Bacteria Our invisible friends Germ Theory of Disease

Bacteria Our invisible friends

Germ Theory of Disease w. Joseph Lister – Aseptic Techniques w. Robert Koch – Germ Theory n A specific microorganism causes a specific disease

Bacteria are prokaryotes w. Pro – before w. Karyon – nucleus w. The simplest forms of life are prokaryotes. w. Earth’s first cells were prokaryotes.

Lots of Them! w Prokaryotes are Earth’s most abundant life forms. w They can survive in many environments. w They can get energy from many different sources.

Prokaryote Review w Mostly single-celled w No nucleus or organelles w Circular chromosomes w Cell walls w Reproduce mostly asexually w Anaerobic or aerobic w Heterotrophic or autotrophic

Archaebacteria w. Methane producers – anaerobic w. Halophiles Halo = salt n Philia = love n w. Thermophiles n Thermo = heat

Eubacteria w Parasitic heterotrophs (Streptococcus) w Saprophages Sapro = death n Phage = eat n w Cyanobacteria (blue-green algae) n Photosynthetic w 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 w Cocci (ball-shaped) n Streptococcus mutans w Bacillus (rod-shaped) n Clostridium botulinum w Spirilli (spiral-shaped) n 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