Plant-Growth-Promoting Effect by Cell Components of Purple Non-Sulfur Photosynthetic Bacteria

Abstract

Rhodobacter sphaeroides, a purple non-sulfur photosynthetic bacterium (PNSB), was disrupted by sonication and fractionated by centrifugation into the supernatant and pellet. The effects of the supernatant and pellet on plant growth were examined using Brassica rapa var. perviridis (komatsuna) in the pot experiments. Both fractions showed growth-promoting effects: the supernatant at high concentrations (1 × 107 to 4 × 107 cfu-equivalent mL−1) and the pellet at a low concentration of 2 × 103 cfu-equivalent mL−1). We expected lipopolysaccharide (LPS) to be the active principle of the pellet fraction and examined the effects of LPS on the growth of B. rapa var. perviridis. The growth of the plants was significantly enhanced by the foliar feeding of R. sphaeroides LPS at concentrations ranging from 10 to 100 pg mL−1. The present study is the first report indicating that LPS acts as one of the active principles of the plant-growth-promoting effect of PNSB.

Dynamic Alteration of Microbial Communities of Duckweeds from Nature to Nutrient-Deficient Condition

“…Members of the genus Rhizobium are well-known as a typical symbiosis of leguminous plants, as well as the other plants [ 25 ]. Several species of Novosphingobium promoted plant growth by the production of indole-3-acetic acid (IAA) [ 26 , 27 , 28 ]; while members of Rhodobacter were recognized as plant growth-promoting bacteria [ 29 , 30 ]. Although many potential DAB have been successfully inocculated to duckweeds through culture-dependent [ 7 , 8 , 16 ] and culture-independent methods [ 12 , 16 ], associations occurred for a short period and then vanished [ 13 ].…”

Effects of LPS from Rhodobacter sphaeroides, a Purple Non-Sulfur Bacterium (PNSB), on the Gene Expression of Rice Root

“…The receptor for LPS in plants, named lipooligosaccharide-specific reduced elicitation (LORE), has also been identified [ 21 ]. In our two previous studies [ 18 , 19 ], we proposed that LPS acts as one of the active principles of plant growth-promoting effects of PNSB. In the first study [ 18 ], we disrupted the PNSB cells by sonication in water, and fractionated the cell lysate by centrifugation into the supernatant and pellet, and examined their effects on the growth of Brassica rapa var.…”

“…In addition to these aforementioned mechanisms, we recently proposed lipopolysaccharide (LPS), a component of the Gram-negative bacterial cell wall, as a new active ingredient in PNSB [ 18 , 19 ]. Hayashi et al [ 18 ] reported the growth-promoting effect of lipopolysaccharide (LPS) from PNSB in plants for the first time, and the effective concentration of LPS from Rhodobacter sphaeroides NBRC 12203 T was 10 pg/mL.…”

“…In addition to these aforementioned mechanisms, we recently proposed lipopolysaccharide (LPS), a component of the Gram-negative bacterial cell wall, as a new active ingredient in PNSB [ 18 , 19 ]. Hayashi et al [ 18 ] reported the growth-promoting effect of lipopolysaccharide (LPS) from PNSB in plants for the first time, and the effective concentration of LPS from Rhodobacter sphaeroides NBRC 12203 T was 10 pg/mL. Iwai et al [ 19 ] reported that biopriming of rice seeds by LPS from R. sphaeroides NBRC 12203 T at a concentration of 5 ng/mL improved the root growth of rice seedlings, providing further evidence of the effectiveness of LPS from PNSB in plants.…”

Special Issue “Biotechnological Application of Photosynthetic Bacteria”

“…Hayashi et al [ 16 ] reported the growth-promoting effect of lipopolysaccharide (LPS) from PNSB in plants for the first time, and the effective concentration of LPS from Rhodobacter sphaeroides was 10 pg/mL. In mammals, LPS acts as an endotoxin through the Toll-like receptor 4 (TLR4) signaling pathway at a concentration of pg/mL to ng/mL, causing inflammatory responses.…”