PHOSPHATE SOLUBILIZATION AND EXOPOLYSACCHARIDE PRODUCTION OF ENDOPHYTIC BACTERIA ISOLATED FROM Echeveria laui

Endophytic microorganisms (fungi or bacteria) are those that inhabit the interior of plant tissues and organs without causing harm to their host. These endophytes have been studied for their contributions in different areas, such as in agriculture. This work was to prospect 15 strains of endophytic bacteria isolated from Echeveria laui, evaluating phosphate solubilization and exopolysaccharide (EPS) production. The endophytic bacteria strains (ELP36, ELP37, ELP38, ELP39, ELP40, ELP41, ELP42, ELP43, ELP44, ELP45, ELP46, ELP47, ELP48, ELP49 e ELP50) belong to the collection of microorganisms of Laboratorio of Biotecnologia Microbiana of Universidade Estadual of Maringá. The endophytic isolates were grown in microtubes containing 500 μL of TSB medium (Tryptone Soy Broth) for 24 h at 28 °C. After, the bacteria were eluted in 5 mL of 0.85% saline solution with the McFarland 0.5 scale. Aliquots of 2 μL of the bacterial cultures were transferred to four points equidistant in the plate, containing insoluble phosphate medium (10 g.L-1 glucose; 5 g.L-1 NH4Cl; 1 g.L-1 MgSO4.7H20; 0,8 g.L-1 CaHPO4; 15 g.L-1 agar; pH 7.2) and medium of production EPS (20 g.L-1 of yeast extract; 15 g.L -1 de K2HPO4 ; 0,2 g.L-1 de MgSO4; 0,015 g.L-1 MnSO4; 0,015 g.L-1 FeSO4; 0,03 g.L-1 CaCl2; 0,015 g.L-1 de NaCl; 15 g.L-1 agar, 10% sucrose; pH 7.3). The phosphate solubilization and EPS production were evaluated by the presence or absence of the halo, with subsequent measurement. To confirm the production of EPS, the bacterial cell material was collected with a toothpick, transferring to tubes containing 2 mL of ethyl alcohol (positive = precipitated cellular material; negative = turbidity). All data were analyzed statistically by analysis of variance compared by the Scott-Knott test (p<0.05). All strains showed different phosphate solubilization and EPS production, with ELP38 (2.06 mm), ELP43 (1.98 mm), ELP36 (1.96 mm), ELP48 (1.96 mm) and ELP41 (25.1 mm), ELP44 (25 mm), ELP45 (25 mm), ELP42 (24.6 mm) and ELP40 (24, 6 mm) for EPS production. We observed that the endophytic isolates of E. laui employed in this work have characteristics of agronomic interest that could be used to assist in agricultural production, promoting plant growth.