Opening Study on the Development of a New Biosensor for Metal Toxicity Based on Pseudomonas fluorescens Pyoverdine

Abstract

To date, different kinds of biosensing elements have been used effectively for environmental monitoring. Microbial cells seem to be well-suited for this task: they are cheap, adaptable to variable field conditions and give a measurable response to a broad number of chemicals. Among different pollutants, heavy metals are still a major problem for the environment. A reasonable starting point for the selection of a biorecognition element to develop a biosensor for metals could be that of a microorganism that exhibits good mechanisms to cope with metals. Pseudomonads are characterized by the secretion of siderophores (e.g., pyoverdine), low-molecular weight compounds that chelate Fe3+ during iron starvation. Pyoverdine is easily detected by colorimetric assay, and it is suitable for simple online measurements. In this work, in order to evaluate pyoverdine as a biorecognition element for metal detection, the influence of metal ions (Fe3+, Cu2+, Zn2+), but also of temperature, pH and nutrients, on microbial growth and pyoverdine regulation has been studied in P. fluorescens. Each of these variables has been shown to influence the synthesis of siderophore: for instance, the lower the temperature, the higher the production of pyoverdine. Moreover, the concentration of pyoverdine produced in the presence of metals has been compared with the maximum allowable concentrations indicated in international regulations (e.g., 98/83/EC), and a correlation that could be useful to build a colorimetric biosensor has been observed.

A Pseudomonas T6SS effector recruits PQS-containing outer membrane vesicles for iron acquisition

“…E. coli strains were grown at 37 °C in either Luria-Bertani (LB) broth or agar. P. aeruginosa strains were grown at 37 °C in either LB, tryptic soy broth (TSB), succinate MM60 or M9 MM (Na 2 HPO 4 6 g l −1 , KH 2 PO 4 3 g l −1 , NaCl 0.5 g l −1 , NH 4 Cl 1 g l −1 , MgSO 4 .7H 2 O 0.25 g l −1 , glucose 2 g l −1 ). The P. aeruginosa PAO1 strain was the parent of all derivatives used in this study.…”

Experimental design of a simple medium for the bioluminescence of Aliivibrio fischeri and mathematical modelling for growth estimation

“…LB20 medium is similar in composition to medium 3 used here, and use of this medium produced a latency phase of 4–6 h, an exponential phase of 10–11 h and a stationary phase after 15 h in the culturing of Vibrio fischeri MJ1 . Seawater medium (DSMZ medium 246), which is close to medium 4, was used to culture Vibrio fischeri NRRL B − 1117 and produced a similar pattern of growth, reaching the stationary phase at 24 h after inoculation. The length of the different growth phases was variable for A. fischeri with the medium evaluated here; the shortest exponential phases were obtained with media 2 and 3, both of which have the lowest salt concentration (20 g/L).…”

“…Aliivibrio fischeri is the most studied member in the Vibrionaceae family, known for their symbiosis with sepiolid squids and monocentrid fish . A. fischeri has been widely studied using different approaches, for example with biosensors, to understand quorum sensing, to perform luciferase synthesis, to study symbiosis, to determine conditions for growth and luminescence, and to establish protocols to measure luminescence…”

“…Among the factors that influence the growth and luminescence of A. fischeri are the medium composition, pH (optimum range between 6.0 and 9.0), temperature (optimum range between 25°C and 30°C) and NaCl (optimum range between 1.75–4%) . These culture media frequently used to grow A. fischeri include seawater complete medium (SWC), which is prepared with artificial seawater (ASW), Photobacterium broth; and high‐salt Luria–Bertani medium (LB) . Other formulations used to grow A. fischeri are composed of yeast extract, tryptone, peptone, sodium chloride, glycerol, magnesium chloride, magnesium sulfate, calcium chloride, and sodium phosphates .…”

Microbes are not bound by sociobiology: Response to Kümmerli and Ross‐Gillespie (2013)

“…It is not necessary to resort to a chemical assay to determine whether KB is low in available iron. Such a claim can be made based on the behavior of the bacterium itself: the bacterium is a biosensor (Joyner and Lindow 2000;Chiadò et al 2013). Pyoverdin is produced as a direct response to low levels of available iron (e.g., Meyer and Abdallah 1978): addition of surplus iron suppresses pyoverdin production (e.g., Meyer and Abdallah 1978).…”