Gram-positive bacteria show blue or purple after gram-staining in a laboratory test. They have thick cell walls. Gram-negative bacteria show pink or red on staining and have thin walls. They release different toxins and affect the body in different ways.
Gram-positive and Gram-negative are types of bacteria.
There are many different types of Gram-positive and Gram-negative bacteria. These bacteria cause a wide range of different health issues.
People categorize gram-positive and gram-negative bacteria based on their structures and their appearance after Gram staining. Gram staining is a process of dying bacteria and then viewing them beneath a microscope.
This article discusses Gram-positive and Gram-negative bacteria. It also outlines their differences, the infections they cause, and discusses antibiotic resistance.
The following table provides an overview on Gram-positive and Gram-negative bacteria:
|Gram-positive bacteria||Gram-negative bacteria|
|Color after gram testing||Blue or purple||Pink or red|
|Cell wall thickness||Thick||Thin|
|Toxins||• emetic toxin|
• diarrheal enterotoxins
|Types||• Staphylococcus aureus|
• Staphylococcus epidermidis
• Staphylococcus saprophyticus
• Streptococcus pneumoniae
• Streptococcus pyogenes
• Streptococcus agalactiae
• Corynebacterium diphtheriae
• Bacillus anthracis
|• Vibrio cholerae|
• Escherichia coli
• Bartonella henselae
• Salmonella typhi
Gram-positive and Gram-negative bacteria are two different types of bacteria.
One method that scientists use to classify bacteria is Gram staining, which is the most commonly performed laboratory procedure in microbiology.
The term “Gram” refers to a specimen staining method developed by Hans Christian Gram in 1884. It involves staining an organism with crystal violet or methylene blue dye and then observing the organism under a microscope.
Gram-positive bacteria can be cocci- (spheres) or bacilli- (rod) shaped, or have branching filaments.
Gram-negative bacteria have an outer membrane. However, they have a thinner peptidoglycan cell wall. This means they do not hold the blue dye used in Gram testing and do not appear blue. Instead, they appear red or pink in color.
Gram-negative bacteria are among the
Below are the specific characteristics of Gram-positive and Gram-negative bacteria.
Gram-positive bacteria have the following characteristics:
- Membranes: Gram-positive bacteria
do not havea protective outer membrane.
- Cell wall: They have a thick peptidoglycan cell wall.
- Shape: Gram-positive bacteria are sphere- or rod-shaped, or they have branching filaments.
- Toxins: These bacteria also contain certain toxins that can cause a number of food-borne diseases.
Toxins presentin Gram-positive bacteria include:
- emetic toxin
- diarrheal enterotoxins
Gram-negative bacteria have the following characteristics:
- Membrane: Gram-negative bacteria have
two membranes— one external and one internal.
- Cell wall: These bacteria also have a thinner peptidoglycan cell wall than Gram-positive bacteria, which sits between their two membranes.
- Shape: They can be spherical-, rod-, or spiral-shaped.
- Toxins: If something disturbs the cell wall of Gram-negative bacteria, they can release endotoxins.
There are a number of different types of Gram-positive bacteria.
Infections it can cause include:
- infective endocarditis, an infection that happens when bacteria enter the bloodstream and settles in the lining of the heart, a blood vessel, or a heart valve
- skin and soft tissue infections, such as impetigo, folliculitis, and cellulitis
- osteomyelitis, an infection that causes pain in the legs
- septic arthritis, a type of join infection
- prosthetic device infections, a complication that can happen after joint replacement surgeries
- pulmonary infections: such as pneumonia
- gastroenteritis, inflammation of the gastrointestinal tract that can cause vomiting and diarrhea
- meningitis, inflammation of the lining that surrounds the brain and spinal cord
- toxic shock syndrome, a rare and life threatening condition that happens when bacteria release harmful toxins
- urinary tract infections (UTIs), an infection of the bladder, urethra, or kidneys
Staphylococcus epidermidis can become infectious if it enters a human host. The bacteria are one of the
It commonly infects the skin around prosthetic devices and catheters, which can then cause blood infections to develop.
