Bacteriocins part 1

Question 1

Biopreservation

Answer 1

The use of biological systems (or products
derived from biological systems) to eliminate
or influence biological populations in specific
ecological niches
EX: Fermentation with food grade microbes, or
incorporation of fermentation products, to enhance the
shelf life, quality or safety of food

Question 2

What are bacteriocins

Answer 2

Peptides secreted by one bacterium which can kill other bacteria
 Short peptides
 Heat stable (can
withstand autoclaving)
 Active at very low
concentrations
(single nanomolar range)
 Many food grade
lactic acid bacteria
produce bacteriocins

Question 3

Why produce bacteriocins

Answer 3

The exact ecological function of bacteriocin production is unknown.
1. Killing peptides
2. Colonizing peptides
3. Bacteriocins as signalling molecules

Question 4

Class I Bacteriocins

Answer 4

• Lantibiotics
• Post transitionally modified peptides containing lanthionine groups
• Lanthionine groups bind to lipid 2. Lipid 2 transports cell wall subunits through the membranes.
• EX: Nisin and lacticin 3147
• Lacticin 3147= 2 component lantibiotic, lactococcus lactis, located on a conjugative plasmid.
• Modified peptides

Question 5

Class III Bacteriocins

Answer 5

• Larger heat labile enzymes, Usually narrow host range.
• Work by hydrolysing peptidoglycan bonds
• Lysostaphin

Question 6

Nisin (E234)

Answer 6

• A lantibiotic (modified peptide)
• Discovered in 1928
• Approved in many countries as a natural
  preservative

Question 7

Lacticin 3147

Answer 7

• Two component lantibiotic
• Lactococcus lactis
• Located on a conjugative
  plasmid

Question 8

Class II Bacteriocins

Answer 8

• Small heat stable unmodified peptides usually with narrow host ranges
• Sakocin P.
• Form pores in the membranes of sensitive bacteria they poke holes and insert.
• Use membrane proteins as receptors
• heat stable
• active at low concentrations
• hydrophillic and hydrophobic