The puzzling taxonomic rank of Pijnackeria hispanica,a chimerical hybrid androgen (Insecta,Phasmida)

Organisms Diversity & Evolution - The stick-insect genus Pijnackeria includes four diploid bisexual and two polyploid (3n, 4n) parthenogenetic species. Earlier analyses of the tetraploid...     

Positive signature-tagged mutagenesis in Pseudomonas aeruginosa: tracking patho-adaptive mutations promoting airways chronic infection

The opportunistic pathogen Pseudomonas aeruginosa can establish life-long chronic infections in the airways of cystic fibrosis (CF) patients. Persistent lifestyle is established with P. aeruginosa patho-adaptive variants, which are clonal with the initially-acquired strains. Several reports indicated that P. aeruginosa adapts by loss-of-function mutations which enhance fitness in CF airways and sustain its clonal expansion during chronic infection. To validate this model of P. aeruginosa adaptation to CF airways and to identify novel genes involved in this microevolution, we designed a novel approach of positive-selection screening by PCR-based signature-tagged mutagenesis (Pos-STM) in a murine model of chronic airways infection. A systematic positive-selection scheme using sequential rounds of in vivo screenings for bacterial maintenance, as opposed to elimination, generated a list of genes whose inactivation increased the colonization and persistence in chronic airways infection. The phenotypes associated to these Pos-STM mutations reflect alterations in diverse aspects of P. aeruginosa biology which include lack of swimming and twitching motility, lack of production of the virulence factors such as pyocyanin, biofilm formation, and metabolic functions. In addition, Pos-STM mutants showed altered invasion and stimulation of immune response when tested in human respiratory epithelial cells, indicating that P. aeruginosa is prone to revise the interaction with its host during persistent lifestyle. Finally, sequence analysis of Pos-STM genes in longitudinally P. aeruginosa isolates from CF patients identified signs of patho-adaptive mutations within the genome. This novel Pos-STM approach identified bacterial functions that can have important clinical implications for the persistent lifestyle and disease progression of the airway chronic infection.     

Suppression of scant identifies Endos as a substrate of greatwall kinase and a negative regulator of protein phosphatase 2A in mitosis

Protein phosphatase 2A (PP2A) plays a major role in dephosphorylating the targets of the major mitotic kinase Cdk1 at mitotic exit, yet how it is regulated in mitotic progression is poorly understood. Here we show that mutations in either the catalytic or regulatory twins/B55 subunit of PP2A act as enhancers of gwl(Scant), a gain-of-function allele of the Greatwall kinase gene that leads to embryonic lethality in Drosophila when the maternal dosage of the mitotic kinase Polo is reduced. We also show that heterozygous mutant endos alleles suppress heterozygous gwl(Scant); many more embryos survive. Furthermore, heterozygous PP2A mutations make females heterozygous for the strong mutation polo(11) partially sterile, even in the absence of gwl(Scant). Heterozygosity for an endos mutation suppresses this PP2A/polo(11) sterility. Homozygous mutation or knockdown of endos leads to phenotypes suggestive of defects in maintaining the mitotic state. In accord with the genetic interactions shown by the gwl(Scant) dominant mutant, the mitotic defects of Endos knockdown in cultured cells can be suppressed by knockdown of either the catalytic or the Twins/B55 regulatory subunits of PP2A but not by the other three regulatory B subunits of Drosophila PP2A. Greatwall phosphorylates Endos at a single site, Ser68, and this is essential for Endos function. Together these interactions suggest that Greatwall and Endos act to promote the inactivation of PP2A-Twins/B55 in Drosophila. We discuss the involvement of Polo kinase in such a regulatory loop.     

Bioluminescence and its application in the monitoring of antimicrobial photodynamic therapy

Light output from bioluminescent microorganisms is a highly sensitive reporter of their metabolic activity and therefore can be used to monitor in real time the effects of antimicrobials. Antimicrobial photodynamic therapy (aPDT) is receiving considerable attention for its potentialities as a new antimicrobial treatment modality. This therapy combines oxygen, a nontoxic photoactive photosensitizer, and visible light to generate reactive oxygen species (singlet oxygen and free radicals) that efficiently destroy microorganisms. To monitor this photoinactivation process, faster methods are required instead of laborious conventional plating and overnight incubation procedures. The bioluminescence method is a very interesting approach to achieve this goal. This review covers recent developments on the use of microbial bioluminescence in aPDT in the clinical and environmental areas.     

Complete genome sequence of Bifidobacterium animalis subsp. lactis BLC1

Bifidobacterium animalis subsp. lactis BLC1 is a probiotic bacterium that is widely exploited by food industries as the active ingredient of various functional foods. Here we report the complete genome sequence of B. animalis subsp. lactis BLC1, which is expected to provide insights into the biology of this health-promoting microorganism and improve our understanding of its phylogenetic relatedness with other members of the B. animalis subsp. lactis taxon.     

