Structure of the atypical bacteriocin pectocin M2 implies a novel mechanism of protein uptake

The colicin-like bacteriocins are potent protein antibiotics that have evolved to efficiently cross the outer membrane of Gram-negative bacteria by parasitizing nutrient uptake systems. We have structurally characterized the colicin M-like bacteriocin, pectocin M2, which is active against strains of Pectobacterium spp. This unusual bacteriocin lacks the intrinsically unstructured translocation domain that usually mediates translocation of these bacteriocins across the outer membrane, containing only a single globular ferredoxin domain connected to its cytotoxic domain by a flexible α-helix, which allows it to adopt two distinct conformations in solution. The ferredoxin domain of pectocin M2 is homologous to plant ferredoxins and allows pectocin M2 to parasitize a system utilized by Pectobacterium to obtain iron during infection of plants. Furthermore, we identify a novel ferredoxin-containing bacteriocin pectocin P, which possesses a cytotoxic domain homologous to lysozyme, illustrating that the ferredoxin domain acts as a generic delivery module for cytotoxic domains in Pectobacterium

Genotyping of carbapenem resistant Acinetobacter baumannii isolated from Egyptian patients

Acinetobacter baumannii has recently been known as a major cause of hospital- and community-acquired infections. Carbapenem resistant A. baumanni (CRAB) has been recorded to be resistant to nearly all antibiotics, including the last resort antibiotics; carbapenems. This study aimed to detect the carbapenem resistance levels and mechanisms, in addition to the genotyping of A. baumanni in Upper Egypt. About 200 clinical samples were collected from different wards of Sohag University Hospital, Egypt, from which 20 A. baumannii isolates were recovered and then identified using conventional methods and Polymerase Chain Reaction (PCR). Antibiotic sensitivity testing was carried out using the Disk diffusion method, followed by PCR testing of the common carbapenemase-encoding genes, including OXA-51, OXA-58, KPC, GES, IMP, NDM, VIM, SIM, and GIM. Genotyping was performed using the Enterobacterial Repetitive Intergenic Consensus-Polymerase chain reaction (ERIC-PCR). About 85 % of A. baumannii strains were multidrug resistant (MDR), and high rate of Extreme drug resistant (XDR) A. baumannii (70 %) was detected. Carbapenem resistance was detected in 65 % of A. baumannii isolates, 70.58 % of MDR isolates, and 85.7 % of XDR isolates, respectively. Carbapenemase- encoding genes, including blaOXA-51, VIM, NDM, and GES, were detected in 100 %, 100 %, 76.9 2 % and 76.92 % of the carbapenem resistant A. baumannii (CRAB) isolates, respectively. The blaIMP and blaKPC genes had lower prevalence rates of 15.38 % and 30.77 %; respectively, whereas the SIM, GIM, and OXA-58 genes were not detected in any of the tested A. baumanni isolates. All of the MDR isolates carried three or more the carbapenemases encoding genes, and 85.7 % of the XDR isolates carried four or more of the carbapenemase-encoding genes. The dendrogram constructed from the ERIC-PCR results showed that the A. baumannii isolates were divided into three different clusters

Global regulation of gene expression by OxyR in an important human opportunistic pathogen

Most bacteria control oxidative stress through the H2O2-responsive transactivator OxyR, a member of the LTTR family (LysR Type Transcriptional Regulators), which activates the expression of defensive genes such as those encoding catalases, alkyl hydroperoxide reductases and superoxide dismutases. In the human opportunistic pathogen Pseudomonas aeruginosa, OxyR positively regulates expression of the oxidative stress response genes katA, katB, ahpB and ahpCF. To identify additional targets of OxyR in P. aeruginosa PAO1, we performed chromatin immunoprecipitation in combination with whole genome tiling array analyses (ChIP-chip). We detected 56 genes including all the previously identified defensive genes and a battery of novel direct targets of OxyR. Electrophoretic mobility shift assays (EMSAs) for selected newly identified targets indicated that ∼70% of those were bound by purified oxidized OxyR and their regulation was confirmed by quantitative real-time polymerase chain reaction. Furthermore, a thioredoxin system was identified to enzymatically reduce OxyR under oxidative stress. Functional classification analysis showed that OxyR controls a core regulon of oxidative stress defensive genes, and other genes involved in regulation of iron homeostasis (pvdS), quorum-sensing (rsaL), protein synthesis (rpsL) and oxidative phosphorylation (cyoA and snr1). Collectively, our results indicate that OxyR is involved in oxidative stress defense and regulates other aspects of cellular metabolism as well

Morphological, morphometrical and molecular identification of root-knot nematode (Meloidogyne javanica) infecting banana in Assiut governorate, Egypt

Plant-parasitic nematodes are extremely dangerous pests in a variety of economically important crops. Root-knot nematodes (RKN) Meloidogyne spp. are between the major important pests causing serious crops havoc worldwide because of their wide geographical distribution and variety of hosts. Therefore, both of identification that is true and trustworthy of these pests is required for evaluating various suitable management strategies. This study, aimed to characterize morphological, morphometric and molecularly isolate of Meloidogyne related to banana plants. Second-stage juveniles (body length, tail length, stylet length, hyaline terminus length, and DEGO) were used in morphometric and morphological studies and female in perineal patterns. The results revealed that the identified nematode species, Meloidogyne javanica, is the most common root knot nematode species in all three localities. To prove the identification, a polymerase chain reaction (PCR)-based experiment using a species-specific sequence described amplified regions (SCAR) primer series was used. The Fjav/Rjav primer effectively enhanced SCAR markers of 670 bp previously identified in M. javanica. This study confirms the use of an effective and reliable diagnosis of RKN using the three approaches