Bacteria and VirusesBacteria and Viruses

© Lisa Michalek

BacteriaBacteria BacteriaBacteria are microscopic, are microscopic,

unicellular (one-celled) unicellular (one-celled) organisms that lack a nuclear organisms that lack a nuclear membrane.membrane.

Bacteria can live on land, in water, and Bacteria can live on land, in water, and in the air.in the air.– They also live in and on both living and They also live in and on both living and

dead plants and animals.dead plants and animals. Most bacteria are heterotrophs.Most bacteria are heterotrophs.

– HeterotrophsHeterotrophs are organisms that cannot are organisms that cannot make their own food.make their own food.

Shapes of BacteriaShapes of Bacteria

CoccusCoccus - round shaped - round shaped

BacillusBacillus – rod shaped – rod shaped

SpirillumSpirillum – spiral shaped – spiral shaped

Structure of BacteriaStructure of Bacteria

A bacterium A bacterium is made up is made up of a thick of a thick cell wall cell wall that encloses that encloses and protects and protects cellular cellular material.material.

Bacterial NutritionBacterial Nutrition

Some bacteria live separately and Some bacteria live separately and others remain together to others remain together to form colonies.form colonies.– ColoniesColonies are are

large groups of large groups of bacteria.bacteria.

Bacterial NutritionBacterial Nutrition

There are bacteria that live as There are bacteria that live as parasites.parasites.– A A parasiteparasite absorbs food materials from absorbs food materials from

other living organisms called their hosts.other living organisms called their hosts. Others digest and absorb food Others digest and absorb food

materials from dead organisms.materials from dead organisms.– These bacteria are called These bacteria are called saprophytes.saprophytes.

Beneficial BacteriaBeneficial Bacteria

Most bacteria are beneficial (helpful) to Most bacteria are beneficial (helpful) to humans.humans.

Bacteria are decomposers that cause Bacteria are decomposers that cause decay.decay.– DecomposersDecomposers are organisms that break are organisms that break

down dead organisms and return the down dead organisms and return the nutrients to the soil.nutrients to the soil.

Beneficial BacteriaBeneficial Bacteria

Many bacteria are used Many bacteria are used to produce food and to produce food and life-saving drugs.life-saving drugs.– Bacteria are used to Bacteria are used to

make cheese, pickles, make cheese, pickles, yogurt, vinegar, and yogurt, vinegar, and sauerkraut.sauerkraut.

Beneficial BacteriaBeneficial Bacteria

By using methods of gene transplanting, By using methods of gene transplanting, bacteria have been encouraged to bacteria have been encouraged to produce substances such as insulin.produce substances such as insulin.

Beneficial BacteriaBeneficial Bacteria

The human intestinal The human intestinal tract contains tract contains millions of bacteria.millions of bacteria.– Many of these bacteria Many of these bacteria

help the digestive help the digestive process and others process and others produce vitamins.produce vitamins.

Beneficial BacteriaBeneficial Bacteria

Bacteria are also used Bacteria are also used in the tanning of in the tanning of leather, the curing of leather, the curing of tobacco, and the tobacco, and the production of food for production of food for feeding cows.feeding cows.

Harmful BacteriaHarmful Bacteria Some bacteria are not Some bacteria are not

beneficial to man.beneficial to man. Bacteria spoil food by Bacteria spoil food by

secreting enzymes into secreting enzymes into the food causing it to rot.the food causing it to rot.– Along with enzymes, other Along with enzymes, other

substances produced by substances produced by bacteria are released into the food.bacteria are released into the food.

– Some of these substances are toxic, Some of these substances are toxic, making the food poisonous to making the food poisonous to humans and other organisms.humans and other organisms.

Harmful BacteriaHarmful Bacteria

Bacteria in large Bacteria in large numbers can numbers can pollute (dirty) pollute (dirty) lakes, streams, lakes, streams, and drinking water.and drinking water.

During respiration, bacteria reduce During respiration, bacteria reduce the dissolved oxygen content in the dissolved oxygen content in water supplies.water supplies.

