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Survival of dessicated root-nodule bacteria


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Bushby, Harold Vivian Anddrew 1974 , 'Survival of dessicated root-nodule bacteria', PhD thesis, University of Tasmania.

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It has been demonstrated that the fast-growing
root-nodule bacteria are more susceptible to desiccation
than the slow-growing species. This reaction to drying
has been related to the amount of water retained by the
two bacteria] groups at any vapour pressure. Invariably,
the fast-growing bacteria retained more water than the
slow-growing species. This may be a reflection of the
higher surface energies involved in 'wetting the fast-growing
species at any vapour pressure, and the larger
surface area available for adsorption of water by these
bacteria relative to the slow-growing rhizobia.
The different responses of the two' bacterial groups to
desiccation is probably related to the different amounts
of water retained rather than to differences in the rate of
movement of water between the bacteria and the environment
on desiccation.
Very little effect of desiccation um lysozyme
sensitivity could be detected for either fast-or slow-growing
rhizobia. Consequently, it is Unlikely that sub-lethal.
damage involves alterations of the integrity of the
lipopolysacchnride layer of the bacteria surviving
desiccation. However, desiccation did cause drastic changes
to the surface features of rhizobia as determined by
fluorescence of bacteria in the presence of
l-anilino-8-naphthalene sulphonate. This could reflect
damage to the cytoplasmic membrane and leakage of
intracellular material from killed bacteria.
Montmorillonite to was found to protect the fast-growing
but pot the slow-growing rhizobia from
desiccation. Protection of the former group of bacteria is
dependent upon the precise clay/bacterium association as not
all combinations resulted in increased ability of these
bacteria to survive drying . It has been postulated that
the mechanism of action or montmorillonite is to decrease
the intracellular water content of desiccated fast -growing
rhizobia below an undefined critical level . As the water
content of desiccated slow-growing rhizobia is normally
below this value, further removal intracelluular water
by clay has to effect upon survival .
Of all the other additives tested, only maltose,
sucrose, glucose and polyvinylpyrolidone (PVT) protected
both the fast -and slow -growing rhizohia from dryng. The
effect of polyethylene glycol (MW 6000) was similar t o the
effect of montmorillionite as the polymer protected the fast-
growing bacteria but not the slow-growing species. All other
additives tested were either detrimental or had no effect upon
survival of desiccated bacteria. The mechanism of protection
of sugars and PVP is unknown but it has been suggested that the
site of action may involve the cytoplasmic membrane.

Item Type: Thesis - PhD
Authors/Creators:Bushby, Harold Vivian Anddrew
Keywords: Root-tubercles, Bacterial wilt diseases
Copyright Holders: The Author
Copyright Information:

Copyright 1974 the Author - The University is continuing to endeavour to trace the copyright
owner(s) and in the meantime this item has been reproduced here in good faith. We
would be pleased to hear from the copyright owner(s).

Additional Information:

Thesis (Ph.D.) - University of Tasmania, 1974. Bibliography: l. 343-361

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