MODULE #2: Kingdom Monera Prokaryota (pro kehr ee aht'...
Transcript of MODULE #2: Kingdom Monera Prokaryota (pro kehr ee aht'...
The general name bacteria (singular is
bacterium) can essentially be applied
to all of the organisms
in kingdom Monera.
Pathogen – An organism that
causes disease
cell wall -
1. holds the contents of the
bacterium together,
2. regulates the amount of water
that a bacterium can absorb, and
3. holds the cell into one of three
basic shapes
The plasma membrane – regulates
what the bacterium takes in from the
outside world.
1. protects the interior of the cell by
sensing the nature of the chemicals
in the surroundings and then
determining whether or not they
can enter the cell.
The plasma membrane – regulates
what the bacterium takes in from the
outside world.
2. In some cases, if the cell needs the
chemicals, the plasma membrane
will actually force the chemicals into
the cell, whether they “want” to
come in or not!
Typical Bacterium
Cytoplasm exists throughout the interior of the
cell, supporting the DNA and the ribosomes .
Cytoplasm exists throughout the interior of the cell, supporting the and the (rye' b
DNA holds all of the information required to
make this mass of chemicals a living entity.
Ribosomes are chemical factories that make
proteins,
Positioned throughout the cytoplasm are
thousands of different types of chemicals
which aid the parts of the cell in their tasks.
Typical Bacterium
fimbriae - fibrous bristles used for grasping. If
in reproduction, they’re called sex pili.
Typical Bacterium
flagellum - used for motion. If a bacterium
does not possess a flagellum, it cannot move.
Question: Two different species of bacteria
attempt to infect an organism. One bacterium
succeeds, while the other is destroyed by the
organism's infection-fighting mechanisms. What is
most likely the major difference between these
two bacteria?
Answer:
The bacterium that succeeded most likely has a
capsule while the other does not.
In bacteria, the capsule helps to protect the
organism from infection-fighting mechanisms.
Question: A bacterium is poisoned by a substance
that is allowed into the interior of the cell. What
bacterial component did not do its job?
Answer
The plasma membrane did not do its job.
Since it regulates what moves in and out of the cell,
it should not have allowed the toxin to enter.
Answer:
It is missing a flagellum.
The fimbriae are not for movement; thus, if a
bacterium has no flagellum, it cannot move.
The Eating Habits of Bacteria
Great diversity in the eating habits - there are
producers, consumers, and decomposers
in kingdom Monera.
Most are heterotrophs – rely on other organisms
for food production.
Most are decomposers – referred to as
saprophytes.
The Eating Habits of Bacteria
Some bacteria are parasites.
Parasite – An organism that feeds on a living host
Many parasitic bacteria lack the ability to digest
nutrients, so they need to absorb nutrients that
have already been digested. In addition, they
often lack the ability to manufacture the complex
chemicals necessary for life. As a result, they
must also absorb those chemicals from their host.
Autotrophic Bacteria
Two different means by which autotrophic
bacteria manufacture their own food:
1.photosynthesis
2.chemosynthesis.
Photosynthesis in Bacteria
Photosynthesis uses the energy from sunlight and certain
chemicals to make food for the autotrophic organism.
In green plants and most of the other photosynthetic
organisms, the byproduct of photosynthesis is oxygen.
In bacteria, photosynthesis does not have oxygen as a
byproduct because the chemicals used are different from
those used by plants.
The byproducts of photosynthesis from bacteria are useful
to certain organisms. (Module #5).
In chemosynthesis, the bacteria promote chemical reactions
which release energy.
The bacteria then use that energy, along with other
chemicals, to manufacture their food.
Usually, the chemical reactions that provide energy to
chemosynthetic bacteria also convert chemicals that living
organisms can't use into chemicals that certain living
organisms can use.
Thus, even though there are only a few types of
chemosynthetic bacteria, they perform an essential function
for many living organisms.
