gram stain

Topics: Bacteria, Staining, Gram staining Pages: 2 (639 words) Published: October 26, 2014

Microbiology Laboratory(TFMB1001) Report
Experiment Tittle Gram stain
Experiment Date 24October2014
Submission Date 31October2014
Students Name Tittle
Gram stain.
Aim of this experiment is to differentiate between the two major categories of bacteria , gram positive and gram negative. Through this experiment, gram staining skills develop. More understanding the types and morphology of bacteria. Expected experimental result, Escherichia coli (E.coli ) is a negative gram bacteria which stain pink colour , while Staphylococcus aureus ( S.aureus ) is a positive gram bacteria which stain purple colour. Materials

Bacteria : Escherichia coli , Staphylococcus aureus
Crystal Violet
Gram’s iodine
Absolute alcohol
As per manual.
Gram staining is a very importance preliminary step to differentiate the bacteria into gram positive and gram negative and also enable the bacteria to be examined using a light microscope . Bacteria are very small unicellular microorganisms. They have cell wall of peptidoglycan can reproduce by binary fission. The functions of cell wall are strength , shape , protect from osmotic lysis . It also protect cell from toxic substances and contributes to their pathogenicity . The gram stain differentiate bacteria by the chemical and physical properties of cell wall. Bacteria which stain purple are called Gram-positive while stained pink colour are called gram negative bacteria. From the results, purple stained are obtained for E.coli and S.aurues . E.coli is a rod shaped bacteria, therefore it described as bacillus. S.aureus has irregular grapelike clusters, therefore is it coccus bacteria. Through this experiment, purple stained obtained for both bacteria, E.coli and S.aureus. But compared to same experiment carried out by others, E.coli should be pink stained. There might be some human error in this experiment. The error most probably occur at stage of decolourisation of bacteria...
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