Download Prokaryotes Chap 18 Smallest (1-5 microns) and most

Why study bacteria?
https://www.youtube.com/watch?v=qCn92mbWxd4
Prokaryotes
Chap 18
Smallest (1-5 microns) and most common
living microorganism
Unicellular, lack nucleus, have cell walls
• Prokaryotes are widespread on the earth:
only 1% have been
discovered.
• Two groups of
prokaryotes are
Bacteria
Archaea
About 250,000 bacteria could fit on the period at the
end of a sentence.
PROKARYOTES: 2 domains
Bacteria
•Largest group
•Lives everywhere
•Cell wall made of
peptidoglycan
Archaea
• Live in extreme conditions
• Cell walls lack
peptidoglycans, have different
lipids
• Their DNA is more similar to
the eukaryotes’ DNA
• Different flagella structure
How are they alike?
• Small, single-celled, cell walls
• No membrane-bound organelles,
including nuclei
• Circular chromosome (DNA in circle),
may have plasmids (smaller circular
pieces of DNA)
• Move by flagella or gliding
• Have pili (hairs) to stick to each other
Endosymbiosis
Genetic Material
• DNA in a circular chromosome,
may have plasmids (small circles
of DNA)
Movement
• Flagella
• Some glide in
slime
• Some don’t
move
• Have pili –
small hairs for
attachment
archaea
Bacteria
Archaea’s DNA is more similar to
that of the eukaryotes.
eukaryotes
bacteria
archaea
ancestor
They have been around for awhile!
Fossils of early cyanobacteria
Bacterial shapes
Bacilla - rods
Coccus - spherical
Spirilla- spirals
Staphylococcus aureus
Streptococcus bacteria
Strep throat
What shape?
bacillus
What are gram stains used for?
• To identify bacteria
• To select antibiotics to use for bacterial
infections
Cell walls and gram stains
Lipids
Peptidoglycan
layer
GRAM POSITIVE
GRAM NEGATIVE
Peptidoglycan is a carbohydrate in the cell walls of eubacteria.
GRAM POSITIVE BACTERIA
GRAM NEGATIVE BACTERIA
Is this bacteria Gram-negative or Gram positive?
Six common gram-positive bacteria that infect
humans and their shapes follow:
- Streptococcus (cocci)
-Staphylococcus (cocci)
-Bacillus - causes
anthrax and
gastroenteritis
-Clostridium- causes
botulism,tetanus
-Corynebacterium causes diphtheria
-Listeria (bacilli)- causes
meningitis
Staph infection
Gram-negative bacteria that infect
humans and their shapes follow:
Spirochetes (spiral-shaped) - causes
syphilis, lyme disease
Neisseria (cocci) - causes meningococcus,
gonorrhea
Obtaining Energy
• Photoautotrophs – photosynthesize
ex-cyanobacteria
• Chemoautotrophs – break down
chemicals such as hydrogen sulfide,
ammonia, nitrites, sulfur, or iron
ex – those found in deep ocean vents or hot springs
• Heterotrophs – eat other things
• Photoheterotrophs – use light for
energy but use food for nutrients
Evidences of bacteria
Banded iron
formations from iron
oxidizing bacteria
chemoautotrophic
cyanobacteria
photoautotrophic
• Some don’t
need oxygen to
live: obligate
anaerobes
(oxygen kills
them)
• These are found
in marshes, lake
bottoms,
digestive tracts
of herbivores
Releasing energy
• Obligate aerobes – need oxygen and carry
on cellular respiration
• Obligate anaerobes – do NOT need
oxygen, carry on fermentation, found in
marshes, lake bottoms, digestive tracts of
herbivores
ex – Clostridium botulinum – food
poisoning; most potent poison, also botox
• Facultative aerobes – can live with or
without oxygen, can live anywhere
Growth and reproduction
• Divide asexually by binary fission as
often as every 20 minutes
• Reproduce sexually by forming
conjugation tubes between
cells
bacteria
1 bacterial cell weighs
0.000000000001 g (1 x 10-12g)
After 44 hours given optimum
growth conditions and generation
times of 20 minutes, what is the
theoretical weight of bacteria
produced?
The weight of the earth!
