bluuebunny/crossref_metadata_2025_split huggingface dataset:
Determination of the Genetic Support for
tet
(W) in Oral Bacteria
Authors: Villedieu A. , Roberts A. P. , Allan E. , Hussain H. , McNab R. , Spratt D. A. , Wilson M. , Mullany P. 
Published: March 2007

ABSTRACT

The DNA sequence flanking a
tet
(W) gene in an oral
Rothia
sp. was determined. The gene was linked to two different transposases, and these were flanked by two almost identical
mef
(macrolide efflux) genes. This structure was found in 4 out of 20
tet
(W)-containing oral bacteria investigated.
Cold-Active Chemoorganotrophic Bacteria from Permanently Ice-Covered Lake Hoare, McMurdo Dry Valleys, Antarctica
Authors: Clocksin Kate M. , Jung Deborah O. , Madigan Michael T. 
Published: March 2007

ABSTRACTEight strains of chemoorganotrophic bacteria were isolated from the water column of Lake Hoare, McMurdo Dry Valleys, Antarctica, using cold enrichment temperatures. The isolates wereAlpha-,Beta-, andGammaproteobacteriaandActinobacteriaspp. All isolates grew at 0°C, and all but one grew at subzero temperatures characteristic of the water column of Lake Hoare. Growth temperature optima varied among isolates, but the majority showed optima near 15°C, indicative of cold-active phenotypes. One isolate was truly psychrophilic, growing optimally around 10°C and not above 20°C. Half of the isolates grew at 2% salt while the other half did not, and all but one isolate grew at 2 atm of O2. Our isolates are the first prokaryotes from the water column of Lake Hoare to be characterized phylogenetically and physiologically and show that cold-active species of at least two major phyla ofBacteriainhabit Lake Hoare.
Phylogenetic Diversity and Cosymbiosis in the Bioluminescent Symbioses of “Photobacterium mandapamensis”
Authors: Kaeding Allison J. , Ast Jennifer C. , Pearce Meghan M. , Urbanczyk Henryk , Kimura Seishi , Endo Hiromitsu , Nakamura Masaru , Dunlap Paul V. 
Published: March 2007

ABSTRACT“Photobacterium mandapamensis” (proposed name) andPhotobacterium leiognathiare closely related, phenotypically similar marine bacteria that form bioluminescent symbioses with marine animals. Despite their similarity, however, these bacteria can be distinguished phylogenetically by sequence divergence of their luminescence genes,luxCDAB(F)E, by the presence (P. mandapamensis) or the absence (P. leiognathi) ofluxFand, as shown here, by the sequence divergence of genes involved in the synthesis of riboflavin,ribBHA. To gain insight into the possibility thatP. mandapamensisandP. leiognathiare ecologically distinct, we used these phylogenetic criteria to determine the incidence ofP. mandapamensisas a bioluminescent symbiont of marine animals. Five fish species,Acropoma japonicum(Perciformes, Acropomatidae),Photopectoralis panayensisandPhotopectoralis bindus(Perciformes, Leiognathidae),Siphamia versicolor(Perciformes, Apogonidae), andGadella jordani(Gadiformes, Moridae), were found to harborP. mandapamensisin their light organs. Specimens ofA. japonicus,P. panayensis, andP. bindusharboredP. mandapamensisandP. leiognathitogether as cosymbionts of the same light organ. Regardless of cosymbiosis,P. mandapamensiswas the predominant symbiont ofA. japonicum, and it was the apparently exclusive symbiont ofS. versicolorandG. jordani. In contrast,P. leiognathiwas found to be the predominant symbiont ofP. panayensisandP. bindus, and it appears to be the exclusive symbiont of other leiognathid fishes and a loliginid squid. A phylogenetic test for cospeciation revealed no evidence of codivergence betweenP. mandapamensisand its host fishes, indicating that coevolution apparently is not the basis for this bacterium's host preferences. These results, which are the first report of bacterial cosymbiosis in fish light organs and the first demonstration thatP. leiognathiis not the exclusive light organ symbiont of leiognathid fishes, demonstrate that the host species ranges ofP. mandapamensisandP. leiognathiare substantially distinct. The host range difference underscores possible differences in the environmental distributions and physiologies of these two bacterial species.
Effect of Bovine Manure on Fecal Coliform Attachment to Soil and Soil Particles of Different Sizes
Authors: Guber Andrey K. , Pachepsky Yakov A. , Shelton Daniel R. , Yu Olivia 
Published: March 2007

