bluuebunny/crossref_metadata_2025_split huggingface dataset:
Surfactant Protein D Enhances Phagocytosis and Killing of Unencapsulated Phase Variants ofKlebsiella pneumoniae
Authors: Ofek Itzhak , Mesika Adi , Kalina Moshe , Keisari Yona , Podschun Ranier , Sahly Hany , Chang Donald , McGregor David , Crouch Erika 
Published: July 2002

ABSTRACTPulmonary surfactant protein D (SP-D) is a collagenous C-type lectin (collectin) that is secreted into the alveoli and distal airways of the lung. We have studied the interactions of SP-D and alveolar macrophages withKlebsiella pneumoniae, a common cause of nosocomial pneumonia. SP-D does not agglutinate encapsulatedK. pneumoniaebut selectively agglutinates spontaneous, unencapsulated phase variants, such asKlebsiellastrain K50-3OF, through interactions with their lipopolysaccharides (LPS). These effects are calcium dependent and inhibited with maltose but not lactose, consistent with involvement of the SP-D carbohydrate recognition domain. Precoating of K50-3OF with SP-D enhances the phagocytosis and killing of these organisms by rat alveolar macrophages in cell culture and stimulates the production of nitric oxide by the NR-8383 rat alveolar macrophage cell line. SP-D similarly enhances the NO response to K50-3OF LPS adsorbed to Latex beads under conditions where soluble LPS or SP-D, or soluble complexes of SP-D and LPS, do not stimulate NO production. Our studies demonstrate that interactions of SP-D with exposed arrays ofKlebsiellaLPS on a particulate surface can enhance the host defense activities of alveolar macrophages and suggest that activation of macrophages by SP-D requires binding to microorganisms or other particulate ligands. Because unencapsulated phase variants are likely to be responsible for the initial stages of tissue invasion and infection, we speculate that SP-D-mediated agglutination and/or opsonization ofK. pneumoniaeis an important defense mechanism for this respiratory pathogen in otherwise healthy individuals.
TonB-Dependent Systems of UropathogenicEscherichia coli: Aerobactin and Heme Transport and TonB Are Required for Virulence in the Mouse
Authors: Torres Alfredo G. , Redford Peter , Welch Rodney A. , Payne Shelley M. 
Published: July 2002

ABSTRACTThe uropathogenicEscherichia colistrain CFT073 has multiple iron acquisition systems, including heme and siderophore transporters. AtonBmutant derivative of CFT073 failed to use heme as an iron source or to utilize the siderophores enterobactin and aerobactin, indicating that transport of these compounds in CFT073 is TonB dependent. The TonB−derivative showed reduced virulence in a mouse model of urinary tract infection. Virulence was restored when thetonBgene was introduced on a plasmid. To determine the importance of the individual TonB-dependent iron transport systems during urinary tract infections, mutants defective in each of the CFT073 high-affinity iron transport systems were constructed and tested in the mouse model. Mouse virulence assays indicated that mutants defective in a single iron transport system were able to infect the kidney when inoculated as a pure culture but were unable to efficiently compete with the wild-type strain in mixed infections. These results indicate a role for TonB-dependent systems in the virulence of uropathogenicE. colistrains.
Regulatory Effects of Macrophage Inflammatory Protein 1α/CCL3 on the Development of Immunity toCryptococcus neoformansDepend on Expression of Early Inflammatory Cytokines
Authors: Olszewski Michal A. , Huffnagle Gary B. , Traynor Timothy R. , McDonald Roderick A. , Cook Donald N. , Toews Galen B. 
Published: July 2002

