Abstract
Two types of nitrosoguanidine-induced rifampicin-resistant mutants ofNostoc muscorum were isolated and characterized. Compared with the wild type, the strainrif-1 (rifrhet+nif+blu) revealed high growth rate, heterocyst frequency (10%–12%), nitrogenase activity, phycocyanin pigment, photosynthetic O2 evolution, and higher activities of phosphoribulokinase and Fd-NADP+-oxidoreductase. The heterocyst spacing pattern in the mutant was altered and did not respond to 7-azatryptophan, β-2-thienylalanine, rifampicin, andl-methionine-dl-sulfoximine treatment. The second type of mutantrifr-2 (rifrhet+nif−) did not show nitrogenase activity and was unable to grow on molecular nitrogen even under microaerobic conditions, although it produced heterocysts (6%–7%) under these conditions of incubation. The pattern of macromolecular synthesis, particularly of RNA and protein, the rate of acetylene reduction, and photosynthetic O2 evolution were not affected in the mutant strains with the treatment of drug. The characteristics of the mutants reflected the possibility of pleiotropic mutation and also suggested that therif marker is most likely associated in close genetic proximity with regulatory gene(s) ofhet andnif system.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
