Influence of a fish bacterium Lactobacillus sp. on the production of swordtail xiphophorus helleri (Heckel 1848)

The influence of a fish gut bacterium Lactobacillus sp on the production of swordtail Xiphophorus helleri was studied for a period of one year. The Lactobacillus sp P21 produced bacteriocin-like inhibitory substance and exhibited wide spectrum of action against Aeromonas hydrophila, Bacillus spp, Pseudomonas spp and Citrobacter freundi in vitro. The growth performance of X. helleri reared in the presence of Lactobacillus P21 at 106/ml rearing water was better than the control. The total plate counts, total MRS agar counts and the counts of motile aeromonads, presumptive pseudomonads, lactose fermenters and lactose non-fermenters in the gut of probiotic group were comparatively low than the control. On day 60 the count of Lactobacillus sp P21 was observed to be log 5.28/g in the gut of X. helleri indicating colonization of this bacterium in the gastrointestinal tract. The fecundity of X. helleri was in the range of 9-134. On average, it produced from 39.42±18.72 fry/female in control group to 53.00±23.57 fry/female in probiotic group. The increase in average fecundity in probiotic group over the control group was about 25%. There existed significant difference between probiotic group and control in respect of average fecundity/female (p<0.02), average number of fry survived /female (p<0.006) and average number of fry dead/female (p<0.029). The results of the present study demonstrated that the rearing of X. helleri in probiotic-enriched water have growth inducing ability and favourably influenced the reproductive performance in terms of high fecundity, high fry survival, reduced fry mortality and reduced fry deformity

Evaluation of Enterobacter sp. strain G87 as potential probiont against Vibrio harveyi infection in Artemia nauplii and Asian seabass (Lates calcarifer) larvae

Probiotic has gained many interests as an alternative method in preventing and treating diseases in aquaculture. The benefits include improving feed value, inhibition of pathogenic microorganisms, anti-mutagenic and anti-carcinogenic activity, growth promoting factors, and increase host immune response. This research was carried out in order to evaluate the potential of probiont Enterobacter sp. G87 in conferring protection to Artemia and seabass larvae against Vibrio harveyi infection. In preliminary in vivo test, Artemia nauplii was treated with Enterobacter sp. G87 at three different concentrations 104, 106 and 108 CFU mL-1 and challenged with V. harveyi at 105 CFU mL-1. After challenged, significant increased survival was found in Artemia (78±2%) treated with 106 CFU mL-1 of Enterobacter sp. G87 compared with challenged group with no probiont added (48±2%). From the results, two concentrations of probiont (106 and 108 CFU mL-1) were selected to be used in seabass larvae in vivo challenge assay. After challenged with V. harveyi at 105 CFU mL-1 highest survival was found in seabass larvae treated with 106 CFU mL-1 of Enterobacter sp. G87 (95±3%). Additionally, Enterobacter sp. G87 was also able to reduce Vibrio counts both in Artemia and seabass larvae culture. This study showed that probiont Enterobacter sp. G87 was able to protect Artemia nauplii and seabass larvae from Vibrio harveyi infection and has a potential to be further studied in a larger scale

Role of Gut Probionts in Enhancing Growth and Disease Resistance in Rainbow Trout (Oncorhynchus mykiss, Walbaum) Fingerlings

Seven out of 34 isolates were selected as putative probionts. These were mixed with an equal volume of a lipid oralizer and incorporated into compounded feed pellets to achieve a dose of 5 x 107 bacterial cells•g-1 of fish food and fed to Rainbow trout Oncorhynchus mykiss fingerlings (average weight 23.69 g) for a period of 25 days. Superior growth (SGR) ranging between 0.32 to 0.57 (P<0.05) as compared to 0.05 of the control group was obtained in fingerlings maintained on the probiotic incorporated diets. A comparatively lower growth of 0.12 was obtained in group F5 but this was still higher than that of the animals maintained on a feed devoid of probiotics. Feed efficiencies ranging between 0.36 for group F5 to 1.03 for group F7 (P< 0.05) as compared to 0.08 of the control group were obtained in animals fed the probiotic feeds

Screening and evaluation of local bacteria isolated from shellfish as potential probiotics against pathogenic Vibrios

The present study was carried out to isolate, screen and evaluate potential candidates of local bacteria isolated from tiger shrimp Penaeus monodon and slipper cupped oysters Crassostrea iredalei as probiotics in shellfish aquaculture. A total of 144 of bacteria were successfully isolated from the intestine and stomach of 20 tails of healthy adult tiger shrimp P. monodon, while 136 were successfully isolated from the digestive tract, gills and inner shells of 10 healthy adult C. iredalei. The number of potential isolates was narrowed down to two from tiger shrimp, and one from slipper cupped oyster after in vitro screening assays. The three isolates, labeled as G11, I24 and S66, were identified as Virgibacillus sp., Bacillus sp. and Exiquobacterium sp., respectively, using 16S rDNA gene analysis. The antagonistic ability of the isolates towards Vibrio alginolyticus and Vibrio harveyi were conducted in stagnant and liquid modes via spot lawn and broth co-culture assay, respectively. In these assays, all the potential probionts were inhibitory to both pathogenic vibrios. In the in-vivo assay, Artemia was used as host and treated with different concentrations of potential probionts (10⁴, 10⁶ and 10⁸ CFU ml⁻¹), and challenged with V. alginolyticus ana V. harveyiat 10⁵ CFU ml⁻¹ Respectively, Artemia treated with probiont Gl 1 at all concentrations and challenged with V. alginolyticus had increased survival (70-80 %), which was significantly higher as compared with group with only the pathogen (20 %). Meanwhile, probiont I24 increased the survival of Artemia by 70 % at a concentration of 10⁸ CFU ml⁻¹ after being challenged with V. alginolyticus and Artemia treated with 10⁶ CFU ml⁻¹ of probiont S66 had increased survival of 90% after being challenged with V. harveyi. Thus, the three isolates might have potential applications as probiotics in shellfish aquaculture against vibriosis

