PH-Induced Modulation of Vibrio fischeri Population Life Cycle

Dmitri Y Petrovykh,Ruth Schwaiger,Luciana Pereira,Cláudia Sousa,Daniela Exner,Ana Rita Silva,Maria Madalena Alves

doi:10.3390/chemosensors9100283

Abstract

Commonly used as biological chemosensors in toxicity assays, Vibrio fischeri bacteria were systematically characterized using complementary physicochemical and biological techniques to elucidate the evolution of their properties under varying environmental conditions. Changing the pH above or below the optimal pH 7 was used to model the long-term stress that would be experienced by V. fischeri in environmental toxicology assays. The spectral shape of bioluminescence and cell-surface charge during the exponential growth phase were largely unaffected by pH changes. The pH-induced modulation of V. fischeri growth, monitored via the optical density (OD), was moderate. In contrast, the concomitant changes in the time-profiles of their bioluminescence, which is used as the readout in assays, were more significant. Imaging at discrete timepoints by scanning electron microscopy (SEM) and helium-ion microscopy (HIM) revealed that mature V. fischeri cells maintained a rod-shaped morphology with the average length of 2.2 ± 1 µm and diameter of 0.6 ± 0.1 µm. Detailed morphological analysis revealed subpopulations of rods having aspect ratios significantly larger than those of average individuals, suggesting the use of such elongated rods as an indicator of the multigenerational environmental stress. The observed modulation of bioluminescence and morphology supports the suitability of V. fischeri as biological chemosensors for both rapid and long-term assays, including under environmental conditions that can modify the physicochemical properties of novel anthropogenic pollutants, such as nanomaterials and especially stimulus-responsive nanomaterials.

Highlights

IntroductionThe observed modulation of bioluminescence and morphology supports the suitability of V. fischeri as biological chemosensors for both rapid and long-term assays, including under environmental conditions that can modify the physicochemical properties of novel anthropogenic pollutants, such as nanomaterials and especially stimulus-responsive nanomaterials
After the release of nanomaterials in these applications, their eventual fate often leads to accumulation in the soil [11] or aquatic environment [12], where bacterial chemosensors are an important tool for assessment of ecotoxicity, because they are well suited for assays in complex natural environments and because bacteria play a significant published maps and institutional affiliations
Previous reports [28,49] have mum optical density (OD) reached in the stationary phase was only 1.3, a 37% drop from the maximum at established that bioluminescence of V. fischeri is strongly attenuated outside the range of pH 7

Summary

Introduction

The observed modulation of bioluminescence and morphology supports the suitability of V. fischeri as biological chemosensors for both rapid and long-term assays, including under environmental conditions that can modify the physicochemical properties of novel anthropogenic pollutants, such as nanomaterials and especially stimulus-responsive nanomaterials. The responsive nanomaterials are likely to participate in complex interactions with other nanomaterials, compounds, and ionic species that can strongly modulate the combined effect of such mixtures on biological systems [14]. In these complex environments, surface interactions play a important role in modulating the toxic effects of the participating nanomaterials and compounds, as detected by bacterial assays [15].

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