Arthrobacter sp. was the most abund

Arthrobacter sp. was the most abundant genus that exhibited nitrogen-fixing activity. This genus includes bacteria capable of using various nitrogen sources, including atmospheric nitrogen [53], but has rarely been reported as the main nitrogen-fixing genus in the plant rhizosphere environment.Based on the characterization performed in the present study, it is possible to indicate some promising candidates tobe evaluated as inoculants in sugarcane. Pseudomonas is a genus that is abundant in the sugarcane rhizosphere, easy to cultivate at the laboratory scale [30], and includes many strains that are phytohormone producers and phosphate solubilizers,as presented in this work. However, as some Pseudomonas strains may also cause disease in plants, detailed studies of the pathogenicity of the strains should be performed prior to field application [30, 54]. The genus Arthrobacter was found in great abundance in the rhizosphere samples, with many isolates presenting the ability to fix atmospheric nitrogen,suggesting that some strains of this genus might have potential for use as inoculants to increase the supply of nitrogen toplants. The possibility of using Arthrobacter sp. as inoculant for nitrogen fixation differs from previous studies that suggested the application of Azospirilum sp. or Burkholderia sp.to increase the supply of nitrogen in sugarcane [55, 56]. Hence,the present work presents a different genus as an option for the development of these types of inoculum. Finally, the presence of these two genera (Pseudomonas and Arthrobacter) in samples submitted to drought stress showed their ability to survive environmental fluctuations in the rhizosphere environ-ment [57].In conclusion, the cultivable microbial community of the sugarcane rhizosphere was strongly influenced by drought,since the total number of colonies recovered per sample decreased as the period under drought stress increased. However, some groups of bacteria (Bacillus,Pseudomonas, Arthrobacter, Streptomyces, Microbacterium, and Falsibacillus) were not influenced by drought stress, suggesting the ability of these genera to survive in dry environments. In addition,many isolates tested positive for one or more plant growth activities, especially IAA production, which could help the plants to survive under drought conditions. The findings ofthis work, involving the isolation and testing of a large number of bacteria, indicate possible new ways to accelerate the growth of agronomically important plants during conditionsof drought stress.