Other modifications have been specifically developed for staining. The relation of the gram stain to the cell wall and the ribonucleic acid content of the cell. Difference between gram positive and gram negative. In a gram stain test, bacteria are washed with a decolorizing solution after being dyed with crystal violet. Some of these are lipoteichoic acids, which have a lipid component in the cell membrane that can assist in anchoring the peptidoglycan. The stain used during the technique is crystal violet. Some organisms are gramvariable and may appear either gram negative or grampositive according to the conditions. Gram staining or grams method is an emprical method of differentiating bacterial species into two large groups grampositive and gramnegative based on the chemical and physical properties of their cell wall. Gram positive cells have a thick peptidoglycan layer and stain blue to purple.
Heat the slide for few seconds until it becomes hot to the touch so that bacteria are firmly mounted to the slide. On adding a counterstain such as safranin or fuchsine after washing, gramnegative bacteria are stained red or pink while grampositive bacteria retain their crystal violet dye this is due to the difference in the structure of their bacterial cell wall. Gram stain or gram staining, also called gram s method, is a method of staining used to distinguish and classify bacterial species into two large groups. This test differentiates the bacteria into grampositive and gramnegative bacteria, which helps in the classification and differentiation of microorganisms. Jan 08, 2020 the gram staining technique is the most important and widely used microbiological differential staining technique. If the slide is heat fixed, allow it to cool to the touch before applying the stain. Gram positive bacteria are more susceptible to antibiotics due to the lack of an outer membrane. Pdf gram staining is an empirical method of differentiating bacterial species into two large groups grampositive and gramnegative based. This test differentiates the bacteria into gram positive and gram negative bacteria, which helps in the classification and differentiation of microorganisms. The staining procedure differentiates organisms of the domain bacteria according to cell wall structure. Gram positive cell wall contains a thick layer of peptidoglycan with numerous teichoic acid crosslinking which resists the decolorization. This test differentiate the bacteria into gram positive and gram negative bacteria, which helps in the classification and differentiations of microorganisms. For example, gram staining can help clinicians classify bacterial pathogens in a sample into categories associated with specific properties.
The gram stain was developed by christian gram in 1884 and modified by hucker in 1921. Bacteria that are nonresponsive to this technique are known as gram insensitive. The gram staining technique differentiates the mixed culture cells into two terms as grampositive bacteria and gramnegative bacteria. We will discuss this and other applications of gram staining in more detail in later chapters. This method is used to distinguish between gram positive and gramnegative bacteria which have consistent differences in their cell walls. The staining procedure differentiates organisms of the domain. The gram stain is almost always the first step in the identification of a bacterial organism, while gram staining is a valuable. Both bacterias, positive and negative, cell wall is composed of peptidoglycan,the grampositve has a thicker wall and both will take up the crystal violet.
Microbiology lecture 2 gram positive and gram negative. The differences in cell wall composition of gram positive and gram negative bacteria account for the gram staining differences. What is gram stain test staining procedure, principle and. Grampositive vs gramnegative bacteria difference and. Oct 15, 2005 named after hans christian gram who developed the method in 1884, the gram stain allows one to distinguish between gram. Both grampositive and gramnegative bacteria produce exotoxins whereas only gramnegative bacteria produce endotoxins. On adding a counterstain such as safranin or fuchsine after washing, gram negative bacteria are stained red or pink while gram positive bacteria retain their crystal violet dye. Gram stain principle, reagents, procedure, steps, results. A microorganism is grampositive if the stain remains violet secondary to the presence of. Hypothesize that in the cultures used in this lab for gram staining will contain many gram negative and gram positive bacteria. Historically it had been thought that the second membrane found on gram negative bacteria evolved just once and so all gram negative species were more closely related to one. The name comes from the danish bacteriologist hans christian gram, who developed the technique. Difference between grampositive and gramnegative bacteria.
