bluuebunny/crossref_metadata_2025_split huggingface dataset:
Antibiotic and Biosurfactant Properties of Cyclic Lipopeptides Produced by Fluorescent
Pseudomonas
spp. from the Sugar Beet Rhizosphere
Authors: Nielsen T. H. , Sørensen D. , Tobiasen C. , Andersen J. B. , Christophersen C. , Givskov M. , Sørensen J. 
Published: July 2002

ABSTRACT

Cyclic lipopeptides (CLPs) with antibiotic and biosurfactant properties are produced by a number of soil bacteria, including fluorescent
Pseudomonas
spp. To provide new and efficient strains for the biological control of root-pathogenic fungi in agricultural crops, we isolated approximately 600 fluorescent
Pseudomonas
spp. from two different agricultural soils by using three different growth media. CLP production was observed in a large proportion of the strains (approximately 60%) inhabiting the sandy soil, compared to a low proportion (approximately 6%) in the loamy soil. Chemical structure analysis revealed that all CLPs could be clustered into two major groups, each consisting of four subgroups. The two major groups varied primarily in the number of amino acids in the cyclic peptide moiety, while each of the subgroups could be differentiated by substitutions of specific amino acids in the peptide moiety. Production of specific CLPs could be affiliated with
Pseudomonas fluorescens
strain groups belonging to biotype I, V, or VI. In vitro analysis using both purified CLPs and whole-cell
P. fluorescens
preparations demonstrated that all CLPs exhibited strong biosurfactant properties and that some also had antibiotic properties towards root-pathogenic microfungi. The CLP-producing
P. fluorescens
strains provide a useful resource for selection of biological control agents, whether a single strain or a consortium of strains was used to maximize the synergistic effect of multiple antagonistic traits in the inoculum.
Growth in Coculture Stimulates Metabolism of the Phenylurea Herbicide Isoproturon by
Sphingomonas
sp. Strain SRS2
Authors: Sørensen Sebastian R. , Ronen Zeev , Aamand Jens 
Published: July 2002

ABSTRACT

Metabolism of the phenylurea herbicide isoproturon by
Sphingomonas
sp. strain SRS2 was significantly enhanced when the strain was grown in coculture with a soil bacterium (designated strain SRS1). Both members of this consortium were isolated from a highly enriched isoproturon-degrading culture derived from an agricultural soil previously treated regularly with the herbicide. Based on analysis of the 16S rRNA gene, strain SRS1 was assigned to the β-subdivision of the proteobacteria and probably represents a new genus. Strain SRS1 was unable to degrade either isoproturon or its known metabolites 3-(4-isopropylphenyl)-1-methylurea, 3-(4-isopropylphenyl)-urea, or 4-isopropyl-aniline. Pure culture studies indicate that
Sphingomonas
sp. SRS2 is auxotrophic and requires components supplied by association with other soil bacteria. A specific mixture of amino acids appeared to meet these requirements, and it was shown that methionine was essential for
Sphingomonas
sp. SRS2. This suggests that strain SRS1 supplies amino acids to
Sphingomonas
sp. SRS2, thereby leading to rapid metabolism of
14
C-labeled isoproturon to
14
CO
2
and corresponding growth of strain SRS2. Proliferation of strain SRS1 suggests that isoproturon metabolism by
Sphingomonas
sp. SRS2 provides unknown metabolites or cell debris that supports growth of strain SRS1. The role of strain SRS1 in the consortium was not ubiquitous among soil bacteria; however, the indigenous soil microflora and some strains from culture collections also stimulate isoproturon metabolism by
Sphingomonas
sp. strain SRS2 to a similar extent.
Solid-Phase Contact Assay That Uses alux-MarkedNitrosomonas europaeaReporter Strain To Estimate Toxicity of Bioavailable Linear Alkylbenzene Sulfonate in Soil
Authors: Brandt Kristian K. , Pedersen Anders , Sørensen Jan 
Published: July 2002

