Methods of Physical and Chemical Control of Microbial Population

Ignaz Semmelweis

The man who advocated for hand washing and rinsing with mercuric chloride before delivering a baby to reduce the number of cases of puerperal sepsis and postpartum bacterial infections.

Joseph Lister

The English surgeon who introduced the use of phenol to reduce the number of post-surgical infections.

Disinfectants

Chemical agents used to control microbial populations on inanimate surfaces

Antiseptics

Chemicals used on living tissue to control microbial populations. Usually less toxic than disinfectants

Sterilization

Procedures like hand-washing where some bacteria is inhibited or removed but some survivors are tolerated

Sterilization

The complete destruction or death of all microbial life, including endospores. Needed in the preparation of microbial media, surgical instruments, and vaccines.

Zone of Inhibition

Area of no growth around the disc diameter in mm

260-265 nm

What wavelengths of UV light are absorbed by Nucleic Acids?

UV

_______ radiation causes covalent bonds to form between pyrimidines (pyrimidine dimer) which interferes with DNA replication and mRNA synthesis.

Mutations

UV radiation can cause pyrimidine dimers which result in _____________.

Dark Repair

An enzyme system that does not require any outside source to induce its production.

Light Repair

An enzyme repair system that requires visible light for induction of repair

Photoreactivation

The process of repair of mutations and thymine dimers after exposure to visible light

Decontamination

UV radiation can be used for bacterial _____________ because prolonged exposure can create too many pyrimidine dimers for repair systems to fix.

Penetrate

The use of UV radiation is somewhat limited because it is not strong enough to ______ many common materials, including plastic or glass.

Organic

UV radiation cannot penetrate _________ molecules at great depths which is why PABA is effective in sunscreen.

Endospores

The inability of UV radiation to penetrate organic molecules to great depths is why bacterial _______ can survive much longer exposure times than vegetative cells.