The key difference between Klebsiella and Pseudomonas is that Klebsiella is a genus of gram-negative bacteria belonging to the family Enterobacteriaceae, while Pseudomonas is a genus of gram-negative bacteria belonging to the family Pseudomonadaceae.
Gammaproteobacteria is a class of bacteria in the phylum of Pseudomonadota or Proteobacteria. This class contains about 250 genera. Many medically, ecologically, and scientifically important genera of bacteria belong to this class. Gammaproteobacteria is composed of all gram-negative bacteria. Therefore, Klebsiella and Pseudomonas are two different genera belonging to the class Gammaproteobacteria.
CONTENTS
1. Overview and Key Difference
2. What is Klebsiella
3. What is Pseudomonas
4. Similarities – Klebsiella and Pseudomonas
5. Klebsiella vs. Pseudomonas in Tabular Form
6. Summary – Klebsiella vs. Pseudomonas
What is Klebsiella?
Klebsiella is a genus containing bacteria that are Gram-negative, rod-shaped, and non-motile. The genus Klebsiella belongs to the family Enterobacteriaceae. The bacterial species of this genus contains a prominent polysaccharide-based capsule. Generally, Klebsiella species can occur in different environments, such as in soil, water, insects, plants, animals, and humans.

Figure 01: Klebsiella
Klebsiella is named after a German-Swiss microbiologist known as Edwin Klebs. The members of this genus tend to be shorter and thicker than other member in the family of Enterobacteriaceae. Their cells are rod-shaped, which are 0.3 to 1.5 µm wide and 0.5 to 5.0 µm long. The members of Klebsiella can normally be found singly, in pairs, in chains, or linked end to end. Moreover, Klebsiella species can be grown pretty easily in the laboratory as they do not have special growth requirements. However, they are facultatively anaerobic and need an ideal growth temperature of 35° to 37 °C and an ideal pH level of about 7.2. In plants, Klebsiella are found in a variety of plant hosts, and they can fix atmospheric nitrogen into a form that these plants can use. Furthermore, in animals, Klebsiella species like Klebsiella pneumoniae are clinically very important as they cause nosocomial infections and show a great deal of antibiotic resistance.
What is Pseudomonas?
Pseudomonas is a genus of gram-negative bacteria of the family Pseudomonadaceae. Pseudomonas species are rod-shaped and contain polar flagella, which help their mobility. They can be found in environments such as in water and plant seeds.

Figure 02: Pseudomonas
Moreover, members of this genus are aerobic, non-spore-forming, catalase-positive and oxidase-positive. Furthermore, Pseudomonas has been applied to cereal seeds to prevent the growth or establishment of crop pathogens and is also used as a bioremediation agent. However, the members of this genus form biofilms and are naturally resistant to penicillin. As animal pathogens, they cause nosocomial infections; as plant pathogens, they cause bacterial blotch and drippy gills in mushrooms.
What are the Similarities Between Klebsiella and Pseudomonas?
- Klebsiella and Pseudomonas are two different genera belonging to the class
- The members of these genera are rod-shaped and occur naturally.
- They are non-spore forming.
- The members of these genera are useful.
- Some members of these genera are also pathogens.
What is the Difference Between Klebsiella and Pseudomonas?
Klebsiella is a genus of Gram-negative bacteria that belongs to the family Enterobacteriaceae, while Pseudomonas is a genus of Gram-negative bacteria that belongs to the family Pseudomonadaceae. Thus, this is the key difference between Klebsiella and Pseudomonas. Furthermore, the members of Klebsiella are non-motile, while the members of Pseudomonas are motile.
The infographic below presents the differences between Klebsiella and Pseudomonas in tabular form for side-by-side comparison.
Summary – Klebsiella vs. Pseudomonas
Gammaproteobacteria is a class of bacteria in the phylum of Pseudomonadota. The bacteria in this class are medically, ecologically, and scientifically important groups of bacteria. All bacteria in this class are Gram-negative. Klebsiella and Pseudomonas are two different genera belonging to the class Gammaproteobacteria. Klebsiella belongs to the family Enterobacteriaceae, whereas Pseudomonas belongs to the family Pseudomonadaceae. So, this summarizes the difference between Klebsiella and Pseudomonas.
Reference:
1. “Klebsiella – An Overview.” ScienceDirect.
2. “Pseudomonas.” Medical Microbiology – NCBI Bookshelf.
Image Courtesy:
1. “Klebsiella Bacteria” By NIH Image Gallery (Public Domain) via Flickr
2. “Pseudomonas aeruginosa on blood agar” By HansN. – Own work (CC BY-SA 4.0) via Commons Wikimedia
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