DIFFERENCES BETWEEN BACTERIA AND VIRUSES - Bacteria are typically much larger than viruses and can be viewed under a light microscope. Viruses are about 1,000 times smaller than bacteria and are visible under an electron microscope. Bacteria live almost anywhere including within other organisms, on other organisms, and on inorganic surfaces. Much like bacteria, viruses can be found in almost any environment. Viruses can persist on surfaces and on objects we use every day for varying lengths of time (from seconds to years) depending on the type of virus. Bacteria are prokaryotic cells that display all of the characteristics of living organisms. Viruses rely solely on a host for replication. Bacteria can be found in a variety of shapes and sizes. Common bacterial cell shapes include cocci (spherical), bacilli (rod-shaped), spiral, and vibrio. The size and shape of viruses are determined by the amount of nucleic acid and proteins they contain. Viruses typically have spherical (polyhedral), rod-shaped, or helically shaped capsids. Antiviral drugs are used to treat some types of viral infections. Typically the host's immune system is relied upon to fight off viruses. Vaccines can also be used to prevent viral infections.

.................................................................................................................................................................

 Differences Between Bacteria and Viruses

Bacteria are typically much larger than viruses and can be viewed under a light microscope - viruses are about 1,000 times smaller than bacteria and are visible under an electron microscope

By Regina Bailey

Bacteria and viruses are both microscopic organisms that can cause disease in humans.

While these microbes may have some characteristics in common, they are also very different.

Bacteria are typically much larger than viruses and can be viewed under a light microscope.

Viruses are about 1,000 times smaller than bacteria and are visible under an electron microscope.

Bacteria are single-celled organisms that reproduce asexually independently of other organisms.

Viruses require the aid of a living cell in order to reproduce.

Where They Are Found

·      Bacteria: Bacteria live almost anywhere including within other organisms, on other organisms, and on inorganic surfaces. They infect eukaryotic organisms such as animals, plants, and fungi.

Some bacteria are considered to be extremophiles and can survive in extremely harsh environments such as hydrothermal vents and in the stomachs of animals and humans.

·      Viruses: Much like bacteria, viruses can be found in almost any environment. They are pathogens that infect prokaryotic and eukaryotic organisms including animals, plants, bacteria, and archaeans.

Viruses that infect extremophiles such as archaeans have genetic adaptations that enable them to survive harsh environmental conditions (hydrothermal vents, sulphuric waters, etc.).

Viruses can persist on surfaces and on objects we use every day for varying lengths of time (from seconds to years) depending on the type of virus.

Bacterial and Viral Structure

·      Bacteria: Bacteria are prokaryotic cells that display all of the characteristics of living organisms. 

Bacterial cells contain organelles and DNA that are immersed within the cytoplasm and surrounded by a cell wall.

These organelles perform vital functions that enable bacteria to obtain energy from the environment and to reproduce.

·      Viruses: Viruses are not considered cells but exist as particles of nucleic acid (DNA or RNA) encased within a protein shell.

Some viruses have an additional membrane called an envelope that is composed of phospholipids and proteins obtained from the cell membrane of a previously infected host cell.

This envelope helps the virus enter a new cell by fusion with the cell's membrane and helps it exit by budding. non-enveloped viruses typically enter a cell by endocytosis and exit by exocytosis or cell lysis.

Also known as virions, virus particles exist somewhere between living and non-living organisms.

While they contain genetic material, they don't have a cell wall or organelles necessary for energy production and reproduction. Viruses rely solely on a host for replication.

Size and Shape

·      Bacteria: Bacteria can be found in a variety of shapes and sizes. Common bacterial cell shapes include cocci (spherical), bacilli (rod-shaped), spiral, and vibrio.

Bacteria typically range in size from 200-1000 nanometers (a nanometer is 1 billionth of a meter) in diameter. The largest bacterial cells are visible with the naked eye.

Considered the world's largest bacteria, Thiomargarita namibiensis can reach up to 750,000 nanometers (0.75 millimeters) in diameter.

·      Viruses: The size and shape of viruses are determined by the amount of nucleic acid and proteins they contain.

Viruses typically have spherical (polyhedral), rod-shaped, or helically shaped capsids.

Some viruses, such as bacteriophages, have complex shapes which include the addition of a protein tail attached to the capsid with tail fibers extending from the tail.

Viruses are much smaller than bacteria. They generally range in size from 20-400 nanometers in diameter.

The largest viruses known, the pandoraviruses, are about 1000 nanometers or a full micrometer in size.