ABSTRACTMacrophage inflammatory protein 1α (MIP-1α)/CCL3 prevents the development of eosinophilic pneumonia (EP) driven by a nonprotective T2-type immunity during infection with a highly virulent strain ofCryptococcus neoformans. The present study evaluated the interaction of MIP-1α with other innate immune system cytokines by comparing the immune responses that followed pulmonary infections with high- (C. neoformans145A) and low (C. neoformans52D)-virulence strains. In contrast to what was found forC. neoformans145A infection, lack of MIP-1α inC. neoformans52D infection did not cause the development of EP.C. neoformans52D induced tumor necrosis factor alpha (TNF-α), gamma interferon (IFN-γ), and MCP-1 in the lungs of infected wild-type (WT) and MIP-1α knockout (KO) mice by day 7 postinfection. Both WT and MIP-1α KO mice subsequently cleared this infection. Thus, the robust expression of early inflammatory cytokines inC. neoformans52D-infected mice promoted the development of protective immunity even in the absence of MIP-1α. Alternatively,C. neoformans145A-infected WT and MIP-1α KO mice had diminished TNF-α, IFN-γ, and macrophage chemoattractant protein 1 (MCP-1) responses, indicating that virulentC. neoformans145A evaded early innate host defenses. HoweverC. neoformans145A-infected WT mice had an early induction of MIP-1α and subsequently did not develop EP. In contrast,C. neoformans145A-infected MIP-1α KO mice developed EP and had increasedC. neoformansdissemination into the brain by day 35. We conclude that, in the absence of other innate immune response effector molecules, MIP-1α is crucial to prevent the development of EP and to controlC. neoformansdissemination to the brain.
Molecular Evolution of Large Virulence Plasmid in
Shigella
Clones and Enteroinvasive
Escherichia coli
Authors: Lan Ruiting , Lumb Brad , Ryan David , Reeves Peter R. 
Published: July 2002

ABSTRACT

Three genes,
ipgD, mxiC
, and
mxiA,
all in the invasion region of the
Shigella
virulence plasmid, were sequenced from strains representing a range of
Shigella
serotypes and from two enteroinvasive
Escherichia coli
(EIEC) isolates. The plasmids can be classified into two relatively homogeneous sequence forms which are quite distinct. pINV A plasmids are found in
Shigella flexneri
strains F6 and F6A,
S. boydii
strains B1, B4, B9, B10, B14, and B15,
S. dysenteriae
strains D3, D4, D6, D8, D9, D10, and D13, and the two EIEC strains (M519 and M520). pINV B plasmids are present in
S. flexneri
strains F1A, F2A, F3A, F3C, F4A, and FY, two
S. boydii
strains (B11 and B12), and
S. sonnei
. The D1 pINV plasmid is a recombinant with
ipgD
gene more closely related to those of pINV A but with
mxiA
and
mxiC
genes more closely related to those of pINV B. The phylogenetic relationships of the plasmid and those of the chromosomal genes of
Shigella
strains are largely consistent. The cluster 1 and cluster 3 strains tested (G.M. Pupo, R. Lan, and P. R. Reeves, Proc. Natl. Acad. Sci. USA 97:10567–10572, 2000) have pINV A and pINV B plasmids, respectively. However, of the three cluster 2 strains (B9, B11, and B15), B9 and B15 have pINV A while B11 has a pINV B plasmid. Those
Shigella
(D8 and D10 and
S. sonnei
) and EIEC strains which do not group with the main body of
Shigella
strains based on chromosomal genes were found to have plasmids belonging to one or the other of the two types and must have acquired these by lateral transfer.
Endogenous Interleukin-12 Is Not Required for Resolution ofChlamydophila abortus(Chlamydia psittaciSerotype 1) Infection in Mice
Authors: Del Rı́o Laura , Buendı́a Antonio J. , Sánchez Joaquı́n , Gallego Marı́a C. , Caro Marı́a R. , Ortega Nieves , Seva Juan , Pallarés Francisco J. , Cuello Francisco , Salinas Jesús 
Published: July 2002

