Microbial Endocrinology

Dopamine alters phage morphology to exert an anti-infection effect

Antiviral drug development is important for human health, and the emergence of novel COVID-19 variants has seriously affected human lives and safety. A bacteriophage-a bacterial virus with a small and simple structure-is an ideal experimental candidate for studying the interactions between viruses and their hosts. In this study, the effects and mechanisms of catecholamines on phages were explored, and dopamine (DA) was found to have general and efficient anti-infection effects. A clear dose-dependent effect was observed when different phages were treated with DA, with higher DA concentrations exhibiting stronger anti-phage activity. The half maximal inhibitory concentration values of DA for vB-EcoS-IME167, T4 Phage, and VMY22 were determined as 0.26, 0.12, and 0.73 mg mL-1, respectively. The anti-phage effect of DA increased with treatment duration. In addition, the anti-infection activities of DA against vB-EcoS-IME167, T4 Phage, and VMY22 were increased by 105, 104, and 104 folds compared to that of the control. This ability of DA was observed only in phages and not in the host bacteria. Morphological changes of phages were observed under transmission electron microscopy following their treatment with DA, and considerable changes in adsorption were confirmed via quantitative reverse transcription polymerase chain reaction. These results suggest that the anti-phage effect of DA is primarily due to the destruction of the external structure of the phage. This study, to the best of our knowledge, is the first to report the universal anti-phage infection effect of dopamine, which provides novel information regarding DA and forms a basis for further research and development of antiviral drugs. Moreover, it provides a new perspective for the research about the defense and counter-defense of bacteria and bacteriophages.

Inter-Kingdom Signaling of Stress Hormones: Sensing, Transport and Modulation of Bacterial Physiology

Prokaryotes and eukaryotes have coexisted for millions of years. The hormonal communication between microorganisms and their hosts, dubbed inter-kingdom signaling, is a recent field of research. Eukaryotic signals such as hormones, neurotransmitters or immune system molecules have been shown to modulate bacterial physiology. Among them, catecholamines hormones epinephrine/norepinephrine, released during stress and physical effort, or used therapeutically as inotropes have been described to affect bacterial behaviors (i.e., motility, biofilm formation, virulence) of various Gram-negative bacteria (e.g., Escherichia coli, Salmonella enterica serovar Typhimurium, Pseudomonas aeruginosa, Vibrio sp.). More recently, these molecules were also shown to influence the physiology of some Gram-positive bacteria like Enterococcus faecalis. In E. coli and S. enterica, the stress-associated mammalian hormones epinephrine and norepinephrine trigger a signaling cascade by interacting with the QseC histidine sensor kinase protein. No catecholamine sensors have been well described yet in other bacteria. This review aims to provide an up to date report on catecholamine sensors in eukaryotes and prokaryotes, their transport, and known effects on bacteria.

Effect of catecholamine stress hormones (dopamine and norepinephrine) on growth, swimming motility, biofilm formation and virulence factors of Yersinia ruckeri in vitro and an in vivo evaluation in rainbow trout

In this study, we evaluated the impact of the catecholamines on growth, swimming motility, biofilm formation and some virulence factors activities of pathogenic Yersinia ruckeri. Norepinephrine and dopamine (at 100 µM) significantly increased the growth of Y. ruckeri in culture media containing serum. An increase in swimming motility of the pathogen was found following the exposure to the hormones; however, no effect was seen on caseinase, phospholipase and haemolysin productions. Further, antagonists for the catecholamine receptors were observed to block some of the influences of the catecholamines. Indeed, the effects of catecholamines were inhibited by chlorpromazine (the dopaminergic receptor antagonist) for dopamine, labetalol (α-and β-adrenergic receptor antagonist) and phenoxybenzamine (the α-adrenergic receptor antagonist) for norepinephrine, but propranolol (the β-adrenergic receptor antagonist) showed no effect. Pretreatment of Y. ruckeri with the catecholamines resulted in a significant enhancement of its virulence towards rainbow trout and the antagonists could neutralize the effect of the stress hormones in vivo. In summary, our results show that the catecholamines increase the virulence of Y. ruckeri which is pathogenic to trout through increasing the motility, biofilm formation and growth.

