Burkholderia pseudomallei is the causative agent of melioidosis, a disease with high morbidity that is endemic in South East Asia and northern Australia. An unusual feature of the bacterium is its ability to induce multinucleated giant cell formation (MNGC), which appears to be related to bacterial pathogenicity. The mechanism of MNGC formation is not fully understood, but host cell factors as well as known bacterial virulence determinants are likely to contribute. Since members of the tetraspanin family of membrane proteins are involved in various types of cell:cell fusion, their role in MNGC formation induced by Burkholderia thailandensis, a mildly pathogenic species closely related to B. pseudomallei, was investigated. The effect of antibodies to tetraspanins CD9, CD81, and CD63 in MNGC formation induced by B. thailandensis in infected mouse J774.2 and RAW macrophage cell lines was assessed along with that of recombinant proteins corresponding to the large extracellular domain (EC2) of the tetraspanins. B. thailandensis-induced fusion was also examined in macrophages derived from CD9 null and corresponding WT mice, and in J774.2 macrophages over-expressing CD9. Antibodies to CD9 and CD81 promoted MNGC formation induced by B. thailandensis, whereas EC2 proteins of CD9, CD81, and CD63 inhibited MNGC formation. Enhanced MNGC formation was observed in CD9 null macrophages, whereas a decrease in MNGC formation was associated with overexpression of CD9. Overall our findings show that tetraspanins are involved in MNGC formation induced by B. thailandensis and by implication, B. pseudomallei, with CD9 and CD81 acting as negative regulators of this process.

Burkholderia cenocepacia is an opportunistic pathogen that causes severe infections of the cystic fibrosis (CF) lung. To acquire iron, B. cenocepacia secretes the Fe(III)-binding compound, ornibactin. Genes for synthesis and utilisation of ornibactin are served by the iron starvation (IS) extracytoplasmic function (ECF) σ factor, OrbS. Transcription of orbS is regulated in response to the prevailing iron concentration by the ferric uptake regulator (Fur), such that orbS expression is repressed under iron-sufficient conditions. Here we show that, in addition to Fur-mediated regulation of orbS, the OrbS protein itself responds to intracellular iron availability. Substitution of cysteine residues in the C-terminal region of OrbS diminished the ability to respond to Fe(II) in vivo. Accordingly, whilst Fe(II) impaired transcription from and recognition of OrbS-dependent promoters in vitro by inhibiting the binding of OrbS to core RNA polymerase (RNAP), the cysteine-substituted OrbS variant was less responsive to Fe(II). Thus, the cysteine residues within the C-terminal region of OrbS contribute to an iron-sensing motif that serves as an on-board ‘anti-σ factor’ in the presence of Fe(II). A model to account for the presence two regulators (Fur and OrbS) that respond to the same intracellular Fe(II) signal to control ornibactin synthesis and utilisation is discussed.

Pathogenic bacteria are constantly adapted against antimicrobial drugs by arising new traits of drug resistance. The genes of such resistance are mostly possessed by pathogens due to the random use of antibiotics and commonly held on plasmid DNA. Plasmid-mediated antimicrobial resistance genes are easily transferred horizontally from one bacterial cell to another in an epidemic manner causing an increasing and serious challenge to clinicians to overcome the infectious pathogens. UTI is the most common infection caused by bacteria which has become hard to be treated due to the emerging problem of antibiotic resistance. The current study correlates plasmid DNA diversity and antibiotic resistance in E. coli; the common causative agent of UTI. Obtaining plasmid restriction maps provides a clear view about how DNA could be diversified in one bacteria. The result showed a clear DNA polymorphism in plasmids purified from E. coli. There has been 10 forms of different restriction plasmid profiles among 63 sample of E. coli. The 10 forms of plasmid profiles have been classified into two groups: highly diversified and lowly diversified profiles. Strains of highly diversified plasmid profiles showed significantly more resistance toward antibiotics than strains of less diversified plasmid profiles. Measuring plasmid DNA diversity together with the antibiotic resistance indicates an epidemic transfer and acquisition of different plasmids in pathogenic E. coli as a result of antibiotic random treatment.

In the original article, incorrect Figures were published with incorrect captions. The correct Figs. 1, 2, 3, 4, 5, 6, 7 and 8 and captions are given below.