Download Bacteria and Viruses - kristi

Bacteria and
Viruses
Biology II
2007
Bacteria
 All bacteria are prokaryotes.
 Prokaryotes are single-celled organisms
that lack nuclei.
 They are identified by their shapes, the
chemical nature of their cell walls, the
ways they move, and the ways they obtain
energy.
 Prokaryotes typically range from 1 to 5
micrometers, making them much smaller
than eukaryotes (10 to 100).
Bacteria
 Bacteria are vital to maintaining the living
world.
 Some are producers that capture energy by
photosynthesis.
 Others help to break down the nutrients in dead
matter and the atmosphere, allowing other
organisms to use the nutrients.
 There are two kingdoms of prokaryotes or
bacteria: Eubacteria and Archaebacteria.
Eubacteria
 Eubacteria is the larger of the two
bacteria kingdoms.
 They live almost everywhere.
 Some live in the soil, while others infect
large organisms and cause disease.
 Eubacteria are usually surrounded by a
cell wall that protects the cell form injury
and determines its shape.
Eubacteria
 The cell wall of
eubacteria consists
of a carbohydrate
called
peptidoglycan.
 Inside the cell wall
is the cell
membrane and then
the cytoplasm.
Archaebacteria
 Under a microscope, archaebacteria are very
similar to eubacteria.
 Archaebacteria lack peptidoglycan in the cell
wall and their membrane lipids are quite
different.
 The DNA sequence of key archaebacterial
genes are more like those of eukaryotes than
those of eubacteria.
 Many scientists believe that archaebacteria may
be the ancestors of eukaryotes.
 Most archaebacteria live in very harsh
environments.
Identifying Prokaryotes--Shapes
 Rod-shaped prokaryotes are called bacilli.
 Spherical prokayotes are called cocci.
 Spiral and corkscrew-shaped prokaryotes are called
spirilla.
 Some bacteria form long chains or gather in clusters.
Identifying Prokaryotes—Cell
Walls
 Scientists use a method called
gram staining to differentiate
between the two different types
of cell walls in eubacteria.
 Gram-positive bacteria have a
cell wall of peptidoglycan and
absorb only the violet stain.
 Gram-negative bacteria have an
additional lipid layer and absorb
the red counter-stain.
Identifying Prokaryotes-Movement
 Some bacteria are propelled by flagella,
which are whip-like structures used for
movement.
 Other bacteria lash, snake, and spiral
forward.
 A few bacteria glide slowly across a layer
of slime-like material they secrete.
 Many bacteria do not move at all.
Identifying Prokaryotes—
Energy
 Bacteria can obtain their energy in two
different ways:
 make own food (autotrophs)
 by feeding on other organisms
(heterotrophs)
Autotrophs
 Bacteria that carry out photosynthesis
are called photoautotrophs. These
organisms convert light energy into
chemical energy.
 Bacteria that obtain their energy directly
from inorganic molecules are called
chemoautotrophs.
 get their energy from chemical reactions
involving ammonia, hydrogen sulfide,
nitrites, sulfur, or iron
Heterotrophs
 Many bacteria are like humans and
obtain energy by taking in organic
molecules and breaking them down.
 Other bacteria are photosynthetic but still
need specific organic molecules for
proper nutrition. These organisms are
called photoheterotrophs.
Identifying Prokaryotes—
Energy
 Bacteria need a constant supply of energy.
This energy is released by cellular respiration,
which requires oxygen, and fermentation,
which does not.
 Organisms that require oxygen are called
obligate aerobes.
 Organisms that are poisoned by oxygen are
called obligate anaerobes.
 Organisms that can survive with or without
oxygen are called facultative anaerobes.
Do you think that
chemoautotrophs
are aerobic or
anaerobic?
Explain your
answer.
Identifying Prokaryotes—Growth
and Reproduction
 Many can divide as often as once every 20 minutes.
However, bacteria are limited by food and space like
other organisms.
 Some bacteria under go binary fission, which involves
the organism doubling its DNA and splitting in half to
form two daughter cells.
 Bacteria can undergo conjugation, in which one
bacterium transfers its genetic material to another
bacterium.
 Other bacteria can form spores when conditions are
not favorable. One such spore is called an endospore.
An endospore can remain dormant for months or
centuries.
If I were contaminated by
a single bacterium that
divided every 20
minutes, how many
bacteria would be
present in 48 hours?
