Download Bacteria - Mr. Shanks` Class

Bacteria

Bacteria live in almost
every environment on
Earth, from arctic ice to
volcanic vents.

1 cm2 of your skin has 100,000
bacteria on it.

1 teaspoon of soil has over 1 billion
bacteria in it.
Characteristics of Bacteria

All bacteria are single-celled.

All bacteria are prokaryotic (lack nucleus
and membrane-bound organelles).

All bacteria reproduce asexually by
binary fission.

All bacteria contain DNA arranged into a
single circular chromosome.
Structure of Bacteria
Size
= 1 to 10 µm
(1000 µm = 1 mm)
1. capsule
2. cell wall
3. cell membrane
4. DNA
5. pilus
8. ribosome
9. plasmid
6. cytoplasm
7. flagellum
Structure of Bacteria
1. Capsule: – a sticky protein cover found in some bacteria
2. Cell wall: – a protective coating of all bacteria
3. Cell membrane: – controls entry of molecules
4. Circular chromosome of DNA [not enclosed in a nucleus]
5. Pilus: - a protein tube that attaches to other bacteria
6. Cytoplasm: - contains ions & molecules
7. Flagellum: - whip-like tail for movement
8. Ribosomes: - needed for protein synthesis
9.
Plasmid: - small loop of DNA which contains a few genes
3. Bacteria Reproduction
a. Binary fission
1. Single circular chromosome replicates
2. Attached loops remain near center of cell
3. Replicated loops drift apart
4. Cell pinches in between chromosome loops
5. New cell wall forms to produce two
separate cells
b. Endospore formation
1. Occurs only with gram-positive bacteria.
2. When growth conditions become unfavourable
3. Bacterium makes an endospore (a thick wall that
surrounds its DNA and cytoplasm).
4. The endospore can lie dormant for
a long time, through drought,
heat and radiation, until good
conditions return
c. Conjugation
1. Occurs when conditions are less than
ideal due to shortages of food or
space or exposure to new chemicals.
2. Two bacterial cells connect via a
bridge (a pilus) and exchange a
plasmid (a small ring of DNA).
3. Conjugation increases the genetic
variability in a population of bacteria.
4. Conjugation is the cause of the spread of
anti-biotic resistance.
Conjugation of E. coli
4. Classification of Bacteria
a. Classification by shape:
Cocci (round)
Bacilli (rod-shaped)
Spirilli (spiral)
Staphylo (clusters)
Strepto (chains)
Diplo (pairs)
b. Classification by
Gram Stain:
• Gram-positive: stained purple
[after a dyeing technique with
crystal violet and iodine]
• these bacteria have a thick cell wall
and are mostly harmless
• Gram-negative: stained pink
• these bacteria have a thin cell wall
and many are pathenogenic
[cause disease]
5. Bacteria Nutrition
Heterotrophic: must eat others for food
Autotrophic: able to make own food
(photoautrophic or chemoautotrophic)
Heterotrophic and chemotrophic bacteria
do not change metabolism in light or dark.
Phototrophic bacteria only grow in the light.
6. Bacteria respiration
a. Obligate Aeorbe: must have oxygen to
produce energy from food
b. Obligate Anaerobe: can not survive in the
presence of oxygen, but can still produce
energy from food in absence of oxygen
c. Facultative anaerobe: can survive with or
without oxygen
7. Bacteria in Ecosystems
a. Nitrogen fixation:
Some bacteria take nitrogen directly from
the air to make proteins
These bacteria usually live in nodules
on roots of legumes
b. Carbon-Oxygen Cycle:
Bacteria are key in the breakdown of
dead organisms and the release of
carbon dioxide back into the
atmosphere
8. Bacteria and Disease
Many pathogenic bacteria produce toxins
that cause disease symptoms
Some make people ill and some are fatal
a. Endotoxins:
produced inside bacteria and are only
released when gram-negative
bacteria split
they are seldom toxic, but do cause fever,
diarrhea, and vomitting
Salmonella
b. Exotoxins:
produced and excreted from living
bacteria
they do not produce fevers, they are
often fatal
Clostridium
The Deadliest Bacterium

The bacterium Yersinia pestis
caused the Bubonic Plague (Black
Death) in the 14th century.

Between 1347 and 1351,
75 million people died,
1/3 of northern Europe.