How They Reproduce

·      Bacteria: Bacteria commonly reproduce asexually by a process known as binary fission.

In this process, a single cell replicates and divides into two identical daughter cells. Under proper conditions, bacteria can experience exponential growth.

·      Viruses: Unlike bacteria, viruses can only replicate with the aid of a host cell.

Since viruses don't have the organelles necessary for the reproduction of viral components, they must use the host cell's organelles to replicate.

In viral replication, the virus injects its genetic material (DNA or RNA) into a cell. Viral genes are replicated and provide the instructions for the building of viral components.

Once the components are assembled and the newly formed viruses mature, they break open the cell and move on to infect other cells.

Diseases Caused by Bacteria and Viruses

·      Bacteria: While most bacteria are harmless and some are even beneficial to humans, other bacteria are capable of causing disease. Pathogenic bacteria that cause disease produce toxins that destroy cells.

They can cause food poisoning and other serious illnesses including meningitis, pneumonia, and tuberculosis.

Bacterial infections can be treated with antibiotics, which are very effective at killing bacteria.

Due to the overuse of antibiotics however, some bacteria (E.coli and MRSA) have gained resistance to them.

Some have even become known as superbugs as they have gained resistance to multiple antibiotics.

Vaccines are also useful in preventing the spread of bacterial diseases.

The best way to protect yourself from bacteria and other germs is to properly wash and dry your hands often.

·      Viruses: Viruses are pathogens that cause a range of diseases including chickenpox, the flu, rabies, Ebola virus disease, Zika disease, and HIV/AIDS.

Viruses can cause persistent infections in which they go dormant and can be reactivated at a later time.

Some viruses can cause changes within host cells that result in the development of cancer.

These cancer viruses are known to cause cancers such as liver cancer, cervical cancer, and Burkitt's lymphoma.

Antibiotics do not work against viruses.

Treatment for viral infections typically involve medicines that treat the symptoms of an infection and not the virus itself.

Antiviral drugs are used to treat some types of viral infections. Typically the host's immune system is relied upon to fight off viruses.

Vaccines can also be used to prevent viral infections.

Differences Between Bacteria and Viruses Chart

	Bacteria	Viruses
Cell Type	Prokaryotic Cells	Acellular (not cells)
Size	200-1000 nanometers	20-400 nanometers
Structure	Organelles and DNA within a cell wall	DNA or RNA within a capsid, some have an envelope membrane
Cells They Infect	Animal, Plant, Fungi	Animal, Plant, Protozoa, Fungi, Bacteria, Archaea
Reproduction	Binary fission	Rely on host cell
Examples	E.coli, Salmonella, Listeria, Mycobacteria, Staphylococcus,   Bacillus anthracis	Influenza viruses, Chickenpox viruses, HIV, Polio virus, Ebola virus
Diseases Caused	Tuberculosis, Food poisoning, Flesh-eating disease, Meningococcal meningitis, Anthrax	Chickenpox, polio, flu, measles, rabies, AIDS
Treatment	Antibiotics	Antiviral drugs

Regina Bailey , RN

Biology Expert

Education

B.A., Biology, Emory University

A.S., Nursing, Chattahoochee Technical College

Introduction

Biology expert for ThoughtCo (formerly About Education) since 1997

Author of the forward to The Complete Idiot's Guide to Understanding Cloning

Experience

Regina is a board-certified registered nurse and owner of a content development firm specializing in the development of biology and science-related content. She has written about biology for ThoughtCo (formerly About Education) since 1997.

Regina's expertise has been featured and/or referenced in Kaplan AP Biology 2016, The Internet for Cellular and Molecular Biologists, and The Seven Disciplines of Wellness: The Spiritual Connection to Good Health.

Regina also wrote the forward to The Complete Idiot's Guide to Understanding Cloning.

Education

Regina holds a B.A. in biology from Emory University and an A.S. in Nursing from Chattahoochee Technical College.

ThoughtCo and Dotdash

ThoughtCo is a premier reference site focusing on expert-created education content. We are one of the top-10 information sites in the world as rated by comScore, a leading Internet measurement company. Every month, more than 13 million readers seek answers to their questions on ThoughtCo.

For more than 20 years, Dotdash brands have been helping people find answers, solve problems, and get inspired. We are one of the top-20 largest content publishers on the Internet according to comScore, and reach more than 30% of the U.S. population monthly. Our brands collectively have won more than 20 industry awards in the last year alone, and recently Dotdash was named Publisher of the Year by Digiday, a leading industry publication.

https://www.thoughtco.com/differences-between-bacteria-and-viruses-4070311