Glucose inhibits the formation of gas vesicles in Haloferax volcanii transformants

Abstract

The effect of glucose on the formation of gas vesicles was investigated in Haloferax mediterranei and Hfx.volcanii transformants containing the mc-gvp gene cluster of Hfx. mediterranei (mc-vac transformants). Increasing amounts of glucose in the medium resulted in a successive decrease in the amount of gas vesicles in both species, with a complete inhibition of their formation at glucose concentrations of > 70 mM in mc-vac transformants, and 100 mM in Hfx. mediterranei. Maltose and sucrose imposed a similar inhibitory effect, whereas xylose, arabinose, lactose, pyruvate and 2-deoxy-glucose had no influence on the gas vesicle formation in mc-vac transformants. The activities of the two mc-vac promoters were strongly reduced in mc-vac transformants grown in the presence of > 50 mM glucose. The gas vesicle overproducing Delta D transformant (lacking the repressing protein GvpD) also showed a glucose-induced lack of gas vesicles, indicating that GvpD is not involved in the repression. The addition of glucose was useful to block gas vesicle formation at a certain stage during growth, and vice versa, gas vesicle synthesis could be induced when a glucose-grown culture was shifted to medium lacking glucose. Both procedures will enable the investigation of defined stages during gas vesicle formation.

Haloarchaea and the Formation of Gas Vesicles

“…Oxygen availability, temperature, salt concentration and carbon sources all influence the formation of gas vesicles in Haloarchaea [ 18 , 26 , 44 , 45 , 46 ]. Growth under anoxic conditions is supported by nitrate respiration ( Hfx.…”

“…The amount of the mc- gvpA transcripts is seven-fold enhanced in cells grown in 25%-salt compared to the 15%-salt culture [ 18 ]. Glucose also influences the P mcA promoter activity, since the addition of 50, 100 or 200 mM glucose results in a 10-fold reduction of the basal activity of P mcA , whereas the activity of the promoter of the housekeeping ferredoxin gene, P fdx , is almost unaffected [ 44 ]. A complete inhibition of gas vesicle formation is observed at glucose concentrations above 100 mM.…”

“…A complete inhibition of gas vesicle formation is observed at glucose concentrations above 100 mM. Maltose and sucrose impose a similar effect, whereas xylose, arabinose, lactose, pyruvate and 2-deoxy-glucose have no influence [ 44 ]. Also in this case, ∆D transformants lack gas vesicles in the presence of glucose, demonstrating that the repressing protein, GvpD, is not involved.…”

Regulatory Multidimensionality of Gas Vesicle Biogenesis inHalobacterium salinarumNRC-1

“…An extension of this hypothesis was used to explain the large increases in gas vesicle abundance observed in batch cultures entering the comparatively oxygen-depleted stationary phase of growth [11, 12]. Two recent studies, however, obfuscate this simple functional interpretation by demonstrating that arginine and citrate may also contribute to the regulation of gas vesicle biogenesis in Halobacterium salinarum strains PHH1, PHH4, and NRC-1 [1] and that glucose may also impact gas vesicle biogenesis in Haloferax mediterranei [13]. Hechler and Pfeifer [1] have also suggested that anaerobic conditions inhibit gas vesicle biogenesis.…”

Anaerobic Metabolism in Haloferax Genus

“…volcanii (Hechler & Pfeifer, 2009), and glucose also inhibits the formation of gas vesicles in Hfx. volcanii transformants (Hechler, Frech & Pfeifer, 2008).…”