Nitrogen Source Affects Glycolipid Production and Lipid Accumulation in the Phytopathogen Fungus <i>Ustilago maydis</i>

Abstract

When cultured in medium limited of nitrogen sources, the phytopathogen Ustilago maydis produces two amphipathic glycolipids: Ustilagic acid (UA) and Mannosylerythritol lipid (MEL), which in addition to the hydrophilic moiety, contain di-or tri-hydroxylated C16 fatty acids (UA), or C8 and C16 saturated fatty acids (MEL). We compared the growth and morphology of cells in YPD and in minimum media containing glucose and nitrogen sources such as nitrate or urea and those deprived of nitrogen. Nitrogen-starved cells showed a dramatic accumulation of internal lipids identified as lipid droplets when stained with the hydrophobic probe BODIPY; these lipid droplets were enriched in unsaturated fatty acids. Fatty acids in YPD or medium containing nitrate as nitrogen source showed a combination of saturated/unsaturated lipids, but when urea was the nitrogen source, cells only contained saturated fatty acids. The glycolipid profiles produced in the presence or absence of nitrogen showed preferences towards the production of one kind of glycolipid: cells in media containing nitrate or urea produced different proportions of UA/MEL, but under nitrogen starvation cells contained only UA. The emulsification capacity of the glycolipids produced in media with or without nitrogen was similar (72% -76%). HPLC of the glycolipids allowed the separation of fractions with different emulsifying characteristics. Our results indicate that U. maydis accumulates lipid droplets when deprived of nitrogen source and confirm that UA is not under nitrogen control, but rather that MEL and lipid droplets are produced and oppositely regulated by nitrogen. * Corresponding author.A. Zavala-Moreno et al. 935

Isolation and characterization of glycolipid biosurfactant produced by a Pseudomonas otitidis strain isolated from Chirimiri coal mines, India

“…No growth and BS production was observed in the medium without any nitrogen source (nitrogen starvation) in the present study. Zavala-Moreno et al (Zavala-Moreno et al 2014) have reported that the production of glycolipids enhanced when grown in nitrogen limiting or starving conditions. According to Maneerat (2005), production of surface active compounds increases when the concentration of nitrogen depleted in the medium which is due to reduction in the activity of isocitrate dehydrogenase.…”

Ustilago Rabenhorstiana—An Alternative Natural Itaconic Acid Producer

“…For this reason, it can be assumed that an ammonium limitation caused the itaconic acid overproduction of U. rabenhorstiana. Further, the nitrogen limitation caused the accumulation of intracellular lipid droplets, which are mostly triacylglycerols [21,34]. A secretion of cellobiose lipids and mannosylerythritol lipids in the form of needle-like crystals or oily droplets of U. maydis [20], could not be verified for U. rabenhorstiana.…”

“…In general, it is possible to generate a stable unicellular growth by deleting several genes [24]. The filamentous growth involved the accumulation of intracellular lipid droplets, which is initiated by nitrogen limitation, which in turn is needed for itaconic acid overproduction [5,19,34]. Furthermore, 89% of all fatty acids in U. rabenhorstiana were long-chain fatty acids C16:0, C18:0, and C18:2 and suggested the accumulation of triacylglycerols in the cells.…”

Monitoring of the enzymatic activity of intracellular lipases of <em>Ustilago maydis</em> expressed during the growth under nitrogen limitation and its correlation in lipolytic reactions

“…We previously reported the accumulation of lipids as LDs in U. maydis under nitrogen starvation (MM-N) (Zavala-Moreno et al, 2014). Also, the dynamics of LDs under different nitrogen sources were analyzed (Romero-Aguilar et al, 2017).…”