Micrococcus luteus characteristics, morphology, diseases

Simon Doyle

Micrococcus luteus It is a bacterium that belongs to the group of gram-positive ones. It is found as part of the microbiota of the body surfaces of mammals, as well as some internal areas of the body.

It was discovered by Sir Alexander Fleming. Through multiple studies and investigations, Fleming determined that this bacterium is highly sensitive to lysozyme. It is also susceptible to bacitracin. Even this characteristic is what allows it to be differentiated from other similar bacteria, the Staphylococcus aureus.

Micrococcus luteus bacterial cells. Source: By Photo Credit: Janice CarrContent Providers (s): CDC / Janice Carr [Public domain], via Wikimedia Commons

Generally the Micrococcus luteus it is a non-pathogenic bacteria. However, when certain conditions such as immunosuppression of the individual or the passage of the bacteria into the bloodstream occur, certain pathologies can be generated.

As a bonus, the Micrococcus luteus previously it was known as Micrococcus lysodeikticus.

Article index

  • 1 Taxonomy
  • 2 Morphology
  • 3 General characteristics
    • 3.1 Habitat
  • 4 Diseases
    • 4.1 Endocarditis
    • 4.2 Septic arthritis
    • 4.3 Bacterial meningitis
    • 4.4 Pneumonia
  • 5 Treatment
  • 6 References


The taxonomic classification of the Micrococcus luteus it is:

Domain: Bacteria

Edge: Actinobacteria

Order: Actinomycetales

Family: Micrococcaceae

Gender: Micrococcus

Species: Micrococcus luteus.


The Micrococcus luteus It is a bacterium that has a spherical shape, with an approximate diameter of 0.5 - 3.5 microns. Viewed under the microscope, bacteria are generally seen to group into tetrads (groups of 4). On their surface they do not have cilia or flagella.

The colonies seen in the cultures are circular, smooth, and convex. They can have a shiny or opaque surface. Likewise, they manifest a greenish yellow or yellowish coloration..

The cell wall of these bacteria has peptidoglycan, as well as a long-chain polysaccharide, known as teichuronic acid (TUA). This compound has an important role in the protection of the bacteria, as well as in its interaction with the cells it infects. This polysaccharide is linked through covalent bonds with the peptidoglycan.

General characteristics

They are gram positive

The Micrococcus luteus It is a bacterium that, when subjected to the Gram staining method, acquires a characteristic violet coloration. This is so thanks to the presence of peptidoglycan in its cell wall, which retains the dye particles, resulting in the aforementioned staining..

They are catalase positive

This bacterium has the ability to synthesize the enzyme catalase. Due to this, it is capable of decomposing hydrogen peroxide into water and oxygen, according to the following chemical reaction:

2HtwoORtwo -- 2HtwoO + Otwo

They are urease positive

The Micrococcus luteus synthesizes the enzyme urease. This enzyme is responsible for catalyzing the hydrolysis reaction of urea to form carbon dioxide and ammonia. All this based on the chemical reaction:

CO (NHtwo)two + 2H+ + 2HtwoO - 2NH4+ + COtwo + HtwoOR

Can reduce nitrates to nitrites

Because this bacterium synthesizes the enzyme nitrate reductase, it is capable of reducing nitrates to nitrites as in the following reaction:

NOT3 + 2e- + 2H - NOtwo + HtwoOR

Absorb UV light

Although this is still in an experimental state, certain strains of this bacterium that are capable of absorbing ultraviolet light have been studied, specifically the wavelengths of 350 to 475 nanometers..

If this is reliably verified, it would be very useful in the development of products that help minimize direct skin exposure to these wavelengths of UV light. This is important because that wavelength has been linked to skin cancer..

Micrococcus luteus culture. Source: By A doubt [CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0)], from Wikimedia Commons

They are mesophilic

The approximate optimum growth temperature of the Micrococcus luteus is 30 ° C, so they are considered mesophilic microorganisms.

They are strict aerobics

The Micrococcus luteus You necessarily need oxygen to carry out your metabolic processes. Due to this, it must necessarily be found in environments where there is a high availability of this chemical element..


This bacterium has been isolated from a large number of habitats, such as soil, water, air, and dust. It has been shown to be part of the normal bacterial flora on the body surface of mammals.

It is also capable of colonizing the oral cavity, oropharynx and upper respiratory tract in humans..


Among the most prominent pathologies caused by Micrococcus luteus Endocarditis, septic arthritis, meningitis and lung infections (pneumonia) can be mentioned.


Bacterial endocarditis is a pathology that refers to the inflammation of the internal structures of the heart due to the establishment of bacterial colonies in them. Mainly affects the atrioventricular valves (mitral and tricuspid).


The symptoms are wide and varied, and may be due to other pathologies. This is why it is important to go to the doctor as soon as one appears. Among the most common symptoms are:

  • Fever
  • Shaking chills
  • Heavy sweating
  • Pain in muscles and joints
  • Fatigue
  • Exertional dyspnea with orthopnea (shortness of breath when lying down).

Septic arthritis

It is a rare pathology that occurs when a bacterial agent invades the space of a joint. Bacteria can reach the joint through the bloodstream or through an injury or wound..


The most common symptoms of this disease are:

  • Joint pain and swelling
  • Inability to move the joint
  • Feverish state

Bacterial meningitis

Meningitis is an inflammation of the meninges. These are thin connective tissue membranes that line the organs of the central nervous system..


Symptoms of meningitis include:

  • Headache
  • Fever
  • Stiff neck
  • Sensitivity to light
  • Altered mental state
  • Nausea and vomiting


Pneumonia is an infection that occurs in the lower respiratory tract and can be caused by bacteria or viruses..

In the case of bacterial pneumonia, the bacteria that normally colonize the airways can reach the pulmonary alveoli and cause lesions there.


The most representative symptoms of this pathology are:

  • Fever
  • Excessive sweating
  • Shivering chills
  • Chest pain when coughing or breathing
  • Vomiting
  • Sickness
  • Diarrhea
  • Cough that can carry phlegm
  • In people with a weakened immune system or the elderly over 65, there may be a decrease in body temperature and disorientation..


Because all these pathologies are caused by the bacteria Micrococcus luteus, the treatment to be followed to eradicate it is antibiotic therapy.

In the case of Micrococcus luteus it has been determined to be sensitive to vancomycin and cephalosporin. However, when a bacterial infection is detected, the doctor should request a culture and study the bacterial susceptibility there in order to establish the most effective treatment.


  1. Lingyi Lynn Deng, Alice A. Alexander, Sijin Lei, and John S. Anderson, “The Cell Wall Teichuronic Acid Synthetase (TUAS) Is an Enzyme Complex Located in the Cytoplasmic Membrane of Micrococcus luteus, " Biochemistry Research International, vol. 2010, Article ID 395758, 8 pages, 2010.
  2. Micrococcus. Retrieved from: Microbewiki.com
  3. Micrococcus luteus. Obtained from: bibbiologia.usal.es
  4. Micrococcus luteus. Retrieved from: eol.org
  5. Pneumonia. Obtained from: mayoclinic.org
  6. Souhami, L., Feld, R., Tuffnell, P. and Feller, T. (1979). Micrococcus luteus pneumonia: A case report and review of the literature. Pediatric, blood & cancer. 7 (4). 309-314.

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