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Kingdom Monera – Bacteria
Characteristics and Diversity
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Bacteria were first
identified in 1677 by
Antonie van
Leeuwenhook after
he developed a
primitive version of
the compound
microscope.
He originally called all
single celled
organisms he had
discovered
“animalcules” and
they were later
separated into
groups, one of which
included bacteria.
Bacteria are found in three distinct shapes
1. Rod shaped
termed: Bacilli
Some bacilli have adapted to survival
during unfavorable conditions by forming
dormant or resting cells called
endospores which are resistant to
severe physical and chemical stresses.
Endospores are a core of DNA that is surrounded by an impenetrable layer.
They can last for millions of years and are capable of causing some serious
diseases:
ex. Anthrax (Bacillus anthraxis) & Tetanus (Clostridium tetani)
2. Spherical shaped
Can be found as single cocci, chains, or clumps
termed: Coccus
Diploids – pairs of spherical shaped bacteria
ex. Neisseria (can cause gonorrhea, bacterial meningitis & septicemia)
Chains of spherical shaped bacteria (Strepto)
ex. Streptococcus ( cause a variety of human disease including meningitis, flesh eating
disease, and bacterial pneumonia)
Clusters of spherical shaped bacteria (Staphlo)
ex. Staphylococcus aureous (can cause a variety of human infections including skin
infections, Toxic Shock Syndrome, meningitis….)
Staphylococcus aureous
3. Spiral shaped
Actually are a form of rod
shaped bacteria
Termed Spirilla
Leptospirillum
Bacterial Structure
Example: bacillus structure
Internal
Bacterial Cell Structure
Surrounded by a cell membrane
Single ring of genetic material (chromosome) encased in a nucleoid
External
Cell Wall
• Composed of peptidoglycan (as opposed to cellulose in plant cells)
• Two types
• Gram positive – have a thick cell wall
• Gram negative – have a thin cell wall and most bacteria fall into this
category
• Important in antibiotic use as antibiotics affect the ability to produce a cell
wall
Flagella
• Used for motility and are driven by energy
• Can be found alone, at each end, in clusters at the poles or all over the cell
Pili (sing. Pilus) Primitive Sexual reporduction
• Used for transferring genetic material between cells
Methods of Movement
E.coli
1.
2.
3.
4.
Flagella – rotates and driven by energy at the base
Bacterial gliding –mechanism that includes ejection of slime
and movement of the pili
Twitching motility – special pili are used as a hook that is
extended repeatedly and used to pull the bacterium along
Changes of buoyancy –produce internal gas vesicles
(pockets) that they use to regulate buoyancy in the water to
find food and light
Bacteria have recently been classified by the
environment that they live in
1.
2.
Archaebacteria – live in an environment
without oxygen
Eubacteria – live in an environment with
oxygen
Bacteria can also be grouped according to
their type of respiration
1.
2.
3.
Obligate aerobes – must have oxygen to survive
Obligate anaerobes – can only grow in the absence of
oxygen
Facultative anaerobes – prefer environments with
oxygen but can live in environments without oxygen
Nutrition: How do bacteria get the food and
energy they need to survive?
Some are autotrophs (make their own food)
Photosynthetic - use of light for energy
Chemosynthetic – use of chemical substances for energy
Some are heterotrophs (obtain food from other sources)
Saprophytic (obtain raw materials from dead and
decomposing matter)
Parasitic
Symbiotic / mutualistic (ex. Bacteria in the human colon)
Chemoheterotrophs: must take in organic compounds for
energy and carbon
Photoheterotrophs: make their own energy via
photosynthesis but must take in organic compounds for
carbon
A few bacteria that cause human disease
Salmonella bacteria (red) :
causes Salmonella poisoning
E.Coli bacteria
Helicobacter pylori: can
cause ulcers, stomach
cancer…
Tetanus bacteria
Modes of Bacterial disease transmission
• Direct contact
• Airborne droplets
• Bacterial toxins in
food (ingestion)
• Fecal contamination
of food
• Water
• Vector bites (ex.
Mosquito)
Kingdom Monera - Bacteria
Reproduction and Ecological Roles
www.onacd.ca
Bacterial Reproduction
Bacteria reproduce by a
process known as
BINARY FISSION, a
form of asexual
reproduction
“Splitting into two”
Sexual reproduction via
a process called
CONJUGATION is not
common but does
occur. Genetic material
is exchanged between
cells.
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
Binary Fission Animation
Bacterial cells undergoing different stages of binary fission
Conjugation
A primitive form of sexual reproduction where there is
exchange of chromosome 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
Ecological Roles of Bacteria
• Certain mutualistic bacteria carry out **nitrogen
fixation** in the soil next the roots of some plants.
This allows plants to obtain an easily absorbable
form of nitrogen needed for growth.
• Bacteria can be used to degrade some organic
compounds therefore can be used to aid in
cleaning up oil spills
• Can be used in the place of harmful pesticides
and leave little to no effect on the environment
Beneficial Roles of Bacteria
• Bacteria are found as symbionts in
humans and other organisms. There are
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..)
• 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
• Used for making medicines (Insulin)
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 streptomy
• 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.
Improper usage and
dosaging of antibiotics
also contributes to the
appearance of
resistant bacteria.
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 pictures to
left)
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
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