Biomedical subjects

Xiumei Liu

Publications and source records attributed to Xiumei Liu.

24 records · Page 2Linked to original sources

PubMed2003

Need to differentiate lethal toxin-producing strains of Burkholderia gladioli, which cause severe food poisoning: description of B. gladioli pathovar cocovenenans and an emended description of B. gladioli.

Burkholderia cocovenenans produces a lethal toxin (Bongkrekic acid) that leads to high fatality in food poisoning cases. However, B. cocovenenans was combined in Burkholderia gladioli in 1999. B. gladioli was originally described as a phytopathogenic bacteria that sometimes causes pneumonia in humans and that acts as an opportunistic pathogen. We thought that it was clinically dangerous to describe these two species without considering their pathogenicities. From our data of 16S rRNA sequence analysis, DNA-DNA hybridization, and fatty acid analysis, we could confirm that B. cocovenenans and B. gladioli should be categorized as a single species. However the species really weaved lethal toxin-producing strains with non-lethal strains. To emphasize that B. gladioli contains two different pathogens, we describe a new pathovar, B. gladioli pathovar cocovenenans, for the lethal toxin-producing strains. We provide characteristics that differentiate this lethal toxin-producing pathovar from other phytopathogenic pathovars within B. gladioli, together with an emended description of B. gladioli.

Animals↗

PubMed2003

[Study on the polymerase chain reaction methods for the detection of fumonisin-producing strains of Fusarium moniliforme].

Three pairs of PCR primers P1/P2, P3/P4 and Fum5F21/Fum5R1 specific for Fumonisin-producing were designed, based on the polyketide synthase gene fum5 of Fusarium moniliforme involved in fumonisin biosynthesis. PCR methods for detecting Fumonisin-producing F. moniliforme strains were developed. The specificity of PCR with 3 pairs of primers was detected with 5 standard F. moniliforme strains from ATCC. 880 bp, 702 bp and 1040 bp DNA fragments were amplified with P1/P2, P3/P4 and Fum5F21/Fum5R1, respectively, by using ATCC 52539 (Fumonisin-producing strain) as DNA template. Negative results were obtained by using ATCC 38946, ATCC 26263, ATCC 12763, ATCC 38016 (Fumonisin-non-producing strains), and other negative control strains such as F. gramnearum, F. poae, F. equiseti, F. tricinctum, A. flavus and E. coli O157. The sensitivity of PCR with 3 pairs of primers was detected by applying different dilutions of ATCC 52539 DNA template. The detection limits for PCR with P1/P2 was 100 pg per PCR assay, and with P3/P4 and Fum5F21/Fum5R1 were all 10 pg, equivalently 10(4) and 10(3) spores per PCR assay, respectively. Total 32 strains of F. moniliforme and F. moniliforme var isolated from different regions in China were identified by using PCR with P1/P2, P3/P4 and Fum5F21/Fum5R1. 26 out of them were identified as Fumonisin-producing strains, and other 6 isolates as Fumonisin-non-producing strains. Restriction fragment length polymorphism (RFLP) analysis for PCR (P3/P4) products of some Fumonisin-producing strains were performed by using restriction endonuclease EcoR V and Bam HI. Two DNA fragments 181 bp, 521 bp and three fragments 116 bp, 258 bp, 328 bp were produced, respectively, which accorded with reported reference value. Reliability of the results was confirmed. The results indicated that only one strain, ZJ-fm052, had Fumonisin biosynthesis gene, but negative in detecting fumonisin B1 in culture. Further studies are required. It proved that PCR methods are rapid and reliable to detect Fumonisin-producing strains.

DNA Primers↗

PubMed2003

[Studies on the polyclonal antibody and the double-antibody enzyme-linked immunosorbent assay against E. coli O157 in food].

The polyclonal antibody (PcAb) for E. coli O157:H7 was available by intravenous injection with New Zealand rabbit with E. coli O157:H7 ATCC43895 strain. Together with the monoclonal antibody (McAb) 3A5 specific against E. coli O157 and O113:H21, a double-antibody sandwich enzyme-linked immunosorbent assay (ELISA) was developed with the as the capture antibody and the McAb 3A5 as the detection antibody. The detection limits are 10(3)-10(4) cfu/ml in pure culture of E. coli O157 and without any cross reaction with the non-O157 strains. With 10 h enrichment procedure, E. coli O157:H7 recovered well from inoculated ground poultry meat and pasteurized milk at levels of 0.1 cfu/g(cfu/ml). The results demonstrated that the double-antibody sandwich ELISA is a sensitive and specific method for detecting E. coli O157 in food samples.

Animals↗

PubMed2002

Mechanics of F-actin characterized with microfabricated cantilevers.

In this report we characterized the longitudinal elasticity of single actin filaments manipulated by novel silicon-nitride microfabricated levers. Single actin filaments were stretched from zero tension to maximal physiological tension, P(0). The obtained length-tension relation was nonlinear in the low-tension range (0-50 pN) with a resultant strain of approximately 0.4-0.6% and then became linear at moderate to high tensions (approximately 50-230 pN). In this region, the stretching stiffness of a single rhodamine-phalloidin-labeled, 1-microm-long F-actin is 34.5 +/- 3.5 pN/nm. Such a length-tension relation could be characterized by an entropic-enthalpic worm-like chain model, which ascribes most of the energy consumed in the nonlinear portion to overcoming thermal undulations arising from the filament's interaction with surrounding solution and the linear portion to the intrinsic stretching elasticity. By fitting the experimental data with such a worm-like chain model, an estimation of persistence length of approximately 8.75 microm was derived. These results suggest that F-actin is more compliant than previously thought and that thin filament compliance may account for a substantial fraction of the sarcomere's elasticity.

Actins↗

PubMed2002

[Production and characterization of monoclonal antibody against the O antigen of Enterohemorrhagic Escherichia coli].

Spleen cells collected from Balb/c mice immunized with the somatic antigen of Enterohaemorrhagic E. coli O157:H7 are fused with murine Sp2/0 myeloma cells. A hybridoma cell line specific to E. coli O157 is established after screening and sub-cloning and is designated as 3A5. It belongs to a subtype of IgM and the ascetic titer of the antibody is 1:1 x 10(6). The detection limit is 10(5)-10(6) cfu/ml. This monoclonal antibody(McAb) also has activity with Enterohaemorrhagic E. coli O113:H21.

Animals↗

PubMed2002

[Expression of fused protein A-green fluorescent protein (PA-GFP)].

The green fluorescent protein (GFP) of jellyfish victoria is an unusual protein with strong visible fluorescence both in vivo and in vitro. In this study, about 750 bp fragment of gfp gene was amplified by PCR and was inserted into pRIT2T vector containing protein A gene. The recombinant plasmid was transferred into E. coli JM101. GFP and protein A were fused and expressed in E. coli Top10. The bright green fluorescence on the plates could be visible under UV at 365 nm. The bacteria cells were disrupted by sonic oscillation. The fused protein PA-GFP could be obtained from the supernatants.

Escherichia coli↗