Fructobacillus tropaeoli sp. nov., a fructophilic lactic acid bacterium isolated from a flower

A fructophilic lactic acid bacterium, designated strain F214-1^T, was isolated from a flower of Tropaeolum majus in South Africa. Based on phylogenetic analysis of 16S rRNA gene sequences, the strain formed a subcluster with Fructobacillus ficulneus and Fructobacillus pseudoficulneus and, based on recA gene sequences, the strain formed a subcluster with F. ficulneus. DNA-DNA hybridization studies showed that strain F214-1^T was phylogenetically distinct from its closest relatives. Acid was produced from the fermentation of D-glucose, D-fructose and D-mannitol only. D-Fructose was the preferred sole carbon and energy source and was fermented more rapidly than D-glucose. Growth of the strain on D-glucose under anaerobic conditions was very weak but external electron acceptors such as oxygen and pyruvate enhanced growth on D-glucose. Lactic acid and acetic acid were produced from D-glucose in equimolar amounts. Ethanol was produced at very low levels, despite the strain's obligately heterofermentative metabolism. Based on these data, strain F214-1^T represents a novel species of fructophilic bacteria in the genus Fructobacillus, for which the name Fructobacillus tropaeoli sp. nov. is proposed. The type strain is F214-1^T (=5JCM 16675^T =DSM 23246^T).