|Temporal patterns and intra- and inter-cellular variability in carbon and nitrogen assimilation by the unicellular cyanobacterium Cyanothecesp. ATCC 51142|Polerecky, L.; Masuda, T.; Eichner, M.; Rabouille, S.; Vancová, M.; Kienhuis, M.V.M.; Bernát, G.; Bonomi-Barufi, J.; Campbell, D.A.; Claquin, P.; Červený, J.; Giordano, M.; Kotabová, E.; Kromkamp, J.; Lombardi, A.T.; Lukeš, M.; Prášil, O.; Stephan, S.; Suggett, D.; Zavřel, T.; Halsey, K.H. (2021). Temporal patterns and intra- and inter-cellular variability in carbon and nitrogen assimilation by the unicellular cyanobacterium Cyanothecesp. ATCC 51142. Front. Microbiol. 12: 620915. https://doi.org/10.3389/fmicb.2021.620915
In: Frontiers in Microbiology. Frontiers Media: Lausanne. ISSN 1664-302X; e-ISSN 1664-302X, meer
Crocosphaera subtropica (former Cyanothece sp. ATCC 51142); Cyanothece; photosynthesis; carbon fixation; nitrogen fixation; nanoSIMS; TEM
Unicellular nitrogen fixing cyanobacteria (UCYN) are abundant members of phytoplankton communities in a wide range of marine environments, including those with rapidly changing nitrogen (N) concentrations. We hypothesized that differences in N availability (N2 vs. combined N) would cause UCYN to shift strategies of intracellular N and C allocation. We used transmission electron microscopy and nanoscale secondary ion massspectrometry imaging to track assimilation and intracellular allocation of13C-labeled CO2 and 15N-labeled N2 or NO3 at different periods across a diel cycle in Cyanothece sp. ATCC 51142. We present new ideas on interpreting these imaging data, including the influences of pre-incubation cellular C and N contents and turnover rates of inclusion bodies. Within cultures growing diazotrophically, distinct subpopulations were detected that fixed N2 at night or in the morning. Additional significant within-population heterogeneity was likely caused by differences in the relative amounts of N assimilated into cyanophycin from sources externaland internal to the cells. Whether growing on N2 or NO 3, cells prioritized cyanophycin synthesis when N assimilation rates were highest. N assimilation in cells growing on NO3 switched from cyanophycin synthesis to protein synthesis, suggesting that once a cyanophycin quota is met, it is bypassed in favor of protein synthesis. Growth on NO3 also revealed that at night, there is a very low level of CO2 assimilation into polysaccharides simultaneous with their catabolism for protein synthesis. This studyrevealed multiple, detailed mechanisms underlying C and N management in Cyanothece that facilitate its success in dynamic aquatic environments.