ORIGINAL ARTICLE

Influence of Nitrogen and Carbon Sources on Twitching-Mediated Motility of Lysobacter antibioticus Hz25

Predatory bacteria of the genus Lysobacter are known to utilize type IV pili for substrate translocation (twitching motility); however, the ecological signals regulating the transition to the motile state in Lysobacter remain insufficiently studied. Using the strain Lysobacter antibioticus Hz25, isolated from the rhizosphere of the Baikal endemic Hedysarum zundukii Peschkova, as a model, we investigated the effects of organic nitrogen content, carbohydrate type, and prey proximity on type IV pili-mediated motility. Motility of Hz25 was observed only in the presence of organic nitrogen: within the range of 1–5 g/L yeast extract, the colony front migration speed increased from 15 to 42 µm/h. On media without organic nitrogen (with NH₄Cl), no motility was induced. At 5 g/L yeast extract, replacement of sucrose (10 g/L) with maltose or trehalose increased the speed to 46–57 µm/h; replacement with fructose reduced it to <10 µm/h. Upon contact with live prey cells (Sinorhizobium sp., Planococcus sp.) in the V-test (5 g/L yeast extract, 10 g/L sucrose), the predator migration speed along the prey imprint reached approximately 420 µm/h. Directed migration of Hz25 toward prey from a distance of 30 mm was demonstrated. The speed in this experiment also depended on the sugar type and was maximal on trehalose- and maltose-containing media. These findings suggest that organic nitrogen acts as a key factor triggering twitching motility in Hz25, while the carbohydrate type may serve as a speed modulator. This indicates a multi-level regulation of predatory motility in Hz25. This work contributes to understanding the ecological regulation of type IV pili-mediated motility in the genus Lysobacter.