bacteria - schools.ednet.ns.ca ppt jr.pdf · archaebacteria archae = early or primitive in fact...
TRANSCRIPT
Bacteria are prokaryotes
Pro – before
Karyon – nucleus
The simplest forms of life are prokaryotes.
Earth’s first cells were prokaryotes.
Lots of Them!
Prokaryotes are Earth’s most
abundant life forms.
They can survive in many
environments.
They can get energy from many
different sources.
Archaebacteria
Archae = early or primitive
In fact archaebacteria have a more advanced structure than eubacteria and share characteristics with eukaryotes
Cell wall lacks peptidoglycan
Genes and enzymes behave more like Eukaryotes
Cells have three RNA polymerases like eukaryotes
Archaebacteria
Many Archaebacteria are often referred to as
extremophiles. They have the unique ability
to survive in environments where other
organisms cannot survive.
These extreme environments are anaerobic
(lacking oxygen) and are believed to
resemble conditions that existed when life
first evolved on earth, billions of years ago.
Archaebacteria
Three major groups of archaebacteria
include:
Methanogens – methane-producing organisms
Extreme Thermophiles – thrive in temperatures
up to 110°C
Extreme Halophiles – thrive in very salty
environments
Eubacteria
True bacteria
More primitive than archaebacteria
Cell wall made of peptidoglycan
Cells have only one RNA polymerase
Similarities
Common characteristics of Archaebacteria
and Eubacteria:
1. Cells are prokaryotic, all are single celled
2. Cells contain no membrane-bound organelles
3. Cells reproduce asexually by binary fission or
sexually by conjugation
Eubacteria Classified by Shape
Cocci (ball-shaped)
Streptococcus mutans
Bacillus (rod-shaped)
Clostridium botulinum
Spirilli (spiral-shaped)
Treponema palladium
Reproduction & Growth
Asexual Reproduction – only one parent is
involved
Binary Fission – simpler than mitosis. Single stand of bacterial DNA replicates
This identical genetic material is transferred to each new cell
Bacterium produces a cross wall and divides into two identical
cells
Reproduction & Growth
Sexual Reproduction – two parents involved
Not common in bacteria
Conjugation Transfer of genetic material between bacterial cells by
direct cell-to-cell contact or by a bridge-like
connection between two cells
The recipient cell now has an altered set of
characteristics, due to recombination of the DNA
Factors Influencing Bacterial Growth
Physical Factors: Temperature
Oxygen
pH
Osmosis
Nutritional
Requirements: Energy source
Carbon
Nitrogen
Water
Other Minerals
Organisms having complex nutritional requirements and
needing many growth factors are said to be fastidious
Harmful Effects of Bacteria
Bacteria are best known for being:
pathogenic - disease causing. The anthrax causing bacteria Bacillus anthracis was
the first bacterium proven to cause disease.
Virulence Factors
Virulence factors are molecules expressed
and secreted by bacteria that enable them to
achieve the following: Immunoevasion, evasion of the host's immune
response
Immunosuppression, inhibition of the host’s immune
response
Entry into and exit out of cells
Obtain nutrients from the host
Symptoms
Bacteria cause disease in three major ways:
1. Their sheer numbers burden the host’s tissues
and interfere with normal function
2. The bacteria cells destroy the hosts cells and
tissues
3. Some bacteria produce poison called toxins
which shut down the hosts tissues
Spread and Protection
Infectious bacterial diseases are spread from
one individual to another in a variety of
ways: Moisture droplets in the air
Dust
Direct contact
Fecal contamination
Animal bites
wounds
Spread and Protection
Most people have built in protection
provided by the body’s own defense
mechanisms: Immune System
Other methods of protection include: Sterilization/disinfection
Use of antiseptics
Extermination of animals that carry bacterial disease
Immunizations and administration of antibiotics
Examples of Pathogenic Bacteria
Type of Bacteria Disease/destruction produced
cloasridia botulism, tetanus, and gangrene
streptococci strep throat, scarlet fever, and pneumonia
staphylococci boils, food poisoning, and skin infections
lactobacilli souring of milk
pseudomonads gasoline spoilage
bacilli destruction of silkworms
staphylococci and pseudomonads food spoilage
coliform bacteria Pollution of water sources, soft rot in plants,
gastroenteritis and dysentery in humans
spirilla cholera and syphilis
Bacteria: Friend or Foe?
The usefulness of bacteria far outweigh the
damage they cause.
One of the most important jobs of bacteria
are the recycling they do as decomposers. Bacteria are the primary organism responsible for
converting dead plants and animals into natures raw
materials. These nutrients are essential for living
plants and animals.
Beneficial Effects of Bacteria
Type of Bacteria Beneficial Effects
clostridia production of butanol and acetone from molasses
acetobacter production of vinegar from alcohol
intestinal bacteria food digestion; synthesizing of vitamins in humans
eg. To regulate blood clotting
lactobacilli production of lactic acid form sugar
aztobacter, nitrobacter fixation of nitrogen in soils
streptococci, lactobacilli production of dairy products
eg. Cheese, buttermilk, and yogurt
streptomyces source of antibiotics
eg. Streptomycin, terramycin, neomycin, and
erythomycin
Bacteria Cleaning Crew
Some bacteria literally 'live
on oil,' just as some people
live on meat and potatoes.
And they consume it with
just as much relish.
Such bioremediation cannot
only help to clean up oil
spills, but also chlorinated
chemicals and leaks from
storage tanks.
Probiotics
Probiotics - live microorganisms that are
healthy for the host organism
Lactic acid bacteria (LAB) and bifidobacteria are
the most common types of microbes used as
probiotics
Probiotics are commonly consumed as part
of fermented foods including:Yogurt Dietary Supplements
Buttermilk
Antibacterial Resistance
Over the past 50 years, many disease-causing
bacteria have slowly developed resistance to
antibiotics
This resistance arises due to variations within
a bacterial population allowing for natural
selection
Antibacterial Resistance
Bacteria resistant to antibiotics contain
R (resistance) Factors These R factors are plasmids with special genes that
code for enzymes which inactivate specific drugs
The R factors are transferred and recombined in
conjugation
“The misuse of antibiotics could cause
serious problems for society”