Variation in poly-β-hydroxybutyrate synthesis in rhizobia reflects strain differentiation and temperature regulation

Abstract

Polyβ-hydroxybutyrate (PHB), a carbon storage polymer, occurs widely among prokaryotes including Rhizobium. Screening of 45 strains of rhizobia, isolated from nodules of legumes inhabiting different ecological regimes, showed a wide range of variation in the PHB content. Broadly, this variation is strain- specific and may be used as a taxonomic character for strain differentiation. Rhizobia show minimum PHB content at optimum temperature for growth and relatively higher content at the temperature extremes implying that PHB accumulation in rhizobia is in response to stress imposed by the extremes of temperature. PHB presumably protects membrane structure of rhizobia during this stress.