This type of bacteria can also cause a number of complications such as:
- acute kidney infection
- urethritis, an infection that affects the urethra
Streptococcus pneumoniae is the cause of community-acquired pneumonia (CAP). CAP is the
This type of bacteria also
- ear infections
Streptococcus pyogenes can cause a wide array of health issues that
Streptococcus pyogenes can cause the following infections:
- sore throat
- cellulitis, erysipelas, or impetigo, which are types of skin infections
- scarlet fever
- necrotizing fasciitis, which causes tissue death
- glomerulonephritis, which is damage to the small filters in the kidney
- rheumatic fever, which refers to a condition that affects the heart, joints, skin, and brain
Streptococcus agalactiae colonizes the vagina and is often present in infants.
This type of bacteria can cause illness in people of all ages. However, it is a
Pregnant people require screening for this bacteria at
They make up a core part of a person’s microbiome. The microbiome refers to the entire habitat of a person’s body.
Enterococci can also cause a variety of infections, including biliary tract infections and UTIs.
The toxin-producing strains of this bacteria can
There are different types of diphtheria that can affect the respiratory system and the skin.
Bacillus anthracis is a rod-shaped, Gram-positive bacteria. This type of bacteria occurs naturally in soil around the world and
This bacteria can cause the seriously infectious disease anthrax.
People can develop anthrax if they come in contact with animals that have the bacterial infection or animal products containing the bacteria.
There are a number of different types of anthrax that can affect different parts of the body, such as the skin, respiratory system, or gastrointestinal system.
There are a number of different types of Gram-negative bacteria.
Vibrio cholerae is a type of bacteria that
A person usually develops cholera after the bacteria enter their body through the mouth. This type of bacteria is typically present in food or water that has been contaminated with human waste.
Cholera can cause a person to experience a severe case of watery diarrhea, which can cause extreme loss of fluid and electrolytes. This may also lead to severe dehydration which can be fatal.
Escherichia coli is a type of bacteria that medical professionals often refer to as E. coli. It can cause a number of illnesses
Some cases of this infection are very mild, but others can be severe or life threatening.
Bartonella henselae is a Gram-negative bacteria that
A person usually contracts this bacteria after they receive a bite, scratch, or lick from a cat that has an infection, which leads to the development of cat scratch disease.
Campylobacter is one of the
A person can get a campylobacter infection if they eat raw or undercooked poultry, or eat food that has come into contact with raw or undercooked poultry.
A person may also get this infection from:
- eating other foods containing the bacteria, including seafood, meat, and produce
- contact with animals that have an infection
- drinking untreated water
- drinking raw milk
Legionella is a type of bacteria that is often present in freshwater environments, such as lakes and streams. This type of bacteria can become a health concern if it spreads in human-made building water systems.
This type of bacteria
Salmonella is a bacteria that causes around
The most common way for a person to contract a salmonella infection is through eating food containing the bacteria.
A person can develop typhoid fever if they consume food, drinks, and drinking water with fecal matter containing salmonella typhi.
Doctors can use the following treatment options.
Antibiotics are the
Common antibiotics that healthcare professionals prescribe to treat these infections include:
Treatment options for Gram-negative infections can be limited. Medical professionals will often prescribe antibiotics to treat Gram-negative bacterial infections.
Common antibiotics used to treat these infections include:
Antibiotic resistance occurs when bacteria change and adjust in response to antibiotic medications. They can become resistant to antibiotics. This makes the antibiotics less effective or can cause them to not work at all.
The misuse and overuse of antibiotics can cause antibiotic resistance.
There are a number of things that people can do to help prevent and manage antibiotic resistance. These
- only using antibiotics when a medical professional prescribes them
- never demanding antibiotics if a medical professional advises against their use
- always following a medical professional’s advice when using antibiotics
- never sharing or using leftover antibiotics
Preventing infection can also help prevent and manage antibiotic resistance.
Ways a person can prevent infections include:
- regularly washing their hands
- preparing food hygienically
- avoiding close contact with those who are ill
- keeping vaccinations up to date
Gram-positive and Gram-negative are two distinct types of bacteria.
Gram-positive bacteria appear blue or purple after Gram staining, while Gram-negative bacteria appear red or pink after gram staining.
There are many types of Gram-positive bacteria. These bacteria can cause infective endocarditis, gastroenteritis, meningitis, UTIs, impetigo, and CAP.
There are also a number of types of Gram-negative bacteria. These bacteria can cause salmonella, Legionnaires’ disease, cholera, cat scratch disease, and typhoid fever.
Medical professionals can treat both types of bacteria with antibiotics. However, Gram-negative bacteria are more prone to antibiotic resistance.