title: Porphyrin-accumulating mutants of Escherichia coli.
abstract: Four mutants (pop-1, pop-6, pop-10, and pop-14) which accumulate a red water-insoluble pigment were obtained in Escherichia coli K-12 AB1621. For each mutant, the red pigment was shown to be protoporphyrin IX, a late precursor of heme. Mutagenic treatment of mutant pop-1 yielded a secondary mutant, pop-1 sec-20, which accumulated a brown water-soluble pigment. The brown pigment was shown to be coproporphyrin III. Mutant pop-1 resembled the parental strain in its cytochrome absorption spectrum, catalase activity, and ability to grow on nonfermentable carbon and energy sources; therefore, its ability to produce and utilize heme was unimpaired. Judged on the same criteria, the secondary mutant, pop-1 sec-20, was partially heme and respiratory deficient. Growth in anaerobic conditions decreased by 25% the accumulation of protoporphyrin by pop-1; under the same conditions, pop-1 sec-20 did not accumulate coproporphyrin or coproporphyrinogen. The mutations causing protoporphyrin accumulation in all four pop mutants were found to map in the lac to purE (10-13 min) region of the E. coli chromosome. In the case of mutant pop-1, the mutation was shown to be strongly linked to the tsx locus (12 min). In mutant pop-1 sec-20, the second mutation causing coproporphyrin accumulation was co-transducible with the gal locus at a frequency of 88 to 96%. The mechanism of porphyrin accumulation by the mutants is discussed.
mesh_terms: D000332:Aerobiosis; D000693:Anaerobiosis; D002374:Catalase / Q000378:metabolism; D002854:Chromatography, Paper; D002874:Chromosome Mapping; D003227:Conjugation, Genetic; D003470:Culture Media; D004926:Escherichia coli / Q000201:enzymology / Q000254:growth & development / Q000378:metabolism*; D006418:Heme / Q000096:biosynthesis; D009154:Mutation; D011166:Porphyrins / Q000032:analysis / Q000302:isolation & purification / Q000378:metabolism*; D011995:Recombination, Genetic; D013057:Spectrum Analysis; D014161:Transduction, Genetic
chemical_list: D003470:Culture Media; D011166:Porphyrins; D006418:Heme; D002374:Catalase