Iron is an essential element for living organisms that plays critical roles in the process of bacterial growth and metabolism. However, it remains to be elucidated whether piuB encoding iron-uptake factor is involved in iron uptake and pathogenicity of Xanthomonas axonopodis pv. glycines (Xag). To investigate the function of piuB, we firstly generated a piuB deletion mutant (ΔpiuB) by homologous recombination. Compared with the wild-type, the piuB mutant exhibited significantly reduced growth and virulence in host soybean. The mutant displayed markedly increased siderophore secretory volume, and its sensitivity to Fe³⁺, Cu²⁺, Zn²⁺ and Mn²⁺ was significantly enhanced. Additionally, the H₂O₂ resistance, exopolysaccharide yield, biofilm formation, and cell mobility of ΔpiuB were significantly diminished compared to that of the wild-type. The addition of exogenous Fe³⁺ cannot effectively restore the above characteristics of ΔpiuB. However, expressing piuB in trans rescued the properties lost by ΔpiuB to the levels in the wild-type. Taken together, our results demonstrated that PiuB is a potential factor for Xag to assimilate Fe³⁺, and is necessary for Xag to be pathogenic in host soybean.
Iron ; Glycine max ; Virulence ; Xanthomonas axonopodis/genetics* ; Hydrogen Peroxide

Aims: This study was aimed to evaluate the potential of several carriers to formulate the phages and retain their activity under various pH and temperature conditions. Methodology and results: The skim milk, rice flour, corn flour and CalnuXan (calcium and magnesium) as carriers to formulate the isolated phage to maintain its activity under extreme pH and temperature conditions. Two phages formulated with carriers retained their viability at pH 5, pH 7 and pH 9 compared to that of the unformulated phages. Besides, the formulated phages also retained a high titre compared to the unformulated phages when they were exposed to 37 °C and 45 °C. Based on the in vitro study of the formulation, it was applied in the glass house. The plant height, leaf chlorophyll and disease scoring were recorded and analyzed. In the glass house, the rice plant treated with formulated phages showed higher plant height and chlorophyll content than those treated with unformulated or untreated phages. Nonetheless, both formulated and unformulated protected the rice plant, which showed lower disease severity than the untreated group. Conclusion, significance and impact of study Phage therapy has been used for treating plant diseases caused by pathogenic bacteria. Despite their effectiveness in killing the pathogen in vitro, the results were not reproducible in the field. Bacteriophages (phages) are sensitive to environmental factors and infection efficiency was dropped when exposed to harmful environments. However, this study successfully formulated two novels Xanthomonas phages, as biocontrol agents against bacterial leaf blight (BLB) disease in rice.
Xanthomonas ; Bacteriophages

Xanthomonas campestris pv. campestris (Xcc), the pathogenic agent of black rot disease in cruciferous plants, produces large amount of extracellular polysaccharide (EPS), which has found wide applications in industry. For the great commercial value of the xanthan gum, many of the genes involved in EPS biosynthesis have been cloned and the mechanism of EPS biosynthesis also has been studied. In order to clone genes involved in EPS biosynthesis, Xcc wild-type strain 8004 was mutagenized with transposon Tn5 gusA5, and a number of EPS-defective mutants were isolated in our previous work. The Tn5 gusA5 inserted sites of these mutants were located by using thermal asymmetric interlaced PCR, and results showed that two EPS-defective mutants were insertion mutants of the gene wxcA which involved in lipopolysaccharide (LPS) biosynthesis. The gene wxcA involved in lipopolysaccharide biosynthesis but dose not extracellular polysaccharide in others' report. wxcA::Tn5 gusA5 mutant 021C12, the polar mutant, was complemented with recombinant plasmid pLATC8570 harboring an intact wxcA gene in this work, but the yield of EPS of the wxcA::Tn5 gusA5 mutant was not restored. In order to identify the function of wxcA gene of Xcc 8004 strain, the gene wxcA was deleted by gene replacement strategy, and the no-polar mutant of wxcA was obtained. DeltawxcA mutant strain, named Xcc 8570, was confirmed by using both PCR and southern analysis. Beside the LPS biosynthesis of deltawxcA mutant was affected, The EPS yield of deltawxcA mutant strain reduced by 50% as compared with the wild-type strain 8004. DeltawxcA mutant could be complemented in trans with the intact wxcA gene, and the EPS yield of the mutant was restored. The combined data showed that wxcA gene not only involved in LPS biosynthesis but also EPS yield in Xcc 8004 strain.
Cell Proliferation ; Genes, Bacterial ; physiology ; Lipopolysaccharides ; biosynthesis ; Mutation ; Polysaccharides, Bacterial ; biosynthesis ; Xanthomonas campestris ; genetics