ABSTRACTInformation about in situ toxicity of the bioavailable pools of adsorptive soil pollutants is a prerequisite for proper ecological risk assessment in contaminated soils. Such toxicity data may be obtained by assays allowing for direct exposure of introduced test microorganisms to the toxicants, as they appear in solid solution equilibria in the natural soil. We describe a novel sensitive solid-phase contact assay for in situ toxicity testing of soil pollutants based on a recombinant bioluminescent reporter strain ofNitrosomonas europaea. A slurry of the reporter strain and soil sample was shaken for 1 h, after which bioluminescence was measured either directly (soil slurry protocol) or in the supernatant obtained after centrifugation (soil extract protocol). The assay was validated for both protocols by using linear alkylbenzene sulfonate (LAS) as a toxic and adsorptive model compound in the soil samples. Interestingly, LAS showed the same toxicity to the reporter strain with either soil incubation (both protocols) or pure culture, suggesting that adsorbed LAS pools contributed to the observed toxicity. The solid-phase contact assay that used the reporter strain oflux-markedN. europaeawas slightly more sensitive for the detection of LAS toxicity in soil than activity-based assays targeting indigenous nitrifiers and much more sensitive than assays targeting indigenous heterotrophic microbes. We conclude that the new solid-phase contact assay, which is based on direct interaction of the test microorganisms with bioavailable pools of the toxicants in soil, provides a most sensitive and relevant method for evaluating the in situ toxicity and assessing the risks of soil contaminants.
Site-Specific Recombination-Based Genetic System for Reporting Transient or Low-Level Gene Expression
Authors: Casavant N. Carol , Beattie Gwyn A. , Phillips Gregory J. , Halverson Larry J. 
Published: July 2002

ABSTRACT

We report here the construction, characterization, and application of a plasmid-based genetic system that reports the expression of a target promoter by effecting an irreversible, heritable change in a bacterial cell. This system confers strong repression of the reporter gene
gfp
in the absence of target promoter expression and utilizes the site-specific recombination machinery of bacteriophage P22 to trigger high-level reporter gene expression in the original cell and its progeny after target gene induction. We demonstrate the effectiveness of this genetic system by tailoring it to indicate the availability of arabinose to the biological control agent
Enterobacter cloacae
JL1157 in culture and in the barley rhizosphere. The presence of bioavailable arabinose triggered the production of P22 excisionase and integrase from the reporter plasmid pAraLHB in JL1157, and this led to excision of the
c
I repressor gene, which is flanked by
att
sites, and the subsequent irreversible expression of
gfp
in the original cell and in its progeny. In culture, nearly 100% of an
E. cloacae
JL1157(pAraLHB) population expressed
gfp
after exposure to 6.5 to 65 μM arabinose for 3 h. We used this biosensor to demonstrate that arabinose was released from the seeds of several legumes and grass species during germination and from roots of barley seedlings grown hydroponically or in soil. When introduced into microcosms containing barley, the biosensor permitted the localization of arabinose along the roots. Arabinose was present near the root-seed junction and on the seminal roots but was not detected at the root tips. This recombination-based reporter system should be useful for monitoring bacterial exposure to transient or low levels of specific molecules directly in the environment.
Enrichment Double-Antibody Sandwich Indirect Enzyme-Linked Immunosorbent Assay That Uses a Specific Monoclonal Antibody for Sensitive Detection of
Ralstonia solanacearum
in Asymptomatic Potato Tubers
Authors: Caruso Paola , Gorris María Teresa , Cambra Mariano , Palomo José Luis , Collar Jesús , López María M. 
Published: July 2002

ABSTRACT

Sensitive and specific routine detection of
Ralstonia solanacearum
in symptomless potato tubers was achieved by efficient enrichment followed by a reliable double-antibody sandwich indirect enzyme-linked immunosorbent assay based on the specific monoclonal antibody 8B-IVIA. This monoclonal antibody reacted with 168 typical
R. solanacearum
strains and did not recognize 174 other pathogenic or unidentified bacteria isolated from potato. The optimized protocol included an initial enrichment step consisting of shaking the samples in modified Wilbrink broth for 72 h at 29°C. This step enabled specific detection by the enzyme-linked immunosorbent assay of 1 to 10 CFU of
R. solanacearum
per ml of initial potato extract. Analysis of 233 commercial potato lots by this method provided results that coincided with the results of conventional methods.
Enzymatic Activities of Bovine Peripheral Blood Leukocytes and Milk Polymorphonuclear Neutrophils during Intramammary Inflammation Caused by Lipopolysaccharide
Authors: Prin-Mathieu C. , Le Roux Y. , Faure G. C. , Laurent F. , Béné M. C. , Moussaoui F. 
Published: July 2002

