The role of iron-uptake factor PiuB in pathogenicity of soybean pathogen Xanthomonas axonopodis pv. glycines / 生物工程学报

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.

Role of Iron Uptake Systems in Coordinating Iron Homeostasis in NaCl-resistant Mutant of the Cyanobacterium Nostoc muscorum

Aims: To investigate the effect of NaCl stress on parent Nostoc muscorum and its spontaneously occurring mutant clone showing resistance to growth inhibitory action of NaCl in terms of various physiological parameters. We have further analyzed the role of iron uptake systems in providing a resistant phenotype. Place and Duration of Study: Division of Microbiology, Department of Botany, Government Motilal Science College, Bhopal 462008 (M.P.) India. This work was carried out between August 2021 to May 2022. Methodology: We have examined the various physiological parameters viz. growth, specific growth rate, photosynthetic O2 evolution, and nitrogenase activity as per the prescribed protocol. Further, DNA microarray analysis was carried out using the Agilent platform. Results: NaCl stress adversely affected growth, photosynthetic O2 evolution, and nitrogenase activity of the wild-type Nostoc muscorum, while NaCl-resistant mutant remains unaffected under a given stress. Microarray data analysis identified 24 ORF related to the uptake of iron with fold regulation ?2 in the mutant strain. These ORFs belonging to the ABC-type ferric iron transporter that plays a significant role in the iron acquisition were identified in the mutant strain. Conclusion: The mechanism of iron homeostasis in the NaCl-resistant mutant has been explained. The results presented are essential to explain the regulatory role of the iron uptake system in stressed conditions.

Iron uptake systems of Brucella and anti-infectious immunity of the host / 中华地方病学杂志

Iron is involved in the virulence and pathogenic effects of certain intracellular parasites.In the pathogenic process of Brucella,the uptaking and metabolism of host iron are closely related to intracellular parasitism and immunity escape of Brucella.In this paper,we elucidated the iron transport system,iron response regulators and nutrient immunity of iron based on the latest report and data about Brucella.

Iron uptake and biofilm formation in Pseudomonas aeruginosa / 生物工程学报

Biofilms are surface-associated communities of microorganisms embedded within self-secreted extracellular polymeric substances, and a major cause of chronic and persistent infections. Respiratory Pseudomona aeruginosa infection is the leading reason for morbidity and mortality in cystic fibrosis patients. The formation of biofilms by P. aeruginosa in the airway is thought to increase persistence and antibiotic resistance during infection. Biofilm formation of P. aeruginosa is regulated by complicated signaling systems including quorum sensing and two-component systems that control the synthesis of extracellular polymeric substances. Furthermore, iron is an essential and scarce nutrient for bacteria and an important signal factor. P. aeruginosa has developed multiple iron uptake systems to sequester enough iron for its survival, with important regulatory roles in both release of virulence factors and formation of biofilms. In this review, we summarize recent advances in biofilm formation and its regulation along with the iron-uptake strategies in P. aeruginosa, to provide new insights and understanding to fight bacterial biofilms.

The uptake of different iron salts by the yeast Saccharomyces cerevisiae

Yeasts can be enriched with microelements, including iron; however, special physicochemical conditions are required to formulate a culture media that promotes both yeast growth and iron uptake. Different iron sources do not affect biomass formation; however, considering efficacy, cost, stability, and compatibility with Saccharomyces cerevisiae metabolism, ferrous sulphate is recommended.

Multiple High-affinity Iron-uptake Systems of Vibrio vulnificus

Vibrio vulnificus is a Gram-negative halophilic bacterium that causes necrotizing wound infections and fatal septicemia, which mainly occur in patients with elevated serum or tissue iron levels. Accumulated experimental data clearly show that V. vulnificus is a ferrophilic bacterium that requires more available iron for growth than other pathogenic bacteria, has multiple iron-uptake systems, which play important roles in the pathogenesis of the V. vulnificus infections. This review summarized the composition, regulation and significance of V. vulnificus iron-uptake systems. These iron-uptake systems may be attractive candidates for the development of V. vulnificus vaccine. Iron-chelating therapy can also be a promising modality for the prevention and treatment of V. vulnificus infections.

Cloning and characterization of the iron uptake gene iutA from avian Escherichia coli

The aim of this work was to isolate, clone and characterize the iron uptake gene iutA from avian pathogenic E. coli (APEC). The iutA gene was isolated from the strain APEC 9, serotype O2:H9, which was cloned in the expression vector pET101/D-TOPO. The gene of 2.2 Kb was sequenced (AY602767, which showed high similarity to the iutA gene from three plasmids, two from APEC, pAPEC-02-ColV (AY545598.4) and pTJ100 (AY553855.1), and one from a human invasive E. coli strain, the pColV K30. The recombinant protein IutA was over expressed in E. coli BL21(DE-3) and was solubilized with urea and purified by Ni-NTA column. This method produced a relatively high yield of r-IutA of approximately 74kDa, which was used to produce the antibody anti-IutA. This anti-IutA reacted with the protein r-IutA and native IutA of APEC 9, as demonstrated by Western blot, showing that the r-IutA conserved epitopes and its antigenicity was preserved. The anti-IutA IgY was able to inhibit the IutA biological activity, inhibiting the sensitivity to cloacin DF13 of APEC9. However, it did not inhibit the growth of APEC9 in M9 and did not protect the chickens inoculated with the APEC, suggesting that the APEC possessed another iron acquisition mechanism distinct of aerobactin.

