Probiotic effect of Bacillus spp. isolated from African nightcrawler (Eudrilus eugeniae) on the performance of Nile Tilapia (Oreochromis niloticus L.).

This study evaluated the effects of the probiotic Bacillus spp. isolated from African nightcrawler (Eudrilus eugeniae) on the growth and survival performances of Nile tilapia (Oreochromis niloticus). A total of 400 Nile tilapia fingerlings (1.76 ± 0.07 g) were equally and randomly distributed into 20 glass aquaria and divided into five experimental groups with four replicates. Each experimental group was fed with a commercial diet (control) supplemented (at 108 CFU·g-1) with one of the four Bacillus spp. (ANSCI9, BFAR9, RM3, and RM10) at five percent of their body weight. After 30 days of feeding, the surviving fish were challenged with Aeromonas hydrophila to observe their survival. The treatment groups supplemented with BFAR9 (2.73 ± 0.26 g) and RM10 (3.15 ± 0.30 g) showed significantly higher (P < 0.05) absolute growth than the control (2.20 ± 0.16 g) group. Furthermore, those given with RM10 had better (P < 0.05) specific growth rate (SGR) (1.60 ± 0.10%·day-1) relative growth rate (RGR) (181.39 ± 18.16%) and feed conversion ratio (FCR) (1.99 ± 0.13) compared to the control group (SGR = 1.29 ± 0.07%·day-1; RGR = 129.84 ± 9.77%; FCR = 2.60 ± 0.16). The challenge test revealed that all Bacillus spp.-treated groups showed significantly higher (P < 0.05) survival rates (ANSCI9 = 82.5 ± 8.16%; BFAR9 = 80.0 ± 10.00%; RM3 = 77.5 ± 20.82%; RM10 = 85.0 ± 10.00%) than the control group (55.00 ± 19.15%), with the highest relative level of protection recorded for RM10 (66.67%). These results revealed that the probiotic Bacillus spp. isolated from E. eugeniae improved the growth, feed utilization, waste excretion, and the disease resistance of Nile tilapia.

In silico analysis of PirA- and PirB-like toxin genes of Vibrio spp., present in Asia and Costa Rica.

OBJECTIVE: Acute hepatopancreatic necrosis disease is an emerging infectious disease of Penaeus species. The causative agent is Vibrio species, which dispels binary toxin similar to pirA and pirB, which causes mortality in infected shrimp. The aim of this research was to investigate the evolutionary relationship of pirA and pirB homologous genes present in this Asia and Costa Rica in silico. MATERIALS AND METHODS: The sequences for in silico analysis were all retrieved from the Basic Local Alignment Search Tool Nucleotide (BLASTN) tool of the National Center for Biotechnology Center. For pirA, a total of 25 sequences submitted from different Asian countries and Costa Rica were retrieved for analysis. Meanwhile, for pirB, a total of 11 sequences submitted from five Asian countries were retrieved. Sequences were aligned using the CLUSTAL W alignment tool under Molecular Evolutionary Genetics Analysis (MEGA) 7 software. The evolutionary history was then estimated using the Unweighted Pair Group Method with Arithmetic mean (UPGMA) method, whereas the evolutionary distances were determined using the maximum composite likelihood model with 1,000 bootstrap replications. RESULTS AND DISCUSSION: The results show that, among 27 DNA sequences analyzed for pirA gene, three groups were generated, while for pirB, 13 DNA sequences yielded only one group. The analysis revealed low genetic variation among isolates for both pirA and pirB genes. CONCLUSION: This result suggests that the low frequency of polymorphism and geographic location cannot be attributed to the differences in V. parahaemolyticus isolates in Asian countries relative to Costa Rican isolates in pirA and pirB genes.

Selection and screening of bacteria from African nightcrawler, Eudrilus eugeniae (Kinberg, 1867) as potential probiotics in aquaculture.

Earthworms are used as an alternative protein source in aquaculture. These organisms serve as an ideal and favorable site for bacterial growth and activity. Hence, in our present study, we isolated and screened potential probiotic bacteria from African nightcrawler (Eudrilus eugeniae). Among 45 bacterial isolates, four (ANSCI9, BFAR9, RM3, and RM10) were selected based on their hydrophobicity, hydrolytic enzyme production, pH and fish bile tolerance, aggregation, and antimicrobial properties. The selected isolates showed good hydrophobicity (≥ 30%) and enzyme production (≥ 10 mm clearing zones), tolerance to pH and fish bile, and inhibitory properties against pathogenic microorganisms. The isolates were identified as Bacillus sp. RM3 (MH919306), Bacillus sp. RM10 (MH919308), Bacillus sp. ANSCI9 (MH919310) and Bacillus sp. BFAR9 (MH919302). These isolates were individually incorporated in the diets of Nile tilapia (Oreochromis niloticus) fingerlings for 14 days to assess their biosafety. The results showed that the survival rates in all treated groups (98.75 ± 2.5 to 100.00 ± 0.0%) were not significantly different (P < 0.05) from the control group (commercial diet) (96.25 ± 2.5%), suggesting that isolates have no adverse effect on the host. This study revealed the presence of potential probiotic microorganisms in E. eugeniae that are beneficial to the aquaculture industry.