Identification of two putative acyltransferase genes potentially implicated in dithiolopyrrolone biosyntheses in Saccharothrix algeriensis NRRL B-24137

Efficacy of Saccharothrix algeriensis NRRL B-24137 to suppress Fusarium oxysporum f.sp. vasinfectum induced wilt disease in cotton

Fusarium cotton wilt is a devastating disease of the cotton crop throughout the world, caused by Fusarium oxysporum f.sp. vasinfectum (FOV). Chemical control has many side effects, so, biological controls have been widely used for the management of Fusarium wilt. This study aimed to investigate the possible use of an actinomycetes Saccharothrix algeriensis (SA) NRRL B-24137 to control FOV. To access in-vitro anti-Fusarium ability of SA NRRL B-24137, dual culture assay, spore germination and seed germination tests were carried out. Following in-vitro investigations, several pot tests in a greenhouse environment were used to evaluate the biological control potential of SA NRRL B-24137 against FOV. Dual culture assay and spore germination revealed that SA NRRL B-24137 showed significant anti-Fusarium activity.During spore germination 87.77% inhibition of spore germination were observed. In pot experiments, SA NRRL B-24137 primed cotton seeds resulted in a 74.0% reduction in disease incidence. In soil there was a significant reduction in FOV spores in the presence of SA NRRL B-24137. Positive correlation was also observed on different concentrations of SA NRRL B-24137 towards FOV reduction. The results of this study showed that SA NRRL B-24137 has the potential to be employed as a biocontrol agent against Fusarium cotton wilt, improving cotton growth characteristics and yield.

The final acylation step in aromatic dithiolopyrrolone biosyntheses: identification and characterization of the first bacterium N-benzoyltransferase from Saccharothrix algeriensis NRRL B-24137

The last step in the biosynthesis of dithiolopyrrolone antibiotics was thought to involve the transfer of acyl group from acyl-CoA to pyrrothine/holothin core. In Saccharothrix algeriensis NRRL B-24137, two acyltransferases, an acetyltransferase and a benzoyltransferase were proposed to catalyze this step. We have previously identified, in Sa. algeriensis genome, two open read frames, actA and actB patiently encoded these enzymes. This study focuses primarily on the characterization of the protein encoded by actA. After cloning and expressing of actA in Escherichia coli BL21, the recombinant protein encoded by actA was purified. Selectivity of ActA for pyrrothine/holothin as substrate and different acyl-CoA as co-substrate was evaluated using two acyls-groups, linear and aromatic. The enzyme was shown to prefer aromatic groups over linear groups as donor group; further neither product nor transfer was observed for linear groups. Therefore ActA has been determined to be a pyrrothine/holothin N-benzoyltransferase which can either pyrrothine (Km of 72μM) or holothin (Km of 129.5μM) as substrates and benzoyl-CoA (Km of 348.65 and 395.28μM) as co-substrates for pyrrothine and holothin, respectively. The optimum pH and temperature has been shown to be 8, 40°C, respectively. ActA is the first enzyme characterized as N-benzoyltransferase in bacteria.