capsule

Answer 7

barrier to toxic hydrophobic molecules

contains water so prevents drying out

major virulence factor in streptococcus

contributes to resistance to phagocytosis - streptococcus

Question 8

why is studying bacterial metabolism important ?

Answer 8

essential for transmission

help identify specific nutrient requirements and pathway bottlenecks

help understand metabolic networks and regulation in infection

identify new drug targets

Question 9

calcium

Answer 9

stabilise cell wall

Question 10

magnesium

Answer 10

stabilise ribosomes, membranes, nucleic acid

Question 11

boron

Answer 11

Auto-inducer for quorum sensing

Question 12

passive transport

Answer 12

no energy input
simple diffusion, movement of small hydrophobic molecules down concentration gradient

facilitated diffusion - hydrophilic molecules moving down concentration gradient that need channel or carrier protein

Question 13

active transport

Answer 13

requires energy to move molecules against concentration gradient

Question 14

ion-coupled transport

Answer 14

active transport

driven by electrochemical proton gradient, proton motive force

-

Question 15

what is support and antiport

Answer 15

support = co-transport in same direction - LacY in e.coli

antiport - ion and substance move in opposite directions

Question 16

abc transporters

Answer 16

atp-binding - cassette

hydrolysis of ATP drives transport, specific binding proteins

substrate binds on outside, this closes the inside part of the protein, needing ATP hydrolysis to occur to give energy to open it again to let fully through - highly specific

Question 17

group translocation

Answer 17

substrate that is phosphorylated during transport, energy provided by PEP

transported into cell and chemically modified at the same time

Question 18

how group translocation works

Answer 18

Energy Source:
Uses phosphoenolpyruvate (PEP) as the energy source

Phosphate Transfer Chain:
PEP donates a phosphate → to Enzyme I (EI)
EI passes phosphate to HPr (histidine protein)
HPr passes phosphate to Enzyme II (EII), which has multiple parts (A, B, C)
Transport and Modification:
EII-C transports the sugar into the cell
EII-B phosphorylates the sugar during import
So glucose becomes glucose-6-phosphate, trapped inside the cell (can’t diffuse back out)
Why it’s useful:

Saves energy by modifying the sugar right away
Keeps sugar inside the cell
Prepares sugar for metabolism (e.g., glycolysis)