Gram variable observations in gram staining the gram staining procedure does not always give clearcut results. Staining of the bacteria forms the foremost and the most important step in the identification of bacteria. Introduction gram staining is the most essential and universally used staining technique in bacteriology laboratory. Gram positive bacteria are increasingly becoming resistant to antibiotics. Gram staining was developed by cristian gram in 1884. This staining procedure differentiates microbes into two basic groups. Material and methods the following things are needed to run a gram staining experiment. An alternative qc source is material scraped from between teeth with a wooden applicator stick. Overview of grampositive bacteria infections msd manual. Discuss the distinguishing characteristics of gram positive and gram negative bacteria. Gram staining is a microbiologic procedure used to differentiate gram negative from gram positive bacteria. Introduction to staining live specimens are difficult to see with the bright field microscope.
Oct 24, 2019 the gram stain is a differential method of staining used to assign bacteria to one of two groups gram positive and gram negative based on the properties of their cell walls. Gramnegative cells stain pink during gram staining. Cell wall structure identifies either cell is grampositive or negative in nature during the procedure when we stained by primary stain and secure it by a mordant. Gram negative cells have a thin peptidoglycan layer and stain red to pink. Jul 01, 2019 microbiology lecture 2 gram positive and gram negative bacteria gram staining principle this second microbiology lecture will explain the properties of gram positive and gram negative bacteria.
The cells are colored red or violet so as to distinguish its group. For example, methicillinresistant staphylococcus aureus mrsa bacteria are resistant to most antibiotics that are related to penicillin. Christian gram in 1884, and categorizes bacteria according to their gram character gram positive or gram negative. Major difference between grampositive and gramnegative. The most useful staining procedure in medical microbiology. Discuss bacterial structure and the function of the different bacterial components 4.
Gram positive and gram negative, based on the differences of the chemical and physical properties of the cell wall. The major difference in the modified gram stain procedure occurs during the dehydration process and is the application of alcoholic saffron lower right box, highlighted in red. Grampositive bacteria are increasingly becoming resistant to antibiotics. Grampositive bacteria gramnegative bacteria provides useful information for disease treatment. Basic classification of medically important bacteria nearly all clinically important bacteria can be detectedvisualized using gram staining method the only exceptions being those organisms. Gram negative bacteria tend to be more resistant to certain antibiotics than gram positive bacteria. Gramnegative cells have a thin peptidoglycan layer and stain red to pink. The single membrane of gram positive species is thought to be the ancestral state. Gram positive bacteria stain blue while gram negative stain red. Add the primary stain crystal violet and incubate 1 minute. The main difference between gram positive and gram negative bacteria is that.
The modified procedure provided greater reagent stability and better differentiation of organisms. Jun 12, 2018 gram staining is the common, important, and most used differential staining techniques in microbiology, which was introduced by danish bacteriologist hans christian gram in 1884. Make a slide of tissue or body fluid that is to be stained. Gram staining is the common, important, and most used differential staining techniques in microbiology, which was introduced by danish bacteriologist hans christian gram in 1884. The yellow contrast in the connective tissue collagen within skin tissue is. The two categories of bacteria based on gram staining are gram positive bacteria and gram negative bacteria. This method is used to distinguish between gram positive and gram negative bacteria which have consistent differences in their cell walls. Method of staining used to distinguish and classify bacterial species into two large groups. Therefore, gram negative bacteria are more pathogenic. Gram positive and gram negative bacteria are the two types of bacteria, differentiated by the gram staining technique. Gram positive vs gram negative technology networks. The terms positive and negative have nothing to do with. Pdf lab report of microbiology 3 akbar haqi academia.
An optimized staining technique for the detection of gram. Another note of interest is that variations of the gram stain procedure have been developed over the years. Specific to gram positive bacteria is the presence of teichoic acids in the cell wall. Staining and streaking protocols for simple stain, gram stain, streak plate technique and culture maintenance lab 2a. The gram stain is a differential method of staining used to assign bacteria to one of two groups grampositive and gramnegative based on the properties of their cell walls. Mrsa strains are commonly involved in infections acquired in health care facilities and can. Gram positive bacteria has only the inner plasma membrane and no outer membrane.
For more information on the difference between grampositive and gramnegative bacteria, keep visiting byjus website or download byjus app for further reference. Pdf mlt 415 lab report gram stain techniques muhamad. Gramstaining was firstly introduced by cristian gram in 1883. Pdf difference between gram positive and gram negative. Schematic showing the modified gram stain procedure. The procedure is named for the person who developed the technique, danish bacteriologist hans christian gram.
