RESUMO
The induction of the lateral flagella of Azospirillum brasilense Sp7 was studied by using a translational fusion between the laf1 promoter and gusA. The fusion was induced when cells were grown on solid media but not when they were grown in broth. The fusion was also induced by incubation of liquid-grown cells with an anti-polar flagellum polyclonal antiserum. Hindrance of polar-flagellum rotation is suggested to be the signal for this induction.
Assuntos
Azospirillum brasilense/genética , Azospirillum brasilense/metabolismo , Proteínas de Bactérias , Flagelos/fisiologia , Flagelina/biossíntese , Genes Bacterianos , Sequência de Aminoácidos , Sequência de Bases , Flagelina/genética , Glucuronidase/biossíntese , Cinética , Dados de Sequência Molecular , Regiões Promotoras Genéticas , Biossíntese de Proteínas , Proteínas Recombinantes de Fusão/biossíntese , Transcrição GênicaRESUMO
Azospirillum brasilense can display a single polar flagellum and several lateral flagella. The A. brasilense Sp7 gene laf1, encoding the flagellin of the lateral flagella, was isolated and sequenced. The derived protein sequence is extensively similar to those of the flagellins of Rhizobium meliloti, Agrobacterium tumefaciens, Bartonella bacilliformis, and Caulobacter crescentus. An amino acid alignment shows that the flagellins of these bacteria are clustered and are clearly different from other known flagellins. A laf1 mutant, FAJ0201, was constructed by replacing an internal part of the laf1 gene by a kanamycin resistance-encoding gene cassette. The mutant is devoid of lateral flagella but still forms the polar flagellum. This phenotype is further characterized by the abolishment of the capacities to swarm on a semisolid surface and to spread from a stab inoculation in a semisolid medium. FAJ0201 shows a normal wheat root colonization pattern in the initial stage of plant root interaction.