Strain Improvement & Deterioration

Question 1

define strain

Answer 1

subgroup of a species with 1 or more characteristics that distinguish it from other subgroups of the same species

Question 2

how are strains usually identified

Answer 2

by a name or an alphanumeric descriptor
e.g. Microcystis aeruginosa PCC7813

Question 3

Define strain improvement

Answer 3

the process of manipulating & improving strains to enhance their metabolic capacity

Question 4

in general, why do we need strain improvement

Answer 4

wild types produce low quantities of commercially important metabolites

Question 5

aims of strain improvement

Answer 5

yield can be produced by optimisation of fermentation conditions (medium, temperature, pH, etc.)
major improvements only achieved through strain improvement

Question 6

what are the 9 ideal characteristics of an improved strain

Answer 6

• genetic stability (no mutation)
• rapid growth
• non-toxic
• ability to use cheap substrates
• decreased fermentation time
• reduced by-products interfering with downstream processing
• reduced cultivation cost (low price nutrients, low requirement of O₂)
• increased productivity of target metabolites
• regulated enzyme activity

Question 7

idiolites

Answer 7

(AKA secondary metabolites)
have no function in growth
the vast majority of commercially relevant compounds are idiolites

Question 8

how are idiolites produced

Answer 8

produced in the developmental phase in batch culture after growth (at later stage of fermentation - idiophase)

Question 9

what are idiolites produced by

Answer 9

produced by a narrow taxonomic group of organisms

Question 10

idiolites structures

Answer 10

• have unusual & varied chemical structures
• often found as mixtures of closely related members of a chemical family
• central core molecule stays the same while differing amino acids extend out

Question 11

in nature, what purpose do idiolites serve to the strain

Answer 11

serve the survival of the strain
may be antagonistic or synergistic

Question 12

antagonist properties of idiolites

Answer 12

production of toxins, pheromones, or environmental modulation (biofilm)

Question 13

synergistic properties of idiolites

Answer 13

allelomones (modify other species behaviour)
pheromones (modify same species behaviour)
environmental modulation e.g. biofilms (change environment to more favourable conditions)

Question 14

process of strain improvement using brute force mutagenesis

Answer 14

• undirected/random mutagenesis by irradiation (or chemicals)
• screening and selection of advantageous, desired mutations

Question 15

physical mutagens

Answer 15

UV irradiation
x-ray irradiation

Question 16

insertional mutagens

Answer 16

plasmids

Question 17

chemical mutagens

Answer 17

aminopurine (AT to GC transition)
bisulfite (GC to AT transition)

Question 18

why do we tend to use lethal doses of mutagens

Answer 18

ensures only advantageously mutated individuals survive (we want the strongest to survive)

Question 19

mutational biosynthesis was developed by who and when?

Answer 19

(AKA mutasynthesis) was developed by Kenneth Rinehart & David Gottlieb in 1969

Question 20

describe mutasynthesis

Answer 20

a mutant blocked in idolite production is fed analogues of the subdivision whose synthesis was blocked

Question 21

if mutasynthesis is successful?…

Answer 21

the mutant (idiotroph) produces a new secondary metabolite