Stimulatory and Toxic Effects of Neurotransmitters on the lux Operon-Dependent Bioluminescence of Escherichia coli K12 TGI

Background: The normal functioning of the brain requires neuromediators, i.e., substances that transmit messages between nervous cells. Neurochemicals also function as signals that are involved in communication among the microorganisms that inhabit the human organism. While the impact of “classical” neurotransmitters including catecholamines, serotonin, and histamine on microorganisms has been investigated in a number of recent publications, this work provides evidence for the stimulatory and inhibitory (toxic) effects of some other important neurochemicals that have not received sufficient attention in the literature.Methods: The biosensor was based on a GM Escherichia coli K12 strain (TGI) that contained the lux operon of the luminescent soil bacterium Photorhabdus luminescencens ZMI. The biosensor was exposed to the action of the tested neurotransmitters for 15 mins to 144 hrs. The intensity of bacterial luminescence (counts / second) was monitored in the control and the experimental samples with an 1251 BioOrbit luminometer (Finland).Results: Neurochemicals such as putrescine, acetylcholine, taurin, and indole were found to stimulate, at low concentrations (0.1-10 µM), the luminescence of the strain E. coli K12 TGI containing the lux operon from Photorhabdus luminescencens ZMI. At higher concentrations, putrescine, taurin, and indole exerted a weak toxic influence, i.e. they marginally attenuated the luminescence of E. coli K12 TGI.Conclusions: Based on the data obtained, a regulatory, presumably receptor-dependent, effect is exerted by the tested neurochemicals on the bacterium E. coli K12 TGI, in an analogy to their impact on nervous, immune, and other specialized types of eukaryotic cells. However, high neurochemical concentrations are likely to produce nonspecific effects on the bacterial luciferase system and/or on membrane phosphorylation

Detecting Biogenic Amines in Food and Drug Plants with HPLC: Medical and Nutritional Implications

Background: This work reports the results of the initial stage of the project aimed at detecting neuroactive substances in tropical plants that are widely used as food and/or drugs.Methods: The content of neuroactive biogenic amines, e.g, dopamine (DA), norepinephrine (NE), epinephrine (E), serotonin (5-HT), and others was determined using high-performance liquid chromatography (HPLC) with amperometric detection in leaf samples from Plumeria rubra L. cv. acutifolia, Syzigium jambos (L.) Alston, Buxus megistophylla (or Euonymus japonicas cv. aureoma), and Cinnamomum bodinieri Levl.Results: The total fraction of disintegrated leaves contained (sub)micromolar concentrations of DA, NE, and 5-HT. They lacked E and the catecholamine precursor 2,3-dihydrophenylalanine (DOPA).Conclusions: From the data obtained, it is evident that heretofore unexplored tropical plants used in drug preparations (P. rubra and S. jambos) and as desserts (S. jambos) and spices (C. bodinieri) contain physiologically active concentrations of neurochemicals. The neurochemicals are expected to produce a significant effect on the people who consume preparations and food additives made from the aforementioned plants. Moreover, such plant preparations can potentially be used as psychoactive drugs for the purpose of intentionally manipulating human behavior

