Probiotics play a crucial role in modulating the gut microbiome of farmed fish, potentially improving health and growth performance. This study investigated the effects of dietary supplementation with Lysinibacillus fusiformis, a Ugandan strain - LFUG on the gut microbiome of juvenile Nile tilapia (Oreochromis niloticus) under controlled conditions.
Two concentrations (T1: 1x106 CFU/g; T2: 1x108 CFU/g) and the control (0 CFU/g) were used for 60 days, followed by collecting hindgut tissues from six fish per treatment. Genomic DNA was extracted (QIAamp Fast DNA stool mini kit - Qiagen, Germany) and subjected to full-length 16S rRNA sequencing using a PromethION device. Alpha and beta diversity analyses were conducted, and community differences were assessed.
Despite increasing the bacterial species richness of the microbiome (Fig. 1), LFUG dietary supplementation did not significantly affect both the alpha and beta diversities compared to the control. However, the differentially abundant taxa were detected in the control and LFUGT2 but not LFUGT1 (Table 1). Moreover, LFUGT2 differentially abundant taxa were beneficial bacteria (Romboutsia sp., Allorhizobium−Neorhizobium−Pararhizobium−Rhizobium sp. and Vulcaniibacterium thermophilum) compared to the control (Cetobacterium sp). (Table 1). Cetobacterium sp. is a common bacterium in freshwater fish species including Nile tilapia, whose reduction after probiotic feeding is indicative of microbiome modulation towards proliferation of beneficial taxa, which enhance gut health and overall host wellbeing.
In conclusion, Lysinibacillus fusiformis LFUGT dietary supplementation influenced gut bacterial composition but did not significantly impact overall microbial diversity. Proliferation and dominance by beneficial bacteria was enhanced, which potentially improved fish health while reducing opportunistic pathogens.