Flagellar mutants in Escherichia coli were obtained by selection for resistance to the flagellotropic phage chi. F elements covering various regions of the E. coli genome were then constructed, and, on the basis of the ability of these elements to restore flagellar function, the mutations were assigned to three regions of the E. coli chromosome. Region I is between trp and gal; region II is between uvrC and aroD; and region III is between his and uvrC. F elements carrying flagellar mutations were constructed. Stable merodiploid strains with a flagellar defect on the exogenote and another on the endogenote were then prepared. These merodiploids yielded information on the complementation behavior of mutations in a given region. Region III was shown to include at least six cistrons, A, B, C, D, E, and F. Region II was shown to include at least four cistrons, G, H, I, and J. Examination of the phenotypes of the mutants revealed that those with lesions in cistron E of region III produce "polyhooks" and lesions in cistron F of region III result in loss of ability to produce flagellin. Mutants with lesions in cistron J of region II were entirely paralyzed (mot) mutants. Genetic analysis of flagellar mutations in region III suggested that the mutations located in cistrons A, B, C, and E are closely linked and mutations in cistrons D and F are closely linked.

Antigens, Bacterial↗

PubMed1973

Genetic analysis of bacteriophage Mu-induced flagellar mutants in Escherichia coli.

In previous work, at least 10 discrete cistrons involved in the synthesis of flagella in Escherichia coli were described. Six cistrons were located between his and uvrC on the genetic map. These were referred to as hag, flaA, flaB, flaC, flaD, and flaE. Four cistrons referred to as mot, flaG, flaH, and flaI were located between uvrC and aroD. In order to determine whether these genes are organized into transcriptional units, a series of Mu phage-induced flagellar mutants was studied. The mutant strains behaved as if they were carrying strong polar mutations. Of 228 independent Mu-induced mutants, 114 with mutations in the his-aroD region of the genetic map were tested by preparing partial diploid strains with episomes carrying a variety of previously defined mutations. The pattern of complementation that emerged indicated that cistrons flaB, flaC, and flaE form a transcriptional unit. Cistron flaO, defined in the course of this study, is also a member of this transcriptional unit. The order of transcription is B-C-O-E. flaA was found to be complex, and it included four cistrons, flaA, flaP, flaQ, and flaR, with the transcriptional order A-P-Q-R. Cistrons flaG and flaH are cotranscribed with the transcriptional order G-H. The remaining genes, flaD, flaI, hag, and mot do not belong to multicistronic transcriptional units. Complementation analysis suggested that the cheC locus is the same as cistron flaA.

Chromosome Mapping↗

PubMed1973