ABSTRACT
Manure-borne bacteria can be transported in runoff as free cells, cells attached to soil particles, and cells attached to manure particles. The objectives of this work were to compare the attachment of fecal coliforms (FC) to different soils and soil fractions and to assess the effect of bovine manure on FC attachment to soil and soil fractions. Three sand fractions of different sizes, the silt fraction, and the clay fraction of loam and sandy clay loam soils were separated and used along with soil samples in batch attachment experiments with water-FC suspensions and water-manure-FC suspensions. In the absence of manure colloids, bacterial attachment to soil, silt, and clay particles was much higher than the attachment to sand particles having no organic coating. The attachment to the coated sand particles was similar to the attachment to silt and clay. Manure colloids in suspensions decreased bacterial attachment to soils, clay and silt fractions, and coated sand fractions, but did not decrease the attachment to sand fractions without the coating. The low attachment of bacteria to silt and clay particles in the presence of manure colloids may cause predominantly free-cell transport of manure-borne FC in runoff.
Functional Expression of Human Dihydroorotate Dehydrogenase (DHODH) in
pyr4
Mutants of
Ustilago maydis
Allows Target Validation of DHODH Inhibitors In Vivo
Authors: Zameitat Elke , Freymark Gerald , Dietz Cornelia D. , Löffler Monika , Bölker Michael 
Published: March 2007

ABSTRACT

Dihydroorotate dehydrogenase (DHODH; EC 1.3.99.11) is a central enzyme of pyrimidine biosynthesis and catalyzes the oxidation of dihydroorotate to orotate. DHODH is an important target for antiparasitic and cytostatic drugs since rapid cell proliferation often depends on the de novo synthesis of pyrimidine nucleotides. We have cloned the
pyr4
gene encoding mitochondrial DHODH from the basidiomycetous plant pathogen
Ustilago maydis
. We were able to show that
pyr4
contains a functional mitochondrial targeting signal. The deletion of
pyr4
resulted in uracil auxotrophy, enhanced sensitivity to UV irradiation, and a loss of pathogenicity on corn plants. The biochemical characterization of purified
U. maydis
DHODH overproduced in
Escherichia coli
revealed that the
U. maydis
enzyme uses quinone electron acceptor Q
6
and is resistant to several commonly used DHODH inhibitors. Here we show that the expression of the human DHODH gene fused to the
U. maydis
mitochondrial targeting signal is able to complement the auxotrophic phenotype of
pyr4
mutants. While
U. maydis
wild-type cells were resistant to the DHODH inhibitor brequinar, strains expressing the human DHODH gene became sensitive to this cytostatic drug. Such engineered
U. maydis
strains can be used in sensitive in vivo assays for the development of novel drugs specifically targeted at either human or fungal DHODH.
Global Transcriptional Response of
Nitrosomonas europaea
to Chloroform and Chloromethane
Authors: Gvakharia Barbara O. , Permina Elizabeth A. , Gelfand Mikhail S. , Bottomley Peter J. , Sayavedra-Soto Luis A. , Arp Daniel J. 
Published: March 2007

ABSTRACT

Upon exposure of
Nitrosomonas europaea
to chloroform (7 μM, 1 h), transcripts for 175 of 2,460 genes were found at higher levels in treated cells than in untreated cells and transcripts for 501 genes were found at lower levels. With chloromethane (3.2 mM, 1 h), transcripts for 67 genes were at higher levels and transcripts for 148 genes were at lower levels. Transcripts for 37 genes were at higher levels following both treatments and included genes for heat shock proteins, σ-factors of the extracytoplasmic function subfamily, and toxin-antitoxin loci.
N. europaea
has higher levels of transcripts for a variety of defense genes when exposed to chloroform or chloromethane.
Elucidation of theipso-Substitution Mechanism for Side-Chain Cleavage of α-Quaternary 4-Nonylphenols and 4-t-Butoxyphenol inSphingobium xenophagumBayram
Authors: Gabriel Frédéric L. P. , Cyris Maike , Jonkers Niels , Giger Walter , Guenther Klaus , Kohler Hans-Peter E. 
Published: March 2007

