Previous studies have demonstrated Epigenetics Compound Library that the ability of some species of fungi (El-Azouni, 2008; Jain et al., 2010) and bacteria (Collavino et al., 2010; Mamta et al., 2010) isolated from soil to efficiently solubilize different

sources of inorganic phosphate, which subsequently results in increased availability of phosphate for plants. Aspergillus niger is a fungus that has been extensively studied because of its ability to dissolve various inorganic phosphates (Barroso & Nahas, 2005; Saber et al., 2009). Similarly, several Burkholderia cepacia strains have been reported to solubilize phosphates (Lin et al., 2006; Song et al., 2008). Combining different microorganisms has been successfully used in multiple facets of science to improve biotechnological conditions. In general, studies have been conducted inoculating two or more species of microorganisms, simultaneously. For example, Loperena et al. Palbociclib (2009) significantly improved bioaugmentation and capacity degradation of residual dairy products using a combination of three independent genera of bacteria. Co-inoculation of microorganisms in soil has been successfully used for biological fixation

of nitrogen (Camacho et al., 2001) as well as solubilization of insoluble phosphates (Rojas et al., 2001). However, it is important to understand how and in what proportions PSM compete or cooperate to generate available phosphate in the soil. Thus, we undertook this study to evaluate whether synergistic or antagonistic interactions occur between species of microorganisms that solubilize inorganic phosphate. This study evaluates the effect of co-inoculation of two PSM, the bacterium B. cepacia and the fungus A. niger, both naturally found in soil and seeks to determine whether co-inoculation enhances the ability of

each species to solubilize inorganic phosphate in the growth medium. The fungus A. niger F111 (Barroso & Nahas, 2005) and the bacterium B. cepacia 342 (Nahas, 1996), both isolated from soil, were used in this study. The organisms were maintained at 4 °C on Sabouraud Agar and Nutrient Agar, respectively. The liquid medium contained (g L−1): Ureohydrolase 0.1 NaCl, 1.0  NH4Cl, 0.2  KCl, 0.1  CaCl2·7H2O, 1.2 MgSO4·7H2O, 10.0  glucose, 0.5  yeast extract, and 0.36 P (as CaHPO4·2H2O, CaP; Barroso & Nahas, 2005). The flasks were plugged with cotton and sterilized at 120 °C for 20 min. The pH was adjusted to 7.0 with 0.5 M NaOH. CaP was sterilized separately in Petri dishes for 24 h at 105 °C. Then, the sterilized medium was added and mixed with CaP. Both the fungal and the bacterial inocula were obtained from cultures that had been grown at 30 °C for 7 days. To each fungal and bacterial culture, 10 mL of sterile deionized water was added.