Growth-promoting Effect of Alginate Oligosaccharides on Rhodobacter sphaeroides

Rhodobacter sphaeroides has been well-known for its strong contribution to environment, medicine, food, and cosmetic industry. Here, we first reported the growth-promoting effects of an alginate oligosaccharide mixture (AOS) on R. sphaeroides. AOS exhibited a stimulatory effect on the growth of R. sphaeroides in a dose-dependent manner. The highest growth rate of R. sphaeroides was obtained in LB medium supplemented with 0.5% AOS. AOS exerted a selective growth-promoting effect on R. sphaeroides but not on Escherichia coli, Lysinibacillus xylanilyticus, and Pantoea rwandensis. The growth-promoting effect of AOS is influenced by light and may be involved in the up-regulation of fbp2, RSP-0557, and RegB genes. Our results collectively suggested that AOS should be employed as a growth-promoting factor to enhance the transition of R. sphaeroides to industrial applications.