Journal Of Applied Horticulture ISSN: 0972-1045


Mirta Esther Galelli, Gabriela Cristina Sarti and Silvia Susana Miyazaki

Área de Agroalimentos. Departamento de Biología Aplicada y Alimentos. Facultad de Agronomía. Universidad de Buenos Aires. Av. San Martín 4453, C1417DSE. Argentina.

Key words: Lactuca sativa, biofertilizer, Bacillus subtilis subsp. spizizenii, PGPR activity, biofilm production, glycerol, culture conditions, inmmobilized cells, inoculant, sessile bacteria, planktonic bacteria, rhizosphere.

Journal of Applied Horticulture, 2015, volume 17, issue 3, pages 186-191.

Abstract: Biofertilizers can be an alternative to chemical fertilizer as they increase sustainable soil fertility without causing pollution; however, their major problem is the poor survival of the free cells in the soil. A possible solution is the use of cells immobilized in biofilms; it provides a more suitable microenvironment for prolonged cell survival and allows the interaction of the bacterium and its metabolites with the plant. In this work, the planktonic Bacillus subtilis subsp. spizizenii showed a PGPR activity on Lactuca sativa, increasing the weight, 64 % the aerial part and 68 % the roots growth. This bacterium was able to produce a thick biofilm using glycerol as a sole carbon source. Different culture conditions were evaluated for biofilm production. The shear stress and the oxygenation during bacterial culture affected negatively the biofilm formation; a mechanically disrupted biofilm never recovered its integrity. The optimum temperature for biofilm production was between 30 ºC and 37 °C. The presence of different divalent cations salts affected the biofilm formation; 2 mM MgSO4 and 1 mM FeSO4 in static growth culture increased the biofilm production 36 % and 72 % respectively, and CoSO4 and CuSO4 affected negatively its formation. The immobilized cells had a PGPR effect; it showed a higher benefit as a biofertilizer than the planktonic form, producing an increment of 39 % of the aerial part and 59 % the roots growth.

Lactuca sativa biofertilization using biofilm from Bacillus with PGPR activity

Journal of Applied Horticulture