Genomic insights into Bacillus sp. KNSH11 from Litopenaeus vannamei intestine: Probiotic potential, safety, and aquaculture applications

Abstract

In the context of sustainable aquaculture, probiotics represent a promising alternative to antibiotics for promoting shrimp health and disease resistance. In this study, Bacillus sp. KNSH11, a Gram-positive, rod-shaped bacterium isolated from the intestine of whiteleg shrimp (Litopenaeus vannamei), was characterized to assess its probiotic potential. The strain exhibited excellent sporulation efficiency (> 99 %), supporting its resilience under harsh environmental conditions. Functional assays demonstrated that KNSH11 retained high viability under various stressors, including acidic pH (2–4), bile salts, elevated temperatures (up to 95 °C), and lysozyme exposure, indicating robust tolerance to gastrointestinal and processing challenges. Metabolic profiling revealed substantial lactic acid production with minimal levels of acetate and propionate, distinguishing it from conventional lactic acid bacteria. The strain also exhibited strong antioxidant activity and moderate antibiofilm effects against pathogenic bacteria. Antibiotic susceptibility testing showed sensitivity to amoxicillin, chloramphenicol, kanamycin, and tetracycline (all at 30 μg/disc), while resistance was observed against ampicillin and penicillin (10 μg/disc each). Whole genome sequencing confirmed the absence of virulence genes and identified the presence of mobile genetic elements, a CRISPR/Cas system, and gene clusters potentially responsible for bacteriocin production. Collectively, these results indicate that Bacillus sp. KNSH11 exhibits key probiotic characteristics and genomic features consistent with a safe profile, supporting its potential application in sustainable shrimp aquaculture, pending further in vitro and in vivo validation.