Principles for construction of bioluminescent enzyme biotests for analysis of complex media

We formulated the principles of designing bioluminescent enzyme tests for assessing the quality of complex media which consist in providing the maximum sensitivity to potentially toxic chemicals at a minimal impact of uncontaminated complex media. The developed principles served as a basis for designing a new bioluminescent method for an integrated rapid assessment of chemical safety of fruits and vegetables which is based on using the luminescent bacterium enzymes (NAD(P)H:FMN oxidoreductase and luciferase) as a test system.

Toxicity and disruption of quorum sensing in Aliivibrio fisheri by environmental chemicals: Impacts of selected contaminants and microplastics

The purpose of this study was to examine the effects of dissolved and particulate compounds on quorum sensing in the marine luminescent bacterium Aliivibrio fisheri. Bacteria were exposed to increasing concentrations of CuSO4 (Cu2+), gadolinium chloride (Gd3+), 20-nm silver nanoparticles (nanoAg) and 1-3 μm microplastic polyethylene beads for 250 min. During this period, luminescence measurements were taken at 5-min intervals. Toxicity was first examined by measuring luminescence output at 5-min and 30-min incubation time. Based on the effective concentration that decreases luminescence by 20% (EC20), the compounds were toxic at the following concentrations in decreasing toxicity: Cu2+ (3.2 mg/L) < nanoAg (3.4 mg/L, reported) < Gd3+ (34 mg/L) < microplastics (2.6 g/L). The data revealed that luminescence changed non-linearly over time. In control bacteria, luminescence changed at eight specific major frequencies between 0.04 and 0.27 cycle/min after Fourier transformation of time-dependent luminescence data. The addition of dissolved Cu2+ and Gd3+ eliminated the amplitude changes at these frequencies in a concentration-dependent manner, indicating loss of quorum sensing between bacteria at concentrations below EC20. In the presence of nanoAg and microplastic beads, the decreases in amplitudes were modest but compressed the luminescence profiles, with shorter frequencies appearing at concentrations well below EC20. Thus, loss of communication between bacteria occurs at non-toxic concentrations. In addition, with exposure to a mixture of the above compounds at concentrations that do not produce effects for Gd3+, nanoAg and microplastics, Cu2+ toxicity was significantly enhanced, suggesting synergy. This study revealed for the first time that small microplastic particles and nanoparticles can disrupt quorum sensing in marine bacteria.

Efecto del pH y la salinidad en el crecimiento y luminiscencia de una bacteria marina como biosensor ambiental

Effect of pH and salinity on the growth and luminescence of a marine bacterium as an environmental biosensor Resumen El trabajo se desarrolló en el Centro de Estudios de Proteínas de la Facultad de Biología de la Universidad de La Habana en septiembre de 2012 con el objetivo de evaluar el crecimiento y la luminiscencia de la cepa bacteriana CBM-784 en el medio LM a diferentes intervalos de pH y salinidad y determinar los rangos óptimos para sus crecimiento y luminiscencia. Los resultados demuestran que la bacteria luminiscente CBM-784 mostró su mejor crecimiento y luminiscencia a pH= 8,3 y concentraciones de NaCl entre 2,95 y 3,5%. Palabras clave: bacterias; ecología marina; luciferase; luminiscencia bacteriana; medio de cultivo. Abstract The work was developed at the Center for Protein Studies of the Faculty of Biology of the University of Havana in September 2012 with the objective of evaluating the growth and luminescence of the bacterial strain CBM-784 in the LM medium at different intervals of pH and salinity and to determine the optimal ranges for its growth and luminescence. The results demonstrate that the luminescent bacterium CBM-784 showed its best growth and luminescence at pH = 8.3 and NaCl concentrations between 2.95 and 3.5%. Keywords: bacteria; marine ecology; luciferase; bacterial luminescence; culture medium.