Bacteria

What are Bacteria?• Living• Microscopic• Unicellular• Earliest Prokaryotic Cells

– They DO NOT contain a nucleus or membrane bound organelles

• The most numerous organism on Earth!

• Earliest bacterial fossils date back 2.5 billion years.

What are Bacteria?

• Most grow best at pH of 6.5 to 7.0

• Many act as decomposers recycling nutrients

• Some are beneficial• Some cause disease

Bacterial Structure• Contain ribosomes• Single, circular

chromosome in nucleoid region

• Cell Wall for protection• May have a sticky coating

called the Capsule • Some may have flagella

for locomotion

Bacterial Structure

Pili

Cell Wall

Chromosome

Flagellum

RibosomeCytoplasm

CellMembrane

Print Master

Bacterial Shapes• Coccus: Spherical (round)

• Bacillus: Rod shaped

• Spirillum: Spiral shape

Grouping of Bacteria

• Diplo- Groups of two– Diplococcus

• Strepto- chains– Strephtococcus

• Strep throat• Staphylo- Grapelike clusters

– Staphylococcus

Gram Staining• Developed in 1884 by Hans Gram• Bacteria treated with purple Crystal

Violet & red Safranin stains• Cell walls either stain purple or

reddish pink

Gram Positive• Have thick layer of peptidoglycan

(protein-sugar complex)• Single lipid layer• Stain purple• Can be treated with antibiotics

Gram Negative• Thin layer of peptidoglycan in cell wall• Extra thick layer of lipids

–This keeps out more stain• Stain pink or reddish• Hard to treat with

antibiotics

Bacterial Reproduction

There are 3 ways in which bacteria reproduce

1. Binary Fission

2. Conjugation: Sexual Reproduction

3. Spore Formation

Bacterial Reproduction

1. Binary Fission– Similar to Mitosis: Splitting– New cells are identical

2. Conjugation: Sexual Reproduction– Passing of genetic material– New cells NOT identical

3. Spore Formation– Form endospore (hard coating) for protection

when habitat conditions become harsh (little food)

– Able to survive for long periods of time as endosperm

– Difficult to destroy (heat resistant)

How Do They Eat?

• Saprobes: Decomposers– feed on dead organic matter

• Parasites – feed on a host cell

• Photoautotroph –use sunlight to make food

• Chemoautotroph –oxidize inorganic matter such as iron or

sulfur to make food

Methods of Respiration

• Obligate Aerobes – require O2

• Example: tuberculosis• Obligate Anaerobes

– die if O2 is present • Example: tetanus

• Facultative Anaerobes – don’t need O2, but aren’t killed by it

• Example:

Kingdoms of Bacteria

Archaebacteria: The Extremists• Found in harsh environments

Eubacteria: The True Bacteria• Most bacteria are in this

group

ArchaebacteriaSubdivided into 3 groups:

• Methanogens• Thermoacidophiles• Extreme Halophiles

Archaebacteria1. Methanogens• Break down cellulose in a cow’s

stomach• Produce marsh (methane) gas

Archaebacteria2. Extreme Halophiles• Live in very salty

water• Use salt to generate

ATP (energy)• Dead Sea, Great Salt

Lake inhabitants

Archaebacteria3. Thermoacidophiles or

Thermophiles• Live in extremely hot/acidic

environments• Found in volcanic vents, hot springs,

cracks on ocean floor that leak acid

Eubacteria• May be aerobic or anaerobic• Identified by Gram staining• Three types:

1. Heterotophs : include most bacteria2. Photosynthetic Autotrophs3. Chemosynthetic Autotrophs

Eubacteria1. Heterotophs : include most bacteria

• Use organic molecules as their food source• Some are parasitic

2. Photosynthetic Autotrophs• Live in areas with sun; they use sun to

make their food.• Ex: cyanobacteria ( can be blue-green, red

or yellow; commonly live in ponds)3. Chemosynthetic Autotrophs

• Breakdown inorganic compounds containing sulfur and nitrogen

• Nitrogen Fixation: they convert atmospheric nitrogen in to a compound that plants need to survive

How Does Bacteria Harm Us?

• Bacteria poison our cells with metabolic waste

• Your Immune system usually can not fight bacterial infections alone.

• Antibiotics can kill bacteria!

Diseases of Bacteria• Coccus

– Streptococcus pharyngitis (Strep Throat)– Necrotizing fasciitis (Flesh-eating Bacteria)

• Baccilus– Bacillus anthracis (Anthrax)– Yersinia Pestis (Bubonic Plague)

• Spirillum– Treponema pallidum (Syphilis)– Borellia burgdorferia (Lyme disease)

Penicillin

• Discovered by Alexander Flemming– A complete accident– Mold grew in a petri dishes of

bacterial cultures left in the sink– The mold killed the bacteria

Beneficial Bacteria

• Some bacteria can degrade oil–Used to clean up oil spills

Beneficial Bacteria

• Some bacteria act as decomposers–Break down and recycle dead and

decaying organic matter.

Beneficial Bacteria

• Some bacteria carry out Nitrogen Fixation– transform atmospheric nitrogen into

fixed nitrogen, usable by plants.

Viruses vs. Bacteria

• Living• Non-Living• Genetic Material• Cause Disease• Can be beneficial

• Reproduce on their own

• Contain proteins• Can be treated

with antibiotics• Many different

shapes