Biocontrol of Listeria monocytogenes on Fresh-Cut Produce by Treatment with Lytic Bacteriophages and a Bacteriocin

The fresh-cut produce industry has been the fastest-growing portion of the food retail market during the past 10 years, providing consumers with convenient and nutritious food. However, fresh-cut fruits and vegetables raise food safety concerns, because exposed tissue may be colonized more easily by pathogenic bacteria than intact produce. This is due to the higher availability of nutrients on cut surfaces and the greater potential for contamination because of the increased amount of handling. We found that applied Listeria monocytogenes populations survived and increased only slightly on fresh-cut Red Delicious apples stored at 10°C but increased significantly on fresh-cut honeydew melons stored at 10°C over 7 days. In addition, we examined the effect of lytic, L. monocytogenes-specific phages via two phage application methods, spraying and pipetting, on L. monocytogenes populations in artificially contaminated fresh-cut melons and apples. The phage mixture reduced L. monocytogenes populations by 2.0 to 4.6 log units over the control on honeydew melons. On apples, the reduction was below 0.4 log units. In combination with nisin (a bacteriocin), the phage mixture reduced L. monocytogenes populations by up to 5.7 log units on honeydew melon slices and by up to 2.3 log units on apple slices compared to the control. Nisin alone reduced L. monocytogenes populations by up to 3.2 log units on honeydew melon slices and by up to 2.0 log units on apple slices compared to the control. The phage titer was stable on melon slices, but declined rapidly on apple slices. The spray application of the phage and phage plus nisin reduced the bacterial numbers at least as much as the pipette application. The effectiveness of the phage treatment also depended on the initial concentration of L. monocytogenes.     

Peptides of type II collagen can induce the cleavage of type II collagen and aggrecan in articular cartilage.

The objective of this study was to determine whether a fragment(s) of type II collagen can induce cartilage degradation. Fragments generated by cyanogen bromide (CB) cleavage of purified bovine type II collagen were separated by HPLC. These fragments together with selected overlapping synthetic peptides were first analysed for their capacity to induce cleavage of type II collagen by collagenases in chondrocyte and explant cultures of healthy adult bovine articular cartilage. Collagen cleavage was measured by immunoassay and degradation of proteoglycan (mainly aggrecan) was determined by analysis of cleavage products of core protein by Western blotting. Gene expression of matrix metalloproteinases MMP-13 and MMP-1 was measured using Real-time PCR. Induction of denaturation of type II collagen in situ in cartilage matrix with exposure of the CB domain was identified with a polyclonal and monoclonal antibodies that only react with this domain in denatured but not native type II collagen. As well as the mixture of CB fragments and peptide CB12, a single synthetic peptide CB12-II (residues 195-218), but not synthetic peptide CB12-IV (residues 231-254), potently and consistently induced in explant cultures at 10 microM and 25 microM, in a time, cell and dose dependent manner, collagenase-induced cleavage of type II collagen accompanied by upregulation of MMP-13 expression but not MMP-1. In isolated chondrocyte cultures CB12-II induced very limited upregulation of MMP-13 as well as MMP-1 expression. Although this was accompanied by concomitant induction of cleavage of type II collagen by collagenases, this was not associated by aggrecan cleavage. Peptide CB12-IV, which had no effect on collagen cleavage, clearly induced aggrecanase specific cleavage of the core protein of this proteoglycan. Thus these events involving matrix molecule cleavage can importantly occur independently of each other, contrary to popular belief. Denaturation of type II collagen with exposure of the CB12-II domain was also shown to be much increased in osteoarthritic human cartilage compared to non-arthritic cartilage. These observations reveal that peptides of type II collagen, to which there is increased exposure in osteoarthritic cartilage, can when present in sufficient concentration induce cleavage of type II collagen (CB12-II) and aggrecan (CB12-IV) accompanied by increased expression of collagenases. Such increased concentrations of denatured collagen are present in adult and osteoarthritic cartilages and the exposure of chondrocytes to the sequences they encode, either in soluble or more likely insoluble form, may therefore play a role in the excessive resorption of matrix molecules that is seen in arthritis and development.     

灰金合欢根瘤类菌体繁殖及其宿主细胞的超微结构

根瘤细胞早期发育阶段,以宿主细胞器和根瘤菌转化类菌体的数量增多为特征。随后类菌体增殖到填满宿主细胞内的大部分区域。各个类菌体周膜内含有1至几个类菌体。晚期共生发育阶段,类菌体细胞结构和宿主细胞器数量发生了变化。文中还讨论了根瘤的共生固氮作用。     

Plasmodium falciparum expresses a multidrug resistance-associated protein

Plasmodium falciparum proteins that efflux toxic metabolic products such as oxidised glutathione (GSSG) are possible targets for anti-malarial drug development. Proteins capable of transporting GSSG and glutathione conjugates include the multidrug resistance-associated transporters (MRPs). A gene, PFA0590w, encoding a MRP homologue, has been identified in P. falciparum. Here we show the presence of full-length mRNA (5.5 kb) of this PfMRP in trophozoites by RT-PCR and Northern blotting. A polyclonal anti-PfMRP antibody generated against two unique, hydrophilic peptides in the predicted sequence produced a strong immunoreactive protein band of 210-215 kDa on Western blots of schizonts of chloroquine-sensitive and chloroquine-resistant strains, confirming expression of PfMRP protein. Using confocal microscopy the protein was seen to be localised at the edge of the schizonts with no obvious staining of the food vacuole. We suggest that PfMRP may act as the GSSG transporter in the parasite plasma membrane.     

