Difference Between Parasite and Bacteria

Key Difference – Parasite vs Bacteria

The key difference between parasite and bacteria is that the bacteria are unicellular microscopic prokaryotes living all over while parasites are the organisms that live on or in their hosts while causing infections to hosts. Parasite and bacteria are organisms that resemble very primitive organisms but have great adaptations to survive in different environmental conditions. To humans, these organisms are paramount because the majority of human infections are caused by them. Sometimes, certain bacteria are considered as parasites. In this article, the difference between parasite and bacteria will be conferred.

What is a Parasite?

Parasitism is a form of symbiotic association in which parasite get benefits while harming the host. Thus, parasites cause infections to the host species. If an organism lives in or on a host while obtaining nutrients from the host, that organism is defined as a parasite. Parasites can be multicellular or unicellular and are usually smaller than their hosts. Examples of unicellular parasites include various bacteria and fungi species, and that of multicellular organisms include ticks, lice, and certain worms (Helminthes). The main characteristics of parasites are; undergoing simple and complex life cycles, involving two or more hosts, and showing both sexual and asexual reproduction alternatively. Based on the living place, there are two types of parasites; endoparasites and ectoparasites. Endoparasites live inside the body of their host, and ectoparasites live on the outer surface or in the superficial tissues of the hosts. Hosts are two types; (a) definitive hosts, where sexual reproduction of parasite occurs, and (b) intermediate host, where asexual reproduction of the parasite takes place.

differnce between parasite and bacteria-

Louse – A Parasite

What are Bacteria?

Bacteria are a primitive microscopic unicellular prokaryotes with a great diversity. The first bacterial cells are believed to have appeared about 3.5 billion years ago. Since bacterial species show great species diversity, they live in almost all the habitats (even in some extreme living conditions) on earth. Bacteria do not have an organized nucleus. Instead, they have just a single stranded DNA. In addition, bacterial cells do not contain endoplasmic reticulum, Golgi apparatus, lysosomes, mitochondria, micro-filaments, microtubules, and centrosomes. The cell wall is made up a polymer called peptidoglycan, which is unique to bacterial cells. Bacterial cell exhibit one of three basic shapes, namely: bacillus, coccus, and spirillum. Many bacteria cells possess different types of appendages including flagella and pili that are used mainly for locomotion.

Bacteria can be identified by a staining process called the Gram stain. According to this stain, bacteria can be either gram-positive or gram-negative. The reproduction of bacteria is asexual, and it occurs through budding or fusion. Bacteria are vital organisms to human as some of them cause diseases to human beings and some have benefits. Some disease-causing bacteria and the disease they cause include Vibrio cholera, Corynebacterium diphtheria, Helicobacter pylori, and Rickettsia Typhi causing cholera, diphtheria, peptic ulcers, and typhus respectively. Some benefits of bacteria include nitrogen fixation, genetic engineering, decomposition, and bioremediation.

parasite vs. bacteria

Scanning electron micrograph of Escherichia coli

 What is the difference Parasite and Bacteria?

 Definition of Parasite and Bacteria Parasite

Bacteria: Bacteria are unicellular microscopic prokaryotes live in all over the world.

Parasites: Parasites are the organisms that live on or in their hosts while causing infections to hosts.

Characteristics of Parasite and Bacteria

Bifurcation of Organisms

Bacteria: Bacteria are unicellular organisms.

Parasites: Parasites are either unicellular or multicellular.

Some bacterial species are considered as parasites.

Type of Reproduction

Bacteria: Bacteria show only asexual reproduction.

Parasites: Parasites show both asexual and sexual reproduction alternatively.

Causing diseases/ infections

Parasites: All the parasites cause infections to their hosts.

Bacteria: Only some bacteria cause infections to their hosts.

Requirement of a host

Parasites: Parasites always need a host/hosts to complete their life cycle.

Bacteria: Not all bacteria need hosts for their survival.


Parasites: Parasites always get nutrients from their hosts.

Bacteria: Some bacterial species can produce their own foods (cyanobacteria).


Parasites: Some parasites are microscopic, and some are not.

Bacteria: Bacteria are microscopic organisms.


Parasite: Examples of parasites are ticks, lice, and certain worms (Helminthes)

Bacteria: Examples of parasites are Bacillus antbracis, Clostridium botulinum, Chlamydia trachomatis, Helicobacter pylori, Yersinia pestis.


Image Courtesy:
“Menacanthus-chewing-louse-2″ by Alan R Walker – Own work. (CC BY-SA 3.0) via Wikimedia Commons 
“E. coli Bacteria (7316101966)” by NIAID – E. coli Bacteria. (CC BY 2.0) via Wikimedia Commons