British Library Electronic Table of Contents (United Kingdom)

The type III secretion system among Gram-negative bacteria is known to deliver effectors into host cell to interfere with host cellular processes. The type III secretion system in Yersina, Pseudomonas and Enterohemorrhagic Escherichia coli have been well documented to be involved in the bacterial pathogenicity. The existence of type III secretion system has been demonstrated in neuropathogenic E. coli K1 strains. Here, it is observed that the deletion mutant of type III secretion system in E. coli strain EC10 exhibited defects in the invasion and intracellular survival in Acanthamoeba castellanii (a keratitis isolate) compared to its parent strain. Next, it was determined whether type III secretion system plays a role in E. coli K1 survival inside Acanthamoeba during the encystment process...

International Nuclear Information System (INIS)

In the present study the authors have shown that glycoproteins are present in the plasma membrane of Acanthamoeba castellanii by utilizing different radioactive labeling techniques. Plasma membrane proteins in the amoeba were iodinated by "1"2"5I-lactoperoxidase labeling and the solubilized radiolabeled glycoproteins were separated by lectin-Sepharose affinity chromatography followed by polyacrylamide gel electrophoresis. The periodate/NaB"3H_4 and galactose oxidase/NaB"3H_4 labeling techniques were used for labeling of surface carbohydrates in the amoeba. Several surface-labeled glycoproteins were observed in addition to a diffusely labeled region with M_r of 55,000-75,000 seen on electrophoresis, which could represent glycolipids. The presence of glycoproteins in the plasma membrane of Acanthamoeba castellanii was confirmed by metabolic labeling with ["3"5S]methionine followed by lectin-Sepharose ...

International Nuclear Information System (INIS)

Acanthamoeba castellanii myosins IA and IB demonstrate the catalytic properties of a myosin and can support analogues of contractile and motile activity in vitro, but their single, low molecular weight heavy chains, roughly globular shapes, and inabilities to self-assemble into filaments make them structurally atypical myosins. The authors present the complete amino acid sequence of the 128-kDa myosin IB heavy chain, which they deduced from the nucleotide sequence of the gene and which reveals that the polypeptide is a fusion of myosin-like and non-myosin-like sequences. Specifically, the amino-terminal #approx# 76 kDa of amino acid sequence is highly similar to the globular head sequences of conventional myosins. By contrast, the remaining #approx# 51 kDa of sequence shows no similarity to any portion of conventional myosin sequences, contains regions that are rich in glycine, proline, and alanine residues, and lacks the distinctive sequence ...

International Nuclear Information System (INIS)

A #lambda#gt11 cDNA library was constructed from poly(U)-Spharose-selected Entamoeba histolytica trophozoite RNA in order to clone and identify surface antigens. The library was screened with rabbit polyclonal anti-E. histolytica serum. A 700-base-pair cDNA insert was isolated and the nucleotide sequence was determined. The deduced amino acid sequence of the cDNA revealed a cysteine-rich protein. DNA hybridizations showed that the gene was specific to E. histolytica since the cDNA probe reacted with DNA from four axenic strains of E. histolytica but did not react with DNA from Entamoeba invadens, Acanthamoeba castellanii, or Trichomonas vaginalis. The insert was subcloned into the expression vector pGEX-1 and the protein was expressed as a fusion with the C terminus of glutathione S-transferase. Purified fusion protein was used to generate 22 monoclonal antibodies (mAbs) and a mouse polyclonal antiserum specific for the E. histolytica portion ...

