Exogenous Isolation of Antibiotic Resistance Plasmids from Piggery Manure Slurries Reveals a High Prevalence and Diversity of IncQ-Like Plasmids

Antibiotic resistance plasmids were exogenously isolated in biparental matings with piggery manure bacteria as plasmid donors in Escherichia coli CV601 and Pseudomonas putida UWC1 recipients. Surprisingly, IncQ-like plasmids were detected by dot blot hybridization with an IncQ oriV probe in several P. putida UWC1 transconjugants. The capture of IncQ-like plasmids in biparental matings indicates not only their high prevalence in manure slurries but also the presence of efficiently mobilizing plasmids. In order to elucidate unusual hybridization data (weak or no hybridization with IncQ repB or IncQ oriT probes) four IncQ-like plasmids (pIE1107, pIE1115, pIE1120, and pIE1130), each representing a different EcoRV restriction pattern, were selected for a more thorough plasmid characterization after transfer into E. coli K-12 strain DH5α by transformation. The characterization of the IncQ-like plasmids revealed an astonishingly high diversity with regard to phenotypic and genotypic properties. Four different multiple antibiotic resistance patterns were found to be conferred by the IncQ-like plasmids. The plasmids could be mobilized by the RP4 derivative pTH10 into Acinetobacter sp., Ralstonia eutropha, Agrobacterium tumefaciens, and P. putida, but they showed diverse patterns of stability under nonselective growth conditions in different host backgrounds. Incompatibility testing and PCR analysis clearly revealed at least two different types of IncQ-like plasmids. PCR amplification of total DNA extracted directly from different manure samples and other environments indicated the prevalence of both types of IncQ plasmids in manure, sewage, and farm soil. These findings suggest that IncQ plasmids play an important role in disseminating antibiotic resistance genes.     

The Effect of a Monoclonal Antibody Coupled to Ricin A Chain-Derived Peptides on Endothelial Cells in Vitro: Insights into Toxin-Mediated Vascular Damage

Immunotoxins (ITs) containing plant or bacterial toxins have a dose-limiting toxicity of vascular leak syndrome (VLS) in humans. The active A chain of ricin toxin (RTA), other toxins, ribosome-inactivating proteins, and the VLS-inducing cytokine IL-2 contain the conserved sequence motif (x)D(y) where X = L, I, G, or V and Y = V, L, or S. RTA-derived LDV-containing peptides attached to a monoclonal antibody, RFB4, induce endothelial cell (EC) damage in vitro and vascular leak in two animal models in vivo. We have now investigated the mechanism(s) by which this occurs and have found that (1) the exposed D75 in the LDV sequence in RTA and the C-terminal flanking threonine play critical roles in the ability of RFB4-conjugated RTA peptide to bind to and damage ECs and (2) the LDV sequence in RTA induces early manifestations of apoptosis in HUVECs by activating caspase-3. These data suggest that RTA-mediated inhibition of protein synthesis (due to its active site) and apoptosis (due to LDV) may be mediated by different portions of the RTA molecule. These results suggest that ITs prepared with RTA mutants containing alterations in LDVT may kill tumor cells in vivo in the absence of EC-mediated VLS.     

SEQUENCE ANALYSIS OF THE ITS-2 REGION: A TOOL TO IDENTIFY STRAINS OF SCENEDESMUS (CHLOROPHYCEAE)

The genetic distances between several strains of Scenedesmus obliquus (Turp.) Kütz., S. acutus Hortobagyi, and S. naegelii Chod. calculated from ITS-2 sequences were found to be smaller than the genetic distances within other strains of Scenedesmus —that is, in S. acuminatus (Lagerh.) Chod. and S. pectinatus Meyen. These results confirm that the studied strains were not properly identified and should be renamed S. obliquus , as already suggested in other studies.     

Glyceraldehyde-3-phosphate dehydrogenase is phosphorylated by protein kinase Ciota /lambda and plays a role in microtubule dynamics in the early secretory pathway.

The small GTPase Rab2 immunolocalizes to vesicular tubular clusters (VTCs) that function as transport complexes carrying cargo between the endoplasmic reticulum and the Golgi complex. Our previous studies showed that Rab2 promotes vesicle formation from VTCs and that the released vesicles are enriched in beta-coat protein, protein kinase C iota/lambda (PKCiota/lambda), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), and the recycling protein p53/gp58. Because PKCiota/lambda kinase activity was necessary for vesicle formation, a search was initiated to identify the substrate(s) that potentiate Rab2 function within VTCs. In this study, we found that PKCiota/lambda phosphorylates GAPDH. Moreover, GAPDH interacts directly with the PKCiota/lambda regulatory domain. Based on numerous observations that show (beta-COP) GAPDH associates with cytoskeletal elements, we examined the role of phospho-GAPDH in promoting microtubule (MT) binding to membrane. Using a quantitative microsomal binding assay, we found that membrane association of beta-tubulin was dependent on phospho-GAPDH and was blocked by reagents that interfere with Rab2-dependent GAPDH membrane recruitment or with PKCiota/lambda kinase activity. Furthermore, normal rat kidney cells transfected with a constitutively activated form of Rab2 (Q65L) or with our anti-GAPDH polyclonal antibody displayed a dramatic change in MT organization. These combined results suggest that Rab2 stimulated PKCiota/lambda and GAPDH recruitment to VTCs, and the subsequent PKCiota/lambda phosphorylation of GAPDH ultimately influences MT dynamics in the early secretory pathway.     

The contribution of Kv7 channels to pregnant mouse and human myometrial contractility

Premature birth accounts for approximately 75% of neonatal mortality and morbidity in the developed world. Despite this, methods for identifying and treating women at risk of preterm labour are limited and many women still present in preterm labour requiring tocolytic therapy to suppress uterine contractility. The aim of this study was to assess the utility of Kv7 channel activators as potential uterine smooth muscle (myometrium) relaxants in tissues from pregnant mice and women. Myometrium was obtained from early and late pregnant mice and from lipopolysaccharide (LPS)‐injected mice (day 15 of gestation; model of infection in pregnancy). Human myometrium was obtained at the time of Caesarean section from women at term (38–41 weeks). RT‐PCR/qRT‐PCR detected KCNQ and KCNE expression in mouse and human myometrium. In mice, there was a global suppression of all KCNQ isoforms, except KCNQ3, in early pregnancy (n= 6, P < 0.001 versus late pregnant); expression subsequently increased in late pregnancy (n= 6). KCNE isoforms were also gestationally regulated (P < 0.05). KCNQ and KCNE isoform expression was slightly down‐regulated in myometrium from LPS‐treated‐mice versus controls (P < 0.05, n= 3–4). XE991 (10 μM, Kv7 inhibitor) significantly increased spontaneous myometrial contractions in vitro in both human and mouse myometrial tissues (P < 0.05) and retigabine/flupirtine (20 μM, Kv7 channel activators) caused profound myometrial relaxation (P < 0.05). In summary, Kv7 activators suppressed myometrial contraction and KCNQ gene expression was sustained throughout gestation, particularly at term. Consequently, activation of the encoded channels represents a novel mechanism for treatment of preterm labour.