Kingdom Monera - Bacteria
Reproduction and Ecological Roles
www.onacd.ca
Bacterial Reproduction
Asexual reproduction:
BINARY FISSION
BUDDING
Binary Fission
1. A single
bacterial
cell begins
to make
copies of
its genetic
material
2. The cell membrane begins to elongate and
pulls the genetic material in two different
directions
3. The cell
membrane
grows inward
and separates
the cells. The
cells are
genetically
identical to
one another.
Most bacterial cells will grow to a fixed size and
will then reproduce by binary fission
Note: equal division of cytoplasm and genetic
material
Bacterial cells undergoing different stages of binary fission
Budding
• Results in uneven division of cytoplasm
and even division of nuclear material
• More common with fungi, not bacteria
Benefits and disadvantages of sexual
and asexual reproduction
Asexual
Sexual
Pros
Only 1
organism is
necessary
-very efficient
(20 min life
cycle)
Exchange of
DNA, therefore
high diversity
Cons
Get exact copy
(clone)
therefore, no
species
diversity and 1
thing will kill all
the bacteria
If there is only 1
individual, it will
die with no
offspring
Conjugation – Sexual Reproduction
A primitive form of sexual reproduction where there is
exchange of chromosome (red) material (genetic material)
between two bacterial cells through a structure called a pili.
Enlarged
Examples of bacteria that are known to undergo conjugation include: E. coli, Salmonella
Studying bacteria
• Labs use 2 different growth mediums.
(substances that bacteria grow in)
Petri dish containing agar
• Bacteria are “streaked” across agar –
gelatinous substance made from algae
Innoculating loop used to transfer
bacteria to the agar plate
“Slant Test-tube” containing agar with
bacteria growing on the surface
Nutrient broth
• Nutrient broth
•
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Test-tubes filled with:
Blood
Beef juice
Other stuff
Ecological Roles of Bacteria
• nitrogen fixation in the soil next the roots of some
plants.
-plants obtain an easily absorbable form of
nitrogen needed for growth.
• degrade some organic compounds
-aid in cleaning up oil spills
Beneficial Roles of Bacteria
• symbionts in humans and other organisms.
• over 1000 types of bacteria in the average
human stomach and intestines that
contribute to:
-immunity, vitamin absorption
and synthesis, nutrient conversion and
fermentation. (probiotic supplements contain
many of these bacteria..)
Beneficial Roles of Bacteria
• Used in preparation of fermented foods ex. Yogurt,
cheese, soy sauce…
• Used in the study of genetics, molecular biology and
biochemistry because of their ability to reproduce so
quickly
Some beneficial bacteria
• Escherichia coli – produces vitamin K in
large intestine – necessary for blood
clotting
• Lactobacillus – yogourt
• Streptococcus – to sour milk
• Clostridium acetobutylicum – to make
acetone and butanol at an industrial scale
Antibiotics made by bacteria
•
•
•
•
•
•
Streptomyces – make antibiotics including:
Amphotericin
Kanamycin
Neomycin
Streptomycin
Tetracycline
Harmful bacteria - Pathogenic
•
•
•
•
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•
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Tuberculosis
Meningitis
Botulism
Cholera
Syphilis
Gonorrhea
Diphtheria
Black plague
Gangrene
Treatments for Bacterial Infections
• 1. Antitoxin – to neutralize a chemical
made by bacteria that produce toxins
- ie. Botulism
• 2. Antibiotics – chemicals produced by
other organisms that kill the bacteria in a
form of chemical warfare
- ie. Penicillin (a fungus) makes antibiotics
• 3. disinfectant – to kill all bacteria on
surfaces
• 4. antiseptic – to kill most bacteria on the
body surface
Other ways to slow down growth or
kill bacteria in food
• 1. Keep cold/freeze – slow down
metabolism
• 2. Can – keep air out – slows growth –
heat kills enzymes
• 3. Dry – take away water – needed for
metabolism
• 4. Cure – the salt draws away moisture
from the food – the smoking dries the food
• 5. Preservatives – chemicals that kill
bacteria
• 6. Salt – draw away moisture
• 7. Sugar – draw away moisture
Effective use of antibiotics
• Take only when necessary – don’t work on
viruses
• Take for total length of time – endospores
(protective coat) forms around bacteria for
protection and when the conditions are
good again, the bacteria becomes active
again
• Take complete dose or else you increase
risk of antibiotic resistant bacteria
Antibacterial Agents
and Resistance
www.onacd.ca
Antibiotics
Penicillium fungi : produces
the antibiotic penicillin
Definition: a substance
produced by a
microorganism that
restricts the growth of
another
microorganism
Where do antibiotics come from?
