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Updated: Jun 23, 2026

Induction of Cellular Differentiation and Single Cell Imaging of Vibrio parahaemolyticus Swimmer and Swarmer Cells
Published on: May 15, 2017
SwrAA activates poly-gamma-glutamate synthesis in addition to swarming in Bacillus subtilis
Cecilia Osera1, Giuseppe Amati1, Cinzia Calvio1
1Dipartimento di Genetica e Microbiologia, Università degli Studi di Pavia, via Ferrata 1, 27100 Pavia, Italy.
Abstract:
Poly-gamma-glutamic acid (gamma-PGA) is an extracellular polymer produced by various strains of Bacillus. Iotat was first described as the component of the capsule in Bacillus anthracis, where it plays a relevant role in virulence. gamma-PGA is also a distinctive component of 'natto', a traditional Japanese food consisting of soybean fermented by Bacillus subtilis (natto). Domesticated B. subtilis strains do not synthesize gamma-PGA although they possess the functional biosynthetic pgs operon. In the present work we explore the correlation between the genetic determinants, swrAA and degU, which allow a derivative of the domestic strain JH642 to display a mucoid colony morphology on LB agar plates due to the production of gamma-PGA. Full activation of the pgs operon requires the co-presence of SwrAA and the phosphorylated form of DegU (DegU approximately P). The presence of either DegU approximately P or SwrAA alone has only marginal effects on pgs operon transcription and gamma-PGA production. Although SwrAA was identified as necessary for swarming and full swimming motility together with DegU, we show that motility is not involved in gamma-PGA production. Activation of gamma-PGA synthesis is therefore a motility-independent phenotype in which SwrAA and DegU approximately P display a cooperative effect.
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