An enzyme involved in chlorophyll synthesis, present in all cyanobacteria (fixing and non-nitrogen fixing)  is a member of the NifH family/superfamily. Agrisera anti-NifH antibody will not show a strong reactivity to this target.In photobionts like Anabaena sp., low nitrate growth is required to turn on the NifH expression to high enough levels to detect NifH protein. Immunofluorescence protocol Insect dissected tissues (digestive tract, fat body, carrying NifH positive bacteria) of large workers were fixed in cold methanol (20 min, -20°C) and then permeabilized in cold acetone (5 min, -20°C). Samples were subsequently rinsed three times with PBS with 0.1 % Triton-X 100 at RT (PBST) and incubated for 5 minutes in PBST. This was followed by incubation of tissues for 1 hr with 6 ug/ml affinity purified anti-NifH antibody (Agrisera, AS01 021A) diluted in PBS-TBSA (PBS, 0.1 % v/v Triton-X-100, 1 mg/ml BSA) and 3 washings with PBST. Samples were then incubated in the dark with a goat anti-chicken IgY conjugated to Dylight 488 (Pierce, SA5-10070) for 45 min and were washed twice (PBS, 0.1%v/v Triton-X-100). Finally, the tissues were mounted in Vectashield medium containing DAPI (Vector Laboratories, H-1500) and viewed under a SP5 Leica confocal microscope with 10X and 63X objectives. Courtesy of Drs. Panagiotis Sapountzis and Mariya Zhukova, University of Copenhagen, Danmark