MarR family transcription regulators are ubiquitous among bacteria and archaea. They extensively control multiple cellular processes and elaborately regulate the expression of genes involved in virulence, stress response and antibiotics at translational level. In Xanthomonas campestris pv. campestris, insertional inactivation of MarR family transcription regulator HpaR (XC2827) resulted in significantly decrease in virulence and increase in the production of the extracellular proteases. Here, we reported that the genome of Xcc 8004 encodes nine MarR family transcription regulators. The MarR family transcription regulators, HpaR (XC2827) and XC0449, were heterologous expressed and purified. In vitro MST and Pull-down assay confirmed the physical interaction between HpaR and XC0449. Phenotypical assay determined that deletion of XC0449 resulted in substantial virulence attenuation. In vitro EMSA, in vivo qRT-PCR and GUS activity assay identified that HpaR and XC0449 coordinately act as the transcriptional activator to regulate the expression of the virulence-associated gene XC0705, and eventually control the bacterial virulence and the production of extracellular proteases.
Bacterial Proteins ; Gene Expression Regulation, Bacterial ; Transcription Factors ; Virulence ; Xanthomonas campestris

Xanthomonas albilineans (Ashby) Downson is a quarantine pest for importing plants to China that causes leaf scald bacterial disease on sugarcane. X. albilineans produces a potent phytotoxin/antibiotic called albicidin. As a pathogenic factor, albicidin causes typical white leaf stripes by inhibiting plastid DNA gyrase and disturbing chloroplast differentiation. Meanwhile, the antibacterial activity of albicidin gives X. albilineans a competitive advantage against rival bacteria during their colonization. Furthermore, albicidin has a rapid bactericidal activity against a variety of Gram-positive and Gram-negative pathogenic bacteria of human species at nanomolar concentrations, making it a potential antimicrobial drug for clinical application. This article reviews the advances of albicidin from the aspects of its molecular structure, traditional extraction methods, mechanism of action, biosynthetic genes and processes, chemical synthesis method and improvement, in order to provide insights into the prevention and treatment of the sugarcane leaf scald disease, and the development of new antibiotics.
Anti-Bacterial Agents/pharmacology* ; China ; Humans ; Organic Chemicals ; Xanthomonas/genetics*

In this study, a new Bacillus velezensis strain Bv-303 was identified and its biocontrol effect against rice bacterial-blight (BB) disease caused by Xanthomonas oryzae pv. oryzae (Xoo) was investigated. Cell-free supernatant (CFS) of strain Bv-303 under different growth conditions were prepared to test the antagonistic activity and stability against Xoo by the Oxford-cup method in vitro. The antibacterial effect of strain Bv-303 to BB disease in rice were further analyzed in vivo by spraying the cell-culture broth (CCB), CFS and cell-suspension water (CSW), respectively, on the rice leaves inoculated with Xoo. Additionally, rice seeds germination rate and seedling growth under the strain Bv-303 CCB treatment were tested. The results showed that the strain Bv-303 CFS significantly inhibited Xoo growth by 85.7%‒88.0% in vitro, which was also stable under extreme environment conditions such as heat, acid, alkali and ultraviolet light. As tested in vivo, spraying the CCB, CFS or CSW of strain Bv-303 on the Xoo-infected leaves enhanced rice plant resistance to BB disease, with CCB showing the highest increase (62.7%) in disease-resistance. Notably, CCB does not have negative effects on rice seed germination and seedling growth. Therefore, strain Bv-303 has great potential for biocontrol of the rice BB disease.
Oryza ; Fatigue Syndrome, Chronic ; Bacillus ; Xanthomonas ; Plant Diseases/microbiology*

