Bacteria and Bacteria and VirusesVirusesBiology IIBiology II

20072007

BacteriaBacteria All bacteria are prokaryotes.All bacteria are prokaryotes. Prokaryotes are single-celled organisms Prokaryotes are single-celled organisms

that lack nuclei. that lack nuclei. They are identified by their shapes, the They are identified by their shapes, the

chemical nature of their cell walls, the chemical nature of their cell walls, the ways they move, and the ways they obtain ways they move, and the ways they obtain energy.energy.

Prokaryotes typically range from 1 to 5 Prokaryotes typically range from 1 to 5 micrometers, making them much smaller micrometers, making them much smaller than eukaryotes (10 to 100).than eukaryotes (10 to 100).

BacteriaBacteria

Bacteria are vital to maintaining the living Bacteria are vital to maintaining the living world. world. Some are producers that capture energy by Some are producers that capture energy by

photosynthesis.photosynthesis. Others help to break down the nutrients in dead Others help to break down the nutrients in dead

matter and the atmosphere, allowing other matter and the atmosphere, allowing other organisms to use the nutrients.organisms to use the nutrients.

There are two kingdoms of prokaryotes or There are two kingdoms of prokaryotes or bacteria: Eubacteria and Archaebacteria. bacteria: Eubacteria and Archaebacteria.

EubacteriaEubacteria

Eubacteria is the larger of the two Eubacteria is the larger of the two bacteria kingdoms.bacteria kingdoms.

They live almost everywhere. They live almost everywhere. Some live in the soil, while others infect Some live in the soil, while others infect

large organisms and cause disease.large organisms and cause disease.

Eubacteria are usually surrounded by a Eubacteria are usually surrounded by a cell wall that protects the cell form injury cell wall that protects the cell form injury and determines its shape.and determines its shape.

EubacteriaEubacteria

The cell wall of The cell wall of eubacteria consists eubacteria consists of a carbohydrate of a carbohydrate called called peptidoglycan.peptidoglycan.

Inside the cell wall Inside the cell wall is the cell is the cell membrane and then membrane and then the cytoplasm.the cytoplasm.

ArchaebacteriaArchaebacteria Under a microscope, archaebacteria are very Under a microscope, archaebacteria are very

similar to eubacteria.similar to eubacteria. Archaebacteria lack peptidoglycan in the cell Archaebacteria lack peptidoglycan in the cell

wall and their membrane lipids are quite wall and their membrane lipids are quite different.different.

The DNA sequence of key archaebacterial The DNA sequence of key archaebacterial genes are more like those of eukaryotes than genes are more like those of eukaryotes than those of eubacteria.those of eubacteria.

Many scientists believe that archaebacteria may Many scientists believe that archaebacteria may be the ancestors of eukaryotes.be the ancestors of eukaryotes.

Most archaebacteria live in very harsh Most archaebacteria live in very harsh environments.environments.

Identifying Prokaryotes--ShapesIdentifying Prokaryotes--Shapes

Rod-shaped prokaryotes are called bacilli.Rod-shaped prokaryotes are called bacilli. Spherical prokayotes are called cocci.Spherical prokayotes are called cocci. Spiral and corkscrew-shaped prokaryotes are called Spiral and corkscrew-shaped prokaryotes are called

spirilla.spirilla. Some bacteria form long chains or gather in clusters.Some bacteria form long chains or gather in clusters.

Identifying Prokaryotes—Cell Identifying Prokaryotes—Cell WallsWalls

Scientists use a method called Scientists use a method called gram staining to differentiate gram staining to differentiate between the two different types between the two different types of cell walls in eubacteria.of cell walls in eubacteria.

Gram-positive bacteria have a Gram-positive bacteria have a cell wall of peptidoglycan and cell wall of peptidoglycan and absorb only the violet stain.absorb only the violet stain.

Gram-negative bacteria have an Gram-negative bacteria have an additional lipid layer and absorb additional lipid layer and absorb the red counter-stain.the red counter-stain.

Identifying Prokaryotes--Identifying Prokaryotes--MovementMovement

Some bacteria are propelled by flagella, Some bacteria are propelled by flagella, which are whip-like structures used for which are whip-like structures used for movement.movement.

Other bacteria lash, snake, and spiral Other bacteria lash, snake, and spiral forward.forward.

A few bacteria glide slowly across a layer A few bacteria glide slowly across a layer of slime-like material they secrete.of slime-like material they secrete.

Many bacteria do not move at all.Many bacteria do not move at all.

