Butyrivibrio azoria sp. nov., a novel cellulolytic microorganism isolated from the rumen of a Holstein dairy cow

Abstract

This study describes the characteristics of NATIVEDY162T (= JL13D10T = NRRL B-68525T) a novel bacterium isolated from the rumen of a healthy Holstein dairy cow. NATIVEDY162T was discovered to be an obligately anaerobic, slightly curved, rod that stains Gram-negative, and presents as singlets or short chains. Tests confirmed it is indole-, catalase-, oxidase-negative, and it is not motile. NATIVEDY162T indicated a growth preference within the pH range of 6.5-7.5 with optimal growth at pH 7.0. Carbon panel assays found NATIVEDY162T can utilize D-glucose, L-rhamnose, esculin/ferric citrate, D-lactose, and D-trehalose, whereas weak growth was observed on D-xylose and D-cellobiose. It was also capable of degrading starch and digesting both soluble and insoluble forms of cellulose, with genomic analysis providing further support by revealing a diverse array of carbohydrate-active enzymes (CAZymes) targeting starch and plant structural components like pectin and cellulose. Fermentation of glucose by NATIVEDY162T resulted in the major fermentation products lactate and butyrate. Phylogenetic analysis of the 16S rRNA gene positioned NATIVEDY162T in close relation to other Butyrivibrio species. Genome comparisons using BLAST ANI identified its closest relative as Butyrivibrio proteoclasticus (75.7% identity); however, the similarity did not meet the 95% threshold for species identification. Phylogenetic, genomic, and chemotaxonomic findings highlight differences between NATIVEDY162T and other Butyrivibrio species, indicating it is a novel species. NATIVEDY162T was isolated from a lactating Holstein dairy cow located in Californias San Joaquin Valley, a region rich in Portuguese influence from Azorean migrants who played a key role in the development of the California dairy industry, producing most of the states milk by the mid-20th century. Given this historical context, we propose the name Butyrivibrio azoria type strain NATIVEDY162T in honor of the significant contributions of Azorean and Portuguese dairy farmers in the region.