ABSTRACTLeukocytes are recruited from peripheral blood into milk as part of the inflammatory response to mastitis. However, excessive accumulation of inflammatory cells alters the quality of milk and the proteases produced by polymorphonuclear neutrophils (PMNs) and macrophages may lead to mammary tissue damage. To investigate PMN recruitment and the kinetics of their intracytoplasmic enzymes in inflammation, we generated mastitis in six cows by intramammary infusion of lipopolysaccharide (LPS). Clinical signs of acute mastitis were observed in all of the cows, and normal status was resumed by 316 h. Intracytoplasmic elastase, collagenase, and cathepsin activities were measured within live cells by flow cytometry in peripheral blood leukocytes and milk PMNs before and during the inflammatory process (at 10 time points between 4 and 316 h). The proportion of immature PMNs was appreciated by CD33 surface labeling measured in flow cytometry. Leukopenia was observed in the peripheral blood 4 h postinfusion, concomitant to an increase in somatic cell counts in milk. CD33+PMNs were preferentially recruited from the peripheral blood to milk. Enzymatic activities were detected in PMNs, lymphocytes, and monocytes at levels depending on the cell type, sample nature, and time of collection. Milk PMNs had lower enzymatic activities than peripheral blood PMNs. This study showed that milk PMNs recruited during LPS-induced experimental mastitis have an immature phenotype and significantly lower enzymatic activities than peripheral blood PMNs. This suggests that CD33, an adhesion molecule, may be involved in the egress from blood to milk and that the enzymatic contents of PMNs are partly used during this process.
Culture of Protozoan Parasites
Authors: Visvesvara Govinda S. , Garcia Lynne S. 
Published: July 2002

SUMMARY
The in vitro culture of protozoan parasites involves highly complex procedures, which are subject to many variables. These parasites have very complex life cycles and, depending on the life cycle stage, may require different culture parameters. However, in vitro cultivation is important for many reasons, some of which include: diagnosis, antigen and antibody production, assessment of parasite immune modulating capabilities, drug screening, improvements in chemotherapy, differentiation of clinical isolates, determination of strain differences, vaccine production, development of attenuated strains, and the continued supply of viable organisms for studying host-parasite interactions.
Methods for Cultivation of Luminal Parasitic Protists of Clinical Importance
Authors: Clark C. Graham , Diamond Louis S. 
Published: July 2002

SUMMARYCultivation of luminal protistan parasites has a long history. In this review we discuss the methods and media that are most widely used for the establishment and maintenance of the following organisms in culture:Entamoeba histolytica,Giardia intestinalis,Trichomonas vaginalis,Dientamoeba fragilis,Blastocystis hominis, andBalantidium coli. While cultivation is of limited importance in the diagnostic laboratory, it is essential to most research laboratories, and it is toward the latter that this review is primarily aimed.
Vancomycin Resistance in Staphylococci
Authors: Srinivasan Arjun , Dick James D. , Perl Trish M. 
Published: July 2002

SUMMARY

Vancomycin resistance has been reported in clinical isolates of both coagulase-negative staphylococci and
Staphylococcus aureus
. The emerging threat of widespread vancomycin resistance poses a serious public health concern given the fact that vancomycin has long been the preferred treatment of antibiotic-resistant gram-positive organisms. Though major efforts are now being focused on improving our understanding of vancomycin resistance, there is much that remains unknown at this time. This article reviews the major epidemiologic, microbiologic, and clinical characteristics of vancomycin resistance in both coagulase-negative staphylococci and
S. aureus
. The review begins with a discussion of issues common to both coagulase-negative staphylococci and
S. aureus
, such as definitions, laboratory detection of vancomycin resistance, and infection control issues related to vancomycin-resistant staphylococci. The rest of the article is then devoted to a discussion of issues unique to each organism, including epidemiology, risk factors for infection, mechanisms of resistance, and management options.
Current Status of Nonculture Methods for Diagnosis of Invasive Fungal Infections
Authors: Yeo Siew Fah , Wong Brian 
Published: July 2002

SUMMARY
The incidence of invasive fungal infections has increased dramatically in recent decades, especially among immunocompromised patients. However, the diagnosis of these infections in a timely fashion is often very difficult. Conventional microbiologic and histopathologic approaches generally are neither sensitive nor specific, and they often do not detect invasive fungal infection until late in the course of disease. Since early diagnosis may guide appropriate treatment and prevent mortality, there has been considerable interest in developing nonculture approaches to diagnosing fungal infections. These approaches include detection of specific host immune responses to fungal antigens, detection of specific macromolecular antigens using immunologic reagents, amplification and detection of specific fungal nucleic acid sequences, and detection and quantitation of specific fungal metabolite products. This work reviews the current status and recent developments as well as problems in the design of nonculture diagnostic methods for invasive fungal infections.
LeishmaniaPriming of Human Dendritic Cells for CD40 Ligand-Induced Interleukin-12p70 Secretion Is Strain and Species Dependent
Authors: McDowell Mary Ann , Marovich Mary , Lira Rosalia , Braun Michael , Sacks David 
Published: July 2002

