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Parasites vs. Bacteria: What's the Difference?

Edited by Janet White || By Harlon Moss || Updated on October 20, 2023
Parasites are organisms that live on or in a host, deriving benefits at the host's expense; bacteria are single-celled microorganisms.

Key Differences

Parasites are organisms that establish a relationship in which they benefit by deriving nutrients at the expense of another organism, the host. Bacteria, on the other hand, are microscopic single-celled organisms that can be found in diverse environments.
In terms of classification, parasites can belong to various kingdoms, including Animalia and Protozoa. Bacteria are classified under the kingdom Bacteria (or Monera in some older systems).
Many parasites are multicellular, such as tapeworms and lice, and have complex life cycles. Bacteria are unicellular and reproduce primarily through binary fission.
Parasites can cause diseases like malaria (caused by Plasmodium) or sleeping sickness (caused by Trypanosoma). Bacteria can lead to infections such as strep throat, tuberculosis, and bacterial pneumonia.
Both parasites and bacteria can be pathogenic (disease-causing) or non-pathogenic. Some parasites live in harmony with their hosts without causing harm, and some bacteria play vital roles in processes like fermentation and decomposition.

Comparison Chart


Can be unicellular or multicellular
Always unicellular


Varies (e.g., Animalia, Protozoa)
Bacteria (or Monera)


Can cause malaria, sleeping sickness, etc.
Can cause TB, strep throat, etc.


Often complex life cycles
Primarily binary fission


Derive benefits at host's expense
Diverse roles including beneficial ones

Parasites and Bacteria Definitions


Entities that benefit at the expense of another.
Some consider certain apps as digital parasites, draining device resources.


Reproduce by binary fission.
Under favorable conditions, bacteria can reproduce rapidly.


Can be internal or external in hosts.
Tapeworms are internal parasites found in intestines.


Single-celled microorganisms.
Bacteria in yogurt help in its fermentation.


Organisms that live off another organism.
Fleas are parasites that feed on the blood of their hosts.


Can be pathogenic or beneficial.
Some bacteria cause infections, while others aid digestion.


Often cause harm to their hosts.
Parasites can weaken plants, making them susceptible to diseases.


Found in diverse environments.
Bacteria exist in soil, water, air, and even extreme conditions.


Dependent on their hosts for survival.
Lice are parasites that can't survive long without a human host.


Essential for many ecological processes.
Decomposing bacteria help break down dead organic material.


(Biology) An organism that lives and feeds on or in an organism of a different species and causes harm to its host.


Plural of bacterium.


One who habitually takes advantage of the generosity of others without making any useful return.


One who lives off and flatters the rich; a sycophant.


A professional dinner guest, especially in ancient Greece.


Plural of parasite


Can parasites be beneficial?

While many parasites are harmful, some have mutualistic relationships where both the host and parasite benefit.

What are parasites?

Parasites are organisms that live on or in a host, deriving benefits at the host's expense.

Why are some parasites considered vectors?

Some parasites can transmit diseases between hosts, thus acting as vectors.

Are all bacteria harmful?

No, while some bacteria are pathogenic, many are beneficial or neutral to humans.

Can humans have beneficial bacteria?

Yes, the human gut hosts beneficial bacteria vital for digestion and overall health.

Can parasites infect plants?

Yes, parasites can infect both animals and plants.

Are all bacteria unicellular?

Yes, bacteria are single-celled microorganisms.

Can parasites live independently?

Most parasites are dependent on their hosts for survival, but some stages might survive briefly independently.

How can one protect against parasites?

Protective measures vary by parasite but include personal hygiene, safe water and food consumption, and using repellents.

How can harmful bacteria be treated?

Harmful bacterial infections can often be treated with antibiotics.

How do parasites spread?

Parasites spread through various means, including water, air, vectors, or direct contact.

Can bacteria live in extreme conditions?

Yes, certain bacteria, called extremophiles, thrive in extreme environments.

How do bacteria reproduce?

Bacteria primarily reproduce by binary fission.

Are all parasites microorganisms?

No, parasites can range from microscopic entities to larger multicellular organisms like worms.

What's a common disease caused by parasites?

Malaria is a common disease caused by the Plasmodium parasite.

How do bacteria benefit the environment?

Bacteria play roles in decomposition, nitrogen fixation, and other vital ecological processes.

Are bacteria visible to the naked eye?

Most bacteria are microscopic, but some colonies are visible when they aggregate.

Do all hosts harmed by parasites?

While many hosts are harmed, some coexist with parasites without noticeable harm.

How do beneficial bacteria aid digestion?

Beneficial bacteria break down complex molecules, helping the host to absorb nutrients.

How do bacteria obtain nutrients?

Bacteria absorb nutrients from their environment.
About Author
Written by
Harlon Moss
Harlon is a seasoned quality moderator and accomplished content writer for Difference Wiki. An alumnus of the prestigious University of California, he earned his degree in Computer Science. Leveraging his academic background, Harlon brings a meticulous and informed perspective to his work, ensuring content accuracy and excellence.
Edited by
Janet White
Janet White has been an esteemed writer and blogger for Difference Wiki. Holding a Master's degree in Science and Medical Journalism from the prestigious Boston University, she has consistently demonstrated her expertise and passion for her field. When she's not immersed in her work, Janet relishes her time exercising, delving into a good book, and cherishing moments with friends and family.

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