Harmful BacteriaHarmful Bacteria

Many bacteria are Many bacteria are pathogenic.pathogenic.– A A pathogenpathogen is an is an

organism that causes organism that causes disease and/or disease and/or infection.infection.

– Some bacterial Some bacterial diseases of humans diseases of humans are tuberculosis, are tuberculosis, tetanus, and strep tetanus, and strep throat.throat.

Controlling Harmful BacteriaControlling Harmful Bacteria

Antiseptics, disinfectants, and antibiotics are Antiseptics, disinfectants, and antibiotics are used to control pathogenic bacteria.used to control pathogenic bacteria.– An An antibioticantibiotic is a chemical that can stop the is a chemical that can stop the

growth of some bacteria.growth of some bacteria.– Bacteria are able to produce types that are Bacteria are able to produce types that are

resistant to certain antibiotics.resistant to certain antibiotics.– When this happens, When this happens,

new antibiotics must new antibiotics must be developed.be developed.

Controlling Harmful BacteriaControlling Harmful Bacteria

Bacteria can also be killed in foods by:Bacteria can also be killed in foods by:– pasteurizationpasteurization– canningcanning– chemical preservativeschemical preservatives– radiationradiation– steam/pressuresteam/pressure– salt curingsalt curing– dehydration (drying)dehydration (drying)

Harmful Anaerobic BacteriaHarmful Anaerobic Bacteria Some bacteria can live anaerobically and cause Some bacteria can live anaerobically and cause

botulism (botulism (Clostridium botulinumClostridium botulinum).). A dangerous type of A dangerous type of food poisoning, in foods that have not been properly canned.food poisoning, in foods that have not been properly canned.

TetanusTetanus is a disease also caused by an anaerobic is a disease also caused by an anaerobic bacteria (bacteria (Clostridium tetaniClostridium tetani) which is closely related to ) which is closely related to botulism. Tetanus is also known as lock jaw. botulism. Tetanus is also known as lock jaw.

Both Botulism and Tetanus are serious illnesses and Both Botulism and Tetanus are serious illnesses and often fatal often fatal

Harmful Anaerobic BacteriaHarmful Anaerobic Bacteria

Two other anaerobic bacteria Two other anaerobic bacteria can cause venereal diseases.can cause venereal diseases.– GonorrheaGonorrhea (causes sterility). (causes sterility).– SyphilisSyphilis (can result in death). (can result in death).

A A venereal diseasevenereal disease is a is a contagious disease that a contagious disease that a person gets through sexual contact.person gets through sexual contact.

Both diseases can be treated successfully by Both diseases can be treated successfully by antibiotics if detected early enough.antibiotics if detected early enough.

VirusesViruses A virus is A virus is notnot a cell. a cell. It is made up of genetic material inside It is made up of genetic material inside

a protein coat.a protein coat. Viruses Viruses

do not do not carry on carry on most most metabolic metabolic activities.activities.

VirusesViruses They can only They can only

reproduce inside reproduce inside a living cell called a living cell called the host cell.the host cell.

Outside the host Outside the host cell, a virus is cell, a virus is “lifeless” and often “lifeless” and often exists as a crystal.exists as a crystal.

A virus has no A virus has no means of locomotion.means of locomotion.

Virus ReproductionVirus Reproduction

Negative Virus InfluencesNegative Virus Influences They cause infections in both They cause infections in both

plants and animals.plants and animals. Some viruses cause tumors and warts.Some viruses cause tumors and warts. They also destroy cells and are They also destroy cells and are

responsible for human diseases such as:responsible for human diseases such as:– poliopolio– measlesmeasles– mumpsmumps– influenzainfluenza– hepatitishepatitis– coldscolds– AIDSAIDS

Human Papilloma Virus - Warts Influenza Virus - Flu

Human Immunodeficiency VirusAIDS

Rabies Virus

Positive Virus InfluencesPositive Virus Influences Certain viruses are Certain viruses are

used in the control used in the control of insect pests.of insect pests.

Others are used in Others are used in genetic research.genetic research.

Scientists have been Scientists have been able to use viruses to able to use viruses to biologically control biologically control caterpillars of the European caterpillars of the European pine sawfly and the gypsy pine sawfly and the gypsy moth.moth.