EliA facilitates the induction of lipase expression by stearyl alcohol inRalstoniasp. NT80

Abstract

Extracellular lipase activity from Ralstonia sp. NT80 is induced significantly by fatty alcohols such as stearyl alcohol. We found that when lipase expression was induced by stearyl alcohol, a 14-kDa protein (designated EliA) was produced concomitantly and abundantly in the culture supernatant. Cloning and sequence analysis revealed that EliA shared 30% identity with the protein-like activator protein of Pseudomonas aeruginosa, which facilitates oxidation and assimilation of n-hexadecane. Inactivation of the eliA gene caused a significant reduction in the level of induction of lipase expression by stearyl alcohol. Furthermore, turbidity that was caused by the presence of emulsified stearyl alcohol, an insoluble material, remained in the culture supernatant of the ΔeliA mutant during the late stationary phase, whereas the culture supernatant of the wild type at 72 h was comparatively clear. In contrast, when lipase expression was induced by polyoxyethylene (20) oleyl ether, a soluble material, inactivation of eliA did not affect the extracellular lipase activity greatly. These results strongly indicate that EliA facilitates the induction of lipase expression, presumably by promoting the recognition and/or incorporation of the induction signal that is attributed to stearyl alcohol.

EliA is required for inducing the stearyl alcohol-mediated expression of secretory proteins and production of polyester in Ralstonia sp. NT80

“…This high induction of lipase expression by stearyl alcohol in Ralstonia sp. NT80 requires the secretory protein EliA, whose orthologues are widely distributed among the Proteobacteria, especially in the Betaproteobacteria and Gammaproteobacteria (Akanuma et al, 2013). Consistent with the above observation, the transcription level of the secretory lipase gene, lipA, in mutant NT80 cells lacking EliA (DeliA) was significantly reduced compared with that in the wild-type NT80 cells when these cells were induced with fatty alcohols, such as stearyl alcohol (Akanuma et al, 2013).…”

“…For example, in Ralstonia sp. NT80, the lipase activity induced by stearyl alcohol was approximately sevenfold higher than that induced either by olive oil or by soybean oil (Ushio et al, 1996;Akanuma et al, 2013). This high induction of lipase expression by stearyl alcohol in Ralstonia sp.…”

“…NT80 (NT80) was isolated in our laboratory from soil as a producer of thermostable lipase (Ushio et al, 1996). The NT80 DeliA mutant (DeliA : : gen) and its complemented strain (DeliA : : gen tlpA : : eliA kan) were described previously (Akanuma et al, 2013).YP, a nutrientrich medium used for culturing Ralstonia strains, was described previously (Akanuma et al, 2013). Strains were precultured at 30 uC for 16 h in 2 ml of YP medium in a test tube with reciprocal shaking (160 r.p.m.).…”

“…NT80 requires the secretory protein EliA, whose orthologues are widely distributed among the Proteobacteria, especially in the Betaproteobacteria and Gammaproteobacteria (Akanuma et al, 2013). Consistent with the above observation, the transcription level of the secretory lipase gene, lipA, in mutant NT80 cells lacking EliA (DeliA) was significantly reduced compared with that in the wild-type NT80 cells when these cells were induced with fatty alcohols, such as stearyl alcohol (Akanuma et al, 2013). However, why EliA is required for the induction of lipA expression by fatty alcohols and whether EliA plays any role in cellular function(s) other than the induction of secretory lipase production remain unclear.…”

“…NT80 cells grown in the presence of 1 % stearyl alcohol (Akanuma et al, 2013). This observation suggested that stearyl alcohol induces expression of many extracellular proteins and prompted us to investigate the multiple aspects of NT80 cells' response to stearyl alcohol.…”