, 1998; Siddiqui & Mahmood, 1999; Siddiqui, 2002), the nematicidal-related genes of B. subtilis were not identified. This study identified nematicidal activity associated with the purL gene that encodes a FGAM synthase Anti-infection Compound high throughput screening II which catalyzes the conversion of FGAR into FGAM in the purine biosynthetic pathway. The purine biosynthesis pathway plays an important

role in metabolism and is involved not only in the synthesis of nucleic acids but also in the synthesis of various intermediates which are the precursors associated with other biosynthetic pathways. Previous studies have reported that purL present in some Rhizobium spp. affected nodulation processes (Newman et al., 1994; Giraud et al., 2007; Xie et al., 2009). In B. subtilis, FGAM synthase activity requires three proteins: smPurL (∼80 kDa), PurQ (∼25 kDa) and PurS (∼10 kDa) at a ratio of 1 : 1 : 2 (Saxild & Nygaard, 2000; Anand et al., 2004; Hoskins et al., 2004). This is the first report demonstrating that the purL gene of OKB105 influenced nematicidal activity. Disruption of purL in the M1 mutant affected FGAM synthase II synthesis, whose amino acid sequence is dissimilar that of bacterial extracellular proteases (Siddiqui et al., 2005; Huang et al., 2005; Niu et al., 2006; Tian et

al., 2006). This observation, in combination with the data presented Forskolin concentration in this report, suggested that FGAM synthase II did not mediate the nematicidal Lck activity observed. Because FGAM synthase II is involved in the purine biosynthesis pathway and some intermediates are produced by this pathway, we deduced that the nematicidal substance was likely derived from these intermediates. Not only did the culture filtrates of complemented M1 show similar nematicidal activity against M. javanica as wild-type OKB105 filtrates, but M1 nematicidal activity was restored following the

addition of adenine and thiamine or AICA-riboside similar to Rhizobium spp. purL mutants showed restored nodulation ability following the addition of adenine and thiamine or AICA-riboside (Ana et al., 2003; Worland et al., 1999; Xie et al., 2009), indicating that OKB105 nematicidal activity was affected by purL via the generation of purine biosynthesis pathway intermediates. The above results demonstrated that the purL gene regulated the production of purine biosynthesis intermediates which affected the nematicidal activity of strain OKB105. However, the specific mechanism of action remains unclear. Further studies will be required to elucidate the nematicidal mechanism. In addition, the purine biosynthesis also involves other genes (Saxild & Nygaard, 1988). Whether disruption of these genes affects nematicidal activity of OKB105 is a matter for further study.