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ABSTRACTEnteropathogenic Escherichia coli(EPEC) specifically recognizes phosphatidylethanolamine (PE) on the outer leaflet of host epithelial cells. EPEC also induces apoptosis in epithelial cells, which results in increased levels of outer leaflet PE and increased bacterial binding. Consequently, it is of interest to investigate whether EPEC infection perturbs host cell phospholipid metabolism and whether the changes play a role in the apoptotic signaling. Our findings indicate that EPEC infection results in a significant increase in the epithelial cell PE level and a corresponding decrease in the phosphatidylcholine (PC) level. PE synthesis via both the de novo pathway and the serine decarboxylation pathway was enhanced, and de novo synthesis of phosphatidylcholine via CDP-choline was reduced. The changes were transitory, and the maximum change was noted after 4 to 5 h of infection. Addition of exogenous PC or CDP-choline to epithelial cells prior to infection abrogated EPEC-induced apoptosis, suggesting that EPEC infection inhibits the CTP-phosphocholine cytidylyltransferase step in PC synthesis, which is reportedly inhibited during nonmicrobially induced apoptosis. On the other hand, incorporation of exogenous PE by the host cells enhanced EPEC-induced apoptosis and necrosis without increasing bacterial adhesion. This is the first report that pathogen-induced apoptosis is associated with significant changes in PE and PC metabolism, and the results suggest that EPEC adhesion to a host membrane phospholipid plays a role in disruption of host phospholipid metabolism.

ABSTRACTThe bundle-forming pilus (BFP) of enteropathogenicEscherichiacoli(EPEC), an established virulence factor encoded on the EPEC adherence factor (EAF) plasmid, has been implicated in the formation of bacterial autoaggregates and in the localized adherence of EPEC to cultured epithelial cells. While understanding of the pathogenic mechanism of this organism is rapidly improving, a receptor ligand for BFP has not yet been identified. We now report, using both solid-phase and liposome binding assays, that BFP expression correlates with phosphatidylethanolamine (PE) binding. In a thin-layer chromatogram overlay assay, specific recognition of PE was documented for BFP-expressing strains, including E2348/69, a wild-type EPEC clinical isolate, as well as a laboratory strain, HB101, transformed with a bfp-carrying plasmid. Strains which did not express BFP did not bind PE, including a bfpAdisruptional mutant of E2348/69, EAF plasmid-cured E2348/69, and HB101. E2348/69 also aggregated PE-containing liposomes but not phosphatidylcholine- or phosphatidylserine-containing liposomes, while BFP-negative strains did not produce aggregates with any tested liposomes. Purified BFP preparations bound commercial PE standards as well as a PE-containing band within lipid extracts from human epithelial cells and from E2348/69. Our results therefore indicate a specific interaction between BFP and PE and suggest that PE may serve as a BFP receptor for bacterial autoaggregation and may promote localized adherence to host cells, both of which contribute to bacterial pathogenesis.

Vacations are an antidote to stress and burnout, but many never take vacations. The average vacation time in America is ten days while in Europe month long vacations are the norm. Psychologists are encouraging not only the recouperative benefits of vacations but the revitalization that getting away from it all provides. Signs of burnout are given. The experience of reformed workaholics are cited.

The first high-resolution (0.002 cm−1) infrared spectrum of the transient molecule formyl chloride, HCOCl, is reported. The ν3type A/Bhybrid band between 1220 and 1390 cm−1has been analyzed in detail, providing assignments for the A- and B-type lines of both HCO35Cl and HCO37Cl. The ground state rotational constants have been refined by a simultaneous fitting of previously reported microwave data and combination differences from the ν3and ν6bands of HCOCl. The excited state constants of both isotopomers have been obtained from fitting assignments over a wide range of Jand Kavalues. By comparing relative intensities, we estimate the ratio of the B-type to A-type transition moments to be 0.25 ± 0.1. The ν3band shows only minor perturbations.

This study was carried out to determine whether animals bearing L1210 leukemia were more susceptible to candida infection in the absence of immunosuppression and to determine also if the L1210 cells suppressed the imflammatory response of the animal host. Systemic infection was studied by intravenous injection of Candida albicans and checking for the number of candida organisms cultured from the blood and the kidneys. Localized infection was studied by intramuscular injection of C. albicans into the thighs and measuring the changes in the thigh size. Compared with tumor-free controls, the intravenous injection resulted in higher counts of C. albicans from the blood and the kidneys of tumor-bearing animals. No significant difference in the localized swelling was noted between tumor- and nontumor-bearing mice with respect to intramuscular injection of C. albicans. The results thus indicate that L1210 leukemia increases susceptibility of tumor-bearing animals to systemic candida infection. L1210 cells were shown to reduce the accumulation of neutrophils and to suppress the inflammatory reaction elicited by C. albicans.