Bacteria
E. coli
Clostridium
Gonnorhoeae
Staphlycoccus
Bacteria in Nature--Decomposers
 If all bacteria died, life could not continue. Plants would
leach all of the nutrients from the soil and would
eventually die. Soon, the animals that depended on the
plants for nourishment would also die.
 As decomposers, bacteria help the ecosystem recycle
nutrients.
 Bacteria break down dead matter into simpler
substances, which are released into the soil and taken
up by the roots of plants.
 As recyclers, bacteria perform important steps in sewage
treatment. Bacteria break down complex compounds in
the sewage into simpler ones, producing purified water,
nitrogen and carbon dioxide gases, and left over
products that are used for fertilizers.
Bacteria—Nitrogen Fixers
 Plants and animals depend on bacteria for
nitrogen, which is the building block for protein.
 Even though the atmosphere is made up of
approximately 80% nitrogen gas, plants cannot
use that nitrogen directly.
 Nitrogen must be “fixed” chemically to
ammonia or other nitrogen compounds.
 Certain bacteria are the only organisms with
the ability to fix nitrogen in such a way.
What it is called
when bacteria
“fixes” nitrogen into
usable ammonia?
Bacteria—Nitrogen Fixers
 Many plants have symbiotic relationships
with nitrogen fixing bacteria.
 The bacterium Rhizobium lives on the
roots of soybeans and other legumes.
The bacteria gets food (sugars) and the
plant receives nitrogen.
Bacteria and Disease
 Bacteria can be found everywhere in nature,
but only a few are actually harmful.
 A bacterium that causes disease is known as a
pathogen.
 Bacteria can cause disease in two general
ways.
 Some damage the tissues of the infected organism
directly by breaking them down for food.
 Other bacteria release toxins (poisons) that harm
the body.
Bacteria and Disease
 Heterotrophic bacteria cause damage by
damaging cells and tissues.
 Most food poisonings are a direct result of
toxins released by bacteria.
 Many bacterial diseases can be prevented by
stimulating the body’s immune system with
vaccines.
 If a bacterial infection does occur, there are a
number of drugs and natural compounds that
can be used to attack and destroy the invading
bacteria.
What do you call
a drug that can
attack and
destroy bacteria?
Common Bacterial
Diseases
Disease
Pathogen
Characteristics
Impetigo
Staphylococcus
Superficial skin infection
aureus;
Streptococcus pyogenes
Folliculitis
Staphylococcus aureus Infection of hair follicle
Toxic Shock
Syndrome
Acne
Staphylococcus aureus Fever, rash, and shock
Botulism
Clostridium botulinum Causes paralysis and
respiratory failure
Propionibacterium
acnes
Inflammatory lesions
origninating with
accumulations of sebum
that rupture a hair follicle
Common Bacterial
Diseases
Disease
Pathogen
Prevention
Tooth decay
Streptococcus mutans
Regular dental hygiene
Lyme disease
Borrelia burgdorferi
Protection from ticks
Tetanus
Clostridium tetani
Current tetanus
vaccination
Salmonella food
poisoning
Salmonella enteritidis
Proper food-handling
Pneumonia
Streptococcus
pneumoniae
Maintaining good health
Human uses of Bacteria
 Humans use bacteria everyday to create
and/or manufacture certain food products.
 Foods in which bacteria is used: cheese,
yogurt, buttermilk, sour cream, pickles,
sauerkraut, and wines.
 Bacteria are also used in industry to digest
petroleum, which help clean up oil spills.
 New research suggests that bacteria adapted
to extreme environments can be used for
medicines and the food industry.
Controlling Bacteria
 Most bacteria are harmless, and many are even
beneficial. However, humans still wish to control
bacterial growth due to outbreaks of “bad” bacteria.
 Sterilization destroys bacteria by subjecting them to
either to great heat or to chemical action. Most
bacteria are killed in boiling water or disinfectants.
 To prevent food spoilage, one can refrigerate foods.
Bacteria grow slowly are cool temperatures.
 Other methods of killing bacteria in foods is by boiling,
frying, or steaming, which raise the temperature of the
food to a point where the bacteria are killed.
Anaerobic
4000 times the
mass of the Earth…
If the bacteria had an unlimited
supply of food and space.
Asexual
Nitrogen fixation
antibiotics