classification of bacteria mrs. dalia kamal eldien msc in microbiology mrs. dalia kamal eldien msc...
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Objectives At the end of this lecture, the student should know:- The types of bacteria classified depending on different methods Emphasis on morphological& staining classificationTRANSCRIPT
Classification of bacteria
Mrs. Dalia Kamal EldienMSC in Microbiology
Lecture NO: 3
Questions for revision the previous lecture
What are the function of bacterial cell wall?The movement organ in bacterial cell is ……Define the germination process in bacteria?
Objectives
• At the end of this lecture, the student should know:-The types of bacteria classified depending on different
methodsEmphasis on morphological& staining classification
IntroductionBased on the difference in cellular organization and
biochemistry, the kingdom protista has been divided into two groups namely prokaryotes and eukaryotes.
Bacteria and blue-green algae are prokaryotes, while fungi, other algae, fungi and parasite are eukaryotes.
Bacteria are prokaryotic microorganisms that do not contain chlorophyll.
They are unicellular and do not show true branching, except in higher bacteria like actinomycetales.
Classification The bacteria are classified depending on different
methods, include:- MorphologyStaining reactionsGrowth Requirements(Cultural characteristics)Biochemical reactionsAntigenic structure Increasingly by their genetic composition using
specialized molecular biology techniques.
Mrs.:Dalia Kamal Eldien MSC in microbiology
Morphological Classification of bacteria
Bacteria are classified according to morphology in to:-Cocci: are spherical or oval cellsBacilli: rod shaped cellsCocobacilliVibrios: comma shaped curved rodsSpiral: rigid spiral formsSpirochetes: flexuous spiral forms
Mrs.:Dalia Kamal Eldien MSC in microbiology
Basic shapes of bacteria
Cocci (Singular: coccus) are spherical or oval cells
Bacteria sometime show characteristic cellular arrangement or grouping
Mrs.:Dalia Kamal Eldien MSC in microbiology
According to the plane of cellular division, cocci may be arranged in
Pairs (diplococci)Chains (streptococci)Grape like clusters (staphylococci).Groups of four (tetrads) or eight (sarcina)
Mrs.:Dalia Kamal Eldien MSC in microbiology
Cocci in pairs
Cocci in cluster
Cocci in chain
Cocci in tetra
Cocci in sarcina
Basic shapes of bacteria
Bacillus (Singular: bacillus) stick-like bacteria, also name rod shaped
Bacilli are arrange in fewer groups, or singly, or in short chain
Mrs.:Dalia Kamal Eldien MSC in microbiology
Bacilli arrangement
Bacilli in chain
Bacilli in chain
Bacilli in single
VibriosVibrios (Singular: vibrio) are small slightly curved rods,
comma shape
Mrs.:Dalia Kamal Eldien MSC in microbiology
Vibrio (Helicobacter pylori)
SpiralSpiral (Singular: spirillum) are small, regularly coiled,
rigid organisms
Mrs.:Dalia Kamal Eldien MSC in microbiology
Spiral bacteria
Spirochetes
Spirochetes (Singular: spirochaete) have a helical shape and flexible bodies
Mrs.:Dalia Kamal Eldien MSC in microbiology
Spirochetes
Identify the following bacteria structure?
Bacterial Classification Staining reaction
Classification according to staining reactions depend in different type of stains
The main stain is Gram stain The Gram staining method is named after the Danish
bacteriologist Hans Christian Gram (1853 – 1938) who originally devised it in 1882 (but published in 1884), to discriminate between pneumococci and Klebsiella pneumoniae bacteria in lung tissue
Mrs.:Dalia Kamal Eldien MSC in microbiology
Principle of Gram stain
The procedure is based on the ability of microorganisms to retain color of the stains used during the gram stain reaction.
Gram-negative bacteria are decolorized by the alcohol, losing the color of the primary stain, purple.
Gram-positive bacteria are not decolorized by alcohol and will remain as purple.
After decolorization step, a counter stain is used to impart a pink color to the decolorized gram-negative organisms.
Gram stain
Gram staining consists of four components: Primary stain (Crystal violet, methyl violet or Gentian
violet) Mordant (Gram's Iodine) Decolourizer (ethyl alcohol, acetone or 1:1 ethanol-acetone) Counter stain (safranin or neutral red, dilute carbol fuchsin)
Technique of Gram stain
Flood the slide with crystal violet solution for one minute. Wash off briefly with tap water
Flood slide with Gram's Iodine solution, and allow to act (as a mordant) for about one minute. Wash off with tap water.
Flood slide with 95% alcohol for 10 seconds and wash off with tap water. It is most important step
Flood slide with safranin solution and allow to counterstain for 30 seconds. Wash off with tap water
All slides of bacteria must be examined under the oil immersion lens of light microscope
Set of Gram stain
Results of Gram stain The results of Gram stain will depend on the cell wallGram-positive bacteria have a thick mesh-like cell wall
which is made up of peptidoglycan (50-90% of cell wall), so it stains as violet.
Gram-negative bacteria have a thinner layer of peptidoglycan (10% of the cell wall) and lose the crystal violet-iodine complex during decolorization with the alcohol rinse, but retain the counter stain Safranin, so it stains as red
Cell wall of Gram positive& negative bacteria
Classification of bacteria according to Gram stain
According to Gram stain, bacteria classify into large groups:-
Gram-positive bacteria (violet color)Gram-negative bacteria (red color)
Gram-positive bacteria
Gram-negative bacteria
Identify ???