Carriers of Disease

Microbes, Germs and Other Scary Things

Bacteria

• Prokaryotic, monera• 2 billion yrs• 1st life on earth• They change and adapt to the

environment• No cell membrane or nucleus• Have cell wall• Many different structures

Habitat

• Extremes– Hot– Cold– Acidic– Alkaline

• Everywhere on earth

• Minority cause disease

• Majority are essential to life on earth

Diversity

• 2 groups– Archeabacteria –halophytes,

themoacidophiles, Methogens – poisoned by O2

– Eubacteria –all others• Pathogenic eubacteria cause about ½ of all human

disease• Some destroy tissue

– Exotoxins secrete substances that cause disease– Endotoxins – parts of the cells cause fever or shock

Motility

• ½ make direct movement

• Flagella – most common form of movement, extension of plasma membrane

• Spirochetes – spiral shaped that may have slimy chemicals excreted and a flagella

• Taxis – have an attraction to chemical that may be beneficial or harmful

Virus

• Simplest form of life– Argument can be made that they may not be

living

• 1st discovered by Dr. Mayor in tobacco plants

• Very small 20nm diameter

• Consist of viral genes enclosed in capsid – a protein shell

• There are multiple types of protein

• Envelopes covering on capsid taken from the membrane of host

• Phages – virus that infect bacteria

RNA viruses

• Single strand of nucleaic acid molecule involved in protein synthesis– Structure is specified by DNA

• Retrovirus – most complicated reproduction– Can reverse DNA to RNA– New DNA integrates into host cell

Evolutionary origins

• Evolved after 1st cells from fragments of nucleacic acid

• Developed capsid to promote infection

• Viral genomes – plasmids – transposes DNA segments that move along genome

• Virus replicate using the entire cell it infects

Prion

• Cause disease but aren’t bacteria, virus, parasite or fungi

• They are protein and not alive

• 1986 1st public awareness with onset of Mad-Cow Disease

• Enter cell where they convert normal protein found within cell into prions like themselves

• When normal cell is transformed into prion the amino acids are folded into alpha helical structures and relax into beta sheets

• Prion then clog cells which decreases function or stops the cell from functioning all together

• In brain tissue prion-bloated brain cells dies and release prion into tissue leaving holes in brain matter

• Cause disease call spongiform encephalopathies

Parasites

• Single cell or multicell organism that feeds off host

• Can survive only if host lives

• Causes disease that are usually not fatal

• Too many variety to list

Fungi

• Ecosystem would collapse without fungi– Decomposers – Recycles chemical elements in the

environment

• Positive uses for humans– Food– Cultures to produce antibiotics– Makes bread rise– Ferments to create beer and wine

Characteristic

• Eukaryote, multicellular

• Heterotrophic

• Excretes enzymes that break down molecules which it then absorbs\

• Can be parasitic or mutualistic

Unique Lifestyles

• Molds – grow as parasites on variety of substrates– Ex. – bread mold

• Yeast – inhabit moist environments or liquids– Ex. - Candida

Pathogenic Yeast in Humans

• Athletes foot

• Ringworm

• Vaginal yeast infections

• Lung infections

• Nail infection