ABSTRACTRecently we showed that degradation of several nonylphenol isomers with α-quaternary carbon atoms is initiated byipso-hydroxylation inSphingobium xenophagumBayram (F. L. P. Gabriel, A. Heidlberger, D. Rentsch, W. Giger, K. Guenther, and H.-P. E. Kohler, J. Biol. Chem. 280:15526-15533, 2005). Here, we demonstrate with18O-labeling experiments that theipso-hydroxy group was derived from molecular oxygen and that, in the major pathway for cleavage of the alkyl moiety, the resulting nonanol metabolite contained an oxygen atom originating from water and not from theipso-hydroxy group, as was previously assumed. Our results clearly show that the alkyl cation derived from the α-quaternary nonylphenol 4-(1-ethyl-1,4-dimethyl-pentyl)-phenol throughipso-hydroxylation and subsequent dissociation of the 4-alkyl-4-hydroxy-cyclohexadienone intermediate preferentially combines with a molecule of water to yield the corresponding alcohol and hydroquinone. However, the metabolism of certain α,α-dimethyl-substituted nonylphenols appears to also involve a reaction of the cation with theipso-hydroxy group to form the corresponding 4-alkoxyphenols. Growth, oxygen uptake, and18O-labeling experiments clearly indicate that strain Bayram metabolized 4-t-butoxyphenol byipso-hydroxylation to a hemiketal followed by spontaneous dissociation to the corresponding alcohol andp-quinone. Hydroquinone effected high oxygen uptake in assays with induced resting cells as well as in assays with cell extracts. This further corroborates the role of hydroquinone as the ring cleavage intermediate during degradation of 4-nonylphenols and 4-alkoxyphenols.
Temporal Expression Analysis of the
Borrelia burgdorferi
Paralogous Gene Family 54 Genes BBA64, BBA65, and BBA66 during Persistent Infection in Mice
Authors: Gilmore Robert D. , Howison Rebekah R. , Schmit Virginia L. , Nowalk Andrew J. , Clifton Dawn R. , Nolder Christi , Hughes Jessica L. , Carroll James A. 
Published: March 2007

ABSTRACT

Members of the
Borrelia burgdorferi
paralogous gene family 54 (pgf 54) are regulated by conditions simulating mammalian infection and are thought to be instrumental in borrelial host survival and pathogenesis. To explore the activities of these genes in vivo, a comprehensive analysis of pgf 54 genes BBA64, BBA65, and BBA66 was performed to assess the genetic stability, host antibody responses, and kinetics of gene expression in the murine model of persistent infection. DNA sequencing of pgf 54 genes obtained from reisolates at 1 year postinfection demonstrated that all genes of this family are stable and do not undergo recombination to generate variant antigens during persistent infection. Antibodies against BBA64 and BBA66 appeared soon after infection and were detectable throughout the infection, suggesting that there was gene expression during infection. However, quantitative reverse transcription-PCR revealed that BBA64 gene expression was considerably decreased in
Borrelia
residing in the mouse ear tissue compared to the expression in cultured spirochetes by 20 days postinfection and that the levels of expression remained low throughout the infection. Conversely, transcription of the BBA65 and BBA66 genes was increased, and both of these genes were continuously expressed until 100 days postinfection; this was followed by periods of differential expression late in infection. The expression profile of the BBA64 gene suggests that this gene has an important role during tick-to-host transmission and early infection, whereas the expression profile of the BBA65 and BBA66 genes suggests that these genes have a role in persistent infection. The differential regulation of pgf 54 genes observed during infection may help confer a survival advantage during persistent infection, influencing mechanisms for
B. burgdorferi
dissemination, tissue tropism, or evasion of the adaptive immune response.
Moraxella catarrhalisStrain O35E Expresses Two Filamentous Hemagglutinin-Like Proteins That Mediate Adherence to Human Epithelial Cells
Authors: Balder Rachel , Hassel Jonathan , Lipski Serena , Lafontaine Eric R. 
Published: March 2007

ABSTRACTTwo-partner secretion (TPS) systems are a family of proteins being rapidly identified and characterized in a growing number of gram-negative bacteria. TPS systems mediate the secretion of proteins, many involved in virulence traits such as hemolysis, adherence to epithelial cells, inhibition of bacterial growth, and immunomodulation of the host. A TPS system typically consists of a transporter located in the bacterial outer membrane (OM) which is responsible for the recognition and secretion of at least one large exoprotein. Two of the better-characterized TPS systems specify theBordetella pertussisFHA andHaemophilus influenzaeHMW1/HMW2 proteins. We identified three gene products ofMoraxella catarrhalisstrain O35E that resemble TPS proteins and designated them MhaC (transporter), MhaB1 (exoprotein), and MhaB2 (exoprotein). Western blot analysis using anti-MhaC, or antibodies reacting to both MhaB1 and MhaB2 (MhaB-reactive), revealed that these antigens are expressed in the OM of 63% of isolates tested. Mutations in themhaCgene specifying the putative transporter of theM. catarrhaliswild-type strains O35E, O12E, and McGHS1 resulted in the absence of MhaB1/MhaB2 in the OM of mutants. These results are therefore consistent with the Mha proteins functioning as a TPS system. Furthermore, we discovered that thesemhaCmutants exhibit markedly decreased binding to human epithelial cells relevant to pathogenesis byM. catarrhalis(Chang, HEp2, A549, and/or 16HBE14o−). Expression of O12E MhaC and MhaB1 in a nonadherent strain ofEscherichia coliwas found to increase the adherence of recombinant bacteria to HEp2 monolayers by sevenfold, thereby demonstrating that thisM. catarrhalisTPS system directly mediates binding to human epithelial cells. The construction of isogenic mutants in themhaB1andmhaB2genes of strain O35E also suggests that the MhaB proteins play distinct roles inM. catarrhalisadherence.
The Relative Susceptibility of Mouse Strains to PulmonaryCryptococcus neoformansInfection Is Associated with Pleiotropic Differences in the Immune Response
Authors: Zaragoza Oscar , Alvarez Mauricio , Telzak Andrew , Rivera Johanna , Casadevall Arturo 
Published: March 2007