Gram staining technique is the widely used differential staining technique in bacteriology. Gram staining is a microbiologic procedure used to differentiate gramnegative from grampositive bacteria. Distinguishes bacteria of two large and medically important groups. Microbiology lecture 2 gram positive and gram negative bacteria gram staining principle this second microbiology lecture will explain the properties of gram positive and gram negative bacteria. Materials and methods aseptic technique was used throughout the experiment. The isolated bacteria are stained by various methods depending upon the bacteria in focus. The gram stain is fundamental to the phenotypic characterization of bacteria. Cell wall of gram positive and gram negative bacteria. This was developed in 1884 by a danish bacteriologist, hans christian gram. Named after hans christian gram who developed the method in 1884, the gram stain allows one to distinguish between gram.
For demonstrating gramnegative and grampositive in tissue. Here are the following main principles of gram staining techniques. Gram staining cannot be used reliably to assess bacterial phylogenetic relationships. Bacteria are first stained with crystal violet or gentian violet. What is gram stain test staining procedure, principle. Gramnegative bacteria tend to be more resistant to certain antibiotics than grampositive bacteria. Grease or oil free slides are essential for the preparation of microbial smears.
Gram staining bacteria requires the use of aseptic technique to ensure the sterility of the experiment. Bacteria that stain purple with the gram staining procedure are termed grampositive. It is called a differential stain since it differentiates between grampositive and gramnegative bacteria. It is also known as gram staining or gram s method. Difference between gram positive and gram negative cell wall is thicker in a gram positive bacteria. Aug 12, 2019 the gram stain is fundamental to the phenotypic characterization of bacteria. Difference between gram positive and gram negative bacteria pdf by easybiologyclass 1. The purpose of the gram stain is to show whether the bacteria are gram positive purplecolored, gram negative pinkcolored, or both. Grampositive cells have a thick peptidoglycan layer and stain blue to purple. Gram stain developed in 1884 by hans gram, a danish microbiologist. The gram stain is the most widely used staining procedure in bacteriology. Grampositive bacteria thick layer of peptidoglycan90% of cell wall stains purple. The following are some common causes of poor gram stain results a.
Summary and explanation the gram stain was originally devised by christian gram in 1884. For use in the grams staining method for the initial differentiation of gram positive and gram negative bacteria. With these types of organisms, grampositive and gramnegative cells may be present within the same preparation 40. Occurrence of a phosphoric ester in certain bacteria. Jan 14, 2017 9 advantages and disadvantages of gram staining jan 14, 2017 oct 26, 2016 by editor in chief gram staining, which is also referred to as the grams method, is a scientific technique of staining that is used to differentiate the species of bacteria into 2 main groups, namely the grampositive and the gramnegative bacteria. The gram staining technique differentiates the mixed culture cells into two terms as gram. The microscopicanalysis using gram staining technique showed that majority of the bacterial isolates were gram positive bacteria while only three of the isolates were gram negative bacteria. Gramnegative bacteria thin layer of peptidoglycan10% of cell wall and high lipid content stains redpink. In 1883 hans christian gram discovered an important differential staining method that is used extensively today.
Gram staining was firstly introduced by cristian gram in 1883. In addition this stain also allows determination of cell morphology, size, and arrangement. All bacterial cells will stain blue or purple colour with crystal violet solution. Aug 21, 2019 gram staining cannot be used reliably to assess bacterial phylogenetic relationships. The traditional gram stain procedure is completed in either case top box. A microorganism is gram positive if the stain remains violet secondary to the presence of. The standard grams staining method can be used to differentiate intact, morphologically similar bacteria into two groups. Pdf difference between gram positive and gram negative bacteria. Nonetheless, it is generally considered good practice to use young cultures of known grampositive and gramnegative bacteria as controls when staining an unknown bacterium. The microscopicanalysis using gram staining technique showed that majority of the bacterial isolates were grampositive bacteria while only three of the isolates were gramnegative bacteria.