UK PubMed Central (United Kingdom)

The genome sequence of the Mamavirus, a new Acanthamoeba polyphaga mimivirus strain, is reported. With 1,191,693 nt in length and 1,023 predicted protein-coding genes, the Mamavirus...Full Text Available

UK PubMed Central (United Kingdom)

Francisella tularensis is a gram negative facultative intracellular bacterium that causes the zoonotic disease tularemia. Free-living amebae, such as Acanthamoeba and...Full Text Available

Science.gov (United States)

The visual outcomes of Acanthamoeba keratitis, a rare cause of corneal infection, can be devastating. This paper reports two contact lens wearers with severe pain and photophobia who presented to the emergency room. Biomicroscopy revealed radial keratoneuritis in both individuals. Tissue culture on a nonnutrient agar plate with Escherichia coli overlay resulted in a heavy growth of Acanthamoeba. The inpatient treatment included 0.02% polyhexamethylene biguanide, chlorhexidine, neomycin/polymyxin B/bacitracin (Neosporin), and oral fluconazole, which successfully controlled the corneal infection and improvement in the best corrected visual acuity in both patients. Infection did not recur during the 12-month follow-up period. Acanthamoeba keratitis can present as radial keratoneuritis, mimicking other common corneal infections resulting in diagnostic and treatment delays. Early diagnosis and prudent treatment of ...

International Nuclear Information System (INIS)

The heavy chains of Acanthamoeba myosins, IA, IB and II, turkey gizzard myosin, and rabbit skeletal muscle myosin subfragment-1 were specifically labeled by radioactive ATP, ADP, and UTP, each of which is a substrate or product of myosin ATPase activity, when irradiated with uv light at 0"0C. With UTP, as much as 0.45 mol/mol of Acanthamoeba myosin IA heavy chain and 1 mol/mol of turkey gizzard myosin heavy chain was incorporated. Evidence that the ligands were associated with the catalytic site included the observations that reaction occurred only with nucleotides that are substrates or products of the ATPase activity; that the reaction was blocked by pyrophosphate which is an inhibitor of the ATPase activity; that ATP was bound as ADP; and that label was probably restricted to a single peptide following limited subtilisin proteolysis of labeled Acanthamoeba myosin IA heavy chain and extensive cleavage with CNBr and ...

Energy Technology Data Exchange (ETDEWEB)

Water and mud samples were collected from canals and rivers which were adjacent to outlets discharging warm water of 3 power plants in Berlin. Downstream samples from 1 bathing resort were also collected. Free living amoebae were isolated from 138 water and 69 mud samples. From these respectively 156 and 73 strains could be cultured and were administered intranasally to mice for pathogenicity tests. Two Acanthamoeba strains from water and 7 from mud could be reisolated from mouse brain and or lungs, although no pathological disorders could be observed. Five Naegleria strains were negative in mouse inoculation tests. Four Acanthamoeba strains which were positive in mice were cultured at + 45 degrees C; no cytopathogenic effects were observed in tissue cultures. Acanthamoeba infective for mice could also be isolated from samples at low water temperatures. Further investigations have to show, whether changes in virulence of ...

British Library Electronic Table of Contents (United Kingdom)

This study investigated the occurrence of free-living amoebae (FLA) in immunodeficiency wards of hospitals in Tehran, Iran. A total of 70 dust and biofilm samples from wards serving transplant, pediatric (malignancies), HIV, leukemia and oncology patients of five university hospitals were collected and examined for the presence of FLA using culturing and molecular approaches. Based on the morphology of the amoebae in plate cultures, primer sets were applied for molecular identification of Acanthamoeba, vahlkampfiid amoebae and Hartmannella. Out of 70 samples, 37 (52.9%) were positive for FLA. Acanthamoeba belonged to the T4 genotype was the most prevalent isolate. Presence of the T4 genotype on medical instruments, including an oxygen mask in an isolation room of an immunodeficiency pediat...

British Library Electronic Table of Contents (United Kingdom)

Mimivirus is the prototype of a new family (the Mimiviridae) of nucleocytoplasmic large DNA viruses (NCLDVs), which already include the Poxviridae, Iridoviridae, Phycodnaviridae and Asfarviridae. Mimivirus specifically replicates in cells from the genus Acanthamoeba. Proteomic analysis of purified mimivirus particles revealed the presence of many subunits of the DNA-directed RNA polymerase II complex. A fully functional pre-transcriptional complex appears to be loaded in the virions, allowing mimivirus to initiate transcription within the host cytoplasm immediately upon infection independently of the host nuclear apparatus. To fully understand this process, a systematic study of mimivirus proteins that are predicted (by bioinformatics) or suspected (by proteomic analysis) to be involved in...

