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Zebrafish larvae require specific strains of bacteria for neurobehavioral development.
Citation:
Kvasnicka, A., S. Gaballah, D. Phelps, T. Catron, N. Brinkman, S. Keely, C. Wood, AND T. Tal. Zebrafish larvae require specific strains of bacteria for neurobehavioral development. NC microbiome Symposium, Durham, NC, May 15, 2018.
Impact/Purpose:
Intestinal microbes are thought to influence mood, anxiety, and increasingly, brain development. To determine the role of microbiota in zebrafish nervous system development, we used axenic (microbe-free) zebrafish and axenic zebrafish colonized on day 1 with either a diverse mixture of bacteria harvested from an aquaculture facility or with single strains of bacteria isolated from 10 day old zebrafish. A standard locomotor behavioral assay was used as a functional readout of the microbiota-gut-brain axis. This study showed that axenic zebrafish colonized with single strains of Actinetobacter, Comamonas, or Comamonadaceae develop a normal behavioral phenotype at 10 days of life. We also showed that colonization with a single strain of Vibrio resulted in abnormal behavioral development. This finding replicates an earlier observation we made with another strain of Vibrio (Phelps et al. Scientific Reports. 2017.). It is currently unknown whether and how microbiota might influence the developmental neurotoxicity of environmental chemicals. These data raise the possibility that environmental chemicals that target microbiota may harbor the ability to select for microbes that allow for abnormal behavioral development.
Description:
There is an increasing appreciation of the relationship between gut microbiota and nervous system development and function. We previously showed that axenic (microbe-free) larvae are hyperactive at 10 days post fertilization (dpf) relative to colonized zebrafish larvae. Interestingly, while exposure to heat-killed bacteria or microbe-associated molecular patterns failed to block hyperactivity in axenic larvae, colonization of axenic larvae with Aeromonas veronii or Vibrio cholerae produced locomotor hypoactivity relative to colonized controls. These data suggest that there is a developmental requirement for certain types of microbes to modulate host behavior. To address this hypothesis, eight bacterial isolates were obtained from 10 dpf conventionally colonized zebrafish larvae. 16S rRNA gene sequencing identified four unique EPA gram-negative isolates: Acinetobacter, Vibrio, Comamonas, and Comamonadaceae. Colonization of axenic embryos at 1 dpf with 100 cells/mL of Acinetobacter, Comamonas, or Comamonadaceae resulted in behavioral profiles that were identical to colonized control larvae at 8 dpf. In comparison, axenic embryos colonized with EPA Vibrio bacteria were hypoactive relative to control larvae. EPA Vibrio-related hypoactivity was prevented in axenic larvae colonized with 25 cells/mL each of Actinetobacter, Vibrio, Comamonas, and Comamonadaceae at 1 dpf. Finally, EPA Vibrio-related hypoactivity was found to persist in 10 dpf larvae. These data suggest that specific bacterial taxa are needed to drive neurobehavioral development while colonization with other strains may result in behavioral hypoactivity. This raises the possibility that environmental chemicals may disrupt neurobehavioral development by selecting for specific classes of host-associated microbes. This abstract does not represent EPA policy.