Key differences |
Bacteria |
Viruses |
Definition |
They are unicellular organisms found in most habitats on earth. |
They are non-living particles consist of genetic material (RNA or DNA) enclosed by a protein core. They are organic structures that interact with living organisms. |
Where do they grow? |
They grow in harsh conditions such as a deep portion of the crust of the earth, radioactive waste, and acidic hot springs. (1, 2, and 3) |
They are infectious agents that need a host to replicate. |
Classification |
They are classified according to their morphology:
- Cocci – spherical-shaped bacteria
- Vibrio – comma-shaped bacteria
- Bacillus – rod-shaped bacteria
- Spirilla – spiral-shaped bacteria
- Spirochaetes – tightly coiled bacteria (3, 4, and 5)
|
They are classified according to core content, presence of outer envelope, the structure of capsid, and the way mRNA is produced. |
What they infect? |
They infect all life forms. |
They can infect all forms of life including bacteria and archaea. |
Where can they be found? |
They are found in the ecosystem. |
They are found in the earth’s ecosystem. |
How are they visualized? |
They are visualized under a light microscope. |
They are visualized by means of negative staining. |
Reproduction requirement |
Bacteria can grow and reproduce without a host. |
Viruses need a host to reproduce as they replicate inside the host. |
Size |
They are large in size (around 1000 nm).
Various shapes and arrangements of Bacterial cells
|
They are small in size (20 to 400 nm) |
Presence of cell Wall |
The cell wall contains peptidoglycan/lipopolysaccharide. |
They don’t have a cell wall but has a protein coat. |
Number of cells |
They are unicellular |
They do not have cells. |
cellular structure |
Bacteria are cells and are prokaryotic in nature (displaying characteristics of a living organism) |
They are not cells and exist as DNA or RNA particles and enveloped within a protein shell. (5, 6)
See: Difference between RNA and DNA
|
Presence of ribosomes |
They contain ribosomes. |
They don’t have ribosomes. |
Genetic materials |
They contain a single circular chromosome. |
They have strands of DNA/RNA. |
Metabolism |
They metabolize within the cell. |
Metabolism is not present in a viral particle. |
Reproduction process |
The reproduction process takes place through the process of binary fission and conjugation. (6, 7) |
They reproduce by invading the host cell and create copies of genetic materials/proteins. They destroy the host cell and release new particles. |
Utilization of cellular machinery |
They possess cellular machinery. |
They don’t have cellular machinery. |
Benefits |
They can be categorized as harmful or beneficial. Some bacteria are considered good or healthy, especially those found in the gut. |
They are harmful, but some are used for genetic engineering purposes. |
Ability to infect/Nature of infection |
They cause localized infections. |
They cause systemic infections. |
How long the infection last? |
They last longer than 10 days. |
The duration of the illness varies between 2 and 10 days. |
Does it cause a fever? |
They cause fever. |
They may or may not cause fever. |
Treatment and management |
They are treated and managed using antibiotics. |
They can be prevented using vaccines. |
Presence of ribosomes |
Yes |
No |
Nucleus |
Absent |
Absent |
Presence of enzymes |
Present |
Present in some |
Virulence |
Yes |
Yes |
Incubation period |
It varies depending on the type of bacteria, but usually within 1 to 2 weeks. |
It primarily depends on what kind of virus causes the disease. The incubation could take a few days to weeks. |
Characteristics |
- They are single-celled organisms.
- Some of them grow as independent single cells while some are multi-cellular fruiting bodies and play an important role in the life cycle.
- They do not have complex organelles in the cell.
- They have an internal organization but don’t have a plasma membrane-like other living cells.
- Bacterial cells have ribosomes (spherical units) where protein assembles from amino acids using the data encoded in the DNA ribosome.
|
- They do not have cellular organelles and cytoplasm.
- They do not perform metabolic activities.
- They may only contain DNA or RNA. They can’t contain both.
- They reproduce at a tremendous amount, but they need a living host to replicate.
- Many viruses have the ability to mutate.
- Viruses are like parasites; they use the host cell’s metabolic machinery.
- They alone cannot grow and divide, they would need a host cell to produce and assemble their viral components. (7, 8, and 9)
|
Which is more fatal? |
Only about 1% of bacteria cause disease. |
The majority of viruses cause diseases. |
Symptoms/clinical manifestations |
The symptoms are confined to a particular infected area of the body as well as the type of bacteria that causes it. Typical clinical manifestations include the following:
- Swelling
- Pain
- Redness
- Nausea and vomiting
- Fever
|
Typical symptoms of viral infections are:
- Respiratory symptoms like cough and cold
- Sneezing
- Tiredness
- Diarrhea
- Nausea and vomiting
Is my cold Viral or Bacterial ? 
|
Difference in transmission |
- Exposure to body fluids
- Close contact with an infectious person
- Touching contaminated surfaces
- Mother to child transmission during childbirth
- Contact with infected animals/carriers
|
- Exposure to body fluids
- Close contact with an infectious person
- Touching contaminated surfaces
- Mother to child transmission during childbirth
- Contact with infected animals/carriers (6, 9, and 10)
|
Examples of diseases and illnesses |
Tuberculosis, strep throat, urinary tract infection |
HIV, herpes zoster, influenza, rabies, common cold, and COVID-19 (coronavirus) |
Common names and strains |
- Bacillus
- Coccus
- Vibrio cholera
- Rickettsia
- Staphylococcus aureus
- Helicobacter bacteria
- Streptococcus pneumonia
|
- Hepatitis A Virus
- Papillomavirus
- Ebola Virus
- Hanta Virus
- Rotavirus
- SARS-CoV
- SARS-CoV-2
- Zika Virus
- Nairovirus
|
How to prevent the spread of infection? |
- Hand washing
- Using alcohol and hand sanitizer
- Practice good hygiene
- Avoid touching the face as organisms can enter through the mucus membranes of the face.
- Cover your mouth and nose when coughing or sneezing.
- Use bleach when disinfecting as it is effective in killing bacteria. (3, 6, and 8)
|
- Hand washing
- Using alcohol and hand sanitizer
- Practice good hygiene
- Avoid touching the face as organisms can enter through the mucus membranes of the face.
- Cover your mouth and nose when coughing or sneezing.
- Use bleach when disinfecting as it is effective in killing viruses. (3, 9, and 10)
|
Similarities |
- Do not have a nucleus
- Both cause diseases
- Both microscopic in size
- Both have virulence
|
- Do not have a nucleus
- Both cause diseases
- Both microscopic in size
- Both have virulence
|