Aresearcher claims that different metabolic pathways allow bacteria to use different molecules as sources of matter and energy. which of the following statements best justify the researcher’s claim by providing a relevant example? a. rhizobia bacteria form close associations with the roots of bean plants. b. coli bacteria reproduce in liquid media containing either glucose or galactose. c.the antibiotic rifampicin inhibits the growth of some bacterial strains but not of others. d. some viruses that infect bacteria reproduce by either the lysogenic cycle or the lytic cycle.

Metabolic pathway is defined as the series of enzyme-linked reaction, which lead to formation of a final product from substrate. The correct answer is:

B. E.coli bacteria reproduce in liquid media containing glucose or galactose.

Explanation:

Escherichia coli is a single-celled bacteria, which can utilize several carbon sources to grow and reproduce. The most common carbon compound used by E.coli bacteria is glucose. The bacteria utilize glucose much faster as compared to other energy sources. However, E.coli can also use alternative sources such as protein, maltose, arabinose, and lactose to obtain energy. Thus, to survive, an organism like E.coli can follow multiple metabolic pathways to derive energy from different sources of energy.

Reasons for incorrect answers:

a. Rhizobia bacteria exists in symbioses with the legume plants. Inside the root nodule, the dinitrogen is reduced to ammonia by the bacteria. The process is performed in exchange to obtain carbon and energy source. Thus, rhizobia require carbon as an energy source.

c. Rifampicin is an antibiotic drug, which prevents bacterial growth by inhibiting RNA synthesis. The anti-biotic is specific for Gram-positive and Gram-negative bacteria.

d. Viruses are organisms, which infect the host by incorporating the genetic material. Viruses that infect bacteria, reproduce either by lytic cycle or lysogenic cycle. In the lytic cycle, new virions are reproduced by the destruction of the host cell. In the lysogenic cycle, the viral genomic sequence is integrated into the host's DNA.

Thus, the correct answer is E.coli requires carbon sources, majorly glucose to reproduce and survive.

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Option B

Explanation:

E.coli has a preference of glucose over other energy molecules and therefore whenever glucose it present, it leaves no chance of metabolizing and using it as a source of energy.  

However, in absence of glucose E.coli uses alternative energy sources such as galactose, maltose, lactose, arabinose etc. Therefore, it is clear that in order to sustain, an organism or bacteria follows multiple metabolic pathways to derive energy from various energy sources.

Hence, option B is correct.

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