Food Microbiology

The toxicity of nickel and vanadium, potentially toxic elements (PTE), in higher organisms has been widely documented because of its impact on crops or human health, however, toxicity in microorganisms has been poorly studied. The objective of this work is to determine the toxicity of nickel and vanadium in the growth of four strains of plant growth promoting microorganisms. Strains

of Candida orthopsilosis B20, Serratia marcescens C753, Pseudomona tolasii P61 and Rhizobium tropici Ciat889 were inoculated into a minimal salt medium at pH of 6.5 at increasing concentrations of VOSO4 (0, 15, 30 and 45 mg • L-1) and NiSO4 (0, 25, 50 and 75 mg • L-1). They were shaken at 140 rpm at 28±2°C for 5 days. Their growth kinetics were measured by the turbidity method in a microplate spectrophotometer. Every 12 h, 200 μl of each sample was taken in triplicate and read at 600 nm, until 120 h. The data were processed by ANOVA, and Tukey's mean comparison test (α=0.05), with the SAS program for Windows 9.0. The growth of C. orthopsilosis B20 was severely affected by the presence of the two metals, R. tropici Ciat889 was highly sensitive to nickel in all concentrations, while in vanadium, in its lower concentration, it promoted its growth. Both strains of S. marcescens C753 and P. tolasii P61 showed tolerance to PTE and their growth was promoted in low concentrations.