Fermentibacillus polygoni gen. nov., sp. nov., an alkaliphile that reduces indigo dye

Area of Science:

• Microbiology
• Bacterial Taxonomy
• Fermentation Science

Background:

• Isolation of novel microorganisms from traditional fermented products offers insights into unique metabolic capabilities.
• Fermented Polygonum indigo liquor is a rich source of microbial diversity, potentially harboring bacteria with specialized functions like indigo reduction.

Purpose of the Study:

• To isolate and characterize novel indigo-reducing bacteria from fermented Polygonum indigo liquor.
• To determine the phylogenetic, chemotaxonomic, and phenotypic properties of the isolated strains.
• To establish the taxonomic classification of the novel isolates, including proposing a new genus and species.

Main Methods:

• Isolation of indigo-reducing bacteria on a medium with indigo fermentation liquor as the sole substrate.
• Phylogenetic analysis using 16S rRNA gene sequencing.
• Determination of phenotypic characteristics (Gram staining, motility, anaerobic growth, temperature and pH ranges).
• Chemotaxonomic analyses including major isoprenoid quinone, DNA G+C content, and whole-cell fatty acid profiling.
• DNA-DNA hybridization for relatedness assessment.

Main Results:

• Two facultatively alkaliphilic strains, IEB3T and IEB14, were isolated and identified as indigo-reducing bacteria.
• Phylogenetic analysis placed the isolates within the genus Bacillus, with Bacillus nanhaiisediminis as the closest neighbor (97.4% 16S rRNA similarity).
• Phenotypic and chemotaxonomic data, including Gram-positive staining, facultative anaerobism, motility, growth conditions (12-40°C, pH 7.5-12), MK-7 quinone, DNA G+C content (39.0-39.1 mol%), and fatty acid profiles, were determined.
• DNA-DNA hybridization showed low relatedness (<7%) to Bacillus nanhaiisediminis, supporting their distinct taxonomic status.
• The isolates were proposed as a novel species within a novel genus, Fermentibacillus polygoni gen. nov., sp. nov., with strain IEB3T as the type strain.

Conclusions:

• The isolated strains IEB3T and IEB14 represent a novel genus and species, Fermentibacillus polygoni gen. nov., sp. nov.
• This discovery expands the known bacterial diversity and highlights the potential of fermented indigo liquor as a source of unique microorganisms.
• The facultatively alkaliphilic and indigo-reducing nature of F. polygoni offers potential applications in bioremediation and dye degradation.