The Pta-AckA pathway is required for acetate assimilation in Bacillus subtilis

LEANDRO NAKAMATSU; DIEGO DE MENDOZA; GUSTAVO E. SCHUJMAN

Puerto Madryn

Congreso; XLVI Reunión Anual de la Sociedad Argentina de Investigadores en Bioquímica (SAIB); 2010

Sociedad Argentina de Investigadores en Bioquímica (SAIB)

Bacteria have developed several mechanisms to sense and to adapt to constant environmental changes. When growing on abundance of nutrients such as glucose, many bacteria excrete partially oxidized carbon compounds, including acetate. Once these nutrients have been depleted, these cells undergo the acetate switch, a metabolic change in which acetate is assimilated, converted to acetyl-CoA and oxidized in the Krebs cycle. In Bacillus subtilis, acetate is excreted through a two-step pathway involving the enzymes phosphotransacetylase (Pta) and acetate kinase (AckA); and its assimilation is believed to be catalyzed mainly through acetyl-CoA sinthetase (AcsA) activity. Additionally, AcsA is negatively regulated by acetylation, in a post-translational mechanism involving the acetylase AcuA and deacetylases AcuC and SrtN. To further study these pathways, we obtained B. subtilis strains containing deletions in pta and acuA genes which conditionally express acsA. We evaluated their ability to incorporate acetate into lipidic and proteic fractions by labeling cultures with [1-14C]- acetate. Our results indicate that pta strains do not efficiently incorporate acetate, even if acsA expression is induced, suggesting that the Pta-AckA pathway has a critical role in acetate assimilation in B. subtilis.