Single-Cell Measurements of Fixation and Intercellular Exchange of C and N in the Filaments of the Heterocyst-Forming Cyanobacterium <italic toggle="yes">Anabaena</italic> sp. Strain PCC 7120

ABSTRACT Under diazotrophic conditions, the model filamentous, heterocyst-forming cyanobacterium Anabaena sp. strain PCC 7120 develops a metabolic strategy based on the physical separation of the processes of oxygenic photosynthesis, in vegetative cells, and N2 fixation, in heterocysts. This strateg...

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Autores principales:	Mercedes Nieves-Morión, Enrique Flores, Martin J. Whitehouse, Aurélien Thomen, Rachel A. Foster
Formato:	article
Lenguaje:	EN
Publicado:	American Society for Microbiology 2021
Materias:	LG-SIMS NanoSIMS carbon fixation cyanobacteria intercellular communication nitrogen fixation Microbiology QR1-502
Acceso en línea:	https://doaj.org/article/633c3ab81a3e4fc396a82eae2e300694
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spelling	oai:doaj.org-article:633c3ab81a3e4fc396a82eae2e3006942021-11-10T18:37:50ZSingle-Cell Measurements of Fixation and Intercellular Exchange of C and N in the Filaments of the Heterocyst-Forming Cyanobacterium <italic toggle="yes">Anabaena</italic> sp. Strain PCC 712010.1128/mBio.01314-212150-7511https://doaj.org/article/633c3ab81a3e4fc396a82eae2e3006942021-08-01T00:00:00Zhttps://journals.asm.org/doi/10.1128/mBio.01314-21https://doaj.org/toc/2150-7511ABSTRACT Under diazotrophic conditions, the model filamentous, heterocyst-forming cyanobacterium Anabaena sp. strain PCC 7120 develops a metabolic strategy based on the physical separation of the processes of oxygenic photosynthesis, in vegetative cells, and N2 fixation, in heterocysts. This strategy requires the exchange of carbon and nitrogen metabolites and their distribution along the filaments, which takes place through molecular diffusion via septal junctions involving FraCD proteins. Here, Anabaena was incubated in a time course (up to 20 h) with [13C]bicarbonate and 15N2 and analyzed by secondary ion mass spectrometry imaging (SIMS) (large-geometry SIMS [LG-SIMS] and NanoSIMS) to quantify C and N assimilation and distribution in the filaments. The 13C/12C and 15N/14N ratios measured in wild-type filaments showed a general increase with time. The enrichment was relatively homogeneous in vegetative cells along individual filaments, while it was reduced in heterocysts. Heterocysts, however, accumulated recently fixed N at their poles, in which the cyanophycin plug [multi-l-arginyl-poly(l-aspartic acid)] is located. In contrast to the rather homogeneous label found along stretches of vegetative cells, 13C/12C and 15N/14N ratios were significantly different between filaments both at the same and different time points, showing high variability in metabolic states. A fraC fraD mutant did not fix N2, and the 13C/12C ratio was homogeneous along the filament, including the heterocyst in contrast to the wild type. Our results show the consumption of reduced C in the heterocysts associated with the fixation and export of fixed N and present an unpredicted heterogeneity of cellular metabolic activity in different filaments of an Anabaena culture under controlled conditions. IMPORTANCE Filamentous, heterocyst-forming cyanobacteria represent a paradigm of multicellularity in the prokaryotic world. Physiological studies at the cellular level in model organisms are crucial to understand metabolic activities and qualify specific aspects related to multicellularity. Here, we used stable isotopes (13C and 15N) coupled to LG-SIMS and NanoSIMS imaging to follow single-cell C and N2 fixation and metabolic dynamics along the filaments in the model heterocyst-forming cyanobacterium Anabaena sp. strain PCC 7120. Our results show a close relationship between C and N fixation and distribution in the filaments and indicate that wild-type filaments in a culture can exhibit a substantial variability of metabolic states. This illustrates how some novel properties can be appreciated by studying microbial cultures at the single-cell level.Mercedes Nieves-MoriónEnrique FloresMartin J. WhitehouseAurélien ThomenRachel A. FosterAmerican Society for MicrobiologyarticleLG-SIMSNanoSIMScarbon fixationcyanobacteriaintercellular communicationnitrogen fixationMicrobiologyQR1-502ENmBio, Vol 12, Iss 4 (2021)
institution	DOAJ
collection	DOAJ
language	EN
topic	LG-SIMS NanoSIMS carbon fixation cyanobacteria intercellular communication nitrogen fixation Microbiology QR1-502
spellingShingle	LG-SIMS NanoSIMS carbon fixation cyanobacteria intercellular communication nitrogen fixation Microbiology QR1-502 Mercedes Nieves-Morión Enrique Flores Martin J. Whitehouse Aurélien Thomen Rachel A. Foster Single-Cell Measurements of Fixation and Intercellular Exchange of C and N in the Filaments of the Heterocyst-Forming Cyanobacterium <italic toggle="yes">Anabaena</italic> sp. Strain PCC 7120
