BacteriaOur invisible friends

Germ Theory of Disease

Joseph Lister – Aseptic Techniques

Robert Koch – Germ Theory A specific microorganism

causes a specific disease

Bacteria are prokaryotes

Pro – beforeKaryon – nucleusThe simplest forms of life are

prokaryotes.Earth’s first cells were

prokaryotes.

Lots of Them!

Prokaryotes are Earth’s most abundant life forms.

They can survive in many environments.

They can get energy from many different sources.

Prokaryote Review

Mostly single-celledNo nucleus or organellesCircular chromosomesCell wallsReproduce mostly asexuallyAnaerobic or aerobicHeterotrophic or autotrophic

ArchaebacteriaMethane producers – anaerobicHalophiles

Halo = salt Philia = love

Thermophiles Thermo = heat

EubacteriaParasitic heterotrophs (Streptococcus)Saprophages

Sapro = death Phage = eat

Cyanobacteria (blue-green algae) Photosynthetic

Chemosynthetic autotrophs (Rhizobium)

Bacteria Structure

Chromosomes – found in cytoplasmPili – hairlike structures made of protein; help bacteria attach to surfacesCapsule – layer outside cell wall; protects cell from white blood cells and antibiotics; keeps the cell from drying out

Bacteria Structure

Bacteria are Named by Shape

Cocci (ball-shaped) Streptococcus mutans

Bacillus (rod-shaped) Clostridium botulinum

Spirilli (spiral-shaped) Treponema palladium

Bacteria Reproduction

Binary fission – asexual; division of bacteria into two identical cells

Conjugation – sexual; two prokaryotes attach to each other and exchange genetic material; creates diversity among bacteria

Bacteria Reproduction

Bacteria Reproduction

Why do we need bacteria?

Our bodies use bacteria – not harmful; help prevent harmful bacteria from causing disease

Foods – cheese, pickles yogurt all made with bacteria

Medicines – make antibiotics such as penicillin

Disease Causing Bacteria

Only a small percentage of bacteria is harmful

Cause disease in two ways:1. multiply quickly so the body cannot defend itself

ex. STDs, strep throat, acne2. secrete a toxin that can be harmful

ex. Cavities – use sugar for energy and secrete acid which can harm teeth