Bacteria Our 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 – before  Karyon – nucleus  The 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-celled  No nucleus or organelles  Circular chromosomes  Cell walls  Reproduce mostly asexually  Anaerobic or aerobic  Heterotrophic or autotrophic

Archaebacteria  Methane producers – anaerobic  Halophiles Halo = salt Philia = love  Thermophiles Thermo = heat

Eubacteria  Parasitic heterotrophs (Streptococcus)  Saprophages Sapro = death Phage = eat  Cyanobacteria (blue-green algae) Photosynthetic  Chemosynthetic autotrophs (Rhizobium)

Bacteria Structure Chromosomes – found in cytoplasm Pili – hairlike structures made of protein; help bacteria attach to surfaces Capsule – 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

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, acne 2. secrete a toxin that can be harmful ex. Cavities – use sugar for energy and secrete acid which can harm teeth