• many are produced from other living organisms
example. Penicillin is collected from the fungi penicillium (above)
Streptomycin comes from the bacteria streptomyces
• some antibiotics are modified chemically and some are produced
synthetically
How do antibiotics work?
Antibiotics that target a wide
range of bacteria are
termed broad spectrum.
Those that target a
narrow range are termed
narrow spectrum.
Above: Wafers containing antibiotics
are placed on an agar plate of
bacteria. The cloudy areas show
bacterial growth. Circles of poor
bacterial growth show that bacteria
will not grow in the presence of that
antibiotic.
Some antibiotics actually
destroy bacteria (inhibit
cell processes) whereas
others keep the bacterial
cell from reproducing
(inhibit binary fission)
Antibiotic Resistance
Failure to take entire
prescribed dosages
of antibiotics can
lead to the growth of
antibiotic resistant
bacteria.
As close as possible to 100% of
harmful bacteria must be killed off
when taking a round of antibiotics.
If not, the surviving bacteria will
most likely carry genes that are
resistant to the initial antibiotic and
will then begin to multiply.
Improper usage and
dosaging of antibiotics
also contributes to the
appearance of
resistant bacteria.
When antibiotics are administered
when they are not needed we are
exposing more bacteria to
selection for resistance.
NOTE: Remember as well that the
genes for antibiotic resistance can
also be transferred to other normal
bacteria through the conjugation.
Staphylococcus aureus bacteria
are one of the types of
bacteria normally found
existing on human skin
surface. They are capable of
causing skin infections in
those with weakened immune
systems. (see picture to left)
Skin infections caused by these
bacteria were treated
successfully in the 1940’s and
50’s with penicillin. Presently,
almost all strains are resistant
to penicillin which leaves only
a small section of drugs
(vancomycin) to treat it.
The picture to the left shows a
new form of S.aureous that is
beginning to show resistance
to vancomycin.
Antiseptics
Definition: Antimicrobial
substances that are applied
to living tissue (skin) to
inhibit the growth of bacteria
• Some destroy bacteria
(germicides) and some inhibit
the growth of bacteria
• Overuse can lead to
increased dangerous resistant
strains of bacteria
Common Types of Antiseptics
Alcohol (surgical alcohol)
– Used to disinfect skin before injections are given
Boric Acid
– Used in yeast infection treatments, cold sore
medications, burn cream and eye contact
solution (although not very effective)
Chlorhexidine Gluconate
– Used in gingivitis treatment
Hydrogen peroxide
– Used for cleaning of wounds (although antibacterial soap and water is
actually more effective)
Iodine
– Used in pre and post operative cleaning and has a very wide scope of
antimicrobial activity
Phenol compounds
– Used in pre operative hand washing, mouth washes and throat lozenges
Natural antiseptics
– Includes saliva, tears, breast milk and gastric acids
Disinfectants
Definition: antimicrobial
agents applied to non-living
objects that destroy
microorganisms
(including bacteria)
• Many disinfectants are harmful
(toxic) to humans, animals and
the environment
• Overuse can lead to resistant
strains of bacteria
Common Types of Disinfectants
Alcohol
• Wide spectrum, highly effective and non-corrosive
but are a fire hazard
Oxidizing Agents (ex. Chlorine, peroxide, iodine…)
• Destroys the cell membrane of bacteria
• Commonly used in
• Bleach, swimming pool cleaners, drinking water
treatment…)
UV light
• Can be used in dental tool disinfection or for
cleaning any other non-porous surfaces