bio102 bacteria

8/15/2019 Bio102 bacteria

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Bacteria

Prokaryote single-celled organisms that lack a

nucleus Generally referred to as microbes or bugs

Two Domains: Archaea and Bacteria

The overwhelming majority of the prokaryotes you have

experience with on a daily basis are from the DomainBacteria

Therefore, we will be mostly speaking of Bacteria


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Sizes

Cells Alive! Magnification Interactive

Scale of Life Diagram Length scales commonly used in to describe the microbial

world:

Micrometer (m)

otherwise known as the micron 10-6 meter

Nanometer (nm)

10-9 meter

Bacterial cells range in size from 10 100 m There have been some recent discoveries that put the

size up to 500 1000 m

Size is limited by fact that cells rely on diffusion to

transport materials into and out of the cell
http://www.cellsalive.com/howbig.htmhttp://www.cellsalive.com/howbig.htm


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Shapes and Cell Types

Microbes come in a not so wide variety of shapes

Diagram of shapes of Bacteria Bacteria and Archaea are single celled organisms, so all

of the processes of life are contained within eachindividual cell

Tree of Life diagram Typical prokaryotic cell diagram

There are microbial or single-celled eukaryotes, whichwe will discuss in more detail later

Typical eukaryotic cell diagram


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Cell Walls!

Found on the outside of the cell membrane

Functions of the cell wall: Maintains the characteristics shape of the bacterium (without cell

wall, cell assumes spherical shape)

Maintains cellular integrity when under osmotic stress

Periplasmic space gap between the plasmamembrane and the cell wall

Storage area for digestive enzymes (destroy toxins) and

transport proteins (move important chemicals into the cell)

Principal component of certain cell membranes is

peptidoglycan

Embedded in the cell wall is the flagellum (molecular

motion that propels the cell); a cell can have more than

one flagellum (then it has flagella)

Flagellum diagram


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Variations on the cell wall theme

Gram-positive bacteria Plasma membrane is covered in a thick layer of

peptidoglycan (~40 layers thick) that can range

between 20-80 nm across

60-90% of cell wall is peptidoglycan Name based on retention of Gram stain (iodine

solution)

Appears purple in color


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Variations on the cell wall theme

Gram-negative bacteria Thinner, more complex cell wall than G+

Only 10-20% of cell wall is peptidoglycan

Remainder: polysaccharides, proteins, and lipids

Most significantly, cell wall is covered in a lipid bilayer Large periplasmic space

Do not stain with Gram stain, hence Gram-

Appears red in color


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Metabolism Heterotrophs consume food made by producers

Chemoheterotrophs energy and nutrients fromorganic compounds (humans are examples of this type

of metabolism)

Photoheterotrophs energy from sunlight and use

organic compounds for nutrients Autotrophs make their own food

Photoautotrophs similar to photosynthesis in plants,

but no 02 is produced; light = energy, organic and

inorganic compounds used for nutrients Chemoautotrophs use inorganic substances to gain

energy instead of sunlight; inorganic chemicals =

energy, organic and inorganic compounds used for

nutrients. Typical examples found in hydrothermalvents


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Metabolism Prokaryotes can be separated based on their need for,

tolerance of, or aversion to oxygen

Obligate aerobes organisms that can only grow in the

presence of oxygen

ex. Bacteria that infect the respiratory system of humans;

microorganisms that live in the water column of lakes, rivers, and

the ocean Facultative anaerobes organisms that can grow in both

in the presence and the absence of oxygen

ex. Bacteria in the human intestines can be exposed to a range of

conditions from fully oxygenated (near the stomach) to completely

without oxygen (further into the intestines); an example of this typeof organism is E. coli.

Obligate anaerobes can only grow in environments

where there is no oxygen

ex. deep wounds on skin (hence the awful smell); deep in the soiland sediments; in certain parts of sewage treatment plants


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Growth and Reproduction

Bacterial cells grow at exponential rates when given the

right amounts of nutrients Exponential growth diagram

This can translate into a doubling of the population every

20 minutes!

The model of growth of bacteria is typically referred to asbinary fission

This is an asexual process and therefore lacks exchange

of genetic material

Bacteria can and do exchange genetic material

Conjugation transfer of genes from one cell to

another (Conjugation diagram)

Increases genetic diversity of a population


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Bacteria in Nature

Decomposers

Bacteria play a critical role in nature by recycling deadorganisms

Nutrients in dead organisms can then be reused, instead

of accumulating

Require the right mix of the following variables formaximum decomposition to occur:

Temperature

Gas availability for terminal electron accepting (O2 is

the best)

Water

Widely used by humans to process dead materials to get

rid of them or to recycle them


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Bacteria in Nature

Nitrogen Fixation

Bacteria play a critical role in nature bringing newnitrogen into the biosphere

Lots of N2 gas in the atmosphere, but very few

organisms can capture it for use

Certain bacterial species can fix the N2 into NH3

(ammonia) or other nitrogen compounds

Once fixed the nitrogen can be used by other

organisms

Legumes plants that harbor nitrogen fixing bacteria in

root nodules

These root nodules are functionally equal to having

fertilizer factory in your roots


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Bacteria in Nature

Bacteria and Disease

Not all bacteria cause disease, but some do. These fewbad bugs give bacteria the group name of germs

Pathogen disease causing agent

Two general ways a pathogen can operate:

Break down tissues for food (ex. Tuberculosis)

Release toxins that harm the host (ex. Food

poisoning)

Many bacteria can be killed or kept in check with

antibiotics or vaccines

However, there is a rising problem with bacteria that

are resistant to our drugs (Imagine that! A bacterium

that doesnt want to die).


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Bacteria in Nature

Human Uses of Bacteria

Many food products are made or modified through theaction of microorganisms

Cheese, yogurt, buttermilk, sour cream, pickles, chocolate, tofu,

etc.

Bacteria can also be used in industry to clean up toxicwaste and to help recover gold

Bacteria can also be used to make medicines

Bio-prospecting looking for medicinally an industrially

important biological products


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Bacteria in Nature

Controlling Bacteria

Sterilization the killing or removal of allmicroorganisms in a material or on an object

High and low temperature

High pressure

Certain chemicals (including antibiotics if taken according toDoctors directions)

Disinfection the reduction of the total number of

pathogenic microorganisms to the point that they pose

no danger

Soap and water

Bleach

Lysol


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Cell shapes Coccus

cocci, plural

spherical cell

Bacillus bacilli, plural

rod-like cell

Coccobacilli

cells in between round and rodshape

Vibrio curved cell

Spirillum spirilla, plural

rigid, wave-like shaped cell

Spirochete Corkscrew shaped cells

Not all cells fit into theseneat categories For example, some square

and triangular Archaeacells have beendiscovered

Pleomorphism variation in cell shape

within a species ofbacteria


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Three Domains of Life


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The Scale of Life


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Typical Prokaryotic Cell


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Typical eukaryotic cell


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Types of bacterial

cell wall/membrane

complexes


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Flagella


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Exponential

growth

Growth video
http://www.cellsalive.com/qtmovs/ecoli_mov.htmhttp://www.cellsalive.com/qtmovs/ecoli_mov.htm


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Conjugation


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Viruses and

Bacteriophages

bio102 bacteria

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