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Osmoregulatory Systems of Escherichia coli: Identification of Betaine-Carnitine-Choline Transporter Family Member BetU and Distributions of betU and trkG among Pathogenic and Nonpathogenic Isolates. Anh Ly, 2004.Multiple transporters mediate osmoregulatory solute accumulation in Escherichia coli K-12 . The larger genomes of naturally occurring strains such as pyelonephritis isolates CFT073 and HU734 may encode additional osmoregulatory systems . CFT073 is more osmotolerant than HU734 in the absence of organic osmoprotectants, yet both strains grew in high osmolality medium at low K+ (micromolar concentrations) and retained locus trkH, which encodes an osmoregulatory K+ transporter . Both lacked the trkH homologue trkG . Transporters ProP and ProU account for all glycine-betaine uptake activity in E . coli K-12 and CFT073, but not in HU734, yet elimination of ProP and ProU impairs the growth of HU734, but not CFT073, in high osmolality human urine . No known osmoprotectant stimulated the growth of CFT073 in high osmolality minimal medium, but putative transporters YhjE, YiaMNO, and YehWXYZ may mediate uptake of additional osmoprotectants . Gene betU was isolated from HU734 by functional complementation and shown to encode a betaine uptake system that belongs to the betaine-choline-carnitine transporter family . The incidence of trkG and betU within the ECOR collection, representatives of the E . coli pathotypes (PATH), and additional strains associated with urinary tract infection (UTI) were determined . Gene trkG was present in 66% of the ECOR collection but only in 16% of the PATH and UTI collections . Gene betU was more frequently detected in ECOR groups B2 and D (50% of isolates) than in groups A, B1, and E (20%), but it was similar in overall incidence in the ECOR collection and in the combined UTI and PATH collections (32 and 34%, respectively) . Genes trkG and betU may have been acquired by lateral gene transfer, since trkG is part of the rac prophage and betU is flanked by putative insertion sequences . Thus, BetU and TrkG contribute, with other systems, to the osmoregulatory capacity of the species E . coli, but they are not characteristic of a particular phylogenetic group or pathotype . Comparative Activities of the Triterpene Saponin Maesabalide III and Liposomal Amphotericin B (AmBisome) against Leishmania donovani in Hamsters. Louis Maes, 2004.Maesabalide III (MB-III), an oleane triterpene saponin isolated from the Vietnamese plant Maesa balansae, is a new antileishmanial lead compound whose activity against Leishmania donovani (MHOM/ET/67/L82) in groups of five golden hamsters was evaluated after administration of a single subcutaneous dose on either day 1 (prophylactic treatment) or day 28 (curative treatment) after infection . Liposomal amphotericin B (AmBisome), administered intravenously at 5 mg/kg of body weight, was used as the reference drug . Amastigote burdens in liver, spleen, and bone marrow were determined either 7 days (early effects) or 56 days (late effects) after treatment . Prophylactic administration of MB-III at 0.2 mg/kg reduced liver amastigote burdens by 99.8 and 83% within 7 and 56 days after treatment, respectively . In the latter group, however, all animals became ill and some died . Both MB-III at 0.8 mg/kg and liposomal amphotericin B were 100% effective against liver stages, but clearance from the spleen and bone marrow was not achieved . Curative administration of MB-III at 0.2 and 0.4 mg/kg was not protective, as no survivors were left at the termination of the experiment on day 84 . Despite the high level of reduction of the liver amastigote burden after treatment with MB-III at 0.8 mg/kg (94.2%) or liposomal amphotericin B (99.4%), clinical protection could not be obtained in either group, with two deaths occurring and the residual liver burdens persisting . It is concluded that administration of a single dose of MB-III at 0.8 mg/kg has efficacy potential comparable to that of a single dose of liposomal amphotericin B at 5 mg/kg and is therefore considered a promising new antileishmanial lead compound . However, multiple-dose pharmacological, toxicological, and pharmacokinetic studies are still needed before it can become a valid drug candidate for development . Microbial Species Involved in Production of 1,2-sn-Diacylglycerol and Effects of Phosphatidylcholine on Human Fecal Microbiota. Jelena Vulevic, 2004.1,2-sn-Diacylglycerols (DAGs) are activators of protein kinase C (PKC), which is involved in the regulation of colonic mucosal proliferation . Extracellular DAG has been shown to stimulate the growth of cancer cell lines in vitro and may therefore play an important role in tumor promotion . DAG has been detected in human fecal extracts and is thought to be of microbial origin . Hitherto, no attempts have been made to identify the predominant fecal bacterial species involved in its production . We therefore used anaerobic batch culture systems to determine whether fecal bacteria could utilize phosphatidylcholine (0.5% [wt/vol]) to produce DAG . Production was found to be dependent upon the presence of the substrate and was enhanced in the presence of high concentrations of deoxycholate (5 and 10 mM) in the growth medium . Moreover, its production increased with the pH, and large inter- and intraindividual variations were observed between cultures seeded with inocula from different individuals . Clostridia and Escherichia coli multiplied in the fermentation systems, indicating their involvement in phosphatidylcholine metabolism . On the other hand, there was a significant decrease in the number of Bifidobacterium spp . in the presence of phosphatidylcholine . Pure-culture experiments showed that 10 of the 12 strains yielding the highest DAG levels (>50 nmol/ml) were isolated from batch culture enrichments run at pH 8.5 . We found that the strains capable of producing large amounts of DAG were predominantly Clostridium bifermentans (8 of 12), followed by Escherichia coli (2 of 12) . Interestingly, one DAG-producing strain was Bifidobacterium infantis, which is often considered a beneficial gut microorganism . Our results have provided further evidence that fecal bacteria can produce DAG and that specific bacterial groups are involved in this process . Future strategies to reduce DAG formation in the gut should target these species . TonB Interacts with Nonreceptor Proteins in the Outer Membrane of Escherichia coli. Penelope I. Higgs, 2002.
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