Phylogenetic Investigations on the Endosymbiotic Bacteria of Axinella donnani

Abstract

The present study focuses on the isolation of endosymbiotic bacteria from eight different types of sponges. The sponges were collected from the southern peninsular coast of India and identified as Sigmadocia carnosa, Ircinia fasciculate, Callyspongia diffusa, Zygomycale angulosa, Clathria vulpine, Clathria gorgonids, Phloeodictyon species and Axinella donnani. For the isolation of endosymbionts, the collected sponge species were cultured in three different media such as Nutrient agar media, Zobell marine agar and Zobell marine agar + sponge extracts. The sponge extracts supplemented media produced high bacterial growth than the other media. The sponge A. donnani, recorded the highest bacterial counts. Of which, 13 endosymbiotic bacterial strains (ESB) of A. donnani were screened against common pathogenic bacteria. The strains ESB-3 and ESB-7 were identified to be potential strains exhibiting significant antibacterial property. The antibacterial activity was evaluated through testing against various shrimp pathogens (Vibrio esturiances, Vibrio alginolyticans, Vibrio harvae, Aeromonas hydrophila and Pseudomonas aerogenosa) as well as human pathogens (Streptococcus hemolyticus, Vibrio fisheri, Escherichia coli, Morgenella morgenii, and Bacillus cereus). The strains exhibited significant activity against all the shrimp and human pathogens. The unknown bacterial strain (ESB3 and ESB7) were identified using 16S rRNA gene technique to be Bacillus subtilis, Further, sequencing methodologies verified that the FASTA sequence of ESB3 contains 994 residues and that of ESB7 contains 1023 residues. The result so these findings are presented and elaborately discussed in the following paper.