title: Bacillus sp. LT3 improves the survival of gnotobiotic brine shrimp (Artemia franciscana) larvae challenged with Vibrio campbellii by enhancing the innate immune response and by decreasing the activity of shrimp-associated vibrios.
abstract: Bacteria belonging to the genus Bacillus are amongst the most intensively studied group of bacteria for use as probiotics in aquaculture. However, the exact mechanism of action of these bacteria is often not well described, and the microbiota that are naturally present in cultures of test organisms often compromise the interpretation of the results. The present study aimed to evaluate the putative probiotic effect of Bacillus sp. LT3 in a model system with gnotobiotic brine shrimp Artemia franciscana larvae. The strain significantly increased the survival of brine shrimp larvae challenged with Vibrio campbellii when administered 6h before the challenge. Under these conditions, LT3 was able to colonize the brine shrimp gastrointestinal tract and to decrease the in vivo pathogen activity as indicated by the bioluminescence of the V. campbellii associated with brine shrimp larvae. In order to investigate the effect of the Bacillus strain on the innate immune system of the brine shrimp larvae, prophenoloxidase and transglutaminase mRNA levels were monitored, while heat shock protein 70 mRNA levels were measured as an indicator of physiological stress. Interestingly, 12h after challenge, the prophenoloxidase mRNA level in the larvae pre-treated with LT3 and challenged with V. campbellii was approximately 8-fold higher than in the other treatments. Further, a decreased mRNA level of transglutaminase gene and heat shock protein 70 gene suggested that pretreatment with LT3 results in less stress and tissue damage in the brine shrimp larvae upon V. campbellii challenge. These results indicated that Bacillus sp. LT3 could improve the survival of brine shrimp larvae when challenged with pathogenic V. campbellii, both by decreasing the in vivo activity of the pathogen and by priming the innate immune response through activating the prophenoloxidase system.
authors.affiliation: Faculty of Bioscience Engineering, Laboratory of Aquaculture & Artemia Reference Center, Ghent University, Rozier 44, Gent, 9000, Belgium; The Key Laboratory of Mariculture, Ministry of Education, Ocean University of China, Qingdao, China.
authors.forename: Yufeng
authors.initials: Y
authors.lastname: Niu
authors.affiliation: Faculty of Bioscience Engineering, Laboratory of Aquaculture & Artemia Reference Center, Ghent University, Rozier 44, Gent, 9000, Belgium; Laboratory of Microbial Ecology and Technology (LabMET), Ghent University, Coupure Links 653, 9000, Gent, Belgium.
authors.forename: Tom
authors.initials: T
authors.lastname: Defoirdt
authors.affiliation: Faculty of Bioscience Engineering, Laboratory of Aquaculture & Artemia Reference Center, Ghent University, Rozier 44, Gent, 9000, Belgium.
authors.forename: Kartik
authors.initials: K
authors.lastname: Baruah
authors.affiliation: Laboratory of Microbial Ecology and Technology (LabMET), Ghent University, Coupure Links 653, 9000, Gent, Belgium.
authors.forename: Tom
authors.initials: T
authors.lastname: Van de Wiele
authors.affiliation: The Key Laboratory of Mariculture, Ministry of Education, Ocean University of China, Qingdao, China.
authors.forename: Shuanglin
authors.initials: S
authors.lastname: Dong
authors.affiliation: Faculty of Bioscience Engineering, Laboratory of Aquaculture & Artemia Reference Center, Ghent University, Rozier 44, Gent, 9000, Belgium. Electronic address: Peter.Bossier@UGent.be.
authors.forename: Peter
authors.initials: P
authors.lastname: Bossier
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D000898:Antibiosis / Q000502:physiology*; D017756:Aquaculture / Q000379:methods; D001156:Artemia / Q000254:growth & development / Q000276:immunology* / Q000382:microbiology*; D001407:Bacillus / Q000276:immunology / Q000502:physiology*; D004156:Catechol Oxidase / Q000378:metabolism; D017931:DNA Primers / Q000235:genetics; D004792:Enzyme Precursors / Q000378:metabolism; D041981:Gastrointestinal Tract / Q000382:microbiology*; D005856:Germ-Free Life / Q000276:immunology; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism; D007113:Immunity, Innate / Q000276:immunology*; D007814:Larva / Q000276:immunology / Q000382:microbiology; D019936:Probiotics / Q000494:pharmacology; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D011503:Transglutaminases / Q000378:metabolism; D014733:Vibrio / Q000187:drug effects / Q000276:immunology*
chemical_list: D017931:DNA Primers; D004792:Enzyme Precursors; D018840:HSP70 Heat-Shock Proteins; D012333:RNA, Messenger; C038451:pro-phenoloxidase; D004156:Catechol Oxidase; D011503:Transglutaminases
keywords: Artemia; Bacillus sp.; Innate immune response; Priming