In:
Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 106, No. 15 ( 2009-04-14), p. 6345-6350
Abstract:
The marine cyanobacterium Trichodesmium is ubiquitous in tropical and subtropical seas and is an important contributor to global N and C cycling. We sought to characterize metabolic uptake patterns in individual Trichodesmium IMS-101 cells by quantitatively imaging 13 C and 15 N uptake with high-resolution secondary ion mass spectrometry (NanoSIMS). Trichodesmium fix both CO 2 and N 2 concurrently during the day and are, thus, faced with a balancing act: the O 2 evolved during photosynthesis inhibits nitrogenase, the key enzyme in N 2 fixation. After performing correlated transmission electron microscopy (TEM) and NanoSIMS analysis on trichome thin-sections, we observed transient inclusion of 15 N and 13 C into discrete subcellular bodies identified as cyanophycin granules. We speculate that Trichodesmium uses these dynamic storage bodies to uncouple CO 2 and N 2 fixation from overall growth dynamics. We also directly quantified both CO 2 and N 2 fixation at the single cell level using NanoSIMS imaging of whole cells in multiple trichomes. Our results indicate maximal CO 2 fixation rates in the morning, compared with maximal N 2 fixation rates in the afternoon, bolstering the argument that segregation of CO 2 and N 2 fixation in Trichodesmium is regulated in part by temporal factors. Spatial separation of N 2 and CO 2 fixation may also have a role in metabolic segregation in Trichodesmium . Our approach in combining stable isotope labeling with NanoSIMS and TEM imaging can be extended to other physiologically relevant elements and processes in other important microbial systems.
Type of Medium:
Online Resource
ISSN:
0027-8424
,
1091-6490
DOI:
10.1073/pnas.0810547106
Language:
English
Publisher:
Proceedings of the National Academy of Sciences
Publication Date:
2009
detail.hit.zdb_id:
209104-5
detail.hit.zdb_id:
1461794-8
SSG:
11
SSG:
12
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