What is the Difference Between Microbes and Bacteria

The main difference between microbes and bacteria is that microbes represent microscopic organisms whereas bacteria are a form of single-celled microbes. Furthermore, microbes can be either prokaryotes or eukaryotes while bacteria are prokaryotes. Moreover, the seven groups of microbes are bacteria, archaea, protozoa, algae, fungi, viruses, and multicellular animal parasites.

Microbes and bacteria are two types of microscopic organisms that are not visible to the naked eye. They can be beneficial for decomposing organic materials, nitrogen fixation, etc, and they can also be harmful as some of them are pathogens or parasites.

Key Areas Covered

1. What are Microbes
     – Definition, Types, Importance
2. What are Bacteria
     – Definition, Types, Importance
3. What are the Similarities Between Microbes and Bacteria
     – Outline of Common Features
4. What is the Difference Between Microbes and Bacteria
     – Comparison of Key Differences

Key Terms

Bacteria, Eukaryotes, Microbes, Microscopic Organisms, Pathogens, Parasites, Prokaryotes

What are Microbes

‘Microbes’ is the general term used to describe all microscopic organisms. They drastically vary in cellular organization and structure. Also, microbes can be either unicellular, multicellular or live in cell clusters. Significantly, microbes are widespread in nature, performing an important role in ecosystems. Bacteria, archaea, protozoa, algae, fungi, viruses, and multicellular animal parasites are the seven types of microbes.

Archaea

Archaea are prokaryotes that live in extreme conditions. They lack a peptidoglycan cell wall. The major types of archaea include methanogens that produce methane, halophiles that live in salty environments, thermophiles that live at extremely hot temperatures, and psychrophiles that live in cold temperatures. Moreover, they have bacteriorhodopsin to capture sunlight.

Protozoa

Protozoa are eukaryotes that are significantly unicellular. They obtain nutrients through ingestion. Their cell wall is made up of cellulose. Generally, protozoans are classified based on their locomotion as flagellates (use flagella for locomotion), ciliates (use cilia for locomotion), amoeboids (use pseudopodia), and sporozoans (non-motile). Also, they can be either autotrophs or heterotrophs in the mode of nutrition.

Figure 1: A Protozoan

Fungi

Fungi are either unicellular or multicellular eukaryotes, including mushroom, molds, and yeast. Their cell wall is made up of chitin. Generally, fungi produce characteristic, filamentous tubes known as hyphae. They can be classified based on their mode of nutrition as decomposers (absorb organic nutrients from the environment), symbionts (maintain beneficial relationships with plants), and parasites (maintain harmful relationships with other organisms). Fungi reproduce through the production of spores.

Figure 2: Fungi

Algae

Algae are either unicellular or multicellular eukaryotes. Also, they either live in water, damp environments or on rocks, undergoing photosynthesis. Green algae, red algae, brown algae, euglenoids, diatoms, etc. are the main types of algae.

Figure 3: Red Algae

Viruses

Viruses are non-living particles that essentially require a host for the replication. Generally, a viral particle consists of a core with genetic material, which can be either DNA or RNA and a protein coat. Viruses often infect both prokaryotic and eukaryotic cells and cause diseases.

Figure 4: H1N1 Influenza Virus Particles

Multicellular Animal Parasites

Multicellular animal parasites include both flatworms and roundworms. Though they are classified under microbes, some of them are large enough to see under the naked eye. But, they spend several stages of their life cycle as microscopic organisms. Generally, they are parasitic on higher organisms.

What are Bacteria

Bacteria are unicellular prokaryotes that lack a nucleus. They can be either autotrophs or heterotrophs. One of the main characteristic features of bacteria is the presence of a cell wall made up of peptidoglycans. However, bacteria do not contain membrane-bound organelles. However, some bacteria contain an envelope surrounding the cell wall. Since bacteria are prokaryotes, their genetic material occurs in the cytoplasm. Another characteristic feature of bacteria is the presence of extrachromosomal DNA elements known as plasmids, which are important in recombinant DNA technology. Also, all of the biochemical reactions of the bacterial cell occur inside the cytosol.

Figure 5: Bacteria

Furthermore, the four major shapes in which bacteria can exist are bacillus (rod shape), coccus (spherical shape), spirilla (spiral shape), and Vibrio (curved shape). In addition, based on the structure of the cell wall, bacteria can be classified as Gram-positive and Gram-negative bacteria. Also, bacteria produce several types of responses to gaseous oxygen. Based on the response, bacteria can be classified as aerobic bacteria, which tend to live in the presence of oxygen, anaerobic bacteria, which tend to live without oxygen, and facultative anaerobes, which can live in both environments.

Similarities Between Microbes and Bacteria

• Microbes and bacteria are two types of microscopic organisms that cannot be observed by the naked eye.
• They can be beneficial in decomposing organic matter, producing oxygen, fixing nitrogen, maintaining human health, etc.
• However, some of them are harmful since they can be pathogenic, causing diseases in humans.

Difference Between Microbes and Bacteria

Definition

Microbes refer to a very small living thing, especially one that causes disease and can only be seen with a microscope, whereas bacteria refer to a large group of unicellular microorganisms that have cell walls, but lack organelles and an organized nucleus, including some which can cause disease. Thus, this is the main difference between microbes and bacteria.

Cellular Organization

Further, the cellular organization is also a major difference between microbes and bacteria. Microbes can be either prokaryotes or eukaryotes while bacteria are prokaryotes.

Number of Cells

Another difference between microbes and bacteria is that microbes can be either unicellular or multicellular while bacteria are unicellular.

Significance

Microbes can be either bacteria, archaea, protozoa, algae, fungi, viruses or multicellular animal parasites while bacteria are a type of microbes. Hence, this is also a difference between microbes and bacteria.

Conclusion

Microbes are a group of microscopic organisms including bacteria, archaea, protozoa, algae, fungi, viruses, and multicellular animal parasites. They can be either prokaryotes or eukaryotes and either unicellular or multicellular. In contrast, bacteria are a type of unicellular, prokaryotic, microbes. Both microbes and bacteria can be either beneficial or harmful. However, the main difference between microbes and bacteria is their organization.

References:

1. “Microbes and the World|Boundless Microbiology.” Lumen Learning, Lumen, Available Here.

Image Courtesy:

1. “Protozoa sp. (16255395372)” By Donald Hobern from Copenhagen, Denmark – Protozoa sp. (CC BY 2.0) via Commons Wikimedia  
2. “Mycena interrupta” By JJ Harrison – Own work (CC BY-SA 3.0) via Commons Wikimedia  
3. “Red Algae on bleached coral” By Johnmartindavies – Own work (CC BY-SA 3.0) via Commons Wikimedia  
4. “H1N1 Influenza Virus Particles (8411599236)” By NIAID – H1N1 Influenza Virus Particles (CC BY 2.0) via Commons Wikimedia  
5. “Bacteria” By Umberto Salvagnin (CC BY 2.0) via Flickr