Physiological and transcriptional comparison of acetate catabolism between Acinetobacter schindleri ACE and Escherichia coli JM101.

Acinetobacter bacteria preferentially use gluconeogenic substrates instead of hexoses or pentoses. Accordingly, Acinetobacter schindleri ACE reaches a high growth rate on acetate but is unable to grow on glucose, xylose or arabinose. In this work, we compared the physiology of A. schindleri ACE and Escherichia coli JM101 growing on acetate as the carbon source. In contrast to JM101, ACE grew on acetate threefold faster, had a twofold higher biomass yield, and a 45% higher specific acetate consumption rate. Transcriptional analysis revealed that genes like ackA, pta, aceA, glcB, fumA, tktA and talA were overexpressed while acsA, sfcA, ppc and rpiA were underexpressed in ACE relative to JM101. This transcriptional profile together with carbon flux balance analysis indicated that ACE forms acetyl-CoA preferentially by the AckA-Pta (acetate kinase-phosphotransacetylase) pathway instead of Acs (acetyl-CoA synthetase) and that the glyoxylate shunt and tricarboxylic acid cycle are more active in ACE than in JM101. Moreover, in ACE, ribose 5-phosphate and erythrose 4-phosphate are formed from trioses, and NADPH is mainly produced by isocitrate dehydrogenase. This knowledge will contribute to an understanding of the carbon metabolism of Acinetobacter species of medical, biotechnological and microbiological relevance.