The bacteria and virus are different set of pathogens or living entities.
Both of them are microscopic but virus is 10 to 100 times smaller than the bacteria.
Infact some viruses act as parasites on bacteria.
The differences between them can be in terms of structure, habits, parasitic nature, and other features.
Bacteria vs. Virus
| Sl.No | Character | Bacteria | Virus |
|---|---|---|---|
| 1 | Living behavior | They are independent Living organisms | They are non-living particles and are physiologically active only inside the host. |
| 2 | Cell feature | Bacteria are single-celled organisms | Viruses are Acellular and it is not a cell but just a particle |
| 3 | Size comparison | Bigger in size and can be seen by a light microscope. | Smaller in size, it cannot be seen by a microscope. Only an image of a virus can be obtained by an electron microscope. |
| 4 | Outer wall | It has a distinct cell wall that is made of peptidoglycan | It has an outer sheath or cover which is made of proteins |
| 5 | Genetic material | Genetic material is DNA | Genetic material can be either RNA or DNA |
| 6 | Ribosomes | Bacteria has its ribosomes for protein synthesis | No ribosomes are present, so they utilize host ribosomes for protein synthesis |
| 7 | Metabolism | Has own metabolic machinery | It has no metabolic machinery and is dependent on the host cell metabolism. |
| 8 | Crystallization | They cannot be crystallized. | A group of viruses can be crystallized |
| 9 | Food habit | Based on food procurement, they are of different types like autotrophs, chemotrophs, saprophytic and parasitic. | Does not need food to survive but act as parasites by taking over host machinery for multiplication. |
| 10 | Life cycle | Irrespective of the host, bacteria have a cell cycle with birth, growth, and cell division. | A virus has only one process, i.e., multiplication, inside a host. |
| 11 | Reproduction | Reproduction occurs by binary fission. | Reproduction occurs by lytic infections. |
| 12 | Reproduction help | It does not need host cells to reproduce. | It needs host cells to reproduce or multiply itself. |
| 13 | Infect | Bacteria infect animals, plants, and fungal cells | Viruses infect bacteria, animals, plants, fungi, archaea, and protozoan cells. |
| 14 | Diseases | Bacteria causes tuberculosis, typhoid, anthrax, and other diseases in humans. | Serious Viral infections include AIDs, rabies, chickenpox, polio, etc. |
| 15 | Drugs | Antibiotics kill bacteria. | Antiviral drugs control viruses. |
| 16 | Support to human | Though bacteria are harmful to man, some are very beneficial for life | Viruses are always destructive. But due to this behavior, they help in the diversity of nature. |
| 17 | Examples | Mycobacterium, vibrio cholera | Human immunodeficiency virus (HIV), Hepatitis. |
Though bacteria and viruses are classified under microorganisms due to their minuscule size and are infectious to humans, in reality, they are pretty different.
We can observe their differences in many contexts.
Bacteria are microscopic, unicellular organisms with simple cell structures with no nucleus or other organelles like mitochondria.
They are classed under prokaryotes as their nuclear material is not enveloped within a membrane inside the cell.
Viruses do not have a cellular structure.
When outside the host organism, the virus has a core of genetic material, which may be either DNA or RNA, that encodes the structure of the proteins.
This core is surrounded by a protective protein code called the capsid, which protects the genetic material within.
In some cases, an outer envelope of lipids is present, which looks like a spiky coat. Viruses can latch onto host cells and insert their genetic material inside.
Living or nonliving?
This is the most important question to be asked when it comes to viruses and bacteria.
Bacteria are considered living organisms and are classed under the Monera kingdom in the ‘Five kingdom classification.’
Most bacteria have a cellular organization and can reproduce without a host.
They use energy for metabolism, can maintain homeostasis, and have the ability to grow.
Viruses do not have a cellular organization; they do not contain cytoplasm or cell organelles.
Outside the host cell, they cannot carry out metabolism, and they can only replicate using the host cell’s metabolic machinery.
Viral components are synthesized within the host cell.
They are dependent and are considered to be between living and nonliving and are not given any kingdom under the ‘Five kingdom classification.’
Size
Bacteria are larger and can be seen with a light microscope.
They have a diameter of about 1000 to 2000 nanometres.
