FEMS Microbiology Letters

Cairns, Timothy; Minuzzi, Florencia; Bignell, Elaine

doi: 10.1111/j.1574-6968.2010.01961.xpmid: 20557573

AbstractThe capture of pathogen gene expression signatures directly from the host niche promises to fuel our understanding of the highly complex nature of microbial virulence. However, obtaining and interpreting biological information from infected tissues presents multiple experimental and intellectual challenges, from difficulties in extracting pathogen RNA and appropriate choice of experimental design, to interpretation of the resulting infection transcriptome, itself a product of responses to multiple host-derived cues. The recent publication of several host-infecting fungal transcriptomes offers new opportunities to study the commonalities of animal and plant pathogeneses, which in turn might direct the rational design of new and broader spectrum antifungal agents. Here, we examine the transcriptional basis of modelled Aspergillus fumigatus, Candida albicans, Cryptococcus neoformans, Ustilago maydis and Magneporthe infections, placing our analysis of the published findings within the context of the various modelling procedures used, and the relevant pathogen lifestyles, to facilitate the first cross-species comparison of fungal transcription during infectious growth. Significant concordance was identified among infecting transcriptomes of the inhaled fungal pathogens C. neoformans and A. fumigatus. The significance of gene clustering and subtelomeric gene repertoires is also discussed.

Chen, Bo; Zhang, Anding; Li, Ran; Mu, Xiaofeng; He, Hongkui; Chen, Huanchun; Jin, Meilin

doi: 10.1111/j.1574-6968.2010.01944.xpmid: 20402782

AbstractStreptococcus suis serotype 2 (SS2) infection is a major cause of sudden death in pigs and is of concern for humans as it has strong zoonotic capabilities. Developing novel effective vaccines would be beneficial to control SS2 infection. HP0272 is a novel immunogenic surface protein; its protective efficacy remains to be evaluated. The present mouse model found that the purified recombinant HP0272 could elicit a significant humoral antibody response, and to confer complete protection against a lethal dose of SS2 infection. In addition, real-time PCR confirmed that in vivo-induced antigen existed in most SS2 field pathogenic strains, and in half of all reference strains of different serotypes of S. suis. The results indicate that HP0272 has the potential as an effective component of a new vaccine.

Holbein, Bruce E.; Mira de Orduña, Ramón

doi: 10.1111/j.1574-6968.2010.01956.xpmid: 20402789

AbstractThe iron requirements of the opportunistic pathogenic yeast, Candida albicans, and the related nonpathogenic spoilage yeast Candida vini were investigated along with their responses to various exogenous iron chelators. The influence of iron as well as the exogenous chelating agents lactoferrin, EDTA, deferiprone, desferrioxamine, bathophenanthroline sulphonate and a novel carried chelator with a hydroxypyridinone-like Fe-ligand functionality, DIBI, on fungal growth was studied in a chemically defined medium deferrated to trace iron levels (<1.2 μg L−1 or 0.02 μM of Fe). Candida albicans competed better at low iron levels compared with C. vini, which was also more susceptible to most added chelators. Candida albicans was resistant to lactoferrin at physiologically relevant concentrations, but was inhibited by low concentrations of DIBI. Candida vini was sensitive to lactoferrin as well as to DIBI, whose inhibitory activity was shown to be Fe reversible. The pathogenic potential of C. albicans and the nonpathogenic nature of C. vini were consistent with their differing abilities to grow under iron-limiting conditions and in the presence of exogenous iron chelators. Both yeasts could be controlled by appropriately strong chelators. This work provides the first evidence of the iron requirements of the spoilage organism C. vini and its response to exogenous chelators. Efficient iron withdrawal has the potential to provide the basis for new fungal growth control strategies.