ABSTRACTCBA/J mice were highly susceptible to intratracheal (i.t.)Cryptococcus neoformansinfection relative to BALB/c mice, while both strains were equally susceptible to intravenous (i.v.) infection. Increased susceptibility in i.t. infection was associated with higher brain CFU, lower serum immunoglobulin M (IgM) and IgG responses to glucuronoxylomannan (GXM), lack of IgE regulation during infection, and alveolar macrophage permissiveness to intracellular replication in vitro. In contrast, for BALB/c mice, relative resistance was associated with increased interleukin-12 (IL-12) and decreased IL-10 pulmonary levels. In CBA/J mice, relative susceptibility was associated with a decreased proportion of CD4+and CD8+T cells and an increase in macrophage percentage in pulmonary infiltrates. In contrast, no significant differences in these cytokines or cell recruitment were observed in the i.v. model, consistent with no differences in the survival rate. Passive antibody (Ab) protection experiments revealed a prozone effect in the BALB/c mice with i.v. infection, such that Ab efficacy decreased at higher doses. In the i.t. model using CBA/J mice, low Ab doses were disease enhancing and protection was observed only at high doses. Our results show (i) that differences in mouse strain susceptibility are a function of the infection model, (ii) that susceptibility to pulmonary infection was associated with macrophage permissiveness for intracellular replication, and (iii) that the efficacy of passive Ab in pulmonary infection is a function of dose and mouse strain. The results highlight significant differences in the pathogenesis of cryptococcal infection among inbred mice and associate their relative susceptibility with differences in numerous components of the innate and adaptive immune responses.
Transcutaneous Immunization withClostridium difficileToxoid A Induces Systemic and Mucosal Immune Responses and Toxin A-Neutralizing Antibodies in Mice
Authors: Ghose Chandrabali , Kalsy Anuj , Sheikh Alaullah , Rollenhagen Julianne , John Manohar , Young John , Rollins Sean M. , Qadri Firdausi , Calderwood Stephen B. , Kelly Ciaran P. , Ryan Edward T. 
Published: March 2007

ABSTRACTClostridium difficileis the leading cause of nosocomial infectious diarrhea.C. difficileproduces two toxins (A and B), and systemic and mucosal anti-toxin A antibodies prevent or limitC. difficile-associated diarrhea. To evaluate whether transcutaneous immunization with formalin-treatedC. difficiletoxin A (CDA) induces systemic and mucosal anti-CDA immune responses, we transcutaneously immunized three cohorts of mice with CDA with or without immunoadjuvantative cholera toxin (CT) on days 0, 14, 28, and 42. Mice transcutaneously immunized with CDA and CT developed prominent anti-CDA and anti-CT immunoglobulin G (IgG) and IgA responses in serum and anti-CDA and anti-CT IgA responses in stool. Sera from immunized mice were able to neutralizeC. difficiletoxin A activity in an in vitro cell culture assay. CDA itself demonstrated adjuvant activity and enhanced both serum and stool anti-CT IgA responses. Our results suggest that transcutaneous immunization with CDA toxoid may be a feasible immunization strategy againstC. difficile, an important cause of morbidity and mortality against which current preventative strategies are failing.
Infection of Mice with Lyme Disease Spirochetes Constitutively Producing Outer Surface Proteins A and B
Authors: Strother Keith O. , Hodzic Emir , Barthold Stephen W. , de Silva Aravinda M. 
Published: March 2007

