INVESTIGADORES
BIANCO Maria Isabel
congresos y reuniones científicas
Título:
The length of the exopolysaccharide xanthan is modulated by in tandem gumB and gumC overexpression
Autor/es:
GALVÁN, EM; BIANCO, MI; IELPI, L
Lugar:
Potrero de los Funes, San Luis
Reunión:
Congreso; XLVII Reunión Anual. Sociedad Argentina de Investigaciones Bioquímicas y Biología Molecular; 2011
Institución organizadora:
Sociedad Argentina de Bioquímica y Biología Molecular
Resumen:
Xanthan is a polymer of pentasaccharide repeat units, secreted by Xanthomonas campestris (Xc). Its biosynthesis involves an operon composed of 12 genes (gumB to gumM). Our aim was to study the roles GumB and GumC play in the polymerization and secretion of xanthan. We have already shown that gumB and gumC mutant strains did not produce xanthan, but synthesized the lipid-linked repeat units. Here, our strategy was to express increasing amounts of GumB and GumC, individually or in tandem, and to analyze the effect on xanthan polymerization. The corresponding genes were cloned in an arabinose-inducible vector and introduced in the wild-type Xc. Overexpression of GumB, GumC, or GumB-GumC neither affected the total amount nor the chemical composition of xanthan. We measured xanthan viscosity as indicator of polymer length. While GumB overexpression did not affect viscosity, a moderate increase in viscosity was achieved by raising GumC levels 5-times. In this condition, GumC was partially degraded. Expression of GumB in tandem with GumC diminished GumC degradation and resulted in higher xanthan viscosity than normal xanthan produced by the wild-type Xc. Moreover, longer polymer chains were observed by atomic force microscopy. These results suggest that modulation of xanthan chain-length involved both GumB and GumC proteins.