BACTERIA

• ARCHAEBACTERIA– Introns in DNA– Lack peptidogycan in

cell walls– Live in extreme

environments

• EUBACTERIA– Includes most bacteria– Most have one of

three shapes– May be divided into up

to 12 phyla– Classification is

controversial

TYPES OF ARCHAEBACTERIA

Thermoacidophilies Living in hot springs

Methanogens living in sewage

Extreme halophile

living in the Great Salt Lake

BASIC SHAPES OF EUBACTERIA

SPHERICAL

ROD-SHAPED

SPIRILLA

Most Species of Eubacteria may be Grouped Based on Staining

• Gram-Negative

– Lack thicker layer of peptidoglycan

– Stain pink

– Endotoxins

• Gram-Positive– Thicker layer of

peptidogycan– Stain purple– Exotoxins (released

when bacteria die)

Gram- negativeGram-positive

Nutrition and Growth

• Saprophtesex: decomposers• Photoautotrophs ex: blue-green algae• Obligate anaerobes ex: tetanus• Facultative anaerobes ex: E.Coli• Obligate aerobesex: tuberculosis• Thermophilic bacteria

Most bacteria grow at at neutral pH but some grow best at a pH of 6 or lower– Bacteria that produce yogurt and sour cream

E. coli

• E. coli is the lab rat of the bacterial world.

• E. coli is a normal resident of the large intestine in healthy people. It is a type of probiotic organism because it crowds out disease causing bacteria. E. coli also makes vitamin K which humans require to be healthy.

• Although it is generally a good microbe, some strains make people sick. The toxic strains of this microbe are responsible for about half of all cases of traveler's diarrhea. One famous strain, O157:H7, has caused disease in people who eat uncooked hamburger.

Thermophiles

• These bacteria feed an animal that cannot eat. The relatives of this microbe make life possible deep beneath the ocean near volcanic vents. This particular microbe lives inside and feeds tall white worms sporting red, feathery caps, that live at the dark bottom of the sea.

• The microbes and the worm depend upon each other for survival in what is called a symbiotic relationship.

Sewage Sludge• Sewage is home to many

microbes. Many of these microbes are the main workers in cleaning up sewage sludge. They eat the sludge and release carbon dioxide gas,water and trace minerals. These weird, coiled-shaped microbes live with other microbes in a culture from sewage sludge.

• The bacterium shown above is unusual because it is coiled. No on knows why they grow in coils.

Serratia marscescens

• This common microbe is found in soil, water, on plants and in animals.

• Most microbiologists are all too familiar with Serratia marscescens, one of the most frequent contaminants of Petri plates in the lab. This same organism also grows on bread and communion wafers which have been stored in a damp place.

Bacillus cereus

• Bacillus cereus is a Gram positive, aerobic, spore-forming, rod-shaped bacterium. Like many bacteria, B. cereus is both a friend and a foe of humans. Sometimes it behaves as a friend in that it is used as a form of biocontrol to help us get rid of unwanted pests. For example, B. cereus deters certain fungi from rotting seedling plants.

• B. cereus can also be a serious foe when it causes food poisoning.

CYANOBACTERIABLUE-GREEN ALGAE

Genetic RecombinationTransformation - Bacteria take in DNA from its external environment.

Conjugation

Transduction – a virus obtains DNA from host bacteris

Conjugation of E. coli

Antibiotics

• Antibiotics are drugs that combat bacteria by interfering with cellular functions– Penicillin – interferes with cell wall production– Tetracycline – interferes with protein

production– Sulfa drugs – produced in the laboratory– Broad-spectrum antibiotics will affect a wide

variety of organisms

Penicillin

• This amazing fungus produces the famous antibiotic, penicillin. In 1928. Alexander Fleming observed that a mold called Penicillium notatum produced a substance, later known as penicillin, that killed bacteria in its presence. This antibiotic was the first of many to be found and used to treat infections.

• Interferes with cell wall production.

This fungus makes antibiotics and cheese. Other varieties of the fungus produce blue cheese and Roquefort cheeses.