Microorganisms play a vital role in maintaining soil fertility and plant health. They can act as biofertilizers and increase the resistance to biotic and abiotic stress. This study aimed at isolating and characterizing plant growth-promoting bacteria associated with sugarcane, as well as assessing their ability to promote plant growth. Endophytic bacteria from leaf, stem, root and rhizosphere were isolated from the RB 867515 commercial sugarcane variety and screened for indole acetic acid (IAA) production, ability to solubilize phosphate, fix nitrogen and produce hydrogen cyanide (HCN), ammonia and the enzymes pectinase, cellulase and chitinase. A total of 136 bacteria were isolated, with 83 of them presenting some plant growth mechanism: 47 % phosphate solubilizers, 26 % nitrogen fixers and 57 % producing IAA, 0.7 % HCN and chitinase, 45 % ammonia, 30 % cellulose and 8 % pectinase. The seven best isolates were tested for their ability to promote plant growth in maize. The isolates tested for plant growth promotion belong to the Enterobacteriaceae family and the Klebsiella, Enterobacter and Pantoea genera. Five isolates promoted plant growth in greenhouse experiments, showing potential as biofertilizers.

Rhizospheric actinobacteria associated to organic cultivation are essential in nutrient cycling and plant growth promotion. The aim of thi s study was to isolate and select in vitro actinobacteria displaying multiple plant growth promoting traits associated with the rhizosphere of sugarcane undergoing organic management. The isolates were evaluated regarding their ability to produce plant growth promoting traits. Of the 21 isolates, 57% produced at least one of the evaluated traits. Isolates ABC92 and ABC32 produced 60.28 and 55.36 μg mL -1 of fitohormone in 21 days, whereas isolates ANC48 and ANU34 were the best solubilizers, solubilizing 8.93 and 8.92 μg mL -1 phosphate. A total of 29% of the microorganisms were able to grow in nitrogen-free media and 24% were ammonia producers. Isolates ABC31, ANC48 and ANU49 were able to inhibit Fusarium moniliforme growth. All actinobacteria identified in this study belonged to the Streptomyces genus and presented potential as plant growth promoting agents.

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Microorganisms associated with organic management are essential in nutrient transformation and release for plant use. The present study aimed to isolate, identify and characterize plant growth promoting diazotrophic rhizobacteria associated with sugarcane under organic management. Rhizospheres of organic sugarcane varieties IAC 911099 and CTC4 were sampled and inoculated onto nitrogen free NFb and Burk media. The isolated microorganisms were screened in vitro concerning their ability to produce plant growth promoting factors. Eighty-one bacteria were isolated; 45.6% were positive for the nifH gene and produced at least one of the evaluated plant growth promotion factors. The production of indole-3-acetic acid was observed in 46% of the isolates, while phosphate solubilization was observed in 86.5%. No isolates were hydrogen cyanide producers, while 81% were ammonia producers, 19% produced cellulases and 2.7%, chitinases. Microorganisms belonging to the Burkholderia genus were able to inhibit Fusarium moniliforme growth in vitro. Plant growth promoting microorganisms associated with organic sugarcane, especially belonging to Burkholderia, Sphingobium, Rhizobium and Enterobacter genera, can be environmentally friendly alternatives to improve sugarcane production.An Acad Bras Cienc (2018) 90 (4) 3814ARIANA A. RODRIGUES et al.

Phenolic compounds are common pollutants in industrial effluents and pose a significant risk to the environment. The microbial capacity to degrade these molecules makes the prospection of bacteria with this ability very strategic for bioremediation processes in contaminated areas. This study was carried out to isolate bacteria with phenol degrading capacity from Brazilian mangrove soil. Microorganisms were evaluated for tolerance and the ability to use this substance as a single source of carbon. Two bacterial isolates were obtained: MF-1 and MF-2. The microorganisms were identified, respectively, as Bacillus cereus and Bacillus circulans by sequencing the 16S rRNA gene. The isolates exhibited tolerance to phenol at concentrations up to 600 mg.L-1 when grown in Bushnell-Haas Agar (BHA) and 1,500 mg.L-1 in nutrient agar (NA). As for the use of phenol as a single carbon source, the microorganisms were grown in concentrations of 100, 200 and 300 mg.L-1 of the compound. The isolate MF-1 presented a percentage consumption of 22.43, 11.52 and 3.33%, respectively, for each tested concentration. Although there was a decrease in phenol consumption in response to the increased concentration of this substance, bacterial growth was not affected. The best results were obtained for the isolate MF-2, in which consumption of phenol was, respectively, 21.54, 20.54 and 28.85% for these concentrations. Likewise, the increase in phenol concentration caused no reduction in the growth of this isolate.