- Smallest micro organisms
- Free living in nature
- Can grow in cell free medium
- Causes human infection
- M. pneumoniae: Pneumonia
- Ureaplasma urealyticum: non-gonococcal urethritis
- M. hominis and M. gentalium: genital tract infections.
- Cell wall absent
- Highly pleomorphic in nature
- Has no fixed shape and size
- Absence of cell wall precursors that are
- Muramic acid
- diaminopimelic acid
- Soft tri-laminar unit membrane present, bound to the cells.
- Such membrane made up of sterols.
- Shows plasticity that enables them to pass through bacterial filters.
- Mistakenly taken as viruses.
- Nocard and Roux (1898) identified the first member of this group.
- Isolated from bovine pleuro-pneumonia.
- Also, similar organism isolated from contagious agalactia in sheep.
- Similar isolates identified form different organisms and environmental sources.
- Thus called, pleuropneumoia-like organisms (PPLO).
- Later replaced by the term mycoplasma.
- Myco: means fungus like branching filaments,
- Whereas, plasma signifies plasticity of shape.
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- Easily passes through filters of pore size 450 nm.
- Presence is seen in granular form.
- Also found in filaments form that varies in sizes.
Granules: coccoid, balloon, ring or star, disc forms.
Filaments: slender, of different length, true branched.
- Multiplies through binary fission
- Genomic replication and cell division are often asynchronous.
- Appears as budding forms or chains of beads.
- Bulbous enlargement with differentiated tip structure in some species.
- Thus, helps in adherence to the host cells having neuraminic acid receptors.
- In some species, also responsible for hemadsorption.
- Non-sporing, non-flagellated or non fimbriated.
- Though Gram negative, better stained by Giemsa stain.
- Some species shows gliding motility.
- Fluid or solid media required for cultivation.
- Facultative anaerobes though better growth in aerobic condition.
- Temperature requirement
- 22-41°C: Temperature range for growth
- 35-37°C: Optimum growth for parasitic species
- Lower temperatures: Saprophytic species
- Enriched media used for cultivation
- 20% horse or human serum
- Yeast extract
- Selective agents used are
- Thallium acetate
- High concentration serum required.
- Fulfills cholesterol and other lipids requirements.
- 2-6 days incubation required for colonies to appear.
- Colonies characteristics
- –10-600 µm size
- -Typically biphasic
- –Fried egg appearance
- -An opaque granular area located centrally
- -Extends into the depth of the medium
- -This area surrounded by a flat translucent peripheral zone
- -Hand lens can be used to observe colonies
- -Staining by Dienes method required for study of colonies
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Dienes method of staining
Following steps are involved in this method of staining.
- Firstly, a block of agar containing colony is cut.
- After it, the block with the colony is placed on the slide.
- Now, cover this slide containing colonies with a cover slip.
- The coverslip used is firstly treated with alcoholic solution of methylene blue and azure and then dried.
- Since, Loops cannot pick up the colonies due to its small size.
- Thus, subculture is carried out by rubbing the cut colonies along with the agar block in the fresh plate.
- In liquid medium
- -No turbidity appreciated
- -Pleomorphic forms are found
- Metabolism: Fermentative
- Source of energy: glucose or arginine(most species)
- Urea hydrolysis: negative (except Ureaplasmas)
- Cholesterol and related sterols incorporated in their surface membranes
- Purines and pyrimidines synthesis absent
- Heat resistance similar to non-sporing bacteria.
- Some strains are more sensitive
- Destroys: exposure to 45°Celsius for 15 minutes.
- Resist: osmolytic shock related lysis.
- Sensitive towards:
- surface active agents related lysis.
- lipolytic agents such as taurocholate and digitonin.
- tetracycline and many other antibiotics
- Penicillin and cephalosporin
- Lysozymes acting on bacterial cell wall
- Susceptible towards erythromycin.
- Gold salt: growth inhibition
- Some macrolide antibiotics: differentiation of species
- 002% methylene blue:
- different species inhibited
- M. pneumoniae can grow
- Serological tests used are:
- Passive haem-agglutination
- Complement fixation
- These tests are performed to identify isolates by detecting antibodies in sera.
- Antigens present are generally surface antigens.
- Mainly glycolipids: identified by complement fixation test
- Proteins: identified by ELISA
- “Growth inhibition test” also helps in identification of the isolates
- It is based on the antisera ability to inhibit the growth of homologous species on solid media specifically.
Mycoplasma: Introduction, Morphology and Biochemical Reactions