ABSTRACTA major question in the study of leishmaniasis is what dictates clinical disease expression produced by differentLeishmaniaspecies, i.e., cutaneous versus systemic and healing versus nonhealing. Animal models using aLeishmaniaspecies associated with self-limiting cutaneous disease (L. major)have revealed that protective immunity requires CD40/CD40 ligand (CD40L)-dependent, interleukin-12 (IL-12)-driven Th1 responses. We recently showed thatL. majorcan prime human dendritic cells (DCs) for CD40L-triggered IL-12p70 secretion and that these cells can drive a Th1 response in autologous T cells from sensitized individuals. Here we show that in contrast toL. major,Leishmaniaspecies responsible for visceral disease (L. donovani), as well as species associated with persistent, cutaneous lesions and occasional systemic disease (L. tropica), did not induce CD40L-dependent IL-12p70 production, despite comparable levels of uptake by DCs. Up-regulated surface expression of CD40 did not correlate with IL-12p70 production, and appreciable CD40L-induced IL-12p40 secretion was observed in uninfected as well as infected DCs, regardless of species. Reverse transcription-PCR analysis confirmed that the production of heterodimeric IL-12 was limited by expression of IL-12p35 mRNA, which was dependent on both a microbial priming signal and CD40 engagement for its high-level induction. The intrinsic differences in the ability ofLeishmaniaspecies to prime DCs for CD40L-dependent IL-12p70 secretion may account, at least in part, for the evolution of healing and nonhealing forms of leishmanial disease.
Salmonella entericaSerovar Typhi Live Vector Vaccines Delivered Intranasally Elicit Regional and Systemic Specific CD8+Major Histocompatibility Class I-Restricted Cytotoxic T Lymphocytes
Authors: Pasetti Marcela F. , Salerno-Gonçalves Rosangela , Sztein Marcelo B. 
Published: July 2002

ABSTRACTWe investigated the ability of live attenuatedSalmonella entericaserovar Typhi strains delivered to mice intranasally to induce specific cytotoxic T-lymphocyte (CTL) responses at regional and systemic levels. Mice immunized with two doses (28 days apart) ofSalmonellaserovar Typhi strain Ty21a, the licensed oral typhoid vaccine, and genetically attenuated mutants CVD 908 (ΔaroCΔaroD), CVD 915 (ΔguaBA), and CVD 908-htrA(ΔaroCΔaroDΔhtrA) induced CTL specific forSalmonellaserovar Typhi-infected cells in spleens and cervical lymph nodes. CTL were detected in effector T cells that had been expanded in vitro for 7 days in the presence ofSalmonella-infected syngeneic splenocytes. A second round of stimulation further enhanced the levels of specific cytotoxicity. CTL activity was observed in sorted αβ+CD8+T cells, which were remarkably increased after expansion, but not in CD4+T cells. CTL from both cervical lymph nodes and spleens failed to recognizeSalmonella-infected major histocompatibility complex (MHC)-mismatched cells, indicating that the responses were MHC restricted. Studies in which MHC blocking antibodies were used showed that H-2Ldwas the restriction element. This is the first demonstration thatSalmonellaserovar Typhi vaccines delivered intranasally elicit CD8+MHC class I-restricted CTL. The results further support the usefulness of the murine intranasal model for evaluating the immunogenicity of typhoid vaccine candidates at the preclinical level.
Phosphoantigen Presentation by Macrophages toMycobacterium tuberculosis-Reactive Vγ9Vδ2+T Cells: Modulation by Chloroquine
Authors: Rojas Roxana E. , Torres Martha , Fournié Jean-Jacques , Harding Clifford V. , Boom W. Henry 
Published: July 2002

