Classification Of Gram Positive And Gram Negative Bacteria Pdf

classification of gram positive and gram negative bacteria pdf

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Gram-negative bacteria are classified by the color they turn after a chemical process called Gram staining is used on them. Gram-negative bacteria stain red when this process is used. Other bacteria stain blue. They are called gram-positive bacteria. Gram-negative and gram-positive bacteria stain differently because their cell walls are different.

Overview of Gram-Negative Bacteria

Gram-positive bacteria are bacteria with thick cell walls. In a Gram stain test , these organisms yield a positive result. Though both groups of bacteria can cause disease, they require different treatments.

If you have a bacterial infection, the Gram stain will determine what kind of medication you need. Read on to learn about gram-positive bacteria and their associated diseases, along with typical treatments. The hallmark trait of gram-positive bacteria is their structure.

Generally, they have the following characteristics:. Gram-positive and gram-negative bacteria have different structures. Typically, gram-negative organisms have the following the traits:. The major difference is the outer lipid membrane. Because of this difference, gram-negative bacteria are harder to kill. This means gram-positive and gram-negative bacteria require different treatments. Though gram-negative bacteria are harder to destroy, gram-positive bacteria can still cause problems.

Many species result in disease and require specific antibiotics. Gram stain testing is a method for classifying bacteria based on their cell wall. It allows scientists to determine whether an organism is gram-positive or gram-negative. The test, which uses a microscope, was created by Hans Christian Gram in During the procedure, crystal violet dye is applied to a sample of bacteria. This chemical dye can stain thick peptidoglycan layers. Under a microscope, gram-positive bacteria appear purple-blue because their thick peptidoglycan membrane can hold the dye.

The bacteria is called gram-positive due to the positive result. Gram-negative bacteria stain pink-red. The test result is negative. In a medical setting, a doctor can send a sample of your blood, urine, or tissue to a lab for Gram stain testing.

This may help them diagnose a bacterial infection. Depending on various traits, gram-positive bacteria are further classified into the following groups:. Gram-positive cocci are circular or oval in shape. Staphylococcus grows in grape-like clusters.

Normally, they exist on our skin and mucous membranes without causing problems. But if staphylococci enter the body, they can cause serious infections.

Streptococcus bacteria grow in chains. Like staphylococci, streptococci normally exist in the body. Most of these bacteria are typically found on the skin, but some can cause serious medical conditions.

Gram-positive bacilli are further categorized based on their ability to make spores. This includes:. Bacillus and Clostridia bacteria can form spores, which help the bacteria survive in harsh conditions like high heat. These bacilli are subdivided based on their need for oxygen. Listeria bacteria are anaerobic, while Corynebacterium are aerobic. If a bacterium is pathogenic, it means it causes disease in humans.

Many gram-positive bacteria are pathogens. While there are more than pathogenic gram-positive bacteria, the most notable species include:. Most cases are caused by the following species. Other pathogenic staphylococci are less common and rarely lead to disease. Often, S. It causes:. Streptococci bacteria are also common pathogenic bacteria. The following organisms are the most prevalent. In general, other streptococci groups may cause foodborne illnesses with a sore throat.

The bacterium S. As spore-forming bacteria, bacilli make spores that release toxins. Humans can get anthrax through inhalation or contact with infected animals.

About 30 Clostridia species cause disease in humans. Like bacilli, these bacteria form toxins that lead to serious conditions. Clostridia are usually involved with foodborne illnesses, but the most concerning bacteria include:. The spores of C. It leads to botulism , including:. If a human eats contaminated meat, they can get food poisoning. Symptoms include diarrhea and abdominal cramps that last for less than 24 hours.

It typically occurs after taking antibiotics. The spores can be found in soil, ash, and on rusty tools. This a serious medical emergency. The only pathogenic Listeria bacteria is L. In healthy people, it typically causes mild symptoms of foodborne illness. But in people with weakened immune systems, the bacterium can cause life-threatening conditions like:. There are about 30 Corynebacterium bacteria associated with human disease.

However, these organisms rarely cause sickness and usually affect people with compromised immune systems. Glycopeptide antibiotics are often used to treat serious infections caused by drug-resistant bacteria.

