REAGENT or RESOURCE	SOURCE	IDENTIFIER
Bacterial and Virus Strains
Anabaena sp. PCC 7120	Rippka et al., 1979	PCC 7120
Nostoc punctiforme PCC 73102	Rippka et al., 1979	PCC 73102
Trichodesmium erythraeum IMS101	Stocker Lab, ETH Zürich	IMS101
E. coli NEB 10-beta (electrocompetent)	NEB	Cat#C3020K
E. coli HB101	Sambrook et al., 1989	N/A
E. coli J53 (RP-4)	Wolk et al., 1984	N/A
Strain details	This study	see Table S1
Chemicals, Peptides, and Recombinant Proteins
Calcein, AM	Invitrogen	Cat#C3099
CCCP (Carbonyl cyanide 3-chlorophenylhydrazone)	Sigma-Aldrich	Cat#C2759; CAS: 555-60-2
30% hydrogen peroxide	Carl Roth	Cat#CP26; CAS: 7722-84-1
Chloramphenicol	Carl Roth	Cat#3886; CAS: 56-75-7
Spectinomycin dihydrochloride pentahydrate	Sigma-Aldrich	Cat#S4014; CAS: 22189-32-8
Neomycin sulfate	Sigma-Aldrich	Cat#PHR1491; CAS: 1405-10-3
Streptomycin sulfate	Sigma-Aldrich	Cat#S1400000; CAS: 3810-74-0
Kanamycin sulfate	Carl Roth	Cat#T832; CAS: 25389-94-0
Critical Commercial Assays
Monarch Plasmid Miniprep Kit	NEB	Cat#T1010S
Monarch DNA Gel Extraction Kit	NEB	Cat#T1020S
Monarch PCR & DNA Cleanup Kit	NEB	Cat#T1030S
ATP Determination Kit (A22066)	Invitrogen	Cat#10700345
Deposited Data
Anabaena sp. PCC 7120 reference genome, CyanoBase	Kazusa DNA Research Institute (KDRI)	http://genome.microbedb.jp/cyanobase/
Anabaena sp. PCC 7120 example tomogram	This study	EMDB: EMD-4949
Anabaena sp. PCC 7120 CCCP treated example tomogram	This study	EMDB: EMD-4957
Anabaena sp. PCC 7120 ΔSepJ example tomogram	This study	EMDB: EMD-4952
Anabaena sp. PCC 7120 ΔSjcF1 example tomogram	This study	EMDB: EMD-4951
Anabaena sp. PCC 7120 ΔAmiC1 example tomogram	This study	EMDB: EMD-4956
Anabaena sp. PCC 7120 ΔFraD example tomogram	This study	EMDB: EMD-4953
Anabaena sp. PCC 7120 ΔFraC example tomogram	This study	EMDB: EMD-4955
Anabaena sp. PCC 7120 ΔFraCD example tomogram	This study	EMDB: EMD-4954
Anabaena sp. PCC 7120 GFP-FraD example tomogram	This study	EMDB: EMD-4950
Subtomogram average of septal junctions of Anabaena sp. PCC 7120	This study	EMDB: EMD-4969
Subtomogram average of septal junctions of Anabaena sp. PCC 7120 after 24h in the dark	This study	EMDB: EMD-4968
Subtomogram average of septal junctions of Anabaena sp. PCC 7120 after CCCP treatment	This study	EMDB: EMD-4962
Subtomogram average of septal junctions of Anabaena sp. PCC 7120 after washing out CCCP	This study	EMDB: EMD-4963
Subtomogram average of septal junctions of Anabaena sp. PCC 7120 ΔSepJ	This study	EMDB: EMD-4965
Subtomogram average of septal junctions of Anabaena sp. PCC 7120 ΔSjcF1	This study	EMDB: EMD-4966
Subtomogram average of septal junctions of Anabaena sp. PCC 7120 ΔAmiC1	This study	EMDB: EMD-4964
Subtomogram average of septal junctions of Anabaena sp. PCC 7120 FraD-GFP	This study	EMDB: EMD-4967
