Use of Genetically Engineered Bacteria

The genetically engineered bacteria have found applications in various areas:

a) Crop production and protection through biological control of insects and fungal diseases, frost damage.

Genetically engineered bacterial strains have been developed to control insects, fungal diseases or frost damage etc.

Table Genetically engineered bacteria in Crop production and protection

Bacterium	Altered trait	Possible use
Rhizobium melilotii	Additional copies of ‘nif’ genes	Increased efficiency of N2 fixation
A. radiobacter	Delection of ‘tra’ gene of Agrocin 84 plasmid	Biological control of crown gall
P. fluorescens	Addition of lac ZY	Assessment of movement of bacteria for biological control
Clavibacter xyli	Transfer of B.thuringiensis delta endotoxin gene	Control of corn ear worm
Pseudomonas fluorescens	Transfer of Serratia marcescens chitinase gene	Control of fungal disease
P. syringae	Deletion of ‘ice’ gene	Control of frost damage

Table Various possible pathways for the production of transgenic plants

Target cell type	Method used for regeneration
1. Cultured cells or protoplasts	Oranogenesis or embryogenesis via callus formation stages
2. Meristem cells from immature embryo or organ	In vitro plant regeneration from transformed cells
3. Cells in immature embryos, shoot and flower meristems	Normal development (in vivo) of embryo, shoot or flower followed by use of transformed pollen  from chimeric plant to produce transformed seed
4. Pollen	Pollen treated with DNA used for pollination leading to the production of transgenic plants
5. Zygote	In vivo development of transgenic plants

 

b) Production of chemicals and fuels like antibiotics, enzymes, diagnostics etc.

Genetically engineered strains of Bacillus amyloliquefaciens and Lactobacillus casei have been prepared for production of amino acids on a large scale. Industrially useful bacteria utilize cheaper feed stocks (substrates) like D-xylulose, cellulose. e.g. Zymomonas mobilis (normally incapable of using lactose) carrying cellulase gene from Cellulomonas uda has six fold increase in cellulose activity. E.coli and Klebsiella planticola carrying genes from Z. mobilis could utilize glucose and xylose to give maximum yield of ethanol.

c) Extraction of metals from ores

Plasmids have been constructed which when present with T. ferroxidans increases its resistance to arsenite and arsenate which inhibit the growth of bacteria, and increases the recovery of gold from arsenopyrite-pyrite ores. Efforts are going on to construct genetically engineered bacteria with enhanced bioleaching or nucleating capabilities which will play important role in mining and metal extraction.

d) Biodegradation of waste from non-biological systems and toxic waste treatments

For efficient biodegradation, efficient and competent biodegraders are being prepared using genetic engineering which will use various catabolic pathways to degrade toxic wastes.

Table Genetically engineered bacteria used for the degradation of xenobiotics and toxic wastes

Bacterium	Substrate that can be degraded
Pseudomonas capacia	2,4,5- trichoro-phenoxyacetic acid
P. putida & other spp (also E.Coli)	2,2,5-dichloropropionate; mono and dichloroaromatics
Alcaligenes sp.	Dichlorophenoxyacetic acid, mixed chlorophenols; 1,4- dichlorobenzene
Acinetobacter sp.	4-chlorobenzene