Difference Between Bacteria and Mollicutes

Bacteria are single-celled creatures characterized by a peptidoglycan-based cell wall. The genomes of mollicutes are extremely basic since they are single-celled creatures with no cell wall.

What are Bacteria?

Definition − Bacteria make up a sizable taxonomic category known as the Domain Bacteria, which includes a wide variety of unicellular creatures distinguished by their peptidoglycan cell wall.

Origins − Bacteria are thought to have originated from an RNA-containing cell around three billion years ago.

Structure − Bacteria are defined as prokaryotic because they lack a nucleus and a nuclear envelope. A cell wall and membrane are present. In contrast to fungus cells, bacterial cells contain a protein and carbohydrate compound termed peptidoglycan for their cell wall. There are no membrane-bound structures in the cell, however, DNA can be detected in one area, and ribosomes may be found in the cytoplasm. Bacteria range in size from 0.2 m to 2.0 m. The size of the genome is around 0.6–0.8 megabases.

Habitat and lifestyles − Bacteria come in many forms and may be found in almost any environment. In both animals and humans, there are beneficial bacteria that dwell in the digestive tract and aid in the breakdown of food and the creation of essential nutrients. Furthermore, there are pathogenic microorganisms that can result in serious, often fatal, diseases in animals. People can get bacterial meningitis and food poisoning from them. An abundance of free-living bacteria decomposes organic materials and returns nutrients to the environment. Parasites are parasites that create sickness by residing within a plant or animal host.

Examples − Bacteria such as Rhizobium are important for plant growth because they enrich the soil with nutrients. Disease-causing microorganisms in animals include E. coli, Clostridium difficile, and Streptococcus (including humans).

What are Mollicutes?

Definition − Mollicutes are defined as a bacterial cellular class since their members lack a cell wall and their sizes range from very tiny to sub-nanometer.

Origins − Mollicutes are generally believed to have evolved from gram-positive cell-walled bacteria around 65 million years ago. They descended from a lineage of bacteria that had a genetic make-up low in cytosine and guanine. The appearance of mollicutes follows the development of bacteria.

Structure − As opposed to bacteria, mollicutes lack a cell wall. They lack the large genomes of bacteria and are often much smaller. They are the simplest creatures capable of self-replication because of the presence of ribosomes and DNA. Flask-shaped or occasionally coiled, their cells are surrounded by a plasma membrane rich in cholesterol. The proteins actin and tubulin are present in the cells.

Habitat and lifestyles − The lifestyle of mollicutes is parasitic, meaning that they inhabit the bodies of other species including plants and animals. Parasites may cause a wide range of health problems for people, from respiratory illness to genitourinary infections. Due to their parasitic nature, mollicutes that infect insects have even been studied as potential agents for biological control of nuisance insects.

Examples − Mycoplasma and Spiroplasma are two common examples of mollicutes. When a person's immune system is compromised, mycoplasma can cause an infection. Several types of plant diseases may be traced back to the Spiroplasma genus.

Differences between Bacteria and Mollicutes

The following table highlights how Bacteria are different from Mollicutes −





The cell wall of bacteria is made of peptidoglycan, making them single-celled prokaryotes.

Mollicutes lack a cell wall and are therefore classified as primitive.

Taxonomic classification

Bacteria are classified as members of the domain of life.

Class Mollicutes describes a group of organisms.


Bacterial cells are typically between 0.5 and 2.0 µm in size.

Mollicute cells are typically between 0.2 and 0.3 µm in size.

Cell wall

The bacterial cell is surrounded by a cell wall that is composed of peptides and glycogen molecules.

The mollicute cell has no cell wall.


The genome size of bacteria is between 0.6 to 0.8 megabases, whereas that of mollicutes is only 0.2 megabases.

Genomes of mollicutes are smaller than those of bacteria, with sizes varying from 578 to 2500 kilobases.


Bacteria may either live alone, or they can live in symbiosis with another organism (called a commensal or a parasite).

Parasitism is a common trait among mollicutes, which can occur in either plant or animal hosts.


In this article, we explained in detail all the differences between Bacteria and Mollicutes.

Updated on: 19-Jan-2023


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