Xanthomonas campestris pv. campestris ( Xcc), causative agent of the black rot disease of cruciferous crops worldwide, produces large amount of extracellular polysaccharide( EPS), which has found wide applications in industry. In order to clone genes involved in EPS biosynthesis, Xcc wild-type strain 8004 was mutagenized with transposon Tn5gus A5, and a number of EPS-defective mutants were isolated. The Tn5gusA5 insertion sites in the mutants were analyzed by using thermal asymmetric interlaced PCR(TAIL-PCR), and the corresponding genes were identified by homology blast to the completely sequenced genome of Xcc 8004 strain. A novel gene, waxE, identified from the EPS-defective mutant 151D09, was found to be disrupted by the insertion of Tn5gusA5 in the open reading frame(ORF) with genome coordinates 4478998bp to 4479819bp.This gene showed 52% similarity to the kdtX gene of Serratia marcescens and 50% to the waaE of Klebsiella pneumoniae at amino acid level, with characteristics of glycostransferase 2 family domain. In order to identify the function of waxE gene, waxE gene deletion mutant of Xcc 8004 was constructed by gene replacement strategy in which waxE gene of genome was replaced by kanamycin resistant gene kan. The waxE gene deletion mutant strain, named Xcc 8570, was confirmed by both PCR and southern analysis. The growth rate of the deletion mutant 8570 in rich medium was not affected, but the EPS yield reduced by 35% as compared with the wildtype strain 8004. The deletion mutant could be completmented in trans with plasmid pLATC8976 harboring an intact waxE gene, and the EPS yield of the mutant was restored. The combined data showed that waxE gene involved in EPS biosynthesis in Xcc.
Amino Acid Sequence ; Bacterial Proteins ; chemistry ; genetics ; metabolism ; Blotting, Southern ; Cloning, Molecular ; DNA Transposable Elements ; genetics ; Molecular Sequence Data ; Polymerase Chain Reaction ; Polysaccharides, Bacterial ; genetics ; metabolism ; Sequence Analysis, DNA ; Sequence Homology, Amino Acid ; Xanthomonas campestris ; genetics ; metabolism

Southern blot analysis with probe from mini-Tn5 gfp-km transposon indicated that 5 non-pathogenic mutants which were generated by insertion of mini-Tn5 gfp-km mutagenesis contained a single copy of the transposon. Using genomic DNA of each mutant as a template, TAIL-PCR was performed with seven arbitrary degenerate (AD) primers pairing with 3 nested specific primers designed based on the sequence of GFP toward outside in mini-Tn5 gfp-km. After 3-step PCR reactions, the flanking sequence of each mutant was obtained. The PCR product was ligated with pGEM-T EASY vector and then was transformed into E. coli DH5 alpha by electroporation. Positive clones were selected by white/blue colony and plasmid was isolated, then digested with EcoRI. Plasmid was sequenced if its insert was longer than 300 bp. Our results indicated that TAIL-PCR was proved to be a simple and efficient approach in identification of gene using insertion mutagenesis.
Base Sequence ; Cloning, Molecular ; methods ; DNA Transposable Elements ; DNA, Bacterial ; isolation & purification ; Genes, Bacterial ; Green Fluorescent Proteins ; Luminescent Proteins ; genetics ; Molecular Sequence Data ; Mutagenesis ; Polymerase Chain Reaction ; methods ; Xanthomonas campestris ; genetics ; pathogenicity

