Fusaricidin A

In this study, we investigated the potential of Paenibacillus kribbensis CU01 in producing fusaricidin, a strong antifungal substance, via optimization of metal ions and carbon and nitrogen source, and continuous fermentation. In the cultivation of a 2-l batch, maximal production of fusaricidins (581 mg l-1) was achieved in a modified M9 medium containing metal ions, 10 g l-1 glucose, and 1 g l-1 ammonium chloride. Most of glucose was consumed at a rate of 0.74 g l-1 h-1 within 24 h and fusaricidin production began 15 h after batch cultivation. Continuous fermentation was performed using a 7-l fermenter with 2-l working volume of modified M9 medium containing 10 g l-1 glucose, 1 × 10-3 M FeSO4, and 1 × 10-6 M MnCl2. After 24 h of the start of cultivation, fresh M9 medium was continuously supplied at a flow rate of 2.5 ml min-1, and simultaneously, the same amount of cell culture broth was removed. In a continuous system, the highest fusaricidin concentration (579 mg l-1) was obtained using a dilution rate of 0.075 h-1 with an average productivity of 10.4 mg l-1 h-1 for 24 to 72 h of incubation. Based on these results, it was found that fusaricidin production using P. kribbens CU01 strain increased by at least 28 times the values reported in previous studies.

The diseases caused by phytopathogens account for huge economic losses in the agricultural sector. Paenibacillus polymyxa is one of the agriculturally important biocontrol agents and plant growth promoting bacterium. This study describes the antifungal potential of P. polymyxa HK4 against an array of fungal phytopathogens and its ability to stimulate seed germination of cumin and groundnut under in vitro conditions. The cumin and groundnut seeds bacterized with HK4 exhibited enhanced germination efficiency in comparison to controls. The use of HK4 as a soil inoculant significantly promoted the shoot length and fresh weight of groundnut plants in pot studies. The draft genome analysis of HK4 revealed the genetic attributes for motility, root colonization, antagonism, phosphate solubilization, siderophore production and production of volatile organic compounds. The bacterium HK4 harnessed several hydrolytic enzymes that may assist its competence in the rhizosphere. The PCR amplification and sequence analysis of the conserved region of the fusA gene amplicon revealed the ability of HK4 to produce fusaricidin. Furthermore, the LC-ESI-MS/MS of crude cell pellet extract of HK4 confirmed the presence of fusaricidin as a major antifungal metabolite. This study demonstrated the potential of HK4 as a biocontrol agent and a plant growth promoter.

Paenibacillus bovis sp. nov BD3526, isolated from raw yak (Bos grunniens) milk, was able to produce antibacterial substances against Micrococcus luteus. The antibacterial substances produced by the strain BD3526 in 3% (w/v) wheat bran broth under aerobic conditions were precipitated from the cultivated broth with ammonium sulfate at 60% saturation. Two antibacterial compounds were obtained by Sephadex LH-20 chromatography and semi-preparative reverse-phase high-performance liquid chromatography (Semi-Pre RP-HPLC). The chemical structures of the two antibacterial compounds were further elucidated by means of ultra high-performance liquid chromatography-mass spectrometer/mass spectrometer (UHPLC-MS/MS). One compound, with a molecular mass of 883.56195 Da (M + H)+, was determined to be identical in chemical structure with that of the well-known compound fusaricidin A. The other antimicrobial compound with a molecular mass of 911.59393 Da (M + H)+ was determined to be a derivative of fusaricidin A by tandem mass spectrometry and amino acid composition analysis and was designed as bovisin. Bovisin possessed the stability against acid/alkali, heat and some proteases treatment, the same with the fusaricidin A. However, the minimal inhibition concentration (MIC) of bovisin on the tested indicator including Staphylococcus aureus, Micrococcus luteus, Listeria monocytogenes and Bacillus subtilis were 50, 50, 50, 50 μg/mL, respectively, slightly higher than those of fusaricidin A (6.25, 6.25, 6.25, 12.5 μg/mL), indicating bovisin with a weaker inhibitory activity.