waseem raza

Allelochemicals from root exudates or decaying residues of watermelon plant may be related to watermelon fusarium wilt. The aim of this work was to study the effect of an artificially applied allelochemical, ferulic acid, on in vitroFusarium oxysporum f. sp. niveum (FON), a causal pathogen of plant wilting in the laboratory setting.The results showed that ferulic acid inhibited growth at

Bioorganic fertilizer containing Paenibacillus polymyxa SQR-21 showed very good antagonistic activity against Fusarium oxysporum. To optimize the role of P. polymyxa SQR-21 in bioorganic fertilizer, we conducted a study of spore germination under various conditions. In this study, l-asparagine, glucose, fructose and K+ (AGFK), and sugars (glucose, fructose, sucrose, and lactose) plus l-alanine were evaluated to determine their ability to induce spore germination of two strains; P. polymyxa ACCC10252 and SQR-21. Spore germination was measured as a decrease in optical density at 600 nm. The effect of heat activation and germination temperature were important for germination of spores of both strains on AGFK in Tris–HCl. l-Alanine alone showed a slight increase in spore germination; however, fructose plus l-alanine significantly induced spore germination, and the maximum spore germination rate was observed with 10 mmol l−1l-alanine in the presence of 1 mmol l−1 fructose in phosphate-buffered saline (PBS). In contrast, fructose plus l-alanine hardly induced spore germination in Tris–HCl; however, in addition of 10 mmol l−1 NaCl into Tris–HCl, the percentages of OD600 fall were increased by 19.6% and 24.3% for ACCC10252 and SQR-21, respectively. AGFK-induced spore germination was much more strict to germination temperature than that induced by fructose plus l-alanine. For both strains, fructose plus l-alanine-induced spore germination was not sensitive to pH. The results in this study can help to predict the effect of environmental factors and nutrients on spore germination diversity, which will be beneficial for bioorganic fertilizer storage and transportation to improve the P. polymyxa efficacy as biological control agent.

An experiment was planned to evaluate the behavior of Paenibacillus polymyxa SQR-21 under differential iron availability. P. polymyxa was grown under three differential iron conditions (0, 2, 20 μM). Iron starvation slowed bacterial growth and at all iron levels, pH of liquid culture was decreased, but maximum decrease was observed at highest iron level. Cell surface ferrireductase activity decreased as culture aged, while extracellular Fe3+-reducing activity constantly increased. Hydroxamates type siderophores production was increased with the decrease in iron levels. Numerous cellular proteins were expressed by P. polymyxa in the range of 5–140 kDa and several of them showed conspicuous differential iron regulation. P. polymyxa seems to have more than one type of iron acquisition mechanism including gradual release of organic acids, cell surface ferrireductases, extracellular reductants, and secretion of low molecular weight hydroxamates chelators. This article is the first to report the kinetic study of P. polymyxa under differential iron availability. The information provided here gives initial information about the iron uptake mechanism of P. polymyxa.

To alleviate the stress of continuous cropping for cucumber continuous cropping (CCC) system, a beneficial fungus Trichoderma harzianum SQR-T037 (SQR-T037) was isolated and applied to soil to degrade allelochemicals exuded from cucumber plants in a Rhizobox experiment. The following phenolic acids (PAs), classified as allelochemicals, were isolated and identified from cucumber rhizospheres: 4-hydroxybenzoic acid, vanillic acid, ferulic acid, benzoic acid, 3-phenylpropionic acid, and cinnamic acid. Mixed PAs added in potato dextrose broth, each with 0.2 gram per liter, were completely degraded by SQR-T037 after 170 h of incubation. In Rhizobox experiments, inoculation of SQR-T037 in the CCC soil also degraded the PAs exuded from cucumber plant roots. This degradation was 88.8% for 4-hydroxybenzoic acid, 90% for vanillic acid, 95% for benzoic acid, and 100% for ferulic acid, 3-phenylpropionic acid, and cinnamic acid at 45 days after plantation. Simultaneously, a significant (p ≥ 0.05) decrease in the disease index of Fusarium wilt and an increase in dry weights of cucumber plants were obtained in pot experiments by application of SQR-T037. This was mostly attributed to degradation of PAs exuded from cucumber roots in CCC soil by SQR-T037 and alleviation of the allelopathic stress. Application of beneficial microorganisms, such as SQR-T037 that biodegrades allelochemicals, is a highly efficient way to resolve the problems associated with continuous cropping system.

