Pathogenic Bacteria and Viruses The bad guys VIRUSES

Pathogenic Bacteria and Viruses The bad guys

VIRUSES VARY IN STRUCTURE due to the different proteins that make up the viral coat HOWEVER the essential design is the same: A core of nucleic acid wrapped in a protein coat. A VIRUS LACKS CELL ‘MACHINERY’ therefore a virus is not alive

Ex: BACTERIOPHAGE –attacks bacteria

BACTERIOPHAGES attack bacteria

Ex: HIV; INFLUENZA These have an additional layer - the envelope surrounding the coat

REPRODUCTION: The LYTIC CYCLE: Virus enters host, destroying host DNA. Replicates self like mad, until cell bursts releasing 100’s of new viruses, ready to invade more host cells.

REPRODUCTION : The LYSOGENIC CYCLE: 1. Virus enters cell; it’s DNA/RNA is incorporated into host DNA. 2. Host cells lives, producing more viral DNA/RNA as it divides. 3. Virus lives on in host for life with periodic outbreaks The original recombinant DNA!

A VIRUS CAN MOVE from the lysogenic to the lytic cycle i. e. herpes viruses have it for life, but only the occasional outbreak

BACTERIA ARE PROKARYOTES: DNA localized (but not bound by a membrane) in the cytoplasm Other Structures: PLASMIDS of DNA RIBOSOMES for protein production CELL MEMBRANE and a CELL WALL FLAGELLA for motion

TYPICAL BACTERIA SHAPES cocci, bacilli, spirilla

Bacteria form ENDOSPORES when conditions are not optimal for survival. Endospores can lie dormant for 1000’s of years!

BINARY FISSION – asexual reproduction

CONJUGATION – sexual reproduction; plasmid DNA moves between two organisms via PILI on cell surface