20 Examples of Gram Positive and Gram Negative Bacteria

The bacterial recognition and classification method by the Tincture of Gram, it was invented by the Danish scientist Christian Gram in 1884 and from there it derives its name.

It consists of adding a specific series of pigments and mordants to a laboratory sample, thus achieving a pink or violet stain, depending on the type of bacteria: Gram positive they respond to pigment and will appear purple under the microscope; while the Gram negative they resist staining and will make it red or pink in color.

This difference in response shows a different composition of the cell envelope, since the gram-positive ones have a thick layer of peptidoglycan (murein), which gives them great resistance but makes them retain the dye much better.

Gram-negative ones, on the other hand, have a double lipid membrane in their envelope, so they require a much thinner peptidoglycan layer and, therefore, do not stain in the same way.

This method reveals a natural bacterial typology, useful when identifying the species and especially the antibiotic required to combat it.

Although gram-positive bacteria are a varied and majority group, with the presence of mobile organisms (flagellates) and even photosynthetic. Gram negatives are responsible for many of the deadliest known bacterial diseases.

Examples of gram-positive bacteria

  1. Staphylococcus aureus. Responsible for abscesses, dermatitis, localized infections and possible gastroenteritis.
  2. Streptococcus pyrogenes. Cause of suppurative infections in the respiratory tract, as well as rheumatic fever.
  3. Streptococcus aglactiae. Common in cases of neonatal meningitis, endometritis and pneumonia.
  4. Streptococcus faecalis. Usual in biliary and urinary tract infections, inhabits the human colon.
  5. Streptococcus pneumoniae. Responsible for pneumonia and respiratory tract infections, as well as otitis, meningitis and peritonitis.
  6. Streptococcus sanguis. Causative of endocarditis, when it enters the bloodstream through lesions in its habitat, the mouth and the dental mucosa.
  7. Clostridium tetani. Bacteria responsible for tetanus enter the body from the ground through trauma to the extremities.
  8. Bacillus anthracis. It is the well-known anthrax bacterium, both in its cutaneous and pulmonary versions.
  9. Clostridium botullinum. Causative of classic and infant botulism, it lives in the soil and in poorly preserved food.
  10. Clostridium perfringes. This bacterium secretes toxins that destroy the cell wall, and is responsible for gaseous gangrenes, necrotizing enteritis, and endometritis.

Examples of gram-negative bacteria

  1. Neisseria meningitidis. Dangerous bacterium that causes meningitis and meningococcemia, colonizes the human respiratory tract and ascends to the meninges via the bloodstream.
  2. Neisseria gonorrhoeae. Known for being the cause of gonorrhea, a common sexually transmitted disease.
  3. Escherichia coli. A usual inhabitant of the human colon, it is involved in the so-called “traveler’s diarrhea”, as well as in neonatal meningitis, sepsis and urinary infections.
  4. Salmonella typhi. Bacteria responsible for the disease known as typhoid fever, is usually transmitted by the fecal-oral route: water contamination, poor disposal of excreta or faulty hygiene.
  5. Salmonella enteritidis. It usually causes enterocoitis and septicemia with abscesses if it passes from the intestine into the blood.
  6. Haemophilus influenzae. Usually aerobic bacillus, it is responsible for numerous meningitis, otitis, sinusitis, bronchopneumonia, cellulitis and septic arthritis.
  7. Bordetella pertussis. Cause of the disease known as whooping cough, with high infant mortality.
  8. Brucella abortus. It causes brucellosis, a disease of cattle that is transmitted to man by contact with animals or by ingesting unpasteurized dairy products.
  9. Francisella tularensis. Responsible for the so-called “rabbit fever” or tularemia, it is transmitted to man by vectors (mites or other types of exoparasites) of rabbits, deer and similar animals.
  10. Pasteurella multocida. Anaerobic bacillus, transmitted by the bite of infected pets, such as cats and dogs. It spreads through the skin and infects the respiratory system, also causing cellulite.