Some form
endospores to
encapsulate their
DNA during harsh
times; remain
dormant until
conditions improve
About rice…
• The main risk with cooked rice is from the food
poisoning bacteria called Bacillus cereus.
• The bacteria forms a hard outer coating called a
spore. This spore protects the bacteria from
heat during cooking. If the rice is then cooled
slowly the spore will germinate producing more
bacteria. These bacteria produce poisons or
toxins.
• Re-heating the rice will destroy some of the
bacteria but they will leave behind their toxins
which are not damaged by heat. These toxins
cause illness.
Beneficial Roles of Bacteria
Bacteria live in animal digestive tracts –
• help break down food
• produce vitamins – ex vitamin K (blood
clotting) in humans
• They also take the place
of pathogenic bacteria.
Some foods are products of fermentation
occurring in bacteria: yogurt, cheese, pickles,
soy sauce, sauerkraut, vinegar
Importances of Bacteria in the
environment
•
•
•
Atmospheric Composition
Cyanobacteria added oxygen to atmosphere
Element Cycling
recycle C, N, H, and S
Nitrogen-fixation
Bacteria take atmospheric nitrogen and
convert it into ammonia so plants can use it
and eventually animals.
These bacteria are found in a symbiotic
relationship with legume-type plants such as
soybeans and stored in their root nodules.
Root nodules in soy beans
that store bacteria for
nitrogen cycling
Other symbiotic associations
• Bioluminescence in fish
• Toxins in skin of organisms
These are due to
bacteria in their skin.
Some bacteria digest oil
• Bioremediation – breaking down pollutants
Bacteria can be good guys!
Bacteria – BAD BOYS
http://www.pbs.org/wgbh/nova/sciencenow/0303/video-extr-w-350-04.html
Bacteria as Disease-causers
• less than 10% are pathogenic
(disease- causing)
Bacteria cause disease in two
ways:
• Some damage tissue by
breaking it down for food; exTB breaks down lung tissue
• Some produce toxins; exStreptococcus in strep throat
Prevention/treatment of disease
• Skin – first defense
• Vaccines – stimulate body to produce
antibodies (proteins made to combat
foreign invaders)
- first person to make a bacterial
vaccine was Pasteur with a vaccine for
anthrax
Anthrax is an infectious disease due to a
type of bacteria called Bacillus anthracis.
Infection in humans most often involves the
skin, gastrointestinal tract, or lungs.
In 2001, anthrax sent through the U.S. Postal Service
infected 22 people; 7 survivors had confirmed anthrax
disease.
Bacteria good or bad?
Can cause food poisoning.
Used in cosmetic industry to
remove wrinkles.
• Antibiotics – compounds that block the
growth and reproduction of bacteria
• First one, penicillin, discovered
by Alexander Fleming in 1928.
• They block the formation of cell walls in
bacteria or protein synthesis.
Do not work against
viruses!
Other ways to control bacterial growth
• Antiseptics: can be used
on living tissues but not
taken internally; Ex –
hydrogen peroxide, germ-x
• Disinfectants: used on
surfaces but not safe to
use on living tissues; Ex –
bleach, counter-cleaners
Testing effectiveness of
antibacterial agents
Somewhat effective
Not effective
Most effective
Testing antibiotics and
antibacterial agents on bacteria
cultures
The larger ring of no growth, the more effective the agent.
Antibiotic resistance in bacteria
https://www.youtube.com/watch?v=xZbcwi7SfZE
Transmission of resistance genes
via plasmid exchange in
conjugation.
What can you do?
Don’t use antibiotics to treat viral
infections.
When treating a bacterial infection with
antibiotics, take all your pills.
http://www.pbs.
org/wgbh/nova/
body/killermicrobe.html
Dr. Collins and the Case of
the Mysterious Infection
Selective pressures that have led to
antibiotic resistance
• Increased antibiotic use in general, particularly
among children
• The misuse of antibacterial products - soaps,
lotions, and dishwashing detergents. These
agents alter the normal mix of bacteria and
give antibiotic-resistant bacteria an
opportunity to proliferate.
• Use of antibiotics in animal husbandry and
agriculture. Promotes resistance in treated
animals, which can be passed on to caretakers
and people who prepare or eat undercooked
meat.