PHB-degrading bacteria isolated from the gastrointestinal tract of aquatic animals as protective actors against luminescent vibriosis

Abstract

The use of poly-β-hydroxybutyrate (PHB) was shown to be successful in increasing the resistance of brine shrimp against pathogenic infections. In this study, we isolated for the first time PHB-degrading bacteria from a gastrointestinal environment. Pure strains of PHB-degrading bacteria were isolated from Siberian sturgeon, European sea bass and giant river prawn. The capability of selected isolates to degrade PHB was confirmed in at least two of three setups: (1) growth in minimal medium containing PHB as the sole carbon (C) source, (2) production of clearing zones on minimal agar containing PHB as the sole C source and (3) degradation of PHB (as determined by HPLC analysis) in 10% Luria-Bertani medium containing PHB. Challenge tests showed that the PHB-degrading activity of the selected isolates increased the survival of brine shrimp larvae challenged to a pathogenic Vibrio campbellii strain by a factor 2-3. Finally, one of the PHB-degrading isolates from sturgeon showed a double biocontrol effect because it was also able to inactivate acylhomoserine lactones, a type of quorum-sensing molecule that regulates the virulence of different pathogenic bacteria. Thus, the combined supplementation of a PHB-degrading bacterium and PHB as a synbioticum provides perspectives for improving the gastrointestinal health of aquatic animals.

Antiadhesive activity of poly-hydroxy butyrate biopolymer from a marine Brevibacterium casei MSI04 against shrimp pathogenic vibrios

“…Recently PHB was proven to be an immunostimulant in fish [29]. The synergistic effect of PHB-degrading probiotic and PHB as a synbioticum elicits a strong protection against luminescent vibriosis [30]. PHB increases growth rate and act as symbiotic of intestinal microglora of fish [31].…”

Phaeobacter inhibens as probiotic bacteria in non-axenic Artemia and algae cultures

“…The effect of the background microbiota was most pronounced after 24 h of incubation and then declined and we attribute the slight reduction rather to an interspecies competition for nutrients and not to a direct bactericidal effect. The difference after 48 h is the same as the start inoculation at time 0 corresponding with the expected outcome derived from former studies (Liu et al, 2010;Niu et al, 2014).…”

“…Ochrobactum sp. strains M13 and M15 have also been shown to have probiotic effects, yet not through antagonism of pathogens, but rather through degradation of poly-β-hydroxybutyrate (Liu et al, 2010), which was not supplied in our experiments. The effect of the background microbiota was most pronounced after 24 h of incubation and then declined and we attribute the slight reduction rather to an interspecies competition for nutrients and not to a direct bactericidal effect.…”

“…Non-axenic Tetraselmis suecica cultures in f/2 medium (Guillard and Ryther, 1962) in 3% IO was acquired from a commercial aquaculture Macrobrachium rosenbergi Liu et al (2010) unit. The concentration of Tetraselmis suecica was determined using a Neubauer-improved counting chamber.…”

Degradation intermediates of polyhydroxy butyrate inhibits phenotypic expression of virulence factors and biofilm formation in luminescent Vibrio sp. PUGSK8

“…55 Vibrio PUGSK8 was inoculated in nutrient rich (ZMA) medium as well as in the minimal media supplemented with various concentration of PHB ranging from 100 mg/l, 200 mg/l, 250 mg/l PHB. The plates were incubated at 28 °C for 48 h and monitored for the formation of zones of clearance.…”