Chemosynthesis in Bacteria
There must be a process by which food is converted
into energy to support life.
In humans, digestion does not give us energy. It simply
breaks food down into smaller molecules. In order to
get energy, we must then combine these molecules with
oxygen (and burn our food).
Since we use oxygen in order to get energy from our
food, humans are called aerobic organisms.
Aerobic organism – An organism that
requires oxygen
Some bacteria do not require oxygen in order to convert
their food into energy. These bacteria are anaerobic
organisms.
Anaerobic organism – An organism that does
not require oxygen
Typically, they live in areas that are barren of oxygen
such as deep underground or in the muck at the bottom of
a swamp. They either decompose dead organisms or
convert useless chemicals into chemicals that can be used
by other life forms.
Answer:
No.
Saprophytic means that it feeds on dead matter.
Autotrophic organisms make their own food.
Answer:
Yes.
Aerobic and anaerobic deal with how the organism
converts its food into useful energy.
Chemosynthetic deals with how the organism gets
the food to begin with. Thus, the bacterium can
make the food chemosynthetically and then
convert it to useable energy aerobically.
Speed of Reproduction & Its Repercussions
Under ideal conditions, a bacterium can divide in
about 20 minutes.
Once it divides, the new bacterium and the old
one can divide again in about 20 minutes.
One bacterium could multiply into more than a
billion bacteria in about 10 hours.
In a week, the bacteria would have a combined
weight that is larger than the entire planet!
Luckily, resources will run out eventually.
Steady state – A state in which members of a
population die as quickly as new members are
born
During the initial stage of population growth, the bacteria are reproducing
unchecked. There are plenty of resources for the population, so the population
grows as quickly as the bacteria can reproduce. This is called exponential growth.
Exponential growth – Population growth that is unhindered because
of the abundance of resources for an ever-increasing population.
When you graph a population that experiences logistic growth, you
get the S-shaped curve (often called a sigmoidal curve) that is
shown in the pink section of the graph.
As the population begins to reach the limits of the environment's resources, it can no
longer grow unchecked. The population growth is controlled by the limited resources of
the environment. This is referred to as logistic growth.
Logistic growth – Population growth that is controlled by limited resources
If you look at Figure 2.5 again, you will see that there is a region that is highlighted in
pink. That is the region over which logistic growth occurs.
Question: A population of bacteria grown from a
single “starter” bacterium is rather fragile. When
conditions are changed, the population dies
quickly. Based on what you have just learned,
develop a hypothesis for why this is the case.
Answer:
Since asexual reproduction allows no variation in
the DNA, an entire population of bacteria started
from a single bacterium have all the same traits. If
the environment changes, an organism might need
new traits to survive. Since the whole population
has essentially the same traits, there is no way to
get the needed new traits, and the population dies.
The variability that exists in sexual reproduction
usually makes a population much more resistant to
changes in the habitat.
Question: A population of bacteria reaches a
steady state and then, after several days, the
population actually increases dramatically. What
could cause such an event?
Answer:
More resources (most likely food) were added to
the habitat.
The only way you can get population
growth after the steady state would be due to an
influx of new resources.
Genetic Recombination in Bacteria
In asexual reproduction the offspring is a genetic copy
of the parent.
It is often beneficial for bacteria to exchange genetic
information in order to increase the genetic diversity of
the population.
Bacteria do this by genetic recombination, which can
occur in one of three ways:
1. conjugation,
2. transformation, or
3. transduction.
Genetic Recombination in Bacteria
Conjugation – A temporary union of two
organisms for the purpose of DNA transfer
Conjugation is not sexual reproduction.
No offspring is formed.
Genetic information is transferred from a
donor bacterium to a recipient.
Genetic Recombination in Bacteria
Desirable traits present in some individuals are contained
in a small, circular strand of DNA called a plasmid. The
plasmid is an extra component, separate from the rest of
the bacterium's DNA.