Viruses are usually smaller in seen and are observed using an electron microscope. They have a size of about 20nm to 1000nm (maximum).
Outer wall
The outer cell wall in bacteria is made up of peptidoglycan(also called murein) and lipopolysaccharides.
In viruses, the cell wall is a protein coat called a capsid present around the inner genetic material.
Sometimes this capsid is surrounded by another spiny coat called an envelope.
Structure
Bacteria are unicellular prokaryotes.
Bacterial cells contain DNA and organelles inside the cytoplasm surrounded by a cell wall.
Bacteria can obtain energy from the environment and reproduce using these organelles. Thus bacteria have their own metabolic machinery.
Viruses are acellular. They have an outer protein coat with the genetic material inside.
They do not possess any metabolic or genetic machinery. They do not have organelles or cellular structures.
Shape
Bacteria can be found in many shapes. The common bacterial shapes are – cocci (spherical), spiral (spiral/helical), vibrio (comma-shaped), bacilli (rod-shaped) etc.
The shape of viruses depends on the structure and composition of the outer protein coat.
The common virus shapes are – polyhedral (in adenovirus), spherical (in influenza), helical (tobacco mosaic), complex (bacteriophage), etc.
Genetic material
The genetic material of bacteria is DNA. The genetic material is naked.
A virus has either DNA or RNA as its genetic material. The nucleic acid can be either single or double-stranded.
Ribosomes
Bacteria contain ribosomes of Type 70S ( 50S and 30S). These ribosomes can participate in translation and code proteins from mRNA.
Thus bacteria have their genetic machinery and do not need host cells to multiply.
Viruses do not contain ribosomes. They have either DNA or RNA.
Thus they cannot make their own proteins and need host cells to reproduce.
Reproduction
Bacteria can reproduce and produce new progeny on their own.
This is due to the presence of ribosomes that can synthesize proteins and other genetic material.
Viruses cannot reproduce on their own. They attach to the host cell and use the genetic machinery of the infected host cell.
Mechanism of reproduction
As bacteria are prokaryotic, they reproduce asexually. This occurs mostly by binary fission. Here one cell divides into two daughter cells. It does not need the host to multiply.
Viruses need a host to multiply. The protein coat of the virus attaches to the host cell and inserts its genetic material into it.
Thus when the host is replicating its DNA, it also forms copies of the virus’s genetic material.
Thus the virus can now multiply. The genetic material of the virus also codes for viral components using the host cell’s ribosomes.
The cell bursts or lyses releasing the copies which infect further cells. This is called lytic infection.
Infected organisms
Bacteria infect the animal, plant, and fungal cells. Viruses infect animals, plants, fungi, and even archaea and bacterial cells.
The type of virus that infects bacteria is known as a bacteriophage.
Treatment
Bacteria are living and thus respond to antibiotic treatments. Viruses are nonliving and thus do not respond to antibiotic treatments.
Antibiotics cannot kill viruses. Viruses are treated with antiviral drugs.
Common diseases
Common diseases caused by bacteria are tuberculosis, typhoid, anthrax, food poisoning, etc.
Common diseases caused by viruses are AIDs, rabies, hepatitis B, chickenpox, polio, flu, measles, etc.
Miscellaneous features
Viruses can be crystallized in the laboratory due to their outer protein structure. Bacteria cannot be crystallized.
Bacteria can be saprophytic or parasitic, while viruses are only parasitic.
Many bacteria are helpful to us, like lactobacillus, gut bacteria, etc. Viruses are always pathogenic.
Frequently asked questions and answers
Can bacteria or viruses be seen with the eye?
In general, individual bacteria or viruses cannot be seen with the naked eye. But bacterial colonies can be seen. However, one bacteria Thiomargarita Magnifica discovered by the US Department of Energy-Joint Genome Institute.
Can bacteria live without a host?
Yes, bacteria can live without a host. But viruses on the other hand cannot live without a host.
Do viruses produce toxins?
No viruses do not produce toxins. Toxins are exclusively produced by bacteria.
What about the transmission of the bacteria and the virus?
Do bacteria have nuclei?
Can bacteria survive freezing?
@Leah Cole, bacteria do not have a nucleus and some of them can survive in freezing temperatures. Only thing is their metabolic activity could be slow.