Antibiofilm activities of extracellular polymeric substances produced by bacterial symbionts of seaweeds

Abstract

<span style="font-size:9.0pt;line-height: 115%;font-family:" times="" new="" roman";mso-fareast-font-family:"times="" roman";="" mso-bidi-font-family:"times="" roman";mso-ansi-language:en-us;mso-fareast-language:="" en-us;mso-bidi-language:hi"="" lang="EN-US">In this study, 9 bacterial strains were collected from the surface of seaweeds (<i style="mso-bidi-font-style:normal">Sargassum </i>sp<i style="mso-bidi-font-style:normal">., Gracillaria </i>sp<i style="mso-bidi-font-style: normal">. </i>and<i style="mso-bidi-font-style:normal"> Ulva </i>sp<i style="mso-bidi-font-style:normal">.</i>) and screened for their antibacterial activity against three biofilm forming bacteria. All the 9 strains inhibited the growth of biofilm-forming bacteria and the best active strains were selected for <i style="mso-bidi-font-style:normal">in vitro</i> and <i style="mso-bidi-font-style:normal">in vivo</i> biofilm control assays. The results showed that the extract of strain S8 controlled the biofilm formation considerably. The toxicity of bacterial extracts was studied by determining the LC₅₀ value against <i style="mso-bidi-font-style:normal">Artemia </i>sp. The LC₅₀values obtained were found to be 0.061 and 0.105 mg/ml for the extracts of strain S1 and S8 respectively. The best active strain S8 was identified as <i style="mso-bidi-font-style:normal">Pseudomonas taiwanensis</i> based on 16S rRNA gene sequencing. The bioactive EPS was partially purified by TLC and HPLC analysis. Besides, the functional groups present in the EPS was analysed using FT-IR, which showed the presence of alcohol, alkenes, amines, esters and carboxylic acid groups.</span>