Which bacterial species is known as the 'natural genetic engineer of plants' because its tumor-inducing (Ti) plasmid naturally transfers T-DNA into the nuclear genome of dicotyledonous host plants?
Answer and explanation
Correct answer: D. Agrobacterium tumefaciens
- Step 1: Agrobacterium tumefaciens is a soil-dwelling phytopathogenic bacterium that infects dicots, causing crown gall tumors.
- Step 2: It harbors a large tumor-inducing (Ti) plasmid that transfers a defined segment of DNA, termed T-DNA (transferred DNA), into plant cells, integrating it into the nuclear genome.
- Step 3: Biotechnologists disarm the Ti plasmid by removing tumor-inducing oncogenes while retaining the T-DNA border sequences, converting it into an efficient vector for plant genetic engineering.
Answer
Agrobacterium tumefaciens.
Why not the others: E. coli is a standard laboratory bacterial host for cloning; Bacillus thuringiensis is the source of insecticidal Bt toxin genes; Rhizobium forms nitrogen-fixing root nodules in legumes.
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