Isolation of agarose digesting Achromobacter sp. and Brevundimonas diminuta using customized earthworm gut as an enrichment system

Abstract

Aim: To isolate potential agarose digesting bacteria from gut of Eisenia fetida fed with agar agar as a major feed. Methodology: E. fetida was fed on agar agar for 17 days in a comprehensive vermicompost unit, and gut-washing was collected. A specially designed dilute nutrient medium containing agarose as a solidifying agent was used to grow and isolate agarose digesting bacteria. Agarose digestion was confirmed by iodine test and novel 'micro-tip’ assay. Results: A selected CFU comprising two bacterial species showed depressions on the media, indicative of agarose digestion. Subsequently, cloning based 16S rRNA gene identification revealed the two isolates to be Brevundimonas diminuta and Achromobacter sp. with 99% similarity. These two could not be separated as pure cultures, indicating a likely associative interaction. Interpretation: The present study is the first of its sort to demonstrate a probable associative interaction between Brevundimonas diminuta and Achromobacter sp. in agarose digestion, while using "Customized Earthworm Gut Enrichment System." Key words: Agarose digesters, Earthworm, Enrichment system, Gut microflora