Contrasting Immunomodulatory Effects of Probiotic and Pathogenic Bacteria on Eastern Oyster, \u3cem\u3eCrassostrea Virginica\u3c/em\u3e, Larvae

Several Vibrio spp. cause acute and severe mortality events in hatcheries where larvae of bivalve mollusks are reared, potentially leading to subsequent shortage of bivalve seed for the grow-out industry. In particular, strains of Vibrio coralliilyticus have been identified as a major cause of disease in Pacific, Crassostrea gigas, and eastern, C. virginica, oyster hatcheries in the United States of America. Probiotic bacteria are an inexpensive, practical, and natural method of disease control. Previous research shows that pretreatment of larval oysters with probiotic bacteria Bacillus pumilus RI06–95 (RI) and Phaeobacter inhibens S4 (S4) significantly decreases mortality caused by experimental challenge with the bacterial pathogen V. coralliilyticus RE22 (RE22). This study aims to characterize the immune response of 6–10-day-old eastern oyster larvae to experimental challenge with pathogen V. coralliilyticus RE22 and probionts RI and S4. Treatments included (a) pathogen and probiont exposure at a concentration of 5 × 104CFU per mL (~2500 bacterial cells per larva) for a duration of 6 h, (b) probiont exposure at the same concentration for a duration of 24 h, and (c) probiont RI daily treatment of larvae in the hatchery for 4, 11, and 15 days. Differential gene expression analysis compared pathogen or probiotic-treated transcriptomes to unexposed controls. Probiotic and pathogen treatment led to upregulation of transcripts coding for several immune pattern recognition receptors (PRRs) involved in environmental sensing and detection of microbes in oyster larvae. Larval oyster responses to pathogen RE22 suggested suppression of expression of genes in immune signaling pathways (myd88, tak1, nkap), failure in upregulation of immune effector genes, high metabolic demand, and oxidative stress that potentially contributed to mortality. On the other hand, the transcriptomic response to probiotic bacteria RI and S4 suggested activation of immune signaling pathways and expression of immune effectors (e.g., Cv-spi2, mucins and perforin-2). These key features of the host immune response to probiotic bacteria were shared despite the length of probiotic exposure, probiotic species, and the type of environment in which exposures were conducted. This study suggests that pre-exposure of eastern oyster larvae to probiotics for 6–24 h prior to pathogenic challenge leads to a robust and effective immune response that may contribute to protecting larvae from subsequent challenge with V. coralliilyticus RE22. This research provides new insights into host-microbe interactions in larval oysters that could be applied in the management of vibriosis in bivalve hatcheries

Screening and evaluation of indigenous bacteria from the Persian Gulf as a probiotic and biocontrol agent against Vibrio harveyi in Litopenaeus vannamei post larvae

Isolation of autochthonous bacteria from marine sources as a potential probiont in biocontrolling against pathogenic Vibrio species in the shrimp culture industry was the aim of current research. A total of 198 bacterial strains were isolated from pond water, sediment, hepatopancreas and gut samples of shrimps after culturing the samples on Tryptic Soy Agar and incubated at 30 °C for 24-48 h. The isolates were tested for their antagonistic activity in contact with Vibrio harveyi. Two strains (IS02 and IS03) that isolated from the gut and pond sediment were showed antagonistic against V. harveyi. According to 16S ribosomal DNA gene sequence analysis, the strain IS02 was identified as Bacillus subtilis and IS03 as B. vallismortis. Further, the two bacterial species, B. subtilis and B. vallismortis were challenged separately for probiotic activity in the post larvae of Litopenaeus vannamei against pathogenic V. harveyi. The present study identified B. subtilis IS02 and B. vallismortis IS03 had biocontrol activity against V. harveyi in vitro and in vivo and they increase growth performance of L. vannamei in post larvae stage

Probiotics as biological control agent in sea bass larviculture

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Evaluation of potential bacteria isolated from marine shellfish as probiotic for Penaeus monodon larviculture against pathogenic Vibrio harveyi

Probiotics have been widely used as an alternative treatment in aquaculture. This study was carried out to determine the ability of two potential probionts; Bacillus strain I24 and Exiguobacterium strain S66 in producing biofilm and reducing hemolysin production in two Vibriosp;Vibrio alginolyticusand Vibrio harveyi.Biofilm assay was carried out to determine the ability of the potential probionts in producing biofilm; a slimy compound that facilitates bacterial attachment. Results showed that all potential probionts able to produce biofilm. Potential probionts started to produce high biofilm formation at 40 hr. For probiont S66, the highest production was recorded at 60 hr, and started to decrease at 70 hr. Meanwhile for potential probiont I24, increased of biofilm formation started at 30 hr until 70 hr. Furthermore, V. harveyi and V. alginolyticushad lower biofilm formation compared with the potential probionts. Thus, results indicated that potential probionts S66 and I24 possibly able to compete with pathogen for adhesion sites hence colonize the host. Hemolysin assay was carried out to determine the ability of potential probionts in reducing hemolysin production that caused hemolysis, which was one of the virulence factor in Vibriosp.. Incubation of potential probionts and pathogen showed no reduction in hemolysin production