PATHOGENS IN OUR ENVIRONMENT slides 3

KOCH’S POSTULATES 1

suspected pathogen must be present in all cases of the diseas and absent from heathly animals

Pathogen:

A biological disease causing organism or agent

KOCH’S POSTULATES 2

pathogen must be grown in pure culture

KOCH’S POSTULATES 3

cells from pure culture must cause disease in heatlthy animal

KOCH’S POSTULATES 4

pathogen must be reisolated and shown to be the same as original

MODES OF TRANSMISSIOn

direct contact

by air

indirect contact

by food

insects

rabid animals

TYPES OF PATHOGENs

bacteria fungi virus protists

bacterial structures

coccus rod spirochete

BACTERIA AND ARCHAEA REPRODUCTION

Asexual binary fission and rapid

ANTIBIOTICS discovery

alexander Fleming (1928)

VIRUSES NEED CELL MACHINERY

Injecting genetic material 2. Using host cell for transcription and translation 3. Assembling proteins and genetic material into new copies of the virus

Lytic cycle

virus begins replicating almost immediately upon entry into the cell. • Its genome is independent of the host genome

Lysogenic cycle:

The genome incorporates with the host genome but remains inactive • Viral reproduction will not occur until an environmental signal induces the viral DNA to be read and processes

Lysogenic cycle examples

HIV, Herpes Simplex, and some Hepatitis viruses