ABSTRACTA Th1 immune response involving gamma interferon (IFN-γ) production is required to eliminateChlamydophila abortusinfections. In this study, the role of interleukin-12 (IL-12) in protecting againstC. abortusinfection was investigated using IL-12−/−and wild-type (WT) C57BL/6 mice to determine the role of this Th1-promoting cytokine. IL-12−/−mice were able to eliminate theC. abortusinfection in a primary infection. However, there was a delay in the clearance of bacteria when IL-12−/−mice were infected with a sublethal dose ofC. abortus, the delay being associated with a lower production of IFN-γ. The low level of IFN-γ was essential for survival of IL-12−/−infected mice. Both WT and IL-12−/−mice developed a Th1 immune response againstC. abortusinfection, since they both produced IFN-γ and immunoglobulin G2a antibody isotype. In addition, when mice were given a secondary infectious challenge withC. abortus, a protective host response which resolved the secondary infection was developed by both WT and IL-12−/−mice. The lack of IL-12 resulted in few infiltrating CD4+T cells in the liver relative to the number in WT mice, although the number of CD8+T cells was slightly higher. The more intense Th1 response presented by WT mice may have a pathogenic effect, as the animals showed higher morbidity after the infection. In conclusion, these results suggest that although IL-12 expedites the clearance ofC. abortusinfection, this cytokine is not essential for the establishment of a protective host response against the infection.
Detection of Melanin-Like Pigments in the Dimorphic Fungal PathogenParacoccidioides brasiliensisIn Vitro and during Infection
Authors: Gómez Beatriz L. , Nosanchuk Joshua D. , Dı́ez Soraya , Youngchim Sirida , Aisen Philip , Cano Luz E. , Restrepo Angela , Casadevall Arturo , Hamilton Andrew J. 
Published: July 2002

ABSTRACTMelanins are implicated in the pathogenesis of several human diseases, including some microbial infections. In this study, we analyzed whether the conidia and the yeasts of the thermally dimorphic fungal pathogenParacoccidioides brasiliensisproduce melanin or melanin-like compounds in vitro and during infection. Growth ofP. brasiliensismycelia on water agar alone produced pigmented conidia, and growth of yeasts in minimal medium withl-3,4-dihydroxyphenylalanine (l-DOPA) produced pigmented cells. Digestion of the pigmented conidia and yeasts with proteolytic enzymes, denaturant, and hot concentrated acid yielded dark particles that were the same size and shape as their propagules. Immunofluorescence analysis demonstrated reactivity of a melanin-binding monoclonal antibody (MAb) with the pigmented conidia, yeasts, and particles. Electron spin resonance spectroscopy identified the yeast-derived particles produced in vitro whenP. brasiliensiswas grown inl-DOPA medium as a melanin-like compound. Nonreducing polyacrylamide gel electrophoresis of cytoplasmic yeast extract revealed a protein that catalyzed melanin synthesis froml-DOPA. The melanin binding MAb reacted with yeast cells in tissue from mice infected withP. brasiliensis. Finally digestion of infected tissue liberated particles reactive to the melanin binding MAb that had the typical morphology ofP. brasiliensisyeasts. These data strongly suggest thatP. brasiliensispropagules, both conidia and yeast cells, can produce melanin or melanin-like compounds in vitro and in vivo. Based on what is known about the function of melanin in the virulence of other fungi, this pigment may play a role in the pathogenesis of paracoccidioidomycosis.
Isolation and Properties of Stachyrase A, a Chymotrypsin-Like Serine Proteinase from
Stachybotrys chartarum
Authors: Kordula Tomasz , Banbula Agnieszka , Macomson Jeremy , Travis James 
Published: July 2002

ABSTRACT

A strain of the common mold
Stachybotrys chartarum
has been isolated from the lung of a child with pulmonary hemorrhage. We report the purification of stachyrase A, a new serine chymotrypsin-like proteinase from
S. chartarum
. This enzyme cleaves major protease inhibitors, several biologically active peptides, and collagen, all of which are found in the lung.
Gastritis and Hypergastrinemia Due toAcinetobacter lwoffiiin Mice
Authors: Zavros Y. , Rieder G. , Ferguson Amy , Merchant J. L. 
Published: July 2002