description	ABSTRACT Under diazotrophic conditions, the model filamentous, heterocyst-forming cyanobacterium Anabaena sp. strain PCC 7120 develops a metabolic strategy based on the physical separation of the processes of oxygenic photosynthesis, in vegetative cells, and N2 fixation, in heterocysts. This strategy requires the exchange of carbon and nitrogen metabolites and their distribution along the filaments, which takes place through molecular diffusion via septal junctions involving FraCD proteins. Here, Anabaena was incubated in a time course (up to 20 h) with [13C]bicarbonate and 15N2 and analyzed by secondary ion mass spectrometry imaging (SIMS) (large-geometry SIMS [LG-SIMS] and NanoSIMS) to quantify C and N assimilation and distribution in the filaments. The 13C/12C and 15N/14N ratios measured in wild-type filaments showed a general increase with time. The enrichment was relatively homogeneous in vegetative cells along individual filaments, while it was reduced in heterocysts. Heterocysts, however, accumulated recently fixed N at their poles, in which the cyanophycin plug [multi-l-arginyl-poly(l-aspartic acid)] is located. In contrast to the rather homogeneous label found along stretches of vegetative cells, 13C/12C and 15N/14N ratios were significantly different between filaments both at the same and different time points, showing high variability in metabolic states. A fraC fraD mutant did not fix N2, and the 13C/12C ratio was homogeneous along the filament, including the heterocyst in contrast to the wild type. Our results show the consumption of reduced C in the heterocysts associated with the fixation and export of fixed N and present an unpredicted heterogeneity of cellular metabolic activity in different filaments of an Anabaena culture under controlled conditions. IMPORTANCE Filamentous, heterocyst-forming cyanobacteria represent a paradigm of multicellularity in the prokaryotic world. Physiological studies at the cellular level in model organisms are crucial to understand metabolic activities and qualify specific aspects related to multicellularity. Here, we used stable isotopes (13C and 15N) coupled to LG-SIMS and NanoSIMS imaging to follow single-cell C and N2 fixation and metabolic dynamics along the filaments in the model heterocyst-forming cyanobacterium Anabaena sp. strain PCC 7120. Our results show a close relationship between C and N fixation and distribution in the filaments and indicate that wild-type filaments in a culture can exhibit a substantial variability of metabolic states. This illustrates how some novel properties can be appreciated by studying microbial cultures at the single-cell level.
format	article
author	Mercedes Nieves-Morión Enrique Flores Martin J. Whitehouse Aurélien Thomen Rachel A. Foster
author_facet	Mercedes Nieves-Morión Enrique Flores Martin J. Whitehouse Aurélien Thomen Rachel A. Foster
author_sort	Mercedes Nieves-Morión
title	Single-Cell Measurements of Fixation and Intercellular Exchange of C and N in the Filaments of the Heterocyst-Forming Cyanobacterium <italic toggle="yes">Anabaena</italic> sp. Strain PCC 7120
title_short	Single-Cell Measurements of Fixation and Intercellular Exchange of C and N in the Filaments of the Heterocyst-Forming Cyanobacterium <italic toggle="yes">Anabaena</italic> sp. Strain PCC 7120
title_full	Single-Cell Measurements of Fixation and Intercellular Exchange of C and N in the Filaments of the Heterocyst-Forming Cyanobacterium <italic toggle="yes">Anabaena</italic> sp. Strain PCC 7120
title_fullStr	Single-Cell Measurements of Fixation and Intercellular Exchange of C and N in the Filaments of the Heterocyst-Forming Cyanobacterium <italic toggle="yes">Anabaena</italic> sp. Strain PCC 7120
title_full_unstemmed	Single-Cell Measurements of Fixation and Intercellular Exchange of C and N in the Filaments of the Heterocyst-Forming Cyanobacterium <italic toggle="yes">Anabaena</italic> sp. Strain PCC 7120
title_sort	single-cell measurements of fixation and intercellular exchange of c and n in the filaments of the heterocyst-forming cyanobacterium <italic toggle="yes">anabaena</italic> sp. strain pcc 7120
publisher	American Society for Microbiology
publishDate	2021
url	https://doaj.org/article/633c3ab81a3e4fc396a82eae2e300694
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Single-Cell Measurements of Fixation and Intercellular Exchange of C and N in the Filaments of the Heterocyst-Forming Cyanobacterium <italic toggle="yes">Anabaena</italic> sp. Strain PCC 7120

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