Plasmid – A small, circular section of extra
DNA that confers one or more traits to a
bacterium and can be reproduced separately
from the main bacterial genetic code
Question: A population of bacteria are living in a
lake. Due to volcanic activity nearby, the lake's
temperature begins to increase. In the population,
there are some bacteria that are resistant to low
temperatures (call them type A) and another type
that are resistant to high temperature (call them
type B). Which type will be the donor and which
the recipient as the population begins to
conjugate?
Answer:
Type B will be the donors and Type A will be the
recipients.
Since the bacteria will need to survive in high
temperatures, they need resistance to high
temperatures. That's what will be donated.
Transformation – The transfer of a DNA segment
from a nonfunctional donor cell to that of a
functional recipient cell
1. A bacterium dies
2. its cell wall falls apart and the components of the cell
(including the DNA) flow into the surroundings.
3. the dead bacterium's DNA seems to break into small
pieces,
4. a living bacterium might “sense” that one or more of
those pieces contains a trait or traits that it could use.
5. The living bacterium then absorbs what it needs,
incorporating the new genetic information as a plasmid.
Transformation
Transduction – The process in which infection
by a virus results in DNA being transferred
from one bacterium to another
A virus can pick up DNA from a bacterium during
infection and that DNA can be inserted into another
bacterium in a subsequent infection.
Transduction
Imagine a sample of water that is filled with
bacteria. You boil the water to try to kill the
bacteria. Will that get rid of the population?
Not necessarily.
Although boiling water will kill the bacteria,
they can actually survive the high
temperature for some period of time by
producing an endospore.
Endospore Formation
Endospore – The DNA and other
essential parts of a bacterium coated
with several hard layers
Endospore Formation
The endospore is formed inside the
bacterium's plasma membrane.
Once an endospore forms, the bacterium
itself might die, but as long as the endospore
survives, the bacterium can reform.
Endospore Formation
An endospore can withstand extreme
situations (boiling/freezing/extreme dryness)
for a lot longer than the bacterium itself.
When favorable conditions return, the hard
layers surrounding the DNA will deteriorate,
and the cell will burst from the endospore,
ready to grow and reproduce again.
Endospore Formation
Many bacteria exist in colonies.
• The individual bacteria group together, but
they all still exist as individuals.
• The bacteria's ability to survive is usually
enhanced when they form a colony.
Bacterial Colonies
As you might expect, bacteria form colonies in
a variety of different ways.
Bacteria take on one of three basic shapes:
coccus (spherical), bacillus (rod-shaped), or
spirillum (helical).
The most common bacterial colonies are
made up of either cocci or bacilli bacteria.
Bacterial Colonies
The shape of the bacteria is often contained in the name so you
automatically know something about the organism from just the
name.
If the bacteria are spherical, the name ends in “coccus.” If they are
rod-shaped, the name ends in “bacillus.”
You are expected to be able to determine the shape of a bacterium
when it is a part of the name.
DNA seems to tell them what colony they should
form.
Exhibit “group” behavior:
Some colonies, for example, will secrete a capsule-like
substance that surrounds and protects the entire colony.
Other colonies have bacteria that actually work together to
capture and eat prey. A Myxococcus xanthus colony, for
example, moves as a unit in search of prey, typically other
bacterial colonies. When they find their prey, they engulf it
and, as a group, secrete a substance that digests it. The
entire colony then feeds on the nutrients.
Question: A bacterial colony is called
staphylobacillus. What shape do the bacteria in the
colony possess: spherical, rod-shaped, or helical?
Classification in Kingdom Monera
Under a Gram stain, some bacteria turn red (Gram-
positive) and others turn blue (Gram-negative).
Reaction caused by differences in the cell wall.
Classification in Kingdom Monera
Phyla
Gracilicutes (gruh' sil uh kyoo' teez) – bacteria has cell wall &
Gram-negative m .