ABSTRACTIn mouse models and humans,Helicobacter pyloriis associated with an increase in serum gastrin and gastrin-expressing (G) cells with a concomitant decrease in somatostatin-expressing D cells. Inflammation of the gastric mucosa can progress to metaplastic changes in the stomach and to decreased colonization byH. pyloriand increased colonization by non-H. pyloriorganisms. In addition, about 20% of individuals with chronic gastritis areH. pylorinegative, suggesting that other organisms may induce gastritis. Consistent with this hypothesis, we report here thatAcinetobacter lwoffiicauses the same histologic changes as doesH. pylori. Gastric epithelial cells were isolated from the entire stomach by an enzymatic method for quantitation by both flow cytometry and morphometric analysis. Two months after mice were inoculated withH. pyloriorA. lwoffii, the mucosal T- and B-cell numbers significantly increased. After 4 months of infection, there was a threefold increase in the number of G cells and a doubling in the number of parietal cells. A threefold decrease in the number of D cells occurred inH. pylori-andA. lwoffii-infected mice. Plasma gastrin levels increased after bothH. pyloriandA. lwoffiiinfection. Histology revealed the presence of inflammation in the gastric mucosa with bothA. lwoffiiandH. pyloriinfection. A periodic acid-Schiff stain-alcian blue stain revealed mucous gland metaplasia of the corpus. Collectively, the results demonstrate that gastritis and hypergastrinemia are not specific forH. pyloribut can be induced by other gram-negative bacteria capable of infecting the mouse stomach.
Initiation of Protein Synthesis in
Saccharomyces cerevisiae
Mitochondria without Formylation of the Initiator tRNA
Authors: Li Yan , Holmes William B. , Appling Dean R. , RajBhandary Uttam L. 
Published: July 2002

ABSTRACT

Protein synthesis in eukaryotic organelles such as mitochondria and chloroplasts is widely believed to require a formylated initiator methionyl tRNA (fMet-tRNA
fMet
) for initiation. Here we show that initiation of protein synthesis in yeast mitochondria can occur without formylation of the initiator methionyl-tRNA (Met-tRNA
fMet
). The formylation reaction is catalyzed by methionyl-tRNA formyltransferase (MTF) located in mitochondria and uses
N
10
-formyltetrahydrofolate (10-formyl-THF) as the formyl donor. We have studied yeast mutants carrying chromosomal disruptions of the genes encoding the mitochondrial C
1
-tetrahydrofolate (C
1
-THF) synthase (
MIS1
), necessary for synthesis of 10-formyl-THF, and the methionyl-tRNA formyltransferase (open reading frame YBL013W; designated
FMT1
). A direct analysis of mitochondrial tRNAs using gel electrophoresis systems that can separate fMet-tRNA
fMet
, Met-tRNA
fMet
, and tRNA
fMet
shows that there is no formylation in vivo of the mitochondrial initiator Met-tRNA in these strains. In contrast, the initiator Met-tRNA is formylated in the respective “wild-type” parental strains. In spite of the absence of fMet-tRNA
fMet
, the mutant strains exhibited normal mitochondrial protein synthesis and function, as evidenced by normal growth on nonfermentable carbon sources in rich media and normal frequencies of generation of
petite
colonies. The only growth phenotype observed was a longer lag time during growth on nonfermentable carbon sources in minimal media for the
mis1
deletion strain but not for the
fmt1
deletion strain.
Entry into and Release of Solvents by
Escherichia coli
in an Organic-Aqueous Two-Liquid-Phase System and Substrate Specificity of the AcrAB-TolC Solvent-Extruding Pump
Authors: Tsukagoshi Norihiko , Aono Rikizo 
Published: July 2002

