Biosynthesis of different polymers in bacteria depends on the genetic traits and on the culture conditions used. Although the separate production of exopolysaccharides (EPS) and poly-3-hydroxybutyrate [P(3HB)] is well documented, less attention has been paid to the possible connection between the two biosynthetic pathways. Some microorganisms can produced EPS and P(3HB) at the same time. In symbiotic nitrogen-fixing bacteria such as rhizobia the general conditions governing both pathways are surely related to the nature and availability of carbon and nitrogen sources, the oxygenation, the energetic and redox states of cells, etc. EPS and P(3HB) production implies a significant energetic cost, thus a sensitive regulatory mechanism is required. Regulation of carbon flux into P(3HB) occurs at multiple levels. Previous studies on other bacterial species indicated that the impaired synthesis of one polymer causes other reserve materials to be turned over [1]. AniA, a putative regulatory protein previously described [2] and identified in the polyhydroxyalkanoates locus in Ensifer meliloti [3], was found to be involved in carbon/energy regulation under normal growth conditions. The occurrence of AniA orthologs (described in some cases as PhaR) and organisation of the respective genes were described in detail in different bacteria [4]. The present work aims to give a contribution to the role of the carbon flux regulator aniA in E. meliloti. A strain carrying a lacZ transcriptional fusion inside the aniA gene was constructed from E. meliloti 41 and from the mutant strain E. meliloti 41003 unable to accumulate polyhydroxyalkanoates [5]. E. meliloti 41003 accumulates less exopolysaccharides as compared to the wild-type strain 41 [5]. We also showed that an EPS negative mutant of E. meliloti 2011 could accumulate more P(3HB) than the wild-type strain 2011. A further effect of aniA on EPS production was revealed by transferring aniA-Kmr mutation to different E. meliloti strains carrying exp-lacZ and exo-lacZ fusions. The results here obtained indicate a clear correlation between P(3HB) and EPS biosynthesis. The information regarding carbon flux between the two polymers is not only essential for understanding their physiological role, but also for possible applications of industrial polyesters production .

A regulatory protein of Ensifer meliloti involved in biopolymers synthesis

POVOLO, SILVANA;CASELLA, SERGIO
2010

Abstract

Biosynthesis of different polymers in bacteria depends on the genetic traits and on the culture conditions used. Although the separate production of exopolysaccharides (EPS) and poly-3-hydroxybutyrate [P(3HB)] is well documented, less attention has been paid to the possible connection between the two biosynthetic pathways. Some microorganisms can produced EPS and P(3HB) at the same time. In symbiotic nitrogen-fixing bacteria such as rhizobia the general conditions governing both pathways are surely related to the nature and availability of carbon and nitrogen sources, the oxygenation, the energetic and redox states of cells, etc. EPS and P(3HB) production implies a significant energetic cost, thus a sensitive regulatory mechanism is required. Regulation of carbon flux into P(3HB) occurs at multiple levels. Previous studies on other bacterial species indicated that the impaired synthesis of one polymer causes other reserve materials to be turned over [1]. AniA, a putative regulatory protein previously described [2] and identified in the polyhydroxyalkanoates locus in Ensifer meliloti [3], was found to be involved in carbon/energy regulation under normal growth conditions. The occurrence of AniA orthologs (described in some cases as PhaR) and organisation of the respective genes were described in detail in different bacteria [4]. The present work aims to give a contribution to the role of the carbon flux regulator aniA in E. meliloti. A strain carrying a lacZ transcriptional fusion inside the aniA gene was constructed from E. meliloti 41 and from the mutant strain E. meliloti 41003 unable to accumulate polyhydroxyalkanoates [5]. E. meliloti 41003 accumulates less exopolysaccharides as compared to the wild-type strain 41 [5]. We also showed that an EPS negative mutant of E. meliloti 2011 could accumulate more P(3HB) than the wild-type strain 2011. A further effect of aniA on EPS production was revealed by transferring aniA-Kmr mutation to different E. meliloti strains carrying exp-lacZ and exo-lacZ fusions. The results here obtained indicate a clear correlation between P(3HB) and EPS biosynthesis. The information regarding carbon flux between the two polymers is not only essential for understanding their physiological role, but also for possible applications of industrial polyesters production .
ISBP 2010: International Symposium on Biopolymers
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11577/2478221
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