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Maroniche GA,
García JE,
Salcedo F,
Creus CM,
( 2017 ) Molecular identification of Azospirillum spp.: Limitations of 16S rRNA and qualities of rpoD as genetic markers. PMID : 28024520 : DOI : 10.1016/j.micres.2016.11.009 Abstract >>
Since their discovery, plant-growth promoting rhizobacteria from the genus Azospirillum have been subjected to intensive research due to their biotechnological potential as crop inoculants. Phylogenetic analysis of Azospirillum spp. is carried out by 16S rRNA sequencing almost exclusively, but inconsistencies and low confidence often arise when working with close species. In this work, it was observed that these difficulties might be explained by a high number of rRNA operons with considerable inter-genic variability within Azospirillum genomes. To search for alternative genetic markers from a list of housekeeping genes, the correlation between pairwise gene and whole-genome similarities was examined. Due to its good performance, rpoD was selected for further analyses. Genus-specific primers for the PCR-amplification and sequencing of rpoD from Azospirillum spp. were designed and tested on 16 type strains of different species. The sequences obtained were used for inferring a phylogenetic tree of the genus, which was in turn used as a reference to successfully identify a collection of 31 azospirilla isolated from many different locations of Argentine. In addition, several strains that might represent novel species were detected. The results indicate that the sequencing of rpoD is a suitable alternative method for a confident molecular identification in Azospirillum spp.
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( 2013 ) Azospirillum fermentarium sp. nov., a nitrogen-fixing species isolated from a fermenter. PMID : 23645021 : DOI : 10.1099/ijs.0.050872-0 DOI : 10.1099/ijs.0.050872-0 Abstract >>
An aerobic, Gram-stain-negative, spiral or rod-shaped, non-spore-forming, diazotrophic bacterium (strain CC-LY743(T)) was isolated from a fermentative tank in Taiwan. Strain CC-LY743(T) was able to grow at 20-37 �XC and pH 6.0-8.0 and tolerated up to 3.0 % (w/v) NaCl. It was positive for nitrogen fixation, with activity of 10.6 nmol ethylene h(-1). 16S rRNA gene sequence analysis of strain CC-LY743(T) showed highest similarity to Azospirillum picis DSM 19922(T) (96.1 %), Azospirillum oryzae JCM 21588(T) (96.0 %) and Azospirillum rugosum DSM 19657(T) (96.0 %) and lower similarity (<96.0 %) to all other Azospirillum species. Highest nifH gene sequence similarities were obtained with Azospirillum brasilense BCRC 12270(T) (92.0 %), Azospirillum formosense BCRC 80273(T) (92.3 %) and A. rugosum DSM 19657(T) (91.8 %). It was positive in the rapid identification by a genus-specific primer set. The predominant quinone system was ubiquinone 10 (Q-10) and the DNA G+C content was 69.6��0.1 mol%. The major fatty acids found in strain CC-LY743(T) were n-C16 : 0, C19 : 0 cyclo �s8c, C14 : 0 3-OH/C16 : 1 iso I, C16 : 1�s7c/C16 : 1�s6c and C18 : 1�s7c/C18 : 1�s6c. Based on its phylogenetic, phenotypic and chemotaxonomic features, strain CC-LY743(T) is considered to represent a novel species within the genus Azospirillum for which the name Azospirillum fermentarium sp. nov. is proposed. The type strain is CC-LY743(T) (= BCRC 80505(T) = JCM 18688(T) = LMG 27264(T)).
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