Bacteria
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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
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