Pseudomonas Luteola: Morphology, Oxidase Test & Gram Stain

Instructor: Adrianne Baron

Adrianne has taught high school and college biology and has a master's degree in cancer biology.

''Pseudomonas luteola'' is a bacteria that is found often in nature. We'll discuss its morphology and how to identify it using Gram stain, oxidase, and catalase tests.

Morphology of Pseudomonas luteola

Doesn't it seem like there is a never-ending list of bacteria to learn about? This is because they outnumber us by far. There are so many species of bacteria that we will probably never identify every single one. This lesson just tackles one today.

Pseudomonas luteola is a yellowish-orange, motile, and strictly aerobic bacteria. P. luteola is rod shaped, is often found in damp soil and is not capable of fermentation, the process of converting sugars into alcohols.

Now, most of the time, one of the first questions asked about bacteria is, 'does it cause a disease or is it a helpful bacteria?' P. luteola do not normally cause diseases, but can cause peritonitis, meningitis and septicemia. These could each potentially be life-threatening, but luckily an infection of this bacteria can easily be treated with antibiotics.

Identification Tests

When a patient presents with what appears to be a bacterial infection, then a sample is taken to identify the bacteria causing the infection. The three tests that are often run are the oxidase, Gram stain, and catalase test.

Oxidase Test

The oxidase test checks a bacteria's ability to produce the enzyme cytochrome c oxidase. This enzyme is important in the electron transport chain portion of aerobic respiration in bacteria. When a bacteria can produce cytochrome c oxidase, it is said to be oxidase-positive, and when bacteria cannot produce the enzyme, they are oxidase-negative. P. luteola is oxidase-negative.

Gram Stain

The Gram stain is a biological test that checks the composition of the bacterial wall, which can be thick and composed of a large amount of peptidoglycan, or thin and composed of just a thin layer of peptidoglycan.

Like P. luteola, this rod-shaped bacteria is Gram-negative, staining red.
Gram-negative test

Bacteria with the thick layer stain purple during the Gram stain tests because the purple crystals get stuck in the peptidoglycan layer. The bacteria is then decolored, and bacteria with the thin layer do not hold the purple crystals and stain red instead. P. luteola is Gram-negative, meaning it stains red and therefore have a thin layer of peptidoglycan.

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