Impact of Biogenic Amines on the Growth of Green Microalgae

Background: The goal of this research project was to test various neuroactive amines in the capacity of growth stimulators/accelerators of the green microalgae Scenedesmus quadricauda and Chlorella vulgaris that have much biotechnological potential because they can be used for producing drugs, food ingredients, cosmetics, and biofuel. The issue of the ecological role of the biogenic amines in terms of interspecies communication in aqueous ecosystems was also addressed in this work. Methods: S. quadricauda strain GEHD and C. vulgaris strain ALP were cultivated in the light with constant aeration at 24oC in a minerals-containing medium. Experimental systems contained 1, 10 or 100 mM of dopamine hydrochloride, histamine hydrochloride, norepinephrine hydrochloride, or serotonin hydrochloride that were added at inoculation as freshly prepared aqueous solutions. Algal cells were counted using a light microscope , and their number in 1 mL of culture was calculated. The culture liquid and sonicated biomass of S. quadricauda and C. vulgaris were tested for the presence of endogenous amines using high-performance liquid chromatography (HPLC) with an amperometric detector. Results: The biogenic amines serotonin, norepinephrine, dopamine, and histamine significantly stimulated the growth of S. quadricauda, at concentrations of 1 and/or 10 mM but not 100 mM. Histamine was the most efficient stimulator, causing an average 65% increase in biomass accumulation at the end of the cultivation period. The effects of serotonin, dopamine and histamine on C. vulgaris were reported in our previous publication [1], but this work contains the results of our experiments with the previously untested norepinephrine that slightly stimulated the growth of C. vulgaris. HPLC analysis failed to reveal any endogenous amines in the culture liquid and biomass of both microalgae. Conclusions: Since biogenic amines stimulate the growth of the microalgae S. quadricauda and C. vulgaris but are not synthesized by them, we suggest that the algae normally respond to amines produced by other components of aqueous ecosystems, including zooplankton and fish that are known to release significant amounts of biogenic amines into the environment. The data obtained hold some promise with regard to developing a relatively economical technique of boosting algal biomass production

Impact of Biogenic Amines on the Growth of a Chlorella vulgaris Culture

The present work aims to develop a new approach enabling biotechnologists to increase the yield of Chlorella vulgaris biomass by means of biogenic amines (serotonin, dopamine, and histamine) that are known to stimulate growth of various unicellular organisms. C. vulgaris strain ALP was cultivated in the light with constant aeration at 24oC in a minerals-containing medium. Experimental systems contained 1, 10, or 100 mM of dopamine, histamine, or serotonin. Algal cells were counted using a light microscope. Serotonin caused a slight increase in biomass yield at a concentration of 10 mM, but not at the other tested concentrations. 1 and 10 mM (but not 100 mM) dopamine increased the cell number in the C. vulgaris culture at early cultivation stages. Histamine is the most efficient growth stimulator at concentrations of 1 and 10 mM, but not at a concentration of 100 mM, which even proved inhibitory to the algal culture. The data obtained demonstrate that the neurochemicals exert a stimulatory influence on the growth of the Chlorella culture at relatively low (micromolar) concentrations. Since animals often produce biogenic amines in response to stress or injury, the data give grounds for the suggestion that planktonic algae can benefit, in terms of growth rate, from the substances released by stressed or wounded representatives of aquatic fauna. In biotechnological terms, the data obtained hold some promise with regard to developing a relatively economical technique of boosting Chlorella biomass production

Testing Neurotransmitters for Toxicity with a Luminescent Biosensor: Implications for Microbial Endocrinology

Background: The human organism is a complex superorganism including numerous eukaryotic, eubacterial, and archaean cells. The qualitative and quantitative assessment of the microbiota toxicity of chemical agents, i.e., their inhibitory effects on the microbial inhabitants of the human organism in health and disease, seems to hold much value in this context. In this work, a bacterial luminescence-based express test system for microbiota toxicity is applied to neurotransmitters such as serotonin, dopamine, norepinephrine, and histamine. Methods: The biosensor was based on a GM Escherichia coli K12 strain (TGI) that contained the lux operon of the luminescent soil bacterium Photorhabdus luminescencens ZMI. The biosensor was exposed to the action of the tested neurotransmitters for 5 to 60 minutes The intensity of bacterial luminescence (counts.sec-1) was monitored in the control and the experimental samples with a Biotoks 6 ms luminometer (Russia); the toxicity index (T) of the neurotransmitters was determined. Results: A marked toxic effect on bioluminescence was produced by serotonin, histamine, and dopamine at concentrations exceeding 80 µg/ml, 100 µg/ml, and 1 mg/ml, respectively. At lower concentration, these neurotransmitters were “negatively toxic”, i.e. stimulatory in terms of the effect on bacterial luminescence. In contrast, norepinephrine inhibited luminescence at all concentrations tested. Conclusions: The bacterial luminescence-based testing method is applicable to the assessment of the destructive and stimulatory effects of neurotransmitters; the data obtained are of microbiological and clinical relevance