This document discusses several types of bacteria that exhibit unusual morphologies or motility mechanisms: - Gliding bacteria move across surfaces without flagella or pili through unknown mechanisms. They leave behind a layer of slime. Myxobacteria can form multicellular fruiting bodies containing spores. - Sheathed bacteria grow as filaments enclosed in an extracellular sheath that may provide protection and concentrate nutrients. Examples are Leptothrix and Sphaerotilus. - Actinomycetes are filamentous, gram-positive bacteria that resemble fungi. They play important roles in soil nitrogen fixation and produce many antibiotics.

1. Bacterial morphology

2. Gliding
and
fruiting
bacteria
• The organisms of this group are Gram-negative,
nonphototrophic, and nonflagellated.
• They exibit a creeping or gliding motility on
solid surfaces.
• It is independent of propulsive structures such
as flagella, pili, and fimbriae. Gliding allows
microorganisms to travel along the surface.
• The exact mechanism of gliding is not known.
• The mechanisms responsible for bacterial
gliding motility have been a mystery for almost
200 years.
• The mechanisms of movement employed by
these bacteria are still a matter of speculation.
Genetic, biochemical, ultrastructural, and
behavioral studies are providing insight into the
machineries employed by these diverse
bacteria that enable them to glide over
surfaces.
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3. • . When the organisms are placed on a solid culture
medium,growth, which is frequently of a slimy consistency,
spreads rapidly over the surface. As the cells glide across the
surface of the medium, they leave a layer of slime behind
them.
• Indeed, the prefix myxo, which occurs in the name of
the order to which these bacteria belong, Myxobacterales,
reflects this property,being derived from the Greek noun
myxo, meaning “mucus, slime”.
• Although there are some exceptions, a remarkable and
striking feature of the myxobacters is that the vegetative cells
at some stage of growth, swarm together
in masses and form fruiting bodies [This behavior bears some
resemblance to that of slime molds.
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4. Myxobacterial gliding motility.
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5. • The fruiting bodies contain myxospores, which are shorter
and thicker than the vegetative cells and are resistant to
desiccation and ultraviolet radiation but not to heat. The
fruiting bodies range from simple to complex.
• The simplest fruiting bodies are merely heaps of myxospores
embedded in a mass of slime.
• The most elaborate fruiting bodies may have a stalk
composed of slime, and walled containers (sporongioles,
sometimes termed cysts) which enclose the myxospores.
• Myxobacters are strictly aerobic organisms found in surface
layers of soil, compost, manure. rotting wood, and animal
dung. Many myxobacters develop very colorful pigments in
their normal environment.
• Some species produce exocellular enzymes that degrade
complex substrates such as cellulose, agar, chitin, and even
the cell walls of other bacteria.
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6. Stages in the
fruiting body formation of
the myxobacter
Chondromyces crocotus. Early
stages: (A) Initial stages of
vegetative cell aggregation;
(B) fried-egg stage showing
orientation of peripheral
cells; (C) bulb formation and
development of stalk. Late
stages: (U) Initial stages of
sporangiole formation; (B)
sporangiole formation after
elongation of stalk to
Maximum length. Structures
range in size from
approximately 10 to 60 p.m.
(From
P. L. Grilione and J. Pangborn
and J Bacterial
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7. Fruiting bodies of
Myxobacteria.
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8. Sheathed
bacteria
• Sheathed bacteria are bacteria that
grow as long filaments whose exterior
is covered by a layer known as a
sheath.
• Bacteria in this group are Gram-
negative, aerobic, and
nonphototrophic.
• Within the sheath, the bacteria can
be capable of growth and division.
• Examples of sheathed bacteria
include Leptothrix discophora (also
known as "iron bacteria"),
and Sphaerotilus natans.
• Sheathed bacteria are common of the
bacterial communities in water and in
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9. • In these environments, the sheath is often coated
with precipitates of elements in the water or soil
environments, such as oxides of iron and manganese.
• The sheath that covers the bacteria can be of varied
construction. Much of the structural information has
been gleaned from the observation of thin slices of
sample using the transmission electron microscope .
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10. • Bacterial sheaths tend to be manufactured when the
bacteria are in an aquatic or soil environment that
contains high amounts of organic matter.
• The sheath may serve to provide protection to the
bacteria in these environments, Also, the ability of
metallic compounds to precipitate on the sheath may
provide the bacteria with a ready supply of such
inorganic nutrients.
• Sheaths may also help the bacteria survive over a wide
range of temperature and pH , by providing a relatively
inert barrier to the external environment.
• The Sphaerotilus-Leptothrix group of organisms, also
known informally and collectively as ‘sewage fungus’.
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11. Sphaerotilus natans
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12. Leptothrix discophora
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13. Actinomycetes
Classification
Kingdom: Bacteria
Phylum : Actinobacteria
Subclass: Actinobacteridae
Order : Actinomycetales
 Actinomycetes are unicellular, Gram-positive bacteria that belong to
the Order Actinomycetales.
 Members of this group are widely distributed in nature and can be
found in a variety of habitats across the world. They have been
shown to share a number of characteristics with fungi .
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16. Actinomycetes are best known for nitogen
fixations in non-leguminous plants.
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17. Microscopic view of actinomycetes .
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20. Reproduction
• Actinomycetales have 2 main forms of
reproduction; spore formation and hyphae
fragmentation. During reproduction,
Actinomycetales can form conidiophores,
sporangiospores, and oidiospores. In
reproducing through hyphae fragmentation,
the hyphae formed by Actinomycetales can be
a fifth to half the size of fungal hyphae, and
bear long spore chains.
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21. Antimicrobial properties:
• Many species of Actinomycetes produce
antimicrobial compounds under certain
conditions and growth
media. Streptomycin, actinomycin, and
streptothricin are all medically important
antibiotics isolated from Actinomycetes
bacteria.[1] Almost two-thirds of the natural
antimicrobial drug compounds used currently are
produced by different species of
Actinomycetes.[2]
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22. Refreneces
• Microbiology by Michael j.pelczar
• www.encyclopedia.com
• www.britannica.com
• www.wikipedia.com
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