Link between domoic acid production and cell physiology after exchange of bacterial communities between toxic Pseudo-nitzschia multiseries and non-toxic Pseudo-nitzschia delicatissima.

Aurélie Lelong,Hélène Hégaret,Philippe Soudant

doi:10.3390/md12063587

Aurélie Lelong, Hélène Hégaret + Show 1 more

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https://doi.org/10.3390/md12063587

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Abstract

Bacteria are known to influence domoic acid (DA) production by Pseudo-nitzschia spp., but the link between DA production and physiology of diatoms requires more investigation. We compared a toxic P. multiseries to a non-toxic P. delicatissima, investigating links between DA production, physiological parameters, and co-occurring bacteria. Bacterial communities in cultures of both species were reduced by antibiotic treatment, and each of the diatoms was inoculated with the bacterial community of the other species. The physiology of P. delicatissima was minimally affected by the absence of bacteria or the presence of alien bacteria, and no DA was detected. P. multiseries grew faster without bacteria, did not produce a significant amount of DA, and exhibited physiological characteristics of healthy cells. When grown with alien bacteria, P. multiseries did not grow and produced more DA; the physiology of these cells was affected, with decreases in chlorophyll content and photosynthetic efficiency, an increase in esterase activity, and almost 50% mortality of the cells. The alien bacterial community had morphological and cellular characteristics very different from the original bacteria, and the number of free-living bacteria per algal cell was much higher, suggesting the involvement of bacteria in DA production.

Highlights

In 1987, three people died after ingesting blue mussels contaminated with domoic acid (DA), a neurotoxin causing amnesic shellfish poisoning [1]
The P. delicatissima cultures reached stationary phase earlier than did the P. multiseries cultures; monitoring was stopped after day 9
Results of this study indicate that changes in co-occurring bacteria can be detrimental to Pseudo-nitzschia cultures, and that increased DA production is associated with several physiological impairments

Summary

Introduction

In 1987, three people died after ingesting blue mussels contaminated with domoic acid (DA), a neurotoxin causing amnesic shellfish poisoning [1]. Pseudo-nitzschia, but only some species, and even strains of some species, are toxic while others are not (reviewed in [2]). Since 1987, many studies have been published trying to understand when and why this toxin is produced (reviewed in [2]). Numerous factors can modulate DA production by Pseudo-nitzschia spp., including: macronutrient concentration [3], nitrogen source [4], micronutrient availability [5], growth phase [3,6], bacterial community [7], or even the age of a cultured isolate [8]. No study to date has succeeded in explaining the role of DA in Pseudo-nitzschia physiology and ecology and how all the external factors can modulate DA production. Very few physiological measurements have been performed to better understand the physiological state of the cell relative to DA production

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