Isolation of potential probiotic Bacillus spp. and assessment of their subcellular components to induce immune responses in Labeo rohita against Aeromonas hydrophila.
Bacillus species isolated from the gut of healthy Labeo rohita (Hamilton) were screened for antibacterial activity against selected fish pathogens. Among the isolates, KADR5 and KADR6 showed antibacterial activity, tolerated low pH and high bile concentrations and were susceptibility to various antibiotics. Based on morphological and biochemical tests and 16S rRNA gene analysis the probiotic strains KADR5 and KADR6 were identified as Bacillus licheniformis and Bacillus pumilus, respectively. The immune stimulatory effect of subcellular components of probiotic Bacillus licheniformis KADR5 and Bacillus pumilus KADR6 in L. rohita against Aeromonas hydrophila infection was studied. Fish were immunized intraperitoneally in case of subcellular components [cell wall proteins (CWPs), extracellular proteins (ECPs), whole cell proteins (WCPs)] and orally in case of live cells (10(8) CFU/g of feed). After 14th day of administration, fishes from each group were challenged intraperitoneally with 0.1 ml of A. hydrophila cell suspension in PBS (10(5) cells ml(-1)). Groups immunized with subcellular components and live cells had significantly lower mortalities of 20-40% and 23-33%, respectively in comparison to control (80% mortality). The non specific immune factors in the cellular components and viable cells of the probiotics increased the expression of lysozyme and respiratory burst. Use of WCPs and CWPs resulted in better protection against A. hydrophila in L. rohita. Our results clearly reflect the potential of cellular components of the probiotics Bacillus species for the protection of fish against A. hydrophila infection by enhancing the immune response.
Department of Marine Biotechnology, Bharathidasan University, Tiruchirapalli 620 024, Tamil Nadu, India. Electronic address: drammicro@gmail.com.
Dharmaraj
D
Ramesh
Department of Industrial Biotechnology, Bharathidasan University, Tiruchirapalli 620 024, Tamil Nadu, India.
Annadurai
A
Vinothkanna
Regional Centre of Institute of Bioresources and Sustainable Development, Tadong 737102, Sikkim, India.
Amit Kumar
AK
Rai
Department of Genetic Engineering and Biotechnology, Bharathidasan University, Tiruchirapalli 620 024, Tamil Nadu, India.
Venkada Subramanian
VS
Vignesh
D016980:Aeromonas hydrophila / Q000276:immunology; D000821:Animal Feed / Q000032:analysis; D000818:Animals; D001407:Bacillus / Q000235:genetics / Q000276:immunology* / Q000302:isolation & purification; D003530:Cyprinidae; D004269:DNA, Bacterial / Q000235:genetics / Q000378:metabolism; D004032:Diet / Q000662:veterinary; D005393:Fish Diseases / Q000276:immunology* / Q000382:microbiology; D016905:Gram-Negative Bacterial Infections / Q000276:immunology / Q000382:microbiology / Q000662:veterinary*; D007113:Immunity, Innate; D008969:Molecular Sequence Data; D010802:Phylogeny; D019936:Probiotics / Q000494:pharmacology*; D012336:RNA, Ribosomal, 16S / Q000235:genetics / Q000378:metabolism; D017422:Sequence Analysis, DNA / Q000662:veterinary
D004269:DNA, Bacterial; D012336:RNA, Ribosomal, 16S
Aeromonas hydrophila; Bacillus spp.; Cellular components; Labeo rohita; Probiotic