Purification and characterization of S-adenosyl-L-methionine:uroporphyrinogen Ⅲ methyltransferase from Rhodobacter capsulatus SB1003 / 生物工程学报

Biosynthesis of vitamin B₁₂ (VB₁₂) requires the methylation at positions C-2 and C-7 of the precursor uroporphyrinogen Ⅲ (urogen Ⅲ) to precorrin-2 by S-adenosyl-L-methionine uroporphyrinogen Ⅲ methyltransferase (SUMT), which is a potential bottleneck step. Most of SUMTs are inhibited by urogen Ⅲ and by-product S-adenosyl-L-homocysteine (SAH). In order to mine an SUMT that lacks such an inhibitory property to drive greater flux through the VB₁₂ biosynthetic pathway, we cloned two SUMT genes (RCcobA1, RCcobA2) from Rhodobacter capsulatus SB1003 and expressed them in Escherichia coli BL21 (DE3). Thereafter, the two enzymes were purified and their specific activity of 27.3 U/mg, 68.9 U/mg were determined respectively. The latter was 2.4 times higher than PDcobA (27.9 U/mg) from Pseudomonas denitrifican. Additionally, RCcobA2 could tolerate over 70 μmol/L urogen Ⅲ, which has never been reported before. Hence, RCcobA2 can be used as an efficient enzyme to regulate the VB₁₂ metabolic pathway and enhance VB₁₂ production in industrial strains.

Effect of bioinoculation of rhodobacter capsulatus KU002 on two rice varieties of India.

In our continuing studies on the potential application of phototrophic bacteria we have tried to investigate the effects of inoculation of phototrophic bacteria on the growth and nitrogen levels in two varieties of rice namely Mashuri and Erramallelu. Mashuri variety was comparatively more responsive to the inoculation of phototrophic bacteria. Increase in shoot length of both the varieties of rice could be recorded. Nitrogen percentage showed a marked increase in both the rice varieties tested. Potential of phototrophic bacteria as a biofertiliser is discussed in this communication.

Bacteriocin from Purple Nonsulfur Phototrophic Bacteria, Rhodobacter capsulatus

To find whether productivity of bacteriocin is controlled between different species under unusual cultural conditions, we used Rhodobacter capsulatus ATCC 17016 as a producer and Rhodopseudomonas palustris ATCC 17003 as an indicator. Rhodobacter capsulatus was cultured under aerobic conditions in the dark in Lascelles medium containing 0.3% Triton X-100. As a result, bacteriocin productivity increased enormously. The optimal pH range of bacteriocin production was 6~7.8. Through partial purification of bacteriocin, the molecular weight was roughly estimated at 14 kDa. Plasmid had no influence on bacteriocin production by Rhodobacter capsulatus. Our findings indicate that culture conditions affect bacteriocin productivity between more distantly related species, and bacteriocin of Rhodobacter capsulatus is not encoded by a plasmid.