British Library Electronic Table of Contents (United Kingdom)

In the present article, the study to examine the ability of free-living amoebae (FLA) to serve as vectors of cryptosporidia is presented. Ten strains of different free-living amoebae of the FLA collection of the Parasitology Lab at Koblenz were cultivated in the presence of Cryptosporidium parvum oocysts. After phagocytosis and ingestion, the oocysts could be found in food vacuoles within the cytoplasm of the trophozoites of two different FLA strains. The uptake and the transport of the oocysts within the trophozoites could be demonstrated in an Acanthamoeba sp. (group II) strain (maximum, three oocysts; average, one oocyst) as well as in a Thecamoeba quadrilineata strain (maximum, 15 oocysts; average, eight oocysts), with the help of light microscopy. We found that these free-living amoeb...

Energy Technology Data Exchange (ETDEWEB)

A 253.7-nm ultraviolet light with an intensity of 1,100 microW/cm2 was tested for its germicidal activity against contact lenses and storage solutions contaminated with various corneal pathogens. The exposure time necessary to reduce a concentration of organisms from 10(6)/ml to less than 10/ml was 30 seconds for Staphylococcus aureus, 60 seconds for Pseudomonas aeruginosa, and 84 seconds for Candida albicans. The time necessary to sterilize a suspension of 10(4)/ml Acanthamoeba polyphaga was less than three minutes with this technique. Four brands of soft contact lenses were exposed to ultraviolet light for over eight hours without changing their appearance, comfort, or refraction.

Energy Technology Data Exchange (ETDEWEB)

Two sources of ultraviolet (UV) radiation with peak wavelengths in the UV-C or UV-B ranges were compared for their ability to sterilize contact lenses infected with Pseudomonas aeruginosa, Streptococcus pneumoniae, Acanthamoeba castellani, Candida albicans, and Aspergillus niger. Also examined was the effect of prolonged UV light exposure on soft and rigid gas permeable (RGP) contact lenses. The UV-C lamp (253.7 nm, 250 mW/cm2 at 1 cm) was germicidal for all organisms within 20 minutes but caused destruction of the soft lens polymers within 6 hours of cumulative exposure. UV-C caused damage to RGP lenses in less than 100 hours. The UV-B lamp (290-310 nm, 500 mW/cm2 at 1 cm) was germicidal for all organisms tested (except Aspergillus) with a 180-minute exposure and caused less severe changes in the soft lens polymers than did the UV-C lamp, although cumulative exposure of 300 hours did substantially weaken the soft lens material. RGP materials were minimally ...

International Nuclear Information System (INIS)

The active site of chicken gizzard myosin was labeled by direct photoaffinity labeling with ["3H]UDP. ["3H] UDP was stably trapped at the active site by addition of vanadate (Vi) and Co"2"+. The extraordinary stability of the myosin.Co2+.[3H]UDP.Vi complex (t1/2 greater than 5 days at 0 degrees C) allowed it to be purified free of extraneous ["3H]UDP before irradiation began. Upon UV irradiation, greater than 60% of the trapped ["3H]UDP was photoincorporated into the active site. Only the 200-kDa heavy chain was labeled, confirming earlier results using ["3H]UTP. Extensive tryptic digestion of photolabeled myosin subfragment 1 followed by high performance liquid chromatography separations and removal of nucleotide phosphates by treatment with alkaline phosphatase allowed two labeled peptides to be isolated. Sequencing of the labeled peptides and radioactive counting showed that Glu185 was the residue labeled. Since UDP is a zero-length cross-linker, Glu185 is located at the ...