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

A comprehensive review on probiotics and their use in aquaculture: Biological control, efficacy, and safety through the genomics and wet methods

Probiotics, defined as viable microorganisms that enhance host health when consumed through the diet, exert their effects through mechanisms such as strengthening the immune system, enhancing resistance to infectious diseases, and improving tolerance to stressful conditions. Driven by a growing market, research on probiotics in aquaculture is a burgeoning field. However, the identification of new probiotics presents a complex challenge, necessitating careful consideration of both the safety and efficacy of the microorganisms employed. This review aims to delineate the most utilized and effective methods for identifying probiotics. The most effective approach currently combines in silico analysis of genomic sequences with in vitro and in vivo experiments. Two main categories of genetic traits are analyzed using bioinformatic tools: those that could harm the host or humans (e.g., toxin production, antibiotic resistance) and those that offer benefits (e.g., production of helpful compounds, and enzymes). Similarly, in vitro experiments allow us to examine the safety of a probiotic but also its effectiveness (e.g., ability to adhere to epithelia). Finally, in vivo experiments allow us to study the effect of probiotics on fish growth and health, including the ability of the probiotic to manipulate the host's microbiota and the ability to mitigate the infections. This review comprehensively analyzes these diverse aspects, with a particular focus on the potential of studying the interaction between bacterial pathogens and probiotics through these integrated methods.

Lysinibacillus capsici 38,328 isolated from agricultural soils as a promising probiotic candidate for intestinal health

There is an increasing interest in the use of spore-forming Bacillus spp. as probiotic ingredients on the market. However, probiotics Bacillus species are insufficient, and more safe Bacillus species were required. In the study, traditional fermented foods and soil samples were collected from more than ten provinces in China, and 506 Bacillus were selected from 109 samples. Using the optimized procedure, we screened nine strains, which successfully passed the acid, alkali, bile salt, and trypsin resistance test. Drug sensitivity test results showed that three Bacillus out of the nine isolates exhibited antibiotic sensitivity to more than 29 antibiotics. The three strains sensitive to antibiotics were identified by 16S ribosomal RNA, recA, and gyrB gene analysis, two isolates (38,327 and 38,328) belong to the species Lysinibacillus capsici and one isolate (37,326) belong to Bacillus halotolerans. Moreover, the three strains were confirmed safe through animal experiments. Finally, L. capsici 38,327 and 38,328 showed protections in the Salmonella typhimurium infection mouse model, which slowed down weight loss, reduced bacterial load, and improved antioxidant capacity. Altogether, our data demonstrated that selected L. capsici strains can be used as novel probiotics for intestinal health.

Single and Multi-Strain Probiotics Supplementation in Commercially Prominent Finfish Aquaculture: Review of the Current Knowledge

The Nile tilapia Oreochromis niloticus, Atlantic salmon Salmo salar, rainbow trout Oncorhynchus mykiss, olive flounder Paralichthys olivaceus, common carp Cyprinus carpio, grass carp Ctenopharyngodon idella and rohu carp Labeo rohita are farmed commercially worldwide. Production of these important finfishes is rapidly expanding, and intensive culture practices can lead to stress in fish, often reducing resistance to infectious diseases. Antibiotics and other drugs are routinely used for the treatment of diseases and sometimes applied preventatively to combat microbial pathogens. This strategy is responsible for the emergence and spread of antimicrobial resistance, mass killing of environmental/beneficial bacteria, and residual effects in humans. As an alternative, the administration of probiotics has gained acceptance for disease control in aquaculture. Probiotics have been found to improve growth, feed utilization, immunological status, disease resistance, and to promote transcriptomic profiles and internal microbial balance of host organisms. The present review discusses the effects of single and multi-strain probiotics on growth, immunity, heamato-biochemical parameters, and disease resistance of the above-mentioned finfishes. The application and outcome of probiotics in the field or open pond system, gaps in existing knowledge, and issues worthy of further research are also highlighted.