This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General Microbiology Pa-2 and Pa-3 (Sterilization and Bacterial Genetics), Subject name: Microbiology
Sterilization of media containing serum is by 
Select and explain. 
A. Autoclaving, B. Micropore filter, C. Gamma radiation, D. Centrifugation
B: Micropore filter
Answer: B: Micropore filter 
Explanation: Autoclave is used for sterlizing : surgical instruments culture media Plastic containers /Pipettes/Tubes . Gloves,aprons, dressing suture material except catgut Membrane/Micropore filter Membrane filters remove microorganisms by screening them out as they have less pore size than bacteria Made up with cellulose acetate, cellulose nitrate, polycarbonate etc. Serum , Trypsin, growth factors, proteins, amino acids, vitamins and hormones are thermolabile and may decompose during autoclaving, so must be sterilized by Membrane filters. Ionising radiations: 1. Examples include, X-rays, gamma rays (from Cobalt 60 source), and cosmic rays. 2. Mechanism: It causes breakage of DNA without temperature rise (hence called as cold sterilization). It is used for: Disposable plastics, e.g. rubber or plastic syringes, infusion sets and catheters. Catgut sutures, bone and tissue grafts and adhesive dressings, antibiotics and hormones. Centrifugation is not a method of sterilization.