To determine fatty acid profiles, lipids were isolated from cell pellets using a modified Bligh-Dyer extraction followed by transesterification with sodium methoxide, and GC-MS analysis. Samples of an exponentially growing culture were collected by centrifugation and CPI-613 resuspended in 0.8 ml of H2O. 3 ml CHCl3:MeOH was added and the vials were vortexed for 1 min. After 1 h incubation at 60uC, 1 ml of CHCl3 was added and the vials were vortexed for 1 min. Then, 1 ml of H2O was added, the vials were vortexed for 1 min and briefly centrifuged. The lower layer was recovered into a fresh vial and solvent was removed under a stream of nitrogen. 1 ml of 0.5 M sodium Rapamycin methoxide in MeOH was used to resuspend the dried crude lipid and the reaction was incubated for 30 min at room temperature. The reaction was quenched with 1 ml of H2O and the resulting methyl esters were recovered into 2 ml of hexane by vortexing for 1 min. The hexane layer was clarified by centrifugation and sampled for GCMS analysis. The extracts were analyzed on an Agilent 6890N GC equipped with a DB-FFAP column coupled to a 5973 inert mass selective detector . Helium was used as the carrier gas with a flow rate of 1.2 ml/min, and 1 ml was injected into the column with a 50:1 split ratio. The column temperature was held at 100uC for 5 min and then ramped at 10uC/min to 250uC and held for 10 min. The total run time was 30 min. Identification of the fatty acids was based on retention times and fragmentation patterns of standards. E. coli strains were grown in 3 ml LB with the appropriate antibiotic and incubated at 37uC overnight. Cells were harvested from 2 ml of each E. coli culture by centrifugation and resuspended in 2 ml fresh LB. This step was repeated twice to wash the cells. After the third centrifugation, the cells were resuspended in 200 ml BG-11. Five milliliters of a growing Leptolyngbya BL0902 culture were harvested by centrifugation at low speed and resuspended in 1 ml BG-11. The filaments were then fragmented in a water bath sonicator for 5 to 15 min so that more than half of the filaments were shorter than 5 cells. Fragmentation of filaments is not essential for efficient conjugation but is required for quantitative experiments. The cyanobacterial cells were collected by centrifugation for 2 min and resuspended in 1 ml BG-11. The cargo strain, the conjugal strain , and Leptolyngbya BL0902 were combined, pelleted by centrifugation, and finally resuspended in 200 ml BG-11. The conjugation mixture was incubated for about 1 h in low light at 30uC; however this incubation step may be unnecessary and is possibly even detrimental to conjugation efficiency. The cells were collected by centrifugation, resuspended with a small volume of BG-11, and then spread on sterile nitrocellulose filters laid on BG211+5% LB agar plates .