In October 2003, a new bacterial disease with symptoms similar to those caused by Xanthomonas axonopodis pv. poinsettiicola was observed on poinsettia leaves at a flower nursery in Zhejiang Province of China. Three Xanthomonas strains were isolated from infected plants and classified as X. axonopodis. They were differentiated from the pathotype strain LMG849 of X. axonopodis pv. poinsettiicola causing bacterial leaf spot of poinsettia by comparison of pathogenicity, substrate utilization and BOX-PCR genomic fingerprints.
Cell Differentiation ; China ; Euphorbia ; microbiology ; Plant Diseases ; microbiology ; Plant Leaves ; microbiology ; Species Specificity ; Xanthomonas ; classification ; genetics ; isolation & purification ; pathogenicity

Relapsing peritonitis are major limitation of CAPD, a common reason for discontinuation of this form of therapy. Inappropriate treatment of previous peritonitis often leads to relapsing peritonitis, especially in patients with catheter-related infections. Although a multitude of therapeutic approaches have been tried, there is a controversy over the optimal antimicrobial treatment. The purposes of this study were: 1) to analyze the causative pathogen; 2) to determine the appropriate treatment regimen and duration; and 3) to evaluate the role of catheter replacement in recurrent peritonitis. Follow-up data were obtained in 43 CAPD patients who experienced 104 episodes of reucrrent peritonitis. 1) Among 104 episodes of recurrent peritonitis, 70 (67%) were culture-positive. The distribution of isolates was as follows : coagulase negative Staphylococci, 39 (38%); Enterococcus, 9 (9%); Staphylococcus aureus, 8 (8%); Pseudomonas, 4 (4%); Serratia, 4 (4%); Xanthomonas, 3 (3%); Klebsiella, 2 (2%); and fungus, 1 (1%). 2) Peritonitis recurred in 46 (50%) and did not recur in the other 46 (50%) of the 92 catheter- maintained peritonitis. After catheters were removed in 12 patients, new catheters were inserted in 3 patients without any more peritonitis. 3) There was no significant difference of recurrence between Gram-positive and Gram-negative peritonitis (56 vs. 50%). 4) Five (29%) of 17 peritonitis treated with vancomycin and amikacin, and 22 (73%) of 30 peritonitis treated with cefazolin and tobramycin experienced recurrence. Compared with cefazolin, initial therapy with vancomycin decreased the recurrence rate (P<0.05). 5) In Gram-positive and Gram-negative peritonitis, there was no reduction of recurrence in peritonitis treated for more than 2 weeks (63 vs. 51%, 40 vs. 60%). In coagulase negative Staphylococcal peritonitis, treatment for more than 2 weeks reduced the recurrence without statistical significance (59 vs. 30%, P=0.10). 6) In Gram-positive and Gram-negative peritonitis, there was no reduction of recurrence in peritonitis treated for more than 10 days after resolution (59 vs. 53%, 40 vs. 69%). In coagulase negative Staphylococcal peritonitis, treatment more than 10 days after resolution reduced the recurrence without statistical significance (50 vs. 26%, P=0.08). In conclusion, treatment with vancomycin and a longer treatment duration seem to be beneficial in relapsing CAPD peritonitis. Moreover, removal and replacement of catheter should be considered in cases unresponsive to antibiotic treatment.
Amikacin ; Catheter-Related Infections ; Catheters ; Cefazolin ; Coagulase ; Enterococcus ; Follow-Up Studies ; Fungi ; Humans ; Klebsiella ; Peritoneal Dialysis, Continuous Ambulatory* ; Peritonitis* ; Pseudomonas ; Recurrence ; Serratia ; Staphylococcus aureus ; Tobramycin ; Vancomycin ; Xanthomonas