ABSTRACT

Growth of
Escherichia coli
is inhibited upon exposure to a large volume of a harmful solvent, and there is an inverse correlation between the degree of inhibition and the log
P
OW
of the solvent, where
P
OW
is the partition coefficient measured for the partition equilibrium established between the
n
-octanol and water phases. The AcrAB-TolC efflux pump system is involved in maintaining intrinsic solvent resistance. We inspected the solvent resistance of Δ
acrAB
and/or Δ
tolC
mutants in the presence of a large volume of solvent. Both mutants were hypersensitive to weakly harmful solvents, such as nonane (log
P
OW
= 5.5). The Δ
tolC
mutant was more sensitive to nonane than the Δ
acrAB
mutant. The solvent entered the
E. coli
cells rapidly. Entry of solvents with a log
P
OW
higher than 4.4 was retarded in the parent cells, and the intracellular levels of these solvents were maintained at low levels. The Δ
tolC
mutant accumulated
n
-nonane or decane (log
P
OW
= 6.0) more abundantly than the parent or the Δ
acrAB
mutant. The AcrAB-TolC complex likely extrudes solvents with a log
P
OW
in the range of 3.4 to 6.0 through a first-order reaction. The most favorable substrates for the efflux system were considered to be octane, heptane, and
n
-hexane.
Gene Conservation and Loss in the
mutS-rpoS
Genomic Region of Pathogenic
Escherichia coli
Authors: Herbelin Corinne J. , Chirillo Samantha C. , Melnick Kristen A. , Whittam Thomas S. 
Published: July 2002

ABSTRACT

The extent and nature of DNA polymorphism in the
mutS-rpoS
region of the
Escherichia coli
genome were assessed in 21 strains of enteropathogenic
E. coli
(EPEC) and enterohemorrhagic
E. coli
(EHEC) and in 6 strains originally isolated from natural populations. The intervening region between
mutS
and
rpoS
was amplified by long-range PCR, and the resulting amplicons varied substantially in length (7.8 to 14.2 kb) among pathogenic groups. Restriction maps based on five enzymes and sequence analysis showed that strains of the EPEC 1, EPEC 2, and EHEC 2 groups have a long
mutS-rpoS
region composed of a ∼6.0-kb DNA segment found in strain K-12 and a novel DNA segment (∼2.9 kb) located at the 3′ end of
rpoS
. The novel segment contains three genes (
yclC
,
pad1
, and
slyA
) that occur in
E. coli
O157:H7 and related strains but are not found in K-12 or members of the ECOR group A. Phylogenetic analysis of the common sequences indicates that the long intergenic region is ancestral and at least two separate deletion events gave rise to the shorter regions characteristic of the
E. coli
O157:H7 and K-12 lineages.
Cloning, Characterization, and Inactivation of the Gene
pbpC
, Encoding Penicillin-Binding Protein 3 of
Staphylococcus aureus
Authors: Pinho Mariana G. , de Lencastre Hermínia , Tomasz Alexander 
Published: July 2002

ABSTRACT

The gene
pbpC
from
Staphylococcus aureus
was sequenced: it encodes a 691-amino-acid protein with all of the conserved motifs of a class B high-molecular-weight penicillin-binding protein (PBP), including the transpeptidase conserved motifs SXXK, SXN, and KTG. Insertional inactivation of
pbpC
and introduction of the intact gene in a laboratory mutant missing PBP 3 showed that the
pbpC
gene encodes the staphylococcal PBP 3. Inactivation of
pbpC
caused no detectable change in the muropeptide composition of cell wall peptidoglycan and had only minimum, if any, effect on growth rates, but caused a small but significant decrease in rates of autolysis. Cells of abnormal size and shape and disoriented septa were produced when bacteria with inactivated
pbpC
were grown in the presence of a sub-MIC of methicillin.
Escherichia coli
RNA Polymerase Is the Target of the Cyclopeptide Antibiotic Microcin J25
Authors: Delgado Mónica A. , Rintoul Marı́a R. , Farı́as Ricardo N. , Salomón Raúl A. 
Published: July 2002

