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Group 4 Rhizobium, Enterobacteria, and Actinomycetes

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Title: Group 4 Rhizobium, Enterobacteria, and Actinomycetes


1
Group 4 Rhizobium, Enterobacteria, and
Actinomycetes
  • By Matt Vermillion, Jennifer LaShell, and Gavin
    Tate

2
What is Rhizobium?
  • Rhizobia comes from the Greek words Riza, which
    means root and Bios, which means life.
  • Rhizobia are soil bacteria that acts a primary
    symbiotic fixer of nitrogen. The bacteria mainly
    infect the roots of plants, which leads to the
    formation of lumps or nodules where the Nitrogen
    fixation takes place.
  • Although much of the nitrogen is removed when
    protein-rich grain or hay is harvested, some
    Nitrogen still remains in the soil for future
    crops.
  • This is very important when nitrogen fertilizer
    is not used, as in organic rotation schemes or
    some less-industrialized countries.
  • The bacteria mainly infect the roots of plants,
    which leads to the formation of lumps or nodules
    where the Nitrogen fixation takes place.

3
Rhizobium Chemical composition, shape,
nutrition and movement.
  • Rhizobium are composed of a number of
    polysaccharides and deal with Nitrogen-Fixing.
  • Rhizobium are regular in structure meaning they
    appear as straight rods, but when rhizobia are in
    root nodules the nitrogen fixing form exists as
    irregular cells that are often club or Y-shaped.
  • Rhizobium that are in the soil are free living
    and motile, feeding on the remains of dead
    organisms.

4
Root Nodule Formation
5
  • The legume-rhizobium symbiosis is a classic
    example of mutualism. Several unrelated strains
    infect each individual plant, any one strain
    could redirect resources from nitrogen fixation
    to its own reproduction without killing the host
    plant upon which they all depend. But this form
    of cheating should be equally tempting for all
    strains, a classic tragedy of the commons. It
    turns out that legume plants guide the evolution
    of rhizobia towards greater mutualism by reducing
    the oxygen supply to nodules that fix less
    nitrogen, thereby reducing the frequency of
    cheaters in the next generation.

6
Rhizobium Unique Characteristics
  • There are several different genera of rhizobia.
    All of them belong to the Rhizobiales, a close
    monophyletic group of proteobacteria.
  • The plant pathogen Agrobacterium is a closer
    relative of Rhizobium than the rhizobia that
    nodulate soybean (and may not really be a
    separate genus). The genes responsible for the
    symbiosis with plants, however, may be closer
    than the organisms themselves, acquired by
    horizontal transfer rather than from a common
    ancestor.

7
Rhizobium - Importance
  • Nitrogen fixation is the second most important
    biological process on earth.
  • Importance in agriculture
  • Legumes such as peas, beans, lentils, soybeans,
    alfalfa, and clover help to feed the
    meat-producing animals which feed humans.
  • Crop yields are greatly improved in nodulated
    plants legumes can grow well in poor soil where
    there is not enough fixed nitrogen to support
    other types of plants.
  • After harvest legume roots left in the soil decay
    easily releasing organic nitrogen compounds for
    uptake by the next generation. Farmers take
    advantage of this natural fertilization by
    rotating a leguminious crop with a non
    leguminious one. This helps the crop grow
    easier.

8
Rhizobium - Importance
  • Although much of the nitrogen is removed when
    protein-rich grain or hay is harvested,
    significant amounts can remain in the soil for
    future crops. This is especially important when
    nitrogen fertilizer is not used, as in organic
    rotation schemes or some less-industrialized
    countries. Nitrogen is the most commonly
    deficient nutrient in many soils around the world
    and it is the most commonly supplied plant
    nutrient. Supply of nitrogen through fertilizers
    has severe environmental concerns. Nitrogen
    fixation by Rhizobium is also beneficial to the
    environment.

9
Enterobacteria What is it?
  • Members of the family Enterobacteriaceae which
    include familiar pathogens such as Salmonella and
    Escherichia coli.
  • Genetic studies place them among the
    Proteobacteria and give them their own order
    Enterobacteriales.

10
Scientific Classification of Enterobacteria
  • Family Enterobacteriaceae
  • Order Enterobacteriales
  • Kingdom Bacteria
  • Phylum Proteobacteria
  • Class Gamma Proteobacteria

11
Morphology of the Enterobacteria
  • Rod Shaped
  • Typically 1-5 µm (micrometers) long
  • Gram Negative stains

Salmonella is a Gram negative Enterobacteria
12
Mode of MovementEnterobacteria
  • Most have flagella, but some are non-motile.
  • Possess Pili

Flagella
13
EnterobacteriaChemical Composition
  • Enterobacteria usually lack Cytochrome C Oxidase.
  • Contains a Capsule Capsule is a polysaccharide
    layer surrounding the surface of some bacterial
    cells and is a major factor that functions as a
    protective barrier .
  • Antigenic structure
  • K (capsular) antigens capsular polysaccharide
  • H (flagellar) antigens flagellar proteins of
    motile genera and species absent in non-motile
    genera
  • O (somatic) antigens O-specific polysaccharide
    side chain of lipopolysaccharide

14
Unique Facts-Enterobacteria
  • Most species grow well at 37 and some grow
    better at 25 -30
  • All species attack glucose, forming acid.
  • All are aerobic but can be facultative anaerobic
  • Over 30 genera and 120 species

15
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16
Enterobacteria Medical and Pathogenic Importance
  • Salmonella
  • E. Coli
  • Pneumonia
  • Meningitis
  • Most members of the Enterobacteriaceae Family
    cause secondary infections of wounds, the urinary
    and respiratory tracts, and the circulatory
    system

17
Actinomycetes-Unique Characteristics
  • Anaerobic
  • Almost always produce granules
  • Can affect cattle, causing the disease Lumpy
    Jaw
  • Produce Spores
  • Needs organic C for energy

18
Medical Importanceof Actinomycetes
  • Most common cause is Actinomyces israelii which
    infects both man and animals
  • Commonly found in the jaw, but can also be found
    in the abdominal area
  • Can produce antibiotics
  • Gram-positive bacteria

19
Morphology-Actinomycetes
  • Rod shape
  • Frequently branches (hyphae) ranging from .5-1.5
    micrometers in length
  • Genetic material is coiled up in the hyphae

20
Actinomycotic mycetomatous granule due to the
bacteria Streptomyces somaliensis. Streptomyces
are Gram-positive aerobic actinomycetes known for
their production of antimicrobial substances.
Though they seldom cause human disease,
infections can cause lesions of the skin.
21
Composition of Actinomycetes
  • They form mycelia of thin branching hyphae.
  • DNA is coiled inside the hyphae.
  • The cell wall of the hyphae is made up of
    cross-linked polymer containing short chains of
    amino acids and long chains of amino sugars
  • No membrane-bound cell organelles

22
  • http//www.life.umd.edu/classroom/bsci424/pathogen
    descriptions/Enterobacteriaceae.htm
  • http//www.microbiologyonline.org.uk/forms/rhizobi
    um.pdf
  • http//pathmicro.med.sc.edu/mycology/mycology-2.ht
    m
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