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<p>In this study, we aimed to isolate potential <i>Bacillus</i> strains from the digestive tract of Nile tilapia (<i>Oreochromis niloticus</i>). Through morphological, biochemical, 16S rDNA sequencing, and evolutionary relationship assessments, we identified the isolated species as <i>Bacillus amyloliquefaciens</i> AV5 (OR647358), <i>Bacillus subtilis</i> AV7 (LC781790), and <i>Bacillus velezensis</i> AV50 (OR647359), designated as AV5, AV7, and AV50 strains, respectively. We evaluated their probiotic potential, including tolerance to high bile salt concentrations, low pH levels, and high temperatures, as well as their adhesion abilities (auto-aggregation and cell-surface hydrophobicity), antimicrobial activity, biosafety, compatibility, hemolytic activity, and antibiotic susceptibility. AV5, AV7, and AV50 strains exhibited <i>γ</i>-hemolytic activity and resistance to low pH (1) and high bile salt concentrations (0.5%). They demonstrated higher viability after exposure to elevated temperatures (80°C, 90°C, and 100°C) and increased cell surface hydrophobicity and autoaggregation. These strains showed positive compatibility, indicating their potential for multispecies use. Strains were susceptible to 17 out of 20 tested antibiotics, and displayed significant antimicrobial activity against <i>Vibrio alginolyticus, Vibrio harveyi, Streptococcus iniae</i>, and <i>Streptococcus agalactiae</i>. Therefore, AV5, AV7, and AV50 are promising probiotic candidates for enhancing the growth and health of aquatic animals, particularly in Nile tilapia (<i>O. niloticus</i>).</p>

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In vitro selection, assessment, and identification of potential probiotic features of the Bacillus strains isolated from the intestine of Nile tilapia (Oreochromis niloticus)

  • 期刊论文

  • 发表日期：

    2025年7月1日

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  • Vicent Michael Shija,
  • Kwaku Amoah,
  • Yi Li,
  • Yong Zhong,
  • Xiaopiao Zhong,
  • Jia Cai

摘要

In this study, we aimed to isolate potential Bacillus strains from the digestive tract of Nile tilapia (Oreochromis niloticus). Through morphological, biochemical, 16S rDNA sequencing, and evolutionary relationship assessments, we identified the isolated species as Bacillus amyloliquefaciens AV5 (OR647358), Bacillus subtilis AV7 (LC781790), and Bacillus velezensis AV50 (OR647359), designated as AV5, AV7, and AV50 strains, respectively. We evaluated their probiotic potential, including tolerance to high bile salt concentrations, low pH levels, and high temperatures, as well as their adhesion abilities (auto-aggregation and cell-surface hydrophobicity), antimicrobial activity, biosafety, compatibility, hemolytic activity, and antibiotic susceptibility. AV5, AV7, and AV50 strains exhibited γ-hemolytic activity and resistance to low pH (1) and high bile salt concentrations (0.5%). They demonstrated higher viability after exposure to elevated temperatures (80°C, 90°C, and 100°C) and increased cell surface hydrophobicity and autoaggregation. These strains showed positive compatibility, indicating their potential for multispecies use. Strains were susceptible to 17 out of 20 tested antibiotics, and displayed significant antimicrobial activity against Vibrio alginolyticus, Vibrio harveyi, Streptococcus iniae, and Streptococcus agalactiae. Therefore, AV5, AV7, and AV50 are promising probiotic candidates for enhancing the growth and health of aquatic animals, particularly in Nile tilapia (O. niloticus).