title: A cyanobacterial mutant resistant against a bleaching herbicide.
abstract: The nitrogen fixing cyanobacterium Nostoc muscorum has been found to be sensitive to the herbicide SAN 6706 [4-chloro-5 (dimethylamino)-2-(a,a,a,-trifluoro-m-tolyl)-3-(2H) pyridazinon] at 30-45 microM within 15 min. The toxicity was more severe in combined nitrogen-free (Ncomb-free) medium than in a combined nitrogen medium; this enhancement was reversible by supplementation of the medium with 3 mM glucose or 5 microM ATP, serving as carbon and/or energy source in this organism. A mutant of this cyanobacterium resistant to 3 mM SAN 6706 has been isolated and characterized to perform nitrogenase activity in exogenous ATP supplemented Ncomb-free medium. However, it exhibited a moderate growth in combined nitrogen media in the absence of external ATP. The resistance factor is higher than 100. Simultaneously, this strain possesses a cross-resistance to methylamine, a well-known inhibitor of photophosphorylation, irrespective of the exogenous ATP supply. The behavior of the mutant suggests a defective phosphorylation in its photosynthetic system.
authors.affiliation: Department of Genetics and Plant Breeding, Banaras Hindu University, Varanasi, India.
authors.forename: A
authors.initials: A
authors.lastname: Vaishampayan
authors.forename: R P
authors.initials: RP
authors.lastname: Sinha
authors.forename: A K
authors.initials: AK
authors.lastname: Gupta
authors.forename: D P
authors.initials: DP
authors.lastname: Häder
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D003470:Culture Media; D000458:Cyanobacteria / Q000187:drug effects* / Q000235:genetics* / Q000254:growth & development; D004352:Drug Resistance, Microbial; D005947:Glucose / Q000378:metabolism; D006540:Herbicides / Q000494:pharmacology*; D009154:Mutation; D009584:Nitrogen / Q000378:metabolism; D011724:Pyridazines / Q000494:pharmacology*
chemical_list: D003470:Culture Media; D006540:Herbicides; D011724:Pyridazines; D000255:Adenosine Triphosphate; D005947:Glucose; D009584:Nitrogen; C001602:metflurazon