Use of Antibiotics in Microbiological Research

Antibiotic is an agent which retards the growth of microorganisms. They belong to broader classification antimicrobial compounds and microbes can be bacteria, virus, fungi and algae. They can be either produced by the microorganisms or isolated from the organisms.  It can be either natural antibiotic or semi synthetic or synthetically made antibiotic. Using antibiotic for treating infection is practiced before 2500 years onwards. Natural antibiotic growth is ultimately based on the microorganism property of antibiosis. Antibiosis is a drug which has the potential of reacting against microorganisms. It means against life in French. Hence it is termed as antibiotic.

Types of antibiotics

They are widely classified on the basis of many criteria. The criteria can be their mechanism of actions, physical structure, chemical structure and spectrum of action. They target to repair cell wall or cell membrane or enzymatic activity or protein synthesis or DNA/RNA synthesis or peptidoglycan synthesis or fatty acid synthesis. Antibiotics are broadly divided into two major classes on the basis of target specificity where it can either kill the microbes or damages the microbes. Ultimate use of antibiotic is to interfere any phase(s) of growth.

• Bactericidal: It is an agent that kills the growth of bacteria. For instance antibiotics like penicillin and cephalosporin are capable of cleaving cell wall, polymixins impair cell membrane and antibiotics such as quinolones and sulfonamides retards the enzyme activity of bacteria.
• Bacteriostatic: It is an agent that damages the growth of bacteria. For instance cholroamphenicol, aminoglycosides, cyclohexamide, tetracyclines and macrolides are capable of interfering in the synthesis of protein.

Actinomycin is used for higher organism. It is used as a poison for killing rat. Actinomycin and rifampin interferes in the synthesis of RNA. Cycloserine inhibits synthesis of peptidoglycan, daunomycin inhibits the fungal RNA synthesis and polyoxin D inhibits the fungal cell wall made of chitin. Antibiotics like nalidixic acid and novobiocin can inhibit DNA synthesis of bacteria, mitomycin interferes with general DNA synthesis and cerulenin inhibits fatty acid synthesis.

Based on the spectrum of activity they are classified in to three types.

• Cyclic lipopeptides for instance daptomycin is lipopeptide antibiotic used against gram positive bacteria.
• Glycylcyclines antibiotic like tigecycline
• Oxazolidinones antibiotic like linezolid

Uses of antibiotic

When a culture is inoculated, antibiotic are injected to maintain sterile offspring. A mixture of antibiotics can be used for growth of tissue culture and virus culture cultivation. It helps in monitoring of cell function.

• Cell wall synthesis can be interfered by cell wall synthesis inhibitors. For instance antibiotics like beta lactums, bacitracin, penicillin and semi synthetic penicillin.
• Antibiotic inhibit the metabolic rate. These drugs are referred as competitive inhibitors and are synthesized in laboratory.  For instance sulfonamides, ethambutol, isoniazid and paraaminosalicylic acid act as competitive inhibitors affects nucleic acids.
• Agents that inhibit the synthesis of DNA and RNA are referred as chemotherapeutic agents.
• Translation of protein is inhibited by protein synthesis inhibitors.
• It helps in administration of antibiotic. For instance bacterial flagella synthesis can be studied. Flagella shall be removed by blending it with mixture of antibiotic agents. When it is inoculated with actinomycin antibiotic it results in growth of sterile culture.