Strain Improvement Techniques

Question 1

Define what a strain is

Answer 1

A Strain is group of species with one/ more characteristics that distinguish it from other sub groups of the same species of the strain. Each strain identified by a name, number or letter. Example: E coli Strain K12

Question 2

Define Strain Improvement

Answer 2

The science and Technology of manipulating and improving microbial strains in order to enhance their metabolic capacity

Question 3

Ideal Characteriztics of Strain

Answer 3

=Rapid growth
=Genetic stability
=Non toxicity to humans
=Ability to use cheaper substrates
=Elimination of the production of compounds that may interfere with downstream processing
=To improve the use of carbon and nitrogen sources
=Reduction of cultivated cost
=Shorter fermentation time

Question 4

Purpose of Strain Improvement

Answer 4

• Increase the productivities
• Regulating the activity of the enzymes
• Introducing new genetic properties into the organism by Recombinant DNA technology/ genetic engineering.

Question 5

Approaches for Strain Improvement

Answer 5

• Mutant Selection
• Recombination
• Recombinant DNA Technology

Question 6

What is a mutation

Answer 6

A sudden and heritable change in the traits of an organism.

Question 7

Mutagenesis

Answer 7

Application of mutagens to induce mutation.

Question 8

What are mutagens, give examples for chemical mutagens

Answer 8

Agents that are capable of inducing mutations.
Example: Alkylating agents, Acridine Dyes.

Question 9

What is the Difference Between spontaneous vs induced mutation

Answer 9

Mutation occurring without any specific treatment are called spontaneous mutation.
Mutation that are resulting due to a treatment with certain agents is known as induced mutations

Question 10

What are major mutations and what can it be used for

Answer 10

A major mutation is when many mutations bring about marked changes in the biochemical characters of practical interest. These can be used in Strain Improvement.
Example: Streptomyces aurofaciens- produce 6- demethyl tetracycline in place of Tetracycline.

Question 11

What has most improvements in biochemical production have been due to?

Answer 11

Stepwise accumulation of minor genes.

Question 12

What are the four methods of isolation of mutants.

Answer 12

1. Replica plating technique
2. Resistance Selection Method
3. Substrate utilization method
4. Carcinogenicity test

Question 13

Describe recombination

Answer 13

Defined as formation of new gene combinations among those present in different strains.
Recombination is used for both genetic analysis as well as strain improvement to generate new products.
Recombination may be based on transformation, conjugation and others like cross over and transduction.

Question 14

Define Protoplast fusion

Answer 14

The fusion between non producing strains of two species (Streptomyces griseus and Streptomyces tenjimariensis) has yielded a strain that produces indolizomycin, a new Indolizine antibiotic.

Question 15

What is recombination DNA technology

Answer 15

rDNA technology or genetic engineering involves the isolation and cloning of genes of interest, production of the necessary gene constructs using appropriate enzymes and then transfer and expression of these genes into an suitable host organism.

Question 16

What are used to achieve 2 broad objectives

Answer 16

• Production of Recombinant proteins
• Metabolic Engineering

Question 17

What are recombinant proteins and give example.

Answer 17

These are the proteins produced by the transferred gene/ transgene. They themselves are of commercial value.
Example: insulin, interferon that are produced in bacteria

Question 18

Briefly describe replica plating technique

Answer 18

Used to detect auxotrophic mutants which differentiates between mutants and wild type strains on the basis of ability to grow in the absence of an amino acid.

Question 19

Describe resistance selection method

Answer 19

Generally the wild type cells are not resistant either to antibiotics or bacteriophages. Therefore, it is possible to grow the bacterium in the presence of the agent (antibiotics or bacteriophage) and look for survivors.

Question 20

Describe the substrate utilization method

Answer 20

This method is employed in the selection of bacteria. Several bacteria utilise only a few primary carbon sources. The cultures are plated onto medium containing an alternate carbon sources. Any colony that grows on medium can use the substrate and are possibly mutants. These can be isolated.