Sahin, Nurettin; Gonzalez, Juan M.; Iizuka, Takashi; Hill, Janet E.

doi: 10.1111/j.1574-6968.2010.01954.xpmid: 20370834

AbstractTwo strains of aerobic, non-spore-forming, Gram-negative, rod-shaped bacteria (ND5 and MY14T), previously isolated from urban soil using the membrane-filter enrichment technique, were characterized. Analysis of their 16S rRNA gene sequence grouped strains ND5 and MY14T within the family Oxalobacteraceae (Betaproteobacteria). The highest pairwise sequence similarities for strain ND5 were found with members of the genus Herminiimonas, namely with Herminiimonas saxobsidens NS11T (99.8%) and Herminiimonas glaciei UMB49T (99.6%). Although some fatty acid profiles, physiological and biochemical differences exist between strain ND5 and the respective Herminiimonas-type strains, DNA–DNA hybridization experiments confirm that strain ND5 is a member of the H. glaciei genospecies. Taxonomical analyses revealed a wider range of variability within this genus than considered previously. The highest pairwise nucleotide similarity for strain MY14T was found with Oxalicibacterium flavum (96.8%). Phylogenetic analyses based on 16S rRNA and cpn60 gene sequences, DNA–DNA hybridization, fatty acid profiles, physiological and biochemical tests allowed genotypic and phenotypic differentiation of strain MY14T from other Oxalicibacterium species representing a new species, for which the name Oxalicibacterium solurbis sp. nov. (type strain MY14T=NBRC 102665T,=CCM 7664T) is proposed.

Balcázar, José Luis; Pintado, José; Planas, Miquel

doi: 10.1111/j.1574-6968.2010.01955.xpmid: 20402780

AbstractA Gram-negative, facultatively anaerobic, motile and slightly curved rod-shaped bacterium (BFLP-4T) was isolated from the faeces of wild seahorses (Hippocampus guttulatus) captured in northwest Spain (Toralla, Galicia). Strain BFLP-4T grew at 10–35 °C and pH 5–9 (optimally at 20 °C and pH 7.2) and at salt concentrations in the range 0–7% w/v NaCl. The G+C content of the DNA was 49.3 mol%. Phylogenetic analysis based on the 16S rRNA gene sequence showed that strain BFLP-4T was a member of the genus Vibrio, being most closely related to Vibrio ichthyoenteri (97.1%), Vibrio mediterranei (96.7%), Vibrio scophthalmi (96.7%) and Vibrio sinaloensis (96.6%). A phylogenetic analysis based on recA gene sequences also supported the affiliation of strain BFLP-4T to the genus Vibrio. Strain BFLP-4T could be readily differentiated from other closely related species by several phenotypic properties and fatty acid profiles. On the basis of phenotypic, chemotaxonomic and phylogenetic data, strain BFLP-4T represents a novel species within the genus Vibrio, for which the name Vibrio hippocampi sp. nov. is proposed. The type strain is BFLP-4T (=DSM 22717T=LMG 25354T).

Rameshkumar, N.; Sproer, Cathrin; Lang, Elke; Nair, Sudha

doi: 10.1111/j.1574-6968.2010.01958.xpmid: 20402787

AbstractThe taxonomic status of a nitrogen-fixing bacterium, strain MSSRF38T, isolated from the rhizosphere of mangrove-associated wild rice (Porteresia coarctata Tateoka), in Pichavaram, India, was studied using a polyphasic approach. Phylogenetic analyses based on 16S rRNA gene sequences indicated that the novel strain MSSRF38T was most closely related to Vibrio ruber DSM 16370T (98.3% gene sequence similarity), Vibrio rhizosphaerae DSM 18581T (98.2% sequence similarity) and <96% to the remaining Vibrio species. Multilocus sequence analysis using ftsZ, gapA, gyrB and mreB genes showed low levels of gene sequence similarities (82–90%) with all species of the genus Vibrio with validly published names, indicating that strain MSSRF38T occupies a distinct phylogenetic position. DNA–DNA hybridization experiments showed that strain MSSRF38T had <70% DNA–DNA similarity to its closest neighbours V. ruber DSM 16370T (27.4%) and V. rhizosphaerae DSM 18581T (12.1%). Strain MSSRF38T could be differentiated from its relatives on the basis of several phenotypic characteristics. The major fatty acids were feature 3 (including C16:1ω7c and/or C15:0 iso 2-OH), C16:0, C18:1ω7c, C14:0 and C12:0. The DNA G+C content was 45.4 mol%. Based on genotypic, phenotypic, chemotaxonomic and DNA–DNA analyses, the name Vibrio mangrovi sp. nov. (type strain MSSRF38T=LMG 24290T=DSM 19641T) is proposed for this novel taxon.