Catecholamine-Modulated Novel Surface-Exposed Adhesin LIC20035 of Leptospira spp. Binds Host Extracellular Matrix Components and Is Recognized by the Host during Infection

In this study, the effect of the host stress hormone catecholamine on Leptospira gene transcripts encoding outer membrane proteins was investigated. There was no impact of catecholamine supplementation on the in vitro growth pattern of Leptospira interrogans; however, 7 genes out of 41 were differentially transcribed, and the effect was reversed to the basal level in the presence of the antagonist propranolol. Comprehensive analysis of one of the differentially regulated proteins, LIC20035 (in serovar Copenhageni)/LB047 (in serovar Lai) (due to catecholamine supplementation), revealed immunogenicity and ability to adhere to host extracellular matrices. Protease accessibility assay and phase partition of integral membrane proteins of Leptospira showed LIC20035/LB047 to be an outer membrane surface-exposed protein. The recombinant LIC20035 protein can be serologically detected using human/bovine sera positive for leptospirosis. Moreover, the recombinant LIC20035 can bind to diverse host extracellular matrices, with a higher affinity toward collagen and chondroitin sulfate.IMPORTANCE Leptospirosis is a neglected tropical disease of global importance. This study aimed to identify outer membrane proteins of pathogenic Leptospira responding to host chemical signals like catecholamines, with the potential to serve as virulence factors, new serodiagnostic antigens, and vaccine candidates. This study mimicked the plausible means by which Leptospira during infection and hormonal stress intercepts host catecholamines to disseminate in host tissues.

Norepinephrine and dopamine increase motility, biofilm formation, and virulence of Vibrio harveyi

Vibrio harveyi is one of the major pathogens of aquatic organisms, affecting both vertebrates and invertebrates, and causes important losses in the aquaculture industry. In order to develop novel methods to control disease caused by this pathogen, we need to obtain a better understanding of pathogenicity mechanisms. Sensing of catecholamines increases both growth and production of virulence-related factors in pathogens of terrestrial animals and humans. However, at this moment, knowledge on the impact of catecholamines on the virulence of pathogens of aquatic organisms is lacking. In the present study, we report that in V. harveyi, norepinephrine (NE) and dopamine (Dopa) increased growth in serum-supplemented medium, siderophore production, swimming motility, and expression of genes involved in flagellar motility, biofilm formation, and exopolysaccharide production. Consistent with this, pretreatment of V. harveyi with catecholamines prior to inoculation into the rearing water resulted in significantly decreased survival of gnotobiotic brine shrimp larvae, when compared to larvae challenged with untreated V. harveyi. Further, NE-induced effects could be neutralized by α-adrenergic antagonists or by the bacterial catecholamine receptor antagonist LED209, but not by β-adrenergic or dopaminergic antagonists. Dopa-induced effects could be neutralized by dopaminergic antagonists or LED209, but not by adrenergic antagonists. Together, our results indicate that catecholamine sensing increases the success of transmission of V. harveyi and that interfering with catecholamine sensing might be an interesting strategy to control vibriosis in aquaculture. We hypothesize that upon tissue and/or hemocyte damage during infection, pathogens come into contact with elevated catecholamine levels, and that this stimulates the expression of virulence factors that are required to colonize a new host.

Communication between Bacteria and Their Hosts

It is clear that a dialogue is occurring between microbes and their hosts and that chemical signals are the language of this interkingdom communication. Microbial endocrinology shows that, through their long coexistence with animals and plants, microorganisms have evolved sensors for detecting eukaryotic hormones, which the microbe uses to determine that they are within proximity of a suitable host and to optimally time the expression of genes needed for host colonisation. It has also been shown that some prokaryotic chemical communication signals are recognized by eukaryotes. Deciphering what is being said during the cross-talk between microbe and host is therefore important, as it could lead to new strategies for preventing or treating bacterial infections.