ABSTRACTVγ9Vδ2+T cells (γδ T cells) are activated byMycobacterium tuberculosisand recognize mycobacterial nonpeptide phosphoantigens. The role of antigen-presenting cells in the processing and presentation of phosphoantigens to Vγ9Vδ2+T cells is not understood. We analyzed the role of macrophages for activation of γδ T cells by a new synthetic phosphoantigen bromohydrin pyrophosphate (BrHPP) andM. tuberculosis. Macrophages greatly increased γδ T-cell activation by both BrHPP andM. tuberculosis. Fixation of macrophages before infection demonstrated that uptake ofM. tuberculosiswas required for presentation to γδ T cells. Antigens ofM. tuberculosisremained stably associated with macrophage surface and were not removed by paraformaldehyde fixation or washing. Macrophages processedM. tuberculosisfor γδ T cells through a brefeldin A-insensitive pathway, suggesting that transport through the endoplasmic reticulum and Golgi complex of a putative presenting molecule is not important in the early processing ofM. tuberculosisantigens for γδ T cells. Processing ofM. tuberculosiswas not eliminated by chloroquine, indicating that processing of γδ antigens is not dependent on acidic pH in the lysosomes. Chloroquine treatment of BrHPP-pulsed macrophages increased activation of γδ T cells. Ammonium chloride treatment of macrophages did not increase reactivity of γδ T cells to BrHPP, indicating that the effect of chloroquine was independent of pH changes in endosomes. Chloroquine, by inhibiting membrane traffic, may increase association and retention of phosphoantigens with cell surface membrane molecules on macrophages.
Bacterium-Induced CXCL10 Secretion by Osteoblasts Can Be Mediated in Part through Toll-Like Receptor 4
Authors: Gasper Nancy A. , Petty Cynthia C. , Schrum Laura W. , Marriott Ian , Bost Kenneth L. 
Published: July 2002

ABSTRACTTwo common pathogens known to cause bone infection,SalmonellaandStaphylococcus aureus, were investigated to determine their abilities to induce chemokine expression in cultured mouse and human osteoblasts. While these cells are responsible for bone formation, we were surprised to find that they could respond to bacterial infection by upregulating expression of the chemokine CXCL10 (IP-10). However, there were significant differences in the abilities of the gram-negative bacteriumSalmonellaand the gram-positive bacteriumS. aureusto induce expression of CXCL10. Reverse transcription-PCR and enzyme-linked immunosorbent assay analyses showed high levels ofSalmonella-induced CXCL10 mRNA and protein expression, respectively, whereas the osteoblast response toS. aureuswas significantly less. Consistent with these findings,Salmonella-derived lipopolysaccharide (LPS), but notS. aureus-derived peptidoglycan, could induce expression of CXCL10. An antibody against toll-like receptor 4 (TLR4) could block the LPS-induced CXCL10 production, demonstrating the functional expression of TLR4 by osteoblasts. Despite the inducible nature of TLR2 mRNA expression by bacterium-infected osteoblasts, peptidoglycan failed to stimulate CXCL10 secretion. Immunofluorescent staining of bacterium-infected calvaria (i.e., skull bone) demonstrated the presence of CXCL10 in osteoblasts. The fact that osteoblasts did not express CXCR3 mRNA, whereas T lymphocytes can express high levels of this receptor, suggests that osteoblast-derived CXCL10 may recruit T lymphocytes to the sites of bone infections.
Modification of the Structure and Activity of Lipid A inYersinia pestisLipopolysaccharide by Growth Temperature
Authors: Kawahara Kazuyoshi , Tsukano Hiroko , Watanabe Haruo , Lindner Buko , Matsuura Motohiro 
Published: July 2002

ABSTRACTYersinia pestisstrain Yreka was grown at 27 or 37°C, and the lipid A structures (lipid A-27°C and lipid A-37°C) of the respective lipopolysaccharides (LPS) were investigated by matrix-assisted laser desorption ionization-time-of-flight (MALDI-TOF) mass spectrometry. Lipid A-27°C consisted of a mixture of tri-acyl, tetra-acyl, penta-acyl, and hexa-acyl lipid A's, of which tetra-acyl lipid A was most abundant. Lipid A-37°C consisted predominantly of tri- and tetra-acylated molecules, with only small amounts of penta-acyl lipid A; no hexa-acyl lipid A was detected. Furthermore, the amount of 4-amino-arabinose was substantially higher in lipid A-27°C than in lipid A-37°C. By use of mouse and human macrophage cell lines, the biological activities of the LPS and lipid A preparations were measured via their abilities to induce production of tumor necrosis factor alpha (TNF-α). In both cell lines the LPS and the lipid A from bacteria grown at 27°C were stronger inducers of TNF-α than those from bacteria grown at 37°C. However, the difference in activity was more prominent in human macrophage cells. These results suggest that in order to reduce the activation of human macrophages, it may be more advantageous forY. pestisto produce less-acylated lipid A at 37°C.