Erythromycin is in a class of antibiotics known as macrolides, which also includes the better-known azithromycin and clarithromycin. Often, erythromycin is prescribed to people who are allergic to penicillin. In some cases, treatment might include fluid therapy. Generally, fluid management is required to treat conditions caused by toxins. For toxin-related illnesses like anthrax and botulism, treatment includes an antitoxin. This medicine works by targeting and removing toxins in the body.

The appropriate antitoxin depends on the specific toxin. The Gram stain test can help doctors diagnose an illness. Most illnesses require antibiotics that destroy or slow down the bacteria. In severe cases, you might require additional treatment like fluid therapy. Bacterial infections can affect wounds, burns, and organs within the body.

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Characteristics Vs. They stain pink instead. Characteristics of gram-positive bacteria. Gram-positive and gram-negative. Gram stain test.

Gram-negative bacteria

Gram-positive bacteria are bacteria with thick cell walls. In a Gram stain test , these organisms yield a positive result. Though both groups of bacteria can cause disease, they require different treatments. If you have a bacterial infection, the Gram stain will determine what kind of medication you need. Read on to learn about gram-positive bacteria and their associated diseases, along with typical treatments.

Show Caption Hide Anthrax gram stain. Gram staining is a common technique used to differentiate two large groups of bacteria based on their different cell wall constituents. The Gram stain procedure distinguishes between Gram positive and Gram negative groups by coloring these cells red or violet. Gram positive bacteria stain violet due to the presence of a thick layer of peptidoglycan in their cell walls, which retains the crystal violet these cells are stained with. Alternatively, Gram negative bacteria stain red, which is attributed to a thinner peptidoglycan wall, which does not retain the crystal violet during the decoloring process.

Gram Positive. Cocci. Gram Negative. Aerobic. Anaerobic Bacillus. Corynebacterium. Erysipelothrix. Listeria. Mycobacterium. Nocardia. Rhodococcus.

Gram-Positive Bacteria Explained in Simple Terms

In bacteriology , gram-positive bacteria are bacteria that give a positive result in the Gram stain test, which is traditionally used to quickly classify bacteria into two broad categories according to their type of cell wall. Gram-positive bacteria take up the crystal violet stain used in the test, and then appear to be purple-coloured when seen through an optical microscope. This is because the thick peptidoglycan layer in the bacterial cell wall retains the stain after it is washed away from the rest of the sample, in the decolorization stage of the test. Conversely, gram-negative bacteria cannot retain the violet stain after the decolorization step; alcohol used in this stage degrades the outer membrane of gram-negative cells, making the cell wall more porous and incapable of retaining the crystal violet stain. Their peptidoglycan layer is much thinner and sandwiched between an inner cell membrane and a bacterial outer membrane , causing them to take up the counterstain safranin or fuchsine and appear red or pink.

In clinical microbiology, phenotypic typing schemes particularly Gram staining are some of the most common and effective techniques for bacteria identification. Discovered in , Gram stain technique has proven to be one of the most useful phenotypic classification systems through which bacteria can be identified based on their staining properties and general morphology. Using this technique, bacteria are classified as either Gram positive or Gram negative. Bacteria are single-celled prokaryotes ubiquitous in nature.

Most bacteria are classified into two broad categories: Gram positive and Gram negative. These categories are based on their cell wall composition and reaction to the Gram stain test. The Gram staining method, developed by Hans Christian Gram , identifies bacteria based upon the reaction of their cell walls to certain dyes and chemicals. The differences between Gram positive and Gram negative bacteria are primarily related to their cell wall composition. Gram positive bacteria have cell walls composed mostly of a substance unique to bacteria known as peptidoglycan , or murein.

Gram-positive bacteria

Prokaryotes are identified as gram-positive if they have a multiple layer matrix of peptidoglycan forming the cell wall. Crystal violet, the primary stain of the Gram stain procedure, is readily retained and stabilized within this matrix, causing gram-positive prokaryotes to appear purple under a brightfield microscope after Gram staining. For many years, the retention of Gram stain was one of the main criteria used to classify prokaryotes, even though some prokaryotes did not readily stain with either the primary or secondary stains used in the Gram stain procedure.

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Gram Positive vs. Gram Negative Bacteria


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Gram positive bacteria stain blue-purple and Gram negative bacteria stain red. •. The difference between the two groups is believed to be due to a much larger.

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Gram positive and gram negative are two differentiations found in bacteria, which can be used to classify.