Subtomogram average of septal junctions of Anabaena sp. PCC 7120 after 45 s CCCP treatment	This study	EMDB: EMD-4961
Experimental Models: Organisms/Strains
Anabaena sp. PCC 7120 SR477	Berendt et al., 2012	N/A
Anabaena sp. PCC 7120 CSVT22	Merino-Puerto et al., 2011	N/A
Anabaena sp. PCC 7120 CSVT2	Merino-Puerto et al., 2010	N/A
Anabaena sp. PCC 7120 CSVT22 pIM496	B. Jan, I.M., and K.F., unpublished data	N/A
Anabaena sp. PCC 7120 CSVM34	Mariscal et al., 2011	N/A
Anabaena sp. PCC 7120 AFS-I-sjcF1	Rudolf et al., 2015	N/A
Anabaena sp. PCC 7120 CSVT22.768	This study	N/A
Anabaena sp. PCC 7120 CSVT2.768	This study	N/A
Anabaena sp. PCC 7120 CSVT2.779	This study	N/A
Strain details	This study	see Table S1
Oligonucleotides
Primer 1998: GATATCCCGCAAGAGGCCCTTTCGTCTT CAAGAATTCTGCCGTTCCTTGTCATCTG	This study	N/A
Primer 2000: ATGAGTAAAGGAGAAGAACTTTTC	This study	N/A
Primer 2001: ACTCCAGTGAAAAGTTCTTCTCCTTTACT CATAGACACTCAACAAAAAAGGGAAACTGTAG	This study	N/A
Primer 2040: CCCTTTTTTGTTGAGTGTCTTGCTAACTC GTTAAGTTAC	This study	N/A
Primer 2041: GTAACTTAACGAGTTAGCAAGACACTCAA CAAAAAAGGGAAAC	This study	N/A
Primer 2042: CACTATAGGGAGACCACAACGGTTTCCCT CTACCGGGATCCTCACTGCTGCGGTGGCGCTG	This study	N/A
Primer 2092: GGCATGGATGAACTATACAAGCTTAATTTA TTATTTAAAGACC	This study	N/A
Primer 2093: AGCTTGTATAGTTCATCCATGCC	This study	N/A
Recombinant DNA
Plasmid: pRL1049	Black and Wolk, 1994	N/A
Plasmid: pIM496	Berendt et al., 2012	N/A
Plasmid: pIM768	This study	N/A
Plasmid: pIM779	This study	N/A
Plasmid: pIM759	This study	N/A
Plasmid: pRL528	Wolk et al., 1984	Addgene Plasmid #58495
Plasmid: pCSVT56	Merino-Puerto et al., 2010	N/A
Plasmid details	This study	see Table S1
Software and Algorithms
ImageJ version 1.51j	Rasband, W.S., ImageJ, U. S. National Institutes of Health, Bethesda, Maryland, USA	https://imagej.nih.gov/ij
ZEN 2.3 (blue edition)	ZEISS	https://www.zeiss.de/mikroskopie/downloads.html?vaURL=www.zeiss.de/mikroskopie/downloads/zen.html
GraphPad PRISM version 6.01 for Windows	La Jolla, CA, USA	https://www.graphpad.com/
ImageJ Time Series Analyzer V3	Balaji, J., Department of Neurobiology, UCLA	https://imagej.nih.gov/ij/plugins/time-series.html
IMOD	Kremer et al., 1996	http://bio3d.colorado.edu/imod/
UCSF Tomography	Zheng et al., 2007	http://msg.ucsf.edu
SerialEM	Mastronarde, 2005	http://bio3d.colorado.edu/SerialEM/
PEET	Nicastro et al., 2006	http://bio3d.colorado.edu/PEET/
Other
Confocal microscope	ZEISS	LSM 800
Plunge freezing robot Vitrobot Mk IV	Thermo Fisher	Vitrobot Mk IV
Dual Beam FIB/SEM microscope Helios NanoLab 600i	Thermo Fisher	Helios Nanolab600i
300kV Cryo-transmission electron microscope Titan Krios	Thermo Fisher	Titan Krios
Luminometer	Berthold Detection System	Sirius