This lecture include introduction, Characteristics and structure of Mycoplasma like organisms,

1. Mollicutes
• In 1967, a group of Japanese workers, Doi et. al
observed that yellow disease of some plants is
caused by mycoplasma like organisms (MLOs).
• The generic name Mycoplasma was given by
Nowak (1929) due to their fungi like
resemblance.
• Later mollicutes, cell wall lacking prokaryotic
with helical structure given the name
‘Spiroplasma’.
• Ovoid to long, spiral mollicutes given the name
‘Phytoplasma’.

2. Properties of True Mycoplasma
• Lacking true cell wall.
• Bounded only by a single triple layered unit membrane.
• They are small, sometime ultra-microscopic cell containing
micro cytoplasm, randomly distributed ribosome and
strands of nuclear material.
• Size is 175 to 250 nm.
• Shapes range from coccid or slightly ovoid to filamentous,
sometimes, they produce branched myceloid structure.
• MLOs are gram-ve and there are no flagella.
• Reproduction by ‘Binary Fission’
• Can be grown on artificial nutrient media in which they
produce “fried egg” appearance colony.
• Most MLOs are resistance to penicillin, but sensitive to
tetracycline, chloramphenicol etc.

3. Structure of Mycoplasma Cell

4. Classification
• In “Bergey’s Manual of Determinative Bacteriology”.
(7th edition, 1957)- assigned a new order Mycoplasma-
tales to these organisms.
• Edward et al (1967) proposed that these organisms
should be placed in a new class mollicutes:
Class – Mollicutes
Order – Mycoplasmatales
Family -1: Mycoplasmataceae
Genus: Mycoplasma
Family -2: Spiroplasmataceae
Genus: Spiroplasma
Family-3: Acholeplasmataceae
Genus: Acholeplasma

5. Properties of Spiroplasma
• Lacking true cell wall only single triple layered unit
membrane present.
• They are small, sometime ultra-microscopic cell containing
micro cytoplasm, randomly distributed ribosome and
strands of nuclear material.
• Shapes are different types.
• In ovoid to egg shape, diameter is 100 to 240 nm. When
they are filamentous or branched than diameter is about
120 nm.
• Reproduction – by Binary Fission.
• Can be grown on artificial media. Colony look like as
“Fried Egg”
• Can move due to helix.
• Sensitive to tetracycline antibiotic.
• Exp of diseases: Corn stunt, Citrus stubborn.

6. Spiroplasma

7. Properties of Phytoplasma
• Lacking true cell wall only single triple layered unit membrane
present.
• They are small, sometime ultra-microscopic cell containing micro
cytoplasm, randomly distributed ribosome and strands of nuclear
material.
• Size is 200 to 800 nm.
• Shapes range from ovoid, filamentous to tubular.
• Mostly transmitted by leaf hopper but may be by Psyllids and Plant
Hopper.
• Grow in intestine, hemolymph and saliva system of insect vectors.
• For multiplication and distribution of these 10-45 days incubation
period in insect body is needed.
• Can not be grown on artificial media.
• Sensitive to tetracycline group antibiotic.
• Exp. of diseases: Pear decline, Grape yellow’s, X disease of peach.

8. Phytoplasma present in plant cells

9. Note: Images used in lecture have been taken from Internet. I am grateful
to authors
Thanks