A proteína de membrane externa IutA (iron uptake transport) é o receptor para aerobactina férrica, um fator de virulência encontrado mais frequentemente entre as amostras de E. coli pathogênicas para aves (APEC) do que entre os isolados fecais de aves saudáveis. O gene iutA da amostra APEC 9, sorotipo O2:H9, foi amplificado e clonado no vetor pET101/D-TOPO. O gene iutA 2.2 Kb foi sequenciado (AY602767) e mostrou alta similaridade para gene iutA de três plasmidios, dois da APEC, pAPEC-02-ColV (AY545598.4) e pTJ100 (AY553855.1), e um da amostra E. coli invasiva humana, pColV K30. A proteína IutA recombinante (r-IutA) foi produzida em Escherichia coli BL21(DE-3), solubilizada com uréia e purificada em coluna de níquel Ni-NTA. A r-IutA tem aproximadamente 74kDa e foi utilizada para produzir anticorpos anti-IutA. Este anticorpo reagiu com a r- IutA e com IutA da APEC13, como demonstrado por Western blot, mostrando que a r-IutA tem epitopos conservados e sua antigenicidade foi preservada. O anticorpo anti-IutA foi capaz de inibir a atividade biológica da IutA, inibindo o teste positivo de sensibilidade à cloacina DF13 apresentada pela APEC 9, contudo não inibiu o crescimento da APEC9 crescida em M9 e não protegeu os pintinhos inoculados com APEC 9, sugerindo que a APEC possui outro mecanismo de captação de íons ferro distinto da aerobactina.

Activity of Iron-uptake System of Staphy lococcus aureus According to the Isolation Sites / 감염

OBJECTIVE: We tried to investigate the activity of iron-uptake system (IUS) of Stap hylococcus aureus according to the isolation sites and thus the relatedness between IUS and virulence. METHODS: Seventy clinical isolates were classified into the isolates from patients (56), from doctors and nurses (7) and from hospital environments (7). The isolates from patients (56) were sub-classified into the isolates from hospitalized patients (40; HP) and from outpatients (16; OP). Siderophore activity was measured CAS agar diffusion assay and transferrin-binding protein (tbp) was detected by receptor-ligand binding assay. RESULTS: There was no difference of siderophore production among the isolates from patients, doctors and nurses, and hospital environments (P>0.05). However, the isolates from patients expressed more tbp than the isolates from doctors and nurses and hospital environments (P<0.05). The isolates from OP produced more siderophore and expressed more tbp than the isolates from HP (P<0.05). CONCLUSION: These results suggested that Staphylococcus aureus with more active IUS is more virulent and more easily causes infection even in patients with relatively good general condition.

Cell Wall Proteins of Staphylococcus aureus Responsive to Oxygen Tension and Iron Concentration / 감염

BACKGROUND: We previously reported that activity of iron-uptake systems (IUS) influenced on the growth of Staphylococcus aureus in laboratory medium and body fluids according to the iron and oxygen concentrations, which they are closely related each other in several microbial metabolism. In the present study, we tried to investigate the profiles of cell wall proteins of S. aureus according to the change of iron and oxygen concentrations. METHODS: SR-1 strain, whose IUS are defective, was isolated from the standard strain ATCC 6538 by repeated exposure against streptonigrin. These two strains were cultured under the aerobic, microaerobic and anaerobic conditions in the iron-sufficient BHI and iron-depleted BHI, respectively. Cell wall proteins were visualized by Coomassie staining after SDS-PAGE. RESULTS: Cell wall proteins of the both strains were expressed more than under the aerobic condition than under the anaerobic condition in the iron-sufficient medium as well as in the iron-deficient medium. However, expression of cell wall proteins of SR-1 strain was markedly inhibited compared to that of parental ATCC 6538 strain, especially in the iron-deficient medium. Among the proteins more expressed under the aerobic culture condition in the iron-deficient medium, about 88, 55, 39, 36, 35 and 33 kDa of proteins were iron-repressible and oxygen-inducible, and corresponded to the iron-repressible proteins which other researchers reported. CONCLUSION: Expression of cell wall proteins of S. aureus was affected by simultaneous and respective change of iron and oxygen concentrations. Activity of IUS influenced more on the expression of cell wall proteins of S. aureus in the iron-deficient environment than in the iron-sufficient environment. These results suggest the possibility that the iron-repressible and oxygen-inducible proteins mimic those (antigens) found commonly in clinical infections.

Effect of Iron-Uptake System on the Growth of Staphylococcus aureus according to the Iron Concentration and Oxygen Tension / 감염

BACKGROUND: We previously reported that activity of iron-uptake systems (IUS) influenced on the growth of Staphylococcus aureus in body fluids which are relatively iron-restrictive conditions. Iron and oxygen are closely related each other in several microbial metabolism. In the present study, we tried to investigate the effect of IUS on the growth of S. aureus according to the iron concentration and oxygen tension. METHODS: SR-1 strain, whose IUS are defective, was isolated from the standard strain, ATCC 6538. These two strains were cultured under the aerobic, microaerobic and anaerobic condition in the iron-sufficient BHI and iron-depleted BHI, respectively. Bacterial growth was measured by optical density. RESULTS: Growth of both strains was inhibited in the iron-depleted BHI. Growth of parental strain was more active in the iron-sufficient BHI as well as in the ion-depleted BHI than that of SR-1 strain. Growth of both strains was more active under the aerobic condition than under the microaerobic or anaerobic condition. In the iron-depleted BHI, parental strain showed a striking difference of growth according to the oxygen tension. In the iron-depleted BHI, growth of SR-1 strain was markedly inhibited regardless of oxygen tension. CONCLUSION: IUS influenced more on the growth of S. aureus in the iron-depleted environments than in the iron-sufficient environments, and under the aerobic condition than under the microaerobic or anaerobic condition in the iron-depleted environments. These results indicated the possibility that oxygen as well as iron regulate activity and expression of IUS.