bluuebunny/crossref_metadata_2025_split huggingface dataset:
Development of Operating Temperature Prediction Method Using Thermophysical Properties Change of Thermal Barrier Coatings
Authors: Fujii T. , Takahashi T. 
Published: March 2004

Abstract
Thermal barrier coatings (TBCs) have become an indispensable technology as the temperature of turbine inlet gas has increased. TBCs reduce the temperature of the base metal, but a reduction of internal pores by sintering occurs when using TBCs, and so the thermal barrier performance of TBCs is deteriorated. This in turn increases the temperature of the base metal and could shorten its lifespan. The authors have already clarified by laboratory acceleration tests that the deterioration of the thermal barrier performance of TBCs is caused by a decrease in the noncontact area that exists inside TBCs. This noncontact area is a slit space that exists between thin layers and is formed when TBCs are coated. This paper examines the relations between the decrease of the noncontact area and the exposure conditions, by measuring the thermal conductivity and the porosity of TBCs exposed to the temperatures that exist in an actual gas turbine, and derives the correlation with exposure conditions. As a result, very high correlations were found between the thermal conductivity and exposure conditions of TBCs, and between the porosity and exposure conditions. A very high correlation was also found between the thermal conductivity and porosity of TBCs. In addition, techniques for predicting TBC operating temperature were examined by using these three correlations. The correlation of diameter and exposure conditions of the gamma prime phase, which exists in nickel base super alloys, is used as a general method for predicting the temperature of parts in hot gas paths. This paper proposes two kinds of operating temperature prediction methods, which are similar to this general method. The first predicts the operating temperature from thermal conductivity measurements of TBCs before and after use, and the second predicts the operating temperature from thermal conductivity measurements of TBCs after use and porosity measurements before use. The TBC operating temperatures of a combustor that had been used for 12,000 hours with an actual E-class gas turbine were predicted by these two methods. The advantage of these methods is that the temperature of all parts with TBC can be predicted.
Role of a Cysteine Synthase in
Staphylococcus aureus
Authors: Lithgow James K. , Hayhurst Emma J. , Cohen Gerald , Aharonowitz Yair , Foster Simon J. 
Published: March 2004

ABSTRACT

The gram-positive human pathogen
Staphylococcus aureus
is often isolated with media containing potassium tellurite, to which it has a higher level of resistance than
Escherichia coli
. The
S. aureus cysM
gene was isolated in a screen for genes that would increase the level of tellurite resistance of
E. coli
DH5α. The protein encoded by
S. aureus cysM
is sequentially and functionally homologous to the
O
-acetylserine (thiol)-lyase B family of cysteine synthase proteins. An
S. aureus cysM
knockout mutant grows poorly in cysteine-limiting conditions, and analysis of the thiol content in cell extracts showed that the
cysM
mutant produced significantly less cysteine than wild-type
S. aureus
SH1000.
S. aureus
SH1000 cannot use sulfate, sulfite, or sulfonates as the source of sulfur in cysteine biosynthesis, which is explained by the absence of genes required for the uptake and reduction of these compounds in the
S. aureus
genome.
S. aureus
SH1000, however, can utilize thiosulfate, sulfide, or glutathione as the sole source of sulfur. Mutation of
cysM
caused increased sensitivity of
S. aureus
to tellurite, hydrogen peroxide, acid, and diamide and also significantly reduced the ability of
S. aureus
to recover from starvation in amino acid- or phosphate-limiting conditions, indicating a role for cysteine in the
S. aureus
stress response and survival mechanisms.
H Protein of Bacteriophage
16-3
and RkpM Protein of
Sinorhizobium meliloti
41 Are Involved in Phage Adsorption
Authors: Putnoky Péter , Deák Veronika , Békási Krisztina , Pálvölgyi Adrienn , Maász Anita , Palágyi Zsuzsanna , Hoffmann Gyula , Kerepesi Ildikó 
Published: March 2004

ABSTRACT

The strain-specific capsular polysaccharide KR5 antigen of
Sinorhizobium meliloti
41 is required both for invasion of the symbiotic nodule and for the adsorption of bacteriophage
16-3
. In order to know more about the genes involved in these events, bacterial mutants carrying an altered phage receptor were identified by using host range phage mutants. A representative mutation was localized in the
rkpM
gene by complementation and DNA sequence analysis. A host range phage mutant isolated on these phage-resistant bacteria was used to identify the
h
gene, which is likely to encode the tail fiber protein of phage
16-3
. The nucleotide sequences of the
h
gene as well as a host range mutant allele were also established. In both the bacterial and phage mutant alleles, a missense mutation was found, indicating a direct contact between the RkpM and H proteins in the course of phage adsorption. Some mutations could not be localized in these genes, suggesting that additional components are also important for bacteriophage receptor recognition.
A Subassembly of R27-Encoded Transfer Proteins Is Dependent on TrhC Nucleoside Triphosphate-Binding Motifs for Function but Not Formation
Authors: Gilmour Matthew W. , Taylor Diane E. 
Published: March 2004

ABSTRACTThe transfer of plasmid DNA molecules between bacterial cells is achieved by a large array of conjugative transfer proteins which assemble into both cytoplasmic and membrane-associated complexes. TrhC is a membrane-associated protein that is required for the transfer of the IncHI1 resistance plasmid R27. Homologous proteins are encoded in all known conjugative systems, and each contains characteristic nucleoside triphosphate (NTP)-binding domains. