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CHAPTER 19 NOTES
BACTERIA
CHARACTERISTICS OF BACTERIA
Prokaryotic or Eukaryotic: Prokaryotic
 Unicellular or Multicellular: Unicellular
 Autotroph or Heterotroph: Autotrophs
and Heterotrophs
 Which Kingdom do they belong in?
Eubacteria & Archaebacteria
 Examples: bacteria, methanogens &
halophiles, cyanobacteria (autotroph)

TYPICAL BACTERIUM
CYTOPLASM
CELL
MEMBRANE
FLAGELLA
DNA
PILI
CELL
WALL
Most Bacteria reproduce by one of 3
means:
1. Asexually
 Also known as binary fission in which the
chromosome replicates and then the cell
divides
 This produces 2 identical cells
2. Sexually
 Also known as conjugation in which
genetic material is exchanged through
cell-to-cell contact
 This increases the genetic diversity of
bacteria
Most Bacteria reproduce by one of 3
means:
3. Spore Formation
 When living conditions become
unfavorable, some bacteria can form
dehydrated cells known as endospores
 Endospores have thick walls and can
resist heat, drought and radiation and
thus they can survive harsh conditions
 When conditions improve, the spore will
germinate and bacteria will grow again
HOW ARE BACTERIA
CLASSIFIED?
Bacteria are divided into 2 main
groups:
1. Archaebacteria
Found living in harsh environments, like
hot springs, near undersea volcanic vents
and in highly salty water
 These bacteria are further divided based
on the environments in which they live

2. Eubacteria
Include all the organisms commonly
called bacteria
 Live in much less harsh environments

Bacteria can also be classified
by their shape:
1. Cocci

Sphere-shaped
2. Bacilli

Rod-shaped
3. Spirilla

Spiral-shaped
Bacteria can be classified by
their cell wall differences:

The technique to see these
differences is called GRAM STAINING
1. Gram-positive (looks purple)
2. Gram-negative (looks red)
Other ways to identify Bacteria

By their Nutrition

1. Autotroph
• Ex. Cyanobacteria

2. Heterotrophs
• Ex. Bacteria

Based on Respiration
1. Aerobes- need oxygen during
respiration
 2. Anaerobes – do not use oxygen
during respiration

IMPORTANCE OF BACTERIA
ECOLOGICAL ROLES
1. Bacteria act as decomposers, which means
they break down dead organic materials
2. They also help recycle carbon, nitrogen and
sulfur and other chemicals needed by living
things
3. Many bacteria live with organisms of other
species in a relationship called symbiosis



bacteria in your mouth (bacteria benefit & you are
harmed)
bacteria in cow intestines (bacteria benefit & cow
benefits)
E. coli, a bacteria found in human intestines, helps
with the process of digestion
DISEASES CAUSED BY BACTERIA
Some bacteria cause diseases in
humans
 Some examples are:



Tuberculosis, anthrax, lyme disease,
strep throat, cholera
Antibiotics can kill harmful bacteria
if used properly
HUMAN USES OF BACTERIA
Bioremediation – use of
microorganisms to help restore natural
environmental conditions; ex. Sewage
treatment plants
 Bacteria are used in the production of
many foods; some examples are:
cheese, yogurt, vinegar, beverages
 Bacteria have applications in medicine;
some bacteria have been genetically
engineered to produce insulin