Jones, Amy M.; Elliott, Thomas

doi: 10.1111/j.1574-6968.2010.01967.xpmid: 20412302

AbstractArchaea, plants, and most bacteria synthesize heme using the C5 pathway, in which the first committed step is catalyzed by the enzyme glutamyl-tRNA reductase (GluTR or HemA). In some cases, an overproduced and purified HemA enzyme contains noncovalently bound heme. The enteric bacteria Salmonella enterica and Escherichia coli also synthesize heme by the C5 pathway, and the HemA protein in these bacteria is regulated by proteolysis. The enzyme is unstable during normal growth due to the action of Lon and ClpAP, but becomes stable when heme is limiting for growth. We describe a method for the overproduction of S. enterica HemA that yields a purified enzyme containing bound heme, identified as a b-type heme by spectroscopy. A mutant of HemA (C170A) does not contain heme when similarly purified. The mutant was used to test whether heme is directly involved in HemA regulation. When expressed from the S. enterica chromosome in a wild-type background, the C170A mutant allele of hemA is shown to confer an unregulated phenotype, with high levels of HemA regardless of the heme status. These results strongly suggest that the presence of bound heme targets the HemA enzyme for degradation and is required for normal regulation.

Bielen, Abraham A.M.; Willquist, Karin; Engman, Jakob; Van Der Oost, John; Van Niel, Ed W.J.; Kengen, Servé W.M.

doi: 10.1111/j.1574-6968.2010.01957.xpmid: 20557574

AbstractThe role of inorganic pyrophosphate (PPi) as an energy carrier in the central metabolism of the extremely thermophilic bacterium Caldicellulosiruptor saccharolyticus was investigated. In agreement with its annotated genome sequence, cell extracts were shown to exhibit PPi-dependent phosphofructokinase and pyruvate phosphate dikinase activity. In addition, membrane-bound pyrophosphatase activity was demonstrated, while no significant cytosolic pyrophosphatase activity was detected. During the exponential growth phase, high PPi levels (approximately 4 ± 2 mM) and relatively low ATP levels (0.43 ± 0.07 mM) were found, and the PPi/ATP ratio decreased 13-fold when the cells entered the stationary phase. Pyruvate kinase activity appeared to be allosterically affected by PPi. Altogether, these findings suggest an important role for PPi in the central energy metabolism of C. saccharolyticus.

Salunke, Bipinchandra K.; Salunkhe, Rahul C.; Dhotre, Dhiraj P.; Khandagale, Avinash B.; Walujkar, Sandeep A.; Kirwale, Gulab S.; Ghate, Hemant V.; Patole, Milind S.; Shouche, Yogesh S.

doi: 10.1111/j.1574-6968.2010.01960.xpmid:

Yu, Shuijing; Chen, Wanyi; Wang, Dapeng; He, Xiaohua; Zhu, Xinna; Shi, Xianming

doi: 10.1111/j.1574-6968.2010.01952.xpmid: 20402781

AbstractVibrio parahaemolyticus is an enteric pathogen, which can cause acute gastroenteritis in humans after consumption of raw or partially cooked seafood, and specific molecular markers are necessary for its accurate identification by PCR methods. In the present study, 23 protein-coding sequences were identified by the comparative genomics method as V. parahaemolyticus-specific candidate markers. We targeted the irgB gene (vp2603), coding for iron-regulated virulence regulatory protein IrgB, in order to develop a PCR method for the detection of V. parahaemolyticus. PCR specificity was identified by amplification of 293 V. parahaemolyticus templates and by the loss of a PCR product with 11 strains from other Vibrio species and 35 non-Vibrio bacterial strains. The PCR assay had the 369-bp fragment and the sensitivity of 0.17 pg purified genomic DNA from V. parahaemolyticus. Furthermore, a multiplex PCR assay for the detection of total and virulent strains of V. parahaemolyticus was developed by targeting irgB, tdh and trh genes. These data indicated that the irgB gene is a new and effective marker for the detection of V. parahaemolyticus. In addition, this study demonstrates that genome sequence comparison has a powerful application in identifying specific markers for the detection and identification of bacterial pathogens.