ABSTRACT

Escherichia coli
microcin J25 (MccJ25) is a plasmid-encoded, cyclic peptide antibiotic consisting of 21 unmodified amino acid residues. It is primarily active on gram-negative bacteria related to the producer strain, inducing cell filamentation in an SOS-independent way. A mutation causing resistance to MccJ25 was isolated. Genetic analysis indicated that it resided in the
rpoC
gene, encoding the β′ subunit of RNA polymerase, at 90 min on the
E. coli
genetic map. The mutation was genetically crossed on to a plasmid containing the wild-type
rpoC
gene. The presence of the recombinant plasmid conferred complete resistance to otherwise sensitive strains. Nucleotide sequencing of the plasmid-borne, mutant
rpoC
gene revealed a ACC (Thr)-to-ATC (Ile) change at codon 931, within homology block G, an evolutionarily conserved region in the large subunits of all RNA polymerases. MccJ25 decreased RNA synthesis both in vivo and in vitro. These results point to the RNA polymerase as the target of microcin action. We favor the possibility that the filamentous phenotype induced by MccJ25 results from impaired transcription of genes coding for cell division proteins. As far as we know, MccJ25 is the first peptide antibiotic shown to affect RNA polymerase.
Hop Resistance in the Beer Spoilage Bacterium
Lactobacillus brevis
Is Mediated by the ATP-Binding Cassette Multidrug Transporter HorA
Authors: Sakamoto Kanta , Margolles Abelardo , van Veen Hendrik W. , Konings Wil N. 
Published: July 2002

ABSTRACT

Lactobacillus brevis
is a major contaminant of spoiled beer. The organism can grow in beer in spite of the presence of antibacterial hop compounds that give the beer a bitter taste. The hop resistance in
L. brevis
is, at least in part, dependent on the expression of the
horA
gene. The deduced amino acid sequence of HorA is 53% identical to that of LmrA, an ATP-binding cassette multidrug transporter in
Lactococcus lactis
. To study the role of HorA in hop resistance, HorA was functionally expressed in
L. lactis
as a hexa-histidine-tagged protein using the nisin-controlled gene expression system. HorA expression increased the resistance of
L. lactis
to hop compounds and cytotoxic drugs. Drug transport studies with
L. lactis
cells and membrane vesicles and with proteoliposomes containing purified HorA protein identified HorA as a new member of the ABC family of multidrug transporters.
External-pH-Dependent Expression of the Maltose Regulon and
ompF
Gene in
Escherichia coli
Is Affected by the Level of Glycerol Kinase, Encoded by
glpK
Authors: Chagneau Claudia , Heyde Martine , Alonso Sylvie , Portalier Raymond , Laloi Patrick 
Published: July 2002

ABSTRACT

The expression of the maltose system in
Escherichia coli
is regulated at both transcriptional and translational levels by the pH of the growth medium (pHo). With glycerol as the carbon source, transcription of
malT
, encoding the transcriptional activator of the maltose regulon, is weaker in acidic medium than in alkaline medium.
malT
transcription became high, regardless of the pHo, when glycerol-3-phosphate or succinate was used as the carbon source. Conversely,
malT
expression was low, regardless of the pHo, when maltose was used as the carbon source. The increase in
malT
transcription, associated with the pHo, requires the presence of glycerol in the growth medium and the expression of the glycerol kinase (GlpK). Changes in the level of
glpK
transcription had a great effect on
malT
transcription. Indeed, a
glpFKX
promoter-down mutation has been isolated, and in the presence of this mutation,
malT
expression was increased. When
glpK
was expressed from a high-copy-number plasmid, the
glpK
-dependent reduced expression of the maltose system became effective regardless of the pHo. Analysis of this repression showed that a
malTp1 malTp10
promoter, which is independent of the cyclic AMP (cAMP)-cAMP receptor protein (CRP) complex, was no longer repressed by
glpFKX
amplification. Thus, GlpK-dependent repression of the maltose system requires the cAMP-CRP complex. We propose that the pHo may affect a complex interplay between GlpK, the phosphotransferase-mediated uptake of glucose, and the adenylate cyclase.