Bacteria

What is a bacterium?

Prokaryote

Unicellular

Has a cell wall, DNA, and ribosomes

Found in variety of places

Fossils

How far back do we

see fossils of

bacteria?

3.5 billion years

Evidence with

stromatolites

Classification

Two kingdoms of Bacteria:

Archaebacteria (ancient bacteria)

Harsh environments

Primitive

Eubacteria (true bacteria)

Found anywhere

Cause diseases

ArchaebacteriaAbsence of

peptidoglycan

(component of

bacterial cell wall)

Live in extreme

environments:

swamps, salt lakes,

hot springs, volcanic

vents, hydrothermal

vents

Examples of ArchaebacteriaMethanogens: found in swamps, intestines of

animals

Extreme halophiles: salt-loving; live in Great Salt

Lake and Dead Sea; use salt to make ATP

Thermoacidophiles: extremely acidic environments

with high temperatures such as a hot spring; survive

in 110 °C (230 °F) and a pH of 2; live near volcanic

or hydrothermal vents

Eubacteria

Presence of peptidoglycan in cell

walls

Live everywhere on earth except

extreme environments

EubacteriaShapes

Cocci – spheres

Bacilli – rod

Spirilla – spiral

Occur in chains: strep

Occur in clusters: staph

Examples: Streptococcus, Staphylobacillus

Spirochaeta: spiral

Bacteria and archaea have similar structures.

flagellum

pili

plasmid

cell wall

chromosome

plasma

membrance

plasmid DNA

flagellum

pili

Cell wall

Circular

DNA

Prokaryotes provide nutrients to

humans and other animals.

Prokaryotes live in digestive systems of

animals.

make vitamins

break down food

Bacteria help ferment many foods.

yogurt, cheese

pickles, sauerkraut

soy sauce, vinegar

Prokaryotes play important roles

in ecosystems. Prokaryotes have many functions in

ecosystems.

recycle carbon, nitrogen,

hydrogen, sulfur

fix nitrogen for plants

Some bacteria cause disease.

Bacteria cause disease by invading

tissues or making toxins.

A toxin is a poison released by an

organism.

Antibiotics are used to fight

bacterial disease. Antibiotics may stop bacterial cell wall

formation.

Prevention is best method to fight bacterial

disease.

Antibiotic

Genetic Recombination

Transformation – takes in DNA from the environment

Conjugation – transferring of DNA between bacteria

Reproduction

Asexual reproduction

Makes more of the

same

Looks like the parent

Bacteria use binary

fission

Bacteria have various strategies

for survival. Prokaryotes

exchange

genes during

conjugation.

conjugation bridge

TEM; magnification 6000x

StructureEndospores

Resistant structure with a thick outer

covering in order to survive harsh

conditions

Environment & Temperature The temperature where bacteria may be

found depends on the species.

Prokaryotes can be grouped by their need

for oxygen.

obligate anaerobes are poisoned by oxygen

obligate aerobes need oxygen

facultative aerobes can live with or without

oxygen

Nutrition

Heterotrophic or autotrophic

Feed on dead and decaying material:

decomposers

Use sunlight: photoautotrophs

Cyanobacteria

Use chemicals as source of carbon:

chemoautotrophs

Found at ocean depths

Bacteria can evolve resistance to

antibiotics. Bacteria are gaining resistance to antibiotics.

A bacterium carries genes for antibiotic

resistance on a plasmid.

A copy of the plasmid is transferred

through conjugation.

Resistance is quickly spread through

many bacteria.

Bacteria and HumansAntibiotic resistance

Because antibiotics have been overused

Some bacteria prevent passage of an

antibiotic

Some secrete enzymes that destroy or

alter the antibiotic (penicillin-resistant)