Firmicutes (fir' muh kyoo' teez) – bacteria has cell wall &
Gram-positive .
Tenericutes (ten' uh ruh kyoo' teez) – bacteria does not have
a cell wall.
Mendosicutes (men' doh suh kyoo' teez) – bacteria has cell
wall but the compounds are different from those that form
Gram-positive or Gram-negative reactions..
Gracilicutes contains all Gram-negative bacteria.
Since the bacterium appears red after the Gram
stain, it is Gram-negative.
Question: A bacterium has a cell wall that is
different from both Gram-positive and Gram-
negative bacteria. To what phylum does it belong?
Question: Construct a biological key that separates
bacteria into their different classes. You can
assume that the only organisms the key will be
used to analyze are bacteria. (HINT: The first
question should determine whether or not the
bacterium has a cell wall.)
Answer: See Table 2.1
1. Cell wall .............................................2
No cell wall ...........................................phylum Tenericutes.......class Mollicutes
2. Gram-positive or Gram-negative.......3
Neither .................................................phylum Mendosicutes.......class Archaebacteria
3. Gram-Positive...................................phylum Firmicutes............4
Gram-Negative.....................................phylum Gracilicutes.........5
4. Bacillus or Coccus........................... .class Firmibacteria
Neither ................................................class Thallobacteria
5.Non-photosynthetic..........................class Scotobacteria
Photosynthetic.....................................6
6. Produces oxygen..............................class Oxyphotobacteria
Does not produce oxygen....................class Anoxyphotobacteria
A Few Words on Other Classification Systems
Six-kingdom system.
• Retains kingdoms Protista, Fungi, Plantae, and
Animalia,
• Splits kingdom Monera into two separate
kingdoms: Archaebacteria and Eubacteria.
Most of the organisms that we have placed in
phylum Mendosicutes, class Archaebacteria are put
into kingdom Archaebacteria,
Most of the rest are placed in kingdom Eubacteria.
Specific Bacteria
Class Archaebacteria
• Have cell walls
• Live in harsh conditions
• Anaerobic chemosynthetic bacteria belong to this class.
Blue-Green Algae (al' jee) or Cyanobacteria (sye' an oh bak tehr'ee
uh)
Look like Algae
Live in freshwater lakes and ponds and are most prevalent in stagnant
waters.
Form the blue-green mats that float on the surface of the water.
Colonies of eukaryotic cells.- living in long, thin strands of cells that
encapsulate themselves (feel slimy)
Photosynthetc – require light to survive
Specific Bacteria
Clostridium (claw strid' ee um) botulinum (bot' yool in um)
Class: Firmibacteria; Phylum: Firmicutes
Source of food poisoning Heat resistant endospores
produces a toxic chemical that causes botulism.
Salmonella (sal muh nell' uh) typhimurium (tye' fim ur ee um) and
S. enteriditis (en' ter uh dye' tus)
Same genus: Salmonella; Phylum Gracilicutes; Class Scotobacteria.
Common contaminants of eggs and poultry.
Specific Bacteria
Escherichia (esh' ur ee' kee uh) coli (koh' lye)
Phylum Gracilicutes; Class Scotobacteria.
Very common, living in your gut.
Its species name, “coli” refers to the “colon,” which
is a part of your gut.
Two Strains.
Strains – Organisms from the same species
that have markedly different traits
Specific Bacteria
• Escherichia (esh' ur ee' kee uh) coli (koh' lye)
1) Nonpathogenic
• One of the byproducts of E. coli's
metabolism is Vitamin K
• Secretes a chemical that helps your body
digest fat.
• Keeps food-borne pathogenic bacteria from
colonizing in your gut.
2) Pathogenic – causes severe diarrhea
Conditions For Bacterial Growth
Moisture
Moderate temperature: 27 °C - 38 °C (80 °F - 100 °F)
Nutrition
Darkness
The proper amount of oxygen