Banca de DEFESA: RAFAELA FERREIRA DA SILVA COSTA

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
STUDENT : RAFAELA FERREIRA DA SILVA COSTA
DATE: 10/09/2021
TIME: 14:00
LOCAL: Via Google Meet
TITLE:

SOLUBILIZATION OF INORGANIC PHOSPHATE BY BACTERIA ISOLATED FROM ANTARCTICA LICHEN

KEY WORDS:

Phosphate-solubilizing bacteria. Stress tolerance. Antarctica. Lichensphere.

PAGES: 87
BIG AREA: Ciências Agrárias
AREA: Agronomia
SUMMARY:

Lichens are pioneer organisms in extreme environments, grow in nutrient-limiting conditions and are recurrent in Antarctica. They represent a rich reservoir for the isolation of bacteria with biotechnological potential of agricultural interest, presenting characteristics that promote plant growth through inorganic phosphate solubilization mechanisms. In this context, the present study aimed to analyze the potential of bacteria isolated from 6 Antarctic lichens for solubilization of inorganic phosphate under the influence of different temperatures, pH variation, NaCl concentrations, carbohydrates and induction of osmotic potential. The collection took place from different lichens on King George Island, during the OPERANTAR XXXVI expedition (summer 2017/2018). Bacteria were tested for phosphate solubilization using solid NBRIP medium (qualitative) and in broth (quantitative). The positive bacteria for solubilization were tested for the ability to fix nitrogen. The quantification of soluble phosphorus in the supernatant of the isolates was estimated by the ammonium vanadate-molybdate method. Of 60 bacteria tested, 15 (25.0%) solubilized tricalcium phosphate at 15.0 ºC. At temperatures of 15.0 ºC (15= 100%) and 25.0 ºC (15= 100%) all strains solubilized phosphate in solid culture medium, whereas at 30.0 ºC 13 strains (13= 87. 5%) and at 35.0ºC there was no growth of any isolate. The enzyme index for phosphate solubilization was measured by the ratio of the diameter of the halo divided by the diameter of the colony. The highest phosphate solubilization indexes at 15.0 ºC were from 1.75 mm to 3.02; at 25.0 °C from 1.84 mm to 2.76 mm and at 30.0 °C from 1.78 mm to 2.70 mm. The best bacteria at the three temperatures were 1B.LQ4; 4BLQ4; 4BLQ4* and 2BLQ1*, together with 7BLQ2 (randomly chosen) were selected for phosphorus quantification in liquid medium at 25.0 ºC ± 2.0 ºC. Strains 1BLQ4 and 4BLQ4 had an average of 605.18 mg/L and reduced the pH to 4.07, while 2BLQ1* solubilized 505.56 mg/L and final pH of 4.29 and 4BLQ4* with 494.05 mg /L and pH 4.17. These four isolated showed no significant difference in soluble P. The lowest mean of soluble P was from strain 7BLQ2 with 365.78 mg/L and pH from 7.0 to 4.33. Of the 15 phosphate solubilizers, 80% (13) grew in selective medium for nitrogen fixatives and the strains that showed the greatest growth were 2BLQ1* and 3BLQ5. Bacteria 1BLQ4 and 2BLQ1* were selected for testing under stress conditions. Both bacteria solubilized phosphate at the concentration of 0.5 M Nacl with averages of 421.81 mg/L and 432.77 mg/L, respectively. At the different pH tested (7, 8 and 9), the two strains continued with high levels of soluble P. When subjected to tests with different carbohydrates (glucose, sucrose, lactose and starch), glucose was the most efficient for the solubilization mechanism of the two isolates. 2% glycerol was used; 5% and 10% to induce osmotic potential and both strains maintained high levels of soluble P in the 3 conditions tested. Assessing the maximum point of bacterial solubilization every 24 hours for 6 consecutive days, the best result for 1BLQ4 was with 96 h of incubation (606.45 mg/L) and for 2BLQ1 * it was with 120 h (565.41 mg/L) L). The results demonstrate that these strains are efficient in the solubilization mechanism of inorganic phosphate at different temperatures, alkaline conditions, osmotic effect and reasonable concentrations of salinity.

BANKING MEMBERS:
Presidente - 1506475 - ALYSSON WAGNER FERNANDES DUARTE
Interno - 287.291.704-78 - JOÃO GOMES DA COSTA - EMBRAPA
Interno - 2626313 - VALDEVAN ROSENDO DOS SANTOS
Externo à Instituição - MICHEL RODRIGO ZAMBRANO PASSARINI - UFPR