Bacteria

Bacteria

Prokaryotic: No nucleus and no organelles

Two SEPARATE kingdoms:

1. Archaebacteria –found in extreme habitats

- extremely hot environments (geysers, oil wells)

- very acidic (digestive tracts of animals)

2. Eubacteria – found in many different habitats

3 Types:

- heterotrophs

- photosynthetic autotrophs

- chemosynthetic autotrophs

BACTERIA are

The smallest and most numerous

organisms on the planet.

The first organisms to exist on the planet.

Now they are also the newest organisms

due to humans genetically engineering

them.

Nutrition

Most bacteria are: – heterotrophic - they use food produced by other

organisms.

– Some are autotrophic - they produce their own food.

Photoautotrophs: use sunlight as a source of energy like plants.

Chemoautotrophs: Use energy from chemical reactions to make food

Bacteria that feed on dead or decaying organic matter are saprobes.

Parts of a bacteria cell

Cell wall: some rigid and other are flexible

Cell membrane: same as other cells

Cytoplasm: same as other cells

DNA: a single, circular chromosome located in the cytoplasm

Capsule: a thick protective coating around some bacteria cells

Some also have flagella for movement and pilus (pilli) for grabbing.

Classification:

Bacterial cells are usually classified by the

shapes of their cells.

Coccus (cocci) : Sphere

Bacillus (bacilli) : Rod

Spirillum (spirilli) : Spiral

Clustering

Colonies of bacteria have specific names

depending on their shape.

– diplo=pairs

diplococcus

– staphylo=clusters

staphylococcus

– strepto=chains

streptococcus

Reproduction:

Binary fission:

– is a type of asexual reproduction

– each new cell receives one copy of the

chromosome

– the daughter cells are identical to the parent cell

– under ideal conditions a bacterium can reproduce

every 20 minutes

The Steps of

Binary Fission

– The bacteria single chromosome is replicated.

– The cell will grow in size and the copies separate.

– When the cell divides each new cell will receive

one copy of the chromosome.

Reproduction Cont.

Conjugation:

– Is a type of sexual reproduction.

Steps of conjugation

1. Two bacterial cells exchange DNA across

the bridge, or pilus.

2. New DNA replaces the old DNA.

– This type of reproduction increases the

genetic variability in the organisms, however it

is not TRUE sexual reproduction.

Rapid Reproducers

In ideal conditions (warm, moist

environments), bacteria can reproduce

every 15 to 20 minutes.

If that rate were maintained, in 48 hours

the bacteria would reach a solid mass

4,000 times bigger than Earth.

What stops this from happening?

Spore Formation

When faced with difficult conditions many bacteria will form spores.

Endospores contain a complete copy of the bacterium’s DNA. The DNA is surrounded by a thick wall.

Some endospores can survive for years in unfavorable conditions.

Later, when the conditions are right the endospore will become active and then grow and divide.

Importance of Bacteria

Digestion: break down organic matter

Food production: cheese, yogurt, pickles

Medicine production: some strains of bacteria

produce antibiotics that are used to fight other

bacteria

Ecological decomposers: Nitrogen Fixation

(converting N2 gas into ammonia)

Cause disease: Pneumonia, tuberculosis

– Pathogens: A disease causing agent

Methods for Killing Bacteria

Antiseptics: Prevents infection by preventing

the growth of microorganisms

Disinfectants: An agent that destroys,

neutralizes, or slows the growth of

microorganisms.

Antibiotics: microbial or fungal product that

kills or slows the growth of bacteria