Expression of Cryptosporidium parvum Cpa135/CpCCP1 chimeras in Giardia duodenalis: organization of the protein domains affects the protein secretion pathway

Cpa135 is a multidomain antigenic protein secreted at the sporozoite stage of the Apicomplexa protozoan Cryptosporidium parvum. Previous studies have shown that the protozoan flagellate parasite Giardia duodenalis is a suitable system for the heterologous expression of secreted proteins of Apicomplexa. Here, we designed three different Cpa135 variants fused to a C-terminal HA tag in order to test their expression in G. duodenalis under the control of the inducible promoter of the cyst wall protein 1 gene (cwp1). The three Cpa135 chimeras encompassed different portions of the protein; CpaG encodes the entire polypeptide of 1574 amino acids (aa); CpaGΔC includes the first 826 aa at the N-terminus; and CpaGΔN consists in of the final 833 aa at the C-terminus. Immunoblot experiments showed that CpaG and CpaGΔN maintained the epitopes recognized by anti-C. parvum-specific human serum. The intracellular localization and transport of the three Cpa135 variants were studied by immunofluorescence in combination with G. duodenalis-specific antibodies. CpaGΔC was mainly accumulated in the endoplasmic reticulum and the intact form was also excreted in the medium. Differently, the Cpa135 chimeras possessing an intact C-terminus (CpaG and CpaGΔN) were transported towards the forming cyst wall possibly and were not detected in the medium. Furthermore, the full-length CpaG was incorporated into the cyst wall. The data presented suggest that the C-terminus of Cpa135, which includes a cysteine reach domain, could influence the secretion of the chimeric proteins.     

Photodynamic antimicrobial chemotherapy in aquaculture: photoinactivation studies of Vibrio fischeri

Background

Photodynamic antimicrobial chemotherapy (PACT) combines light, a light-absorbing molecule that initiates a photochemical or photophysical reaction, and oxygen. The combined action of these three components originates reactive oxygen species that lead to microorganisms'' destruction. The aim was to evaluate the efficiency of PACT on Vibrio fischeri: 1) with buffer solution, varying temperature, pH, salinity and oxygen concentration values; 2) with aquaculture water, to reproduce photoinactivation (PI) conditions in situ.

Methodology/Principal Findings

To monitor the PI kinetics, the bioluminescence of V. fischeri was measured during the experiments. A tricationic meso-substituted porphyrin (Tri-Py⁺-Me-PF) was used as photosensitizer (5 µM in the studies with buffer solution and 10–50 µM in the studies with aquaculture water); artificial white light (4 mW cm⁻²) and solar irradiation (40 mW cm⁻²) were used as light sources; and the bacterial concentration used for all experiments was ≈10⁷ CFU mL⁻¹ (corresponding to a bioluminescence level of 10⁵ relative light units - RLU). The variations in pH (6.5–8.5), temperature (10–25°C), salinity (20–40 g L⁻¹) and oxygen concentration did not significantly affect the PI of V. fischeri, once in all tested conditions the bioluminescent signal decreased to the detection limit of the method (≈7 log reduction). The assays using aquaculture water showed that the efficiency of the process is affected by the suspended matter. Total PI of V. fischeri in aquaculture water was achieved under solar light in the presence of 20 µM of Tri-Py⁺-Me-PF.

Conclusions/Significance

If PACT is to be used in environmental applications, the matrix containing target microbial communities should be previously characterized in order to establish an efficient protocol having into account the photosensitizer concentration, the light source and the total light dose delivered. The possibility of using solar light in PACT to treat aquaculture water makes this technology cost-effective and attractive.     

Structural Insight into Inhibitor of Apoptosis Proteins Recognition by a Potent Divalent Smac-Mimetic

Genetic alterations enhancing cell survival and suppressing apoptosis are hallmarks of cancer that significantly reduce the efficacy of chemotherapy or radiotherapy. The Inhibitor of Apoptosis Protein (IAP) family hosts conserved proteins in the apoptotic pathway whose over-expression, frequently found in tumours, potentiates survival and resistance to anticancer agents. In humans, IAPs comprise eight members hosting one or more structural Baculoviral IAP Repeat (BIR) domains. Cellular IAPs (cIAP1 and 2) indirectly inhibit caspase-8 activation, and regulate both the canonical and the non-canonical NF-κB signaling pathways. In contrast to cIAPs, XIAP (X chromosome-linked Inhibitor of Apoptosis Protein) inhibits directly the effector caspases-3 and -7 through its BIR2 domain, and initiator caspase-9 through its BIR3 domain; molecular docking studies suggested that Smac/DIABLO antagonizes XIAP by simultaneously targeting both BIR2 and BIR3 domains. Here we report analytical gel filtration, crystallographic and SAXS experiments on cIAP1-BIR3, XIAP-BIR3 and XIAP-BIR2BIR3 domains, alone and in the presence of compound 9a, a divalent homodimeric Smac mimetic. 9a is shown to bind two BIR domains inter- (in the case of two BIR3) and intra-molecularly (in the case of XIAP-BIR2BIR3), with higher affinity for cIAP1-BIR3, relative to XIAP-BIR3. Despite the different crystal lattice packing, 9a maintains a right handed helical conformation in both cIAP1-BIR3 and XIAP-BIR3 crystals, that is likely conserved in solution as shown by SAXS data. Our structural results demonstrate that the 9a linker length, its conformational degrees of freedom and its hydrophobicity, warrant an overall compact structure with optimal solvent exposure of its two active moieties for IAPs binding. Our results show that 9a is a good candidate for pre-clinical and clinical studies, worth of further investigations in the field of cancer therapy.