Methylketones are broadly distributed in nature and perform a variety of functions. Most microorganisms are thought to produce methylketone by abortive β-oxidation of fatty acid catalytic metabolism. However, two methylketone synthetase genes in wild tomatoes are reported to synthesize methylketone using intermediates of the fatty acids biosynthetic pathway. In our previous study on Trojan horse-like interactions between the bacterium Bacillus nematocida B16 and its host worm, the chemical 2-heptanone was found to be an important attractant for the hosts. So here we used this model to investigate the genes involved in synthesizing 2-heptanone in microorganisms. We identified a novel methylketone synthase gene yneP in B. nematocida B16 and found enhancement of de novo fatty acid synthesis during 2-heptanone production. Interestingly, a homolog of yneP’ existed in the non-pathogenic species Bacillus subtilis 168, a close relative of B. nematocida B16 that was unable to lure worms, but GC-MS assay showed no 2-heptanone production. However, overexpression of yneP’ from B. subtilis in both heterologous and homologous systems demonstrated that it was not a pseudogene. The transcriptional analysis between those two genes had few differences under the same conditions. It was further shown that the failure to detect 2-heptanone in B. subtilis 168 was at least partly due to its conversion into 6-methyl-2-heptanone by methylation. Our study revealed methylketone biosynthesis of Bacillus species, and provided a co-evolution paradigm of second metabolites during the interactions between pathogenic/non-pathogenic bacteria and host.

No abstract

No abstract

Purpose Arthrobotrys oligospora, a model nematophagous fungus that produces specific adhesive networks to capture nematodes, has been proposed as a potentially effective biological agent to control harmful plant-parasitic nematodes. Although thioredoxin has been characterized as playing important roles in many cellular processes in other species, its function in nematophagous fungi has not been studied. Here, the function of a thioredoxin homolog, Aotrx1, was investigated in A. oligospora. Methods The encoding gene of Aotrx1 in the nematophagous fungus A. oligospora was knocked out by homologous recombination; strain growth was assessed. Results The ΔAotrx1 strain of A. oligospora showed a significant decrease in growth rate on different media (PDA, CMY, and TG), a 70% decrease of conidia production, and a lower germination rate compared with the wild type. The mutant strain was unable to form traps to capture nematodes and was more sensitive to SDS and H 2 O 2. Conclusion Thioredoxin is involved in conidia development, trap formation, normal mycelial growth, and resistance to environmental stresses in the nematode-trapping fungus A. oligospora.

No abstract