5种光合细菌种间原生质体融合及优良农用融合子的筛选鉴定

处于对数生长期的光合细菌球形红假单胞菌(Rhodopseudomonassphaeroides)、沼泽红假单胞菌(Rhodopseudomonaspalustris)、嗜酸红假单胞菌(Rhodopseudomdnasacidophila)、深红红螺菌(Rhodospirarubrum)、万尼氏红微菌(Rhodomocrobiumvannielii),经溶菌酶(3mg/L)处理50min后,获得了它们的菌体形成的原生质体,其再生率分别为80%、71%、82%、61%、74%.取等量的亲本菌株在35%的PEG(MW6000)诱导下两两融合5min,共10种组合.其融合率为球×沼2.5×10-4、球×嗜2.1×10-4、球×深2.0×10-4、球×万2.1×10-4、沼×嗜2.8×10-4、沼×深2.4×10-4、沼×万2.6×10-4、嗜×深2.0×10-4、嗜×万2.3×10-4、深×万2.4×10-4.经影印法鉴定:形成的融合子可以分别生长于以相应的有机物为唯一碳源的培养基上,所有融合子体积均相当于两亲本株体积之和,融合子菌落形态特征介于两亲本株之间.从中随机挑选100个融合子,以辣椒苗作为靶标植物,从上述融合子中筛选到了1株具有显著促进作物生长、提高抗病性的融合子.     

Proteomic identification of the cerebral cavernous malformation signaling complex

Cerebral cavernous malformations (CCM) are sporadic or inherited vascular lesions of the central nervous system characterized by dilated, thin-walled, leaky vessels. Linkage studies have mapped autosomal dominant mutations to three loci: ccm1 (KRIT1), ccm2 (OSM), and ccm3 (PDCD10). All three proteins appear to be scaffolds or adaptor proteins, as no enzymatic function can be attributed to them. Our previous results demonstrated that OSM is a scaffold for the assembly of the GTPase Rac and the MAPK kinase kinase MEKK3, for the hyperosmotic stress-dependent activation of p38 MAPK. Herein, we show that the three CCM proteins are members of a larger signaling complex. To define this complex, epitope-tagged wild type OSM or OSM harboring the mutation of F217-->A, which renders the OSM phosphotyrosine binding (PTB) domain unable to bind KRIT1, were stably introduced into RAW264.7 mouse macrophages. FLAG-OSM or FLAG-OSMF217A and the associated complex members were purified by immunoprecipitation using anti-FLAG antibody. OSM binding partners were identified by gel-based methods combined with electrospray ionization-MS or by multidimensional protein identification technology (MudPIT). Previously identified proteins that associate with OSM including KRIT1, MEKK3, Rac, and the KRIT1-binding protein ICAP-1 were found in the immunoprecipitates. In addition, we show for the first time that PDCD10 binds to OSM and is found in cellular CCM complexes. Other prominent proteins that bound the CCM complex include EF1A1, RIN2, and tubulin, with each interaction disrupted with the OSMF217A mutant protein. We further show that PDCD10 binds phosphatidylinositol di- and triphosphates and OSM binds phosphatidylinositol monophosphates. The findings define the targeting of the CCM complex to membranes and to proteins regulating trafficking and the cytoskeleton.     

Gene expression profile in immunologically injured liver cell of mice

To study the gene expression profiles between immunologically injured liver cell and normal liver cell of mice and to screen on a large scale the differentially expressed genes associated with the formation of liver injury, the experimental mice were randomly divided into the normal group for controlling and the immunologically liver-injured group induced by BCG and LPS. The liver mRNA of the two groups were extracted respectively and reversely-transcribed to cDNA with the incorporation of different fluorescence (Cy3, Cy5) labeled dUTP as the hybridization probes. The mixed probes were hybridized to the cDNA microarray chips. The fluorescent signal results were acquired by scanner ScanArray 4000 and analyzed with software GenePix Pro 3.0. Among the 14112 target genes, 293 genes were found to be significantly differentially expressed, in which 188 genes were up-regulated and 105 genes were down-regulated. Based on the analysis of biological functions of those differentially expressed genes, it was indicated that the occurrence and development of mouse liver damage induced by BCG and LPS were highly correlated with the processes of immune reactions, cell synthesis, metabolism, apoptosis and transportation in liver cell, which might be quite important for elucidating the regulatory network of gene expression associated with the liver damage, also important for finally discovering the pathogenic mechanisms of immunological liver damage.     

Morusin induces apoptosis and suppresses NF-kappaB activity in human colorectal cancer HT-29 cells

Morusin is a pure compound isolated from root bark of Morusaustralis (Moraceae). In this study, we demonstrated that morusin significantly inhibited the growth and clonogenicity of human colorectal cancer HT-29 cells. Apoptosis induced by morusin was characterized by accumulation of cells at the sub-G₁ phase, fragmentation of DNA, and condensation of chromatin. Morusin also inhibited the phosphorylation of IKK-α, IKK-β and IκB-α, increased expression of IκB-α, and suppressed nuclear translocation of NF-κB and its DNA binding activity. Dephosphorylation of NF-κB upstream regulators PI3K, Akt and PDK1 was also displayed. In addition, activation of caspase-8, change of mitochondrial membrane potential, release of cytochrome c and Smac/DIABLO, and activation of caspase-9 and -3 were observed at the early time point. Downregulation in the expression of Ku70 and XIAP was exhibited afterward. Caspase-8 or wide-ranging caspase inhibitor suppressed morusin-induced apoptosis. Therefore, the antitumor mechanism of morusin in HT-29 cells may be via activation of caspases and inhibition of NF-κB.