Ascientist discovers that a soil bacterium he has been studying produces an antimicrobial that kills gram-negative bacteria. she isolates and purifies the antimicrobial compound, then chemically converts a chemical side chain to a hydroxyl group. when she tests the antimicrobial properties of this new version, she finds that this antimicrobial drug can now also kill gram-positive bacteria. the new antimicrobial drug with broad-spectrum activity is considered to be which of the following?
resistant
semisynthetic
synthetic
natural

semisynthetic

Explanation:

Broad spectrum antibacterials are active against the Gram-negative and Gram-positive organisms.  

For example phenicols,  tetracyclines .

Semisynthetic drugs -

As known as the partial chemical synthesis , it is a type of chemical synthesis that uses chemical compounds which are isolated from any natural source .

Semisynthesis is a cheaper method , as the initial substance is extracted from nature and rest few steps require chemical , which make it cheap and quicker process of drug synthesis .

then that particular organisms become extinct.