ABSTRACT

Outer surface protein A (OspA) of the Lyme disease spirochete is primarily produced in the tick vector. OspA, which is a receptor for attaching spirochetes to the tick gut, is down regulated as the spirochetes leave the tick and enter the mammalian host. Although OspA is not a major antigen produced in the mammal, the protein appears to be produced under some conditions and production has been linked to more severe disease. A Lyme disease vaccine based on recombinant OspA has been approved for human use. However, the vaccine is no longer available, in part because of fears that OspA causes arthritis in people. To further understand the consequences of OspA production in the host, we created a
Borrelia burgdorferi
mutant that was unable to down regulate OspA. C3H/HeN mice infected with this mutant developed a specific anti-OspA immune response, and the spirochetes were unable to persist in these mice. In contrast, immunodeficient SCID mice were persistently infected with the mutant. We conclude that spirochetes producing OspA and B from the
flaB
promoter in immunocompetent mice stimulate an immune response that clear the bacteria without any signs of disease development in the mice.
The
pyrH
Gene of
Vibrio vulnificus
Is an Essential In Vivo Survival Factor
Authors: Lee Shee Eun , Kim Soo Young , Kim Choon Mee , Kim Mi-Kwang , Kim Young Ran , Jeong Kwangjoon , Ryu Hwa-Ja , Lee Youn Suhk , Chung Sun Sik , Choy Hyon E. , Rhee Joon Haeng 
Published: March 2007

ABSTRACT

We have suggested an important role of the
pyrH
gene during the infectious process of
Vibrio vulnificus.
Previously, we have identified 12 genes expressed preferentially during human infections by using in vivo-induced antigen technology. Among the in vivo-expressed genes,
pyrH
encodes UMP kinase catalyzing UMP phosphorylation. Introduction of a deletion mutation to the
pyrH
gene was lethal to
V. vulnificus
, and an insertional mutant showed a high frequency of curing. We constructed a site-directed mutant strain (R62H/D77N) on Arg-62 and Asp-77, both predicted to be involved in UMP binding, and characterized the R62H/D77N strain compared with the previously reported insertional mutant. We further investigated the essential role of the
pyrH
gene in the establishment of infection using the R62H/D77N strain. Cytotoxicity was decreased in the R62H/D77N strain, and the defect was restored by an in
trans
complementation. The intraperitoneal 50% lethal dose of the R62H/D77N strain increased by 26- and 238,000-fold in normal and iron-overloaded mice, respectively. The growth of the R62H/D77N strain in 50% HeLa cell lysate, 100% human ascitic fluid, and 50% human serum was significantly retarded compared to that of the isogenic wild-type strain. The R62H/D77N mutant also had a critical defect in the ability to survive and replicate even in iron-overloaded mice. These results demonstrate that
pyrH
is essential for the in vivo survival and growth of
V. vulnificus
and should be an attractive new target for the development of antibacterial drugs and replication-controllable live attenuated vaccines.
Flagella Promote
Escherichia coli
K1 Association with and Invasion of Human Brain Microvascular Endothelial Cells
Authors: Parthasarathy G. , Yao Y. , Kim K. S. 
Published: March 2007

ABSTRACT

Escherichia coli
containing the K1 capsule is the leading cause of gram-negative meningitis, but the pathogenesis of this disease is not completely understood. Recent microarray experiments in which we compared the gene expression profile of
E. coli
K1 associated with human brain microvascular endothelial cells (HBMEC) to the gene expression profile of
E. coli
K1 not associated with HBMEC revealed that there was a threefold increase in the expression of the
fliI
gene, encoding an ATP synthase involved in flagellar synthesis and motility, in HBMEC-associated
E. coli
. In this study, we examined the role of flagella in
E. coli
K1 association with and invasion of HBMEC by constructing isogenic Δ
flhDC
, Δ
fliI
, Δ
fliC
, and Δ
cheW
mutants that represented each class of flagellar genes. Mutations that affected the flagellum structure and flagellum formation (Δ
flhDC
, Δ
fliI
, and Δ
fliC
) resulted in significant defects in motility, as well as in HBMEC association and invasion, compared to the characteristics of the wild-type strain when preparations were examined with or without centrifugation. Transcomplementation with the corresponding genes restored the levels of these mutants to the levels of the parent strain. These findings suggest that the HBMEC association and invasion defects of the mutants are most likely related to flagella and less likely due to their motility defects. This conclusion was supported by our demonstration that the
cheW
mutant was not motile but was able to associate with and invade HBMEC. In addition, purified recombinant flagellin reduced the association of the wild-type strain with HBMEC by ∼40%, while it had no effect on the
fliC
mutant's association with HBMEC. Together, these findings indicate that flagella promote
E. coli
K1 binding to HBMEC.