Novel classes of Azospirillum brasilense mutants with defects in the assembly and functioning of polar and lateral flagella.

Azospirillum brasilense Sp245 has a mixed type of flagellation: a single polar flagellum (Fla) is synthesized constitutively, and abundant lateral flagella (Laf) are produced only in solid and semisolid media. In the present study, Omegon-Km Fla-Laf-, Fla-Laf+, Fla-/Mot-Laf-. Fla-/Mot-Laf+, Mot-Laf-, and Che- mutants of Sp245 were constructed in vivo. In some of the mutants, a number of cells possessed from 1 to 5 subpolar long flagella (Sfl). These Sfl provided the host cells with unusual motility patterns. Mutants producing shortened Fla and Laf were also detected. In the mutants still producing Laf, their expression retained the wild-type inducibility. However, all the mutants described were unable to form swarm rings in semisolid media. The results suggest the existence of common control or structural elements in assembly and rotation apparatus of both Fla and Laf systems. Single Omegon-Km insertions were localized in 85 MD (in two mutants) and in 120 MD (in one mutant) indigenous plasmids, as well as to least in two different regions of chromosomal DNA (in other mutants).