Two field experiments were conducted to evaluate the effect of organic fertilizer application either with or without antagonistic bacteria (Bacillus subtilis SQR-5 and Paenibacillus polymyxa SQR-21) on the control of Fusarium oxysporum f. sp. Cucumerinum J. H. Owen wilt disease in cucumber. The incidence of Fusarium wilt disease was 5.3–13.5% for cucumber plants treated with bioorganic fertilizer, while it was 30.3–51% in controls (only with organic fertilizer). Higher yields and lower disease incidences were observed in the dry season when compared with the wet season for both types of organic fertilizer treatments. Biolog analysis showed a significant change in soil bacterial composition and activity after bioorganic fertilizer application. The numbers of colony-forming units of F. oxysporum f. sp. Cucumerinum J. H. Owen for bioorganic-fertilizer-treated soils were significantly decreased compared with control. Scanning electron micrographs of cucumber basal stems showed a presence of mycelia-like mini strands accompanied by an amorphous substance within the xylem vessels. This amorphous substance and mini strands were richer in calcium and phosphorus but had low carbon and oxygen than the living mycelia. Reverse-phase high-pressure liquid chromatography and mass spectroscopic analysis showed that the antagonistic bacteria produced the antifungal compounds fusaricidin A, B, C, and D with molecular weights of 883.5, 897.5, 947.5, and 961.5 Da, respectively. The application of bioorganic fertilizer has a great potential for the control of F. oxysporum wilt disease in cucumber plants.

The effects of four metal ions (Ca(2+), Ni(2+), Mn(2+) and Cu(2+)) were evaluated on growth and production of antifungal compounds by Paenibacillus polymyxa SQR-21 and a quadratic predictive model was developed using response surface methodology (RSM). The results revealed, Mn(2+) and Ni(2+) showed most positive synergistic interactive affect on production of antifungal compounds followed by the positive interactive synergistic affect of Cu(2+) and Ni(2+) and then Mn(2+) and Cu(2+). While the interactive effect of Ca(2+) with all other three metals inhibited the production of antifungal compounds. The Mn(2+) (P=0.0384), Ni(2+) (P=0.0004) and Cu(2+) (P=0.0117) significantly affected the production of antifungal compounds while the effect of Ca(2+) (P=0.1851) was less significant. The maximum growth (OD(600)=1.55) was obtained at 500 (0), 125 (0), 100 (-2) and 37.5 (0) microM levels and the maximum size of inhibition zone (31 mm) was measured at 400 (-1), 150 (1), 400 (1) and 25 microM (-1) levels of Ca(2+), Mn(2+), Ni(2+) and Cu(2+), respectively. The RSM model provided an easy and effective way to determine the interactive effect of metal ions on production of antifungal compounds by P. polymyxa SQR-21 so that optimum media recipes can be developed to produce maximum amounts of antifungal compounds under laboratory and commercial fermentation conditions.

A bacterial strain was isolated from the rhizosphere of healthy watermelon plants in a heavily wilt-diseased field. This isolate was tentatively identified as Paenibacillus polymyxa (SQR-21) based on biochemical tests and partial 16S rRNA sequence similarity. The purified antifungal compounds were members of the fusaricidin group of cyclic depsipeptides having molecular masses of 883, 897, 947, and 961 Da with an unusual 15-guanidino-3-hydroxypentadecanoic acid moiety, bound to a free amino group. The strain SQR-21 was not able to produce antifungal volatile compounds but was able to produce cellulase, mannase, pectinase, protease, β-1,3-glucanase and lipase enzymes. However, the strain did not show any chitinase activity. Biocontrol potential of this strain was evaluated against Fusarium oxysporum cause of Fusarium wilt disease of watermelon in a greenhouse experiment. This strain combined with organic fertiliser decreased the disease incidence by 70% and increased the dry plant weight by 113% over the control.

Retraction: The following article from the Journal of Basic Microbiology, “A catechol type siderophore, bacillibactin: biosynthesis, regulation and transport in Bacillus subtilis” by Waseem Raza, Hongsheng Wu, Muhammad Ali Abdullah Shah and Qirong Shen, published online on 11 September 2008 in Wiley InterScience (www.interscience.wiley.com), has been retracted by agreement between the authors, the journal Editor-in-Chief, Erika Kothe, and the publisher Wiley-VCH. The retraction has been agreed due to substantial overlap of the content of this article with previously published articles in other journals.The Journal of Basic Microbiology apologises to our readership