Page 2 Plant-Bacteria Interactions Edited by Iqbal Ahmad, John ...
Page 2 Plant-Bacteria Interactions Edited by Iqbal Ahmad, John ...
Page 2 Plant-Bacteria Interactions Edited by Iqbal Ahmad, John ...
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Methylobacterium This genus is formed <strong>by</strong> facultatively methylotrophic bacteria<br />
and is located in the family Methylobacteraceae. Only one species, Methylobacterium<br />
nodulans [46,47], is able to fix dinitrogen in symbiosis with legumes (Crotalaria spp.).<br />
No Methylobacterium species, other than M. nodulans, have been confirmed to have<br />
the ability of symbiotic dinitrogen fixation and the structures of NodA of M. nodulans<br />
and Bradyrhizobium species are similar. These two facts have led to the inference that<br />
M. nodulans gained this ability <strong>by</strong> obtaining symbiotic genes that were horizontally<br />
transferred from Bradyrhizobium species [9].<br />
Devosia The genus Devosia is included in the family Hyphomicrobiaceae of Rhizobiales.<br />
This genus contains a species D. neptuniae [48,49] that is capable of nitrogen<br />
fixation in symbiosis with Neptunia natans.<br />
4.3.1.2 Betaproteobacteria<br />
4.3 Symbiotic <strong>Plant</strong> Growth Promoting <strong>Bacteria</strong>j67<br />
Burkholderia MembersofthegenusBurkholderiaofthefamilyBurkholderiaceaeform<br />
a discrete and compact monophyletic group with a high bootstrap value, which is<br />
composed only of Burkholderia species and its chemotaxonomic and phenotypic charactersare<br />
specific of thisgenus[9].The genusBurkholderia contains diverse species with<br />
different physiological and ecological properties, which were isolated from soils, plants,<br />
animals and humans. However, only two strains (STM678 and STM815) have been<br />
confirmed to have the ability of symbiotic nitrogen fixation [50]. Based on the fact that<br />
high nodAB similarity is observed between these strains and legume symbionts of the<br />
class Alphaproteobacteria, it seems that the symbiotic genes have been horizontally<br />
transferred among strains, crossing the boundary between these classes [50].<br />
Four LNB species of Burkholderia have been published, namely Burkholderia tuberum<br />
sp.nov.[51,52],B.phymatumsp.nov.[51,52],B.mimosariumsp.nov.[53]andB.nodosasp.<br />
nov. [54].<br />
Ralstonia This genus is also allocated in the family Burkholderiaceae and, as the genus<br />
Burkholderia, it is ubiquitous. The definitions and circumscriptions of the genus Ralstonia<br />
are widely accepted because the monophyletic group formed <strong>by</strong> its species is<br />
homogeneous and presents a high bootstrap value [9]. Furthermore, the chemotaxonomic<br />
and phenotypic characters of its species are specific to the group [55].<br />
Onlyonespeciesofthegenus,Ralstoniataiwanensis [56]iscapable ofnitrogenfixation<br />
in symbiosis, but no insight on the acquisition of this trait has yet been obtained.<br />
4.3.2<br />
<strong>Bacteria</strong> Capable of Fixing Dinitrogen in Symbiosis with <strong>Plant</strong>s Other Than Legumes<br />
Special attention has been given to LNB for their agricultural importance. However,<br />
other organisms and symbioses are increasingly seen as major contributors to<br />
overall nitrogen fixation and into sustaining diverse agricultural, forest and ecosystem<br />
settings. These include actinorhizal symbioses (e.g. between Casuarina and<br />
Frankia) and associative relationships including sugarcane (Saccharum officinarum)<br />
and coffee plants with Gluconacetobacter spp. [57,58].
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