Papel del alginato en la agregación de Azotobacter vinelandii en cultivo sumergido / The role of alginate in Azotobacter vinelandii aggregation in submerged culture

El cultivo de la cepa LA21, una cepa no mucoide de Azotobacter vinelandii, derivada de la cepa parentalATCC9046, reveló que el alginato no es necesario para la formacion de los agregados celulares. De hecho, la cepa mutante desarrollo agregados significativamente más grandes que los generados por la cepa parental mucoide (ATCC9046), lo cual sugiere que el alginato ejerce un efecto negativo sobre el tamaño de agregación debido a sus propiedades como agente tensoactivo. Al tratar los agregados con proteasas se produjo una disminucion en el diametro equivalente de las estructuras, sugiriendo la participacion de proteinas extracelulares en el proceso de agregacion de la bacteria.

Effect of some herbicides used in Nigeria on Rhizobium phaseoli, Azotobacter vinelandii and Bacillus subtilis.

The effect of three herbicides namely Agroxone, Atranex 50SC and 2,4-Damine on Azotobacter vinelandii, Rhizobium phaseoli and Bacillus subtilis were studied. These bacteria were isolated from a bean-garden in Lagos. The results revealed that 2, 4-Damine was the most toxic of the three herbicides studied and Azotobacter vinelandii was found to be most sensitive to the herbicides. There was a reduction in LC50 of herbicides with increased number of days. The percentage survival decreased with increased concentration of herbicides and days for Rhizobium phaseoli and Azotobacter vinelandii while an initial reduction in population was followed by increased percentage survival of organisms for Bacillus subtilis.