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- Title
Alteration of the exopolysaccharide production and the transcriptional profile of free-living Frankia strain CcI3 under nitrogen-fixing conditions.
- Authors
Lee, Hae-In; Donati, Andrew; Hahn, Dittmar; Tisa, Louis; Chang, Woo-Suk
- Abstract
We investigated the effect of different nitrogen (N) sources on exopolysaccharide (EPS) production and composition by Frankia strain CcI3, a N-fixing actinomycete that forms root nodules with Casuarina species. Frankia cells grown in the absence of NHCl (i.e., under N-fixing conditions) produced 1.7-fold more EPS, with lower galactose (45.1 vs. 54.7 mol%) and higher mannose (17.3 vs. 9.7 mol%) contents than those grown in the presence of NHCl as a combined N-source. In the absence of the combined N-source, terminally linked and branched residue contents were nearly twice as high with 32.8 vs. 15.1 mol% and 15.1 vs. 8.7 mol%, respectively, than in its presence, while the content of linearly linked residues was lower with 52.1 mol% compared to 76.2 mol%. To find out clues for the altered EPS production at the transcriptional level, we performed whole-gene expression profiling using quantitative reverse transcription PCR and microarray technology. The transcription profiles of Frankia strain CcI3 grown in the absence of NHCl revealed up to 2 orders of magnitude higher transcription of nitrogen fixation-related genes compared to those of CcI3 cells grown in the presence of NHCl. Unexpectedly, microarray data did not provide evidence for transcriptional regulation as a mechanism for differences in EPS production. These findings indicate effects of nitrogen fixation on the production and composition of EPS in Frankia strain CcI3 and suggest posttranscriptional regulation of enhanced EPS production in the absence of the combined N-source.
- Subjects
MICROBIAL exopolysaccharides; NITROGEN-fixing bacteria; FRANKIA; ROOT-tubercles; CASUARINA; MICROARRAY technology; POLYMERASE chain reaction
- Publication
Applied Microbiology & Biotechnology, 2013, Vol 97, Issue 24, p10499
- ISSN
0175-7598
- Publication type
Article
- DOI
10.1007/s00253-013-5277-z