Identifying Prokaryotes—Identifying Prokaryotes—EnergyEnergy

Bacteria can obtain their energy in two Bacteria can obtain their energy in two different ways: different ways: make own food (autotrophs) make own food (autotrophs) by feeding on other organisms by feeding on other organisms

(heterotrophs)(heterotrophs)

AutotrophsAutotrophs

Bacteria that carry out photosynthesis are Bacteria that carry out photosynthesis are called photoautotrophs. These organisms called photoautotrophs. These organisms convert light energy into chemical energy.convert light energy into chemical energy.

Bacteria that obtain their energy directly Bacteria that obtain their energy directly from inorganic molecules are called from inorganic molecules are called chemoautotrophs. chemoautotrophs. get their energy from chemical reactions get their energy from chemical reactions

involving ammonia, hydrogen sulfide, nitrites, involving ammonia, hydrogen sulfide, nitrites, sulfur, or ironsulfur, or iron

HeterotrophsHeterotrophs

Many bacteria are like humans and Many bacteria are like humans and obtain energy by taking in organic obtain energy by taking in organic molecules and breaking them down.molecules and breaking them down.

Other bacteria are photosynthetic but still Other bacteria are photosynthetic but still need specific organic molecules for need specific organic molecules for proper nutrition. These organisms are proper nutrition. These organisms are called photoheterotrophs.called photoheterotrophs.

Identifying Prokaryotes—Identifying Prokaryotes—EnergyEnergy

Bacteria need a constant supply of energy. Bacteria need a constant supply of energy. This energy is released by cellular respiration, This energy is released by cellular respiration, which requires oxygen, and fermentation, which requires oxygen, and fermentation, which does not.which does not.

Organisms that require oxygen are called Organisms that require oxygen are called obligate aerobes.obligate aerobes.

Organisms that are poisoned by oxygen are Organisms that are poisoned by oxygen are called obligate anaerobes.called obligate anaerobes.

Organisms that can survive with or without Organisms that can survive with or without oxygen are called facultative anaerobes.oxygen are called facultative anaerobes.

Do you think that chemoautotrophs

are aerobic or anaerobic?

Explain your answer.

Identifying Prokaryotes—Identifying Prokaryotes—GrowthGrowthand Reproductionand Reproduction

Many can divide as often as once every 20 minutes. Many can divide as often as once every 20 minutes. However, bacteria are limited by food and space like However, bacteria are limited by food and space like other organisms.other organisms.

Some bacteria under go Some bacteria under go binary fissionbinary fission, which involves , which involves the organism doubling its DNA and splitting in half to the organism doubling its DNA and splitting in half to form two daughter cells.form two daughter cells.

Bacteria can undergo Bacteria can undergo conjugationconjugation, in which one , in which one bacterium transfers its genetic material to another bacterium transfers its genetic material to another bacterium.bacterium.

Other bacteria can form Other bacteria can form sporesspores when conditions are not when conditions are not favorable. One such spore is called an endospore. An favorable. One such spore is called an endospore. An endospore can remain dormant for months or centuries.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?

Is binary fission considered sexual or asexual reproduction

Is binary fission considered

sexual or asexual reproduction? Explain your answer.

BacteriaBacteriaE. coli Gonnorhoeae

Clostridium Staphlycoccus

Bacteria in Nature--DecomposersBacteria in Nature--Decomposers If all bacteria died, life could not continue. Plants would If all bacteria died, life could not continue. Plants would

leach all of the nutrients from the soil and would leach all of the nutrients from the soil and would eventually die. Soon, the animals that depended on the eventually die. Soon, the animals that depended on the plants for nourishment would also die.plants for nourishment would also die.

As decomposers, bacteria help the ecosystem recycle As decomposers, bacteria help the ecosystem recycle nutrients. nutrients.

Bacteria break down dead matter into simpler Bacteria break down dead matter into simpler substances, which are released into the soil and taken substances, which are released into the soil and taken up by the roots of plants.up by the roots of plants.

As recyclers, bacteria perform important steps in sewage As recyclers, bacteria perform important steps in sewage treatment. Bacteria break down complex compounds in treatment. Bacteria break down complex compounds in the sewage into simpler ones, producing purified water, the sewage into simpler ones, producing purified water, nitrogen and carbon dioxide gases, and left over nitrogen and carbon dioxide gases, and left over products that are used for fertilizers.products that are used for fertilizers.

Bacteria—Nitrogen FixersBacteria—Nitrogen Fixers

Plants and animals depend on bacteria for Plants and animals depend on bacteria for nitrogen, which is the building block for protein.nitrogen, which is the building block for protein.

Even though the atmosphere is made up of Even though the atmosphere is made up of approximately 80% nitrogen gas, plants cannot approximately 80% nitrogen gas, plants cannot use that nitrogen directly.use that nitrogen directly.

Nitrogen must be “fixed” chemically to Nitrogen must be “fixed” chemically to ammonia or other nitrogen compounds.ammonia or other nitrogen compounds.

Certain bacteria are the only organisms with Certain bacteria are the only organisms with the ability to fix nitrogen in such a way.the ability to fix nitrogen in such a way.

What it is called when bacteria

“fixes” nitrogen into usable ammonia?

Bacteria—Nitrogen FixersBacteria—Nitrogen Fixers

Many plants have symbiotic relationships Many plants have symbiotic relationships with nitrogen fixing bacteria.with nitrogen fixing bacteria.

The bacterium The bacterium Rhizobium Rhizobium lives on the lives on the roots of soybeans and other legumes. roots of soybeans and other legumes. The bacteria gets food (sugars) and the The bacteria gets food (sugars) and the plant receives nitrogen.plant receives nitrogen.

Bacteria and DiseaseBacteria and Disease

Bacteria can be found everywhere in nature, Bacteria can be found everywhere in nature, but only a few are actually harmful.but only a few are actually harmful.

A bacterium that causes disease is known as a A bacterium that causes disease is known as a pathogen.pathogen.

Bacteria can cause disease in two general Bacteria can cause disease in two general ways. ways. Some damage the tissues of the infected organism Some damage the tissues of the infected organism

directly by breaking them down for food. directly by breaking them down for food. Other bacteria release toxins (poisons) that harm Other bacteria release toxins (poisons) that harm

the body.the body.

Bacteria and DiseaseBacteria and Disease

Heterotrophic bacteria cause damage by Heterotrophic bacteria cause damage by damaging cells and tissues.damaging cells and tissues.

Most food poisonings are a direct result of Most food poisonings are a direct result of toxins released by bacteria.toxins released by bacteria.

Many bacterial diseases can be prevented by Many bacterial diseases can be prevented by stimulating the body’s immune system with stimulating the body’s immune system with vaccines.vaccines.

If a bacterial infection does occur, there are a If a bacterial infection does occur, there are a number of drugs and natural compounds that number of drugs and natural compounds that can be used to attack and destroy the invading can be used to attack and destroy the invading bacteria.bacteria.

What do you call a drug that can

attack and destroy bacteria?

Common Bacterial Common Bacterial DiseasesDiseases

DiseaseDisease PathogenPathogen CharacteristicsCharacteristics

Impetigo Staphylococcusaureus;

Streptococcus pyogenes

Superficial skin infection

Folliculitis Staphylococcus aureus Infection of hair follicle

Toxic Shock Syndrome

Staphylococcus aureus Fever, rash, and shock

Acne Propionibacterium acnes

Inflammatory lesions origninating with accumulations of sebum that rupture a hair follicle

Botulism Clostridium botulinum Causes paralysis and respiratory failure

Common Bacterial Common Bacterial DiseasesDiseases

DiseaseDisease PathogenPathogen PreventionPrevention

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 BacteriaHuman uses of Bacteria

Humans use bacteria everyday to create Humans use bacteria everyday to create and/or manufacture certain food products.and/or manufacture certain food products.

Foods in which bacteria is used: cheese, Foods in which bacteria is used: cheese, yogurt, buttermilk, sour cream, pickles, yogurt, buttermilk, sour cream, pickles, sauerkraut, and wines.sauerkraut, and wines.

Bacteria are also used in industry to digest Bacteria are also used in industry to digest petroleum, which help clean up oil spills.petroleum, which help clean up oil spills.

New research suggests that bacteria adapted New research suggests that bacteria adapted to extreme environments can be used for to extreme environments can be used for medicines and the food industry.medicines and the food industry.

Controlling BacteriaControlling Bacteria

Most bacteria are harmless, and many are even Most bacteria are harmless, and many are even beneficial. However, humans still wish to control beneficial. However, humans still wish to control bacterial growth due to outbreaks of “bad” bacteria.bacterial growth due to outbreaks of “bad” bacteria.

Sterilization destroys bacteria by subjecting them to Sterilization destroys bacteria by subjecting them to either to great heat or to chemical action. Most either to great heat or to chemical action. Most bacteria are killed in boiling water or disinfectants. bacteria are killed in boiling water or disinfectants.

To prevent food spoilage, one can refrigerate foods. To prevent food spoilage, one can refrigerate foods. Bacteria grow slowly are cool temperatures. Bacteria grow slowly are cool temperatures.

Other methods of killing bacteria in foods is by boiling, Other methods of killing bacteria in foods is by boiling, frying, or steaming, which raise the temperature of the frying, or steaming, which raise the temperature of the food to a point where the bacteria are killed.food to a point where the bacteria are killed.

AnaerobicAnaerobic

4000 times the 4000 times the mass of the Earth…mass of the Earth…If the bacteria had an unlimited If the bacteria had an unlimited supply of food and space.supply of food and space.

AsexualAsexual

Nitrogen fixationNitrogen fixation

antibioticsantibiotics