Microbial
Cells
Early
in
the
history
of
biology,
biologists
recognized
two
primary
groups
of
organisms
namely
the
plants
and
the
animals.
These
two
groups
or
kingdoms
were
distinguished
by
several
structural
and
functional
characters.
The
major
criteria
that
differentiates
the
plants
from
the
animals
are,
movement
and
the
photosynthetic
ability.
After
the
discovery
of
the
microbial
world,
the
immotile,
multicellular
photosynthetic
algae
were
placed
in
the
plant
kingdom
while
microscopic
motile
forms
were
placed
in
the
animal
kingdom.
Subsequently
when
the
blue
green
bacteria
were
discovered,
the
bacteria
were
placed
in
the
plant
kingdom
in
spite
of
their
generally
non
photosynthetic
character.
Subsequent
experience
showed
that
classifying
protozoa
as
unicellular
animals
was
perhaps
not
correct
since
ciliates
and
amoeba
which
lack
the
cell
wall
could
fit
satisfactorily
into
the
animal
kingdom
while
other
protozoa
could
not.
Careful
examination
showed
that
microorganisms
had
both
plant
as
well
as
animal
like
character
with
the
accumulatior
of
more
information
about
microorganisms
it
became
clear
that
the
division
of
the
living
world
into
two
kingdoms
could
not
be
continued
on
a
logical
basis.
This
led
Haeckel
in
1866
to
propose
a
third
kingdom
called
the
Protista
to
include
the
microorganisms.
This
group
includes
both
the
photosynthetic
as
well
as
nonphotosynthetic
microorganisms
with
some
members
sharing
the
properties
of
both
the
traditional
plant
and
animal
kingdoms.
A
major
feature
of
this
group
is
the
relatively
simple
biological
organization.
Many
members
are
unicellular
and
undifferentiated
unlike
the
plants
and
the
animals.
Further
division
of
this
kingdom
was
based
on
the
degree
of
complexity
of
the
cellular
organization.
the
progress
in
microscopy
and
the
biochemistry
of
microorangisms
has
led
a
better
understanding
of
the
differences
in
the
internal
architecture
of
the
microbial
cells.
Till
recently
the
two
types
of
cells
were
recognized.
The
complex
Eucaryotic
cell
which
is
the
unit
structure
in
all
organisms
other
than
the
bacteria
and
the
structurally
simple
Procaryotic
cell,
representing
the
bacteria.
A
third
type
namely
the
Urkaryotes
which
presumably
are
the
progenerator
of
the
present
day
eucaryotes
is
now
recognized.
|