Abstract
The bacterial storage compound poly-β-hydroxybutyrate, a polymer of the short-chain fatty acid 3-hydroxybutyrate, has been reported to protect various aquatic animals from bacterial disease. In order to obtain a better mechanistic insight, we aimed to (1) investigate whether 3-hydroxybutyrate is released from poly-β-hydroxybutyrate within sterile brine shrimp larvae, (2) determine the impact of 3-hydroxybutyrate on the virulence of Vibrio campbellii to brine shrimp larvae and on its cell density in the shrimp, and (3) determine the impact of this compound on virulence factor production in the pathogen. We detected 3-hydroxybutyrate in poly-β-hydroxybutyrate-fed brine shrimp, resulting in 24 mM 3-hydroxybutyrate in the intestinal tract of shrimp reared in the presence of 1000 mg l−1 poly-β-hydroxybutyrate. We further demonstrate that this concentration of 3-hydroxybutyrate does not affect the growth of V. campbellii, whereas it decreases the production of different virulence factors, including hemolysin, phospholipase and protease activities, and swimming motility. We hypothesize that by affecting all these virulence factors at once, 3-hydroxybutyrate (and thus also poly-β-hydroxybutyrate) can exert a significant impact on the virulence of V. campbellii. This hypothesis was confirmed in a challenge test showing that 3-hydroxybutyrate protected gnotobiotic brine shrimp from pathogenic V. campbellii, without affecting the number of host-associated vibrios.
Highlights
Aquaculture is playing an increasingly important role with respect to food security, and the sector is predicted to dominate aquatic food supply within a few years[1]
Research has revealed that the bacterial storage compound poly-β-hydroxybutyrate, a polymer of the short-chain fatty acid 3-hydroxybutyrate, is able to improve the survival of various aquaculture species[13,17,18,19,20,21,22]
Because poly-β-hydroxybutyrate is water-insoluble, we have hypothesized that in order to exert a beneficial effect, the polymer must be degraded into water-soluble products (e.g. 3-hydroxybutyrate monomers) in the intestinal tract of aquatic animals, and that these water-soluble products are responsible for the beneficial effect[12]
Summary
Aquaculture is playing an increasingly important role with respect to food security, and the sector is predicted to dominate aquatic food supply within a few years[1]. Short-chain fatty acids are able to inhibit the growth of various bacteria, and as a consequence, there is interest in the use of these compounds as biocontrol agents in animal production[10]. These compounds are able to protect aquatic animals from vibriosis[11]. Short-chain fatty acids, including 3-hydroxybutyrate, are capable of inhibiting the growth of vibrios belonging to the Harveyi clade in a pH-dependent manner, with effective concentrations within the range of 10–100 mM11,13. The impact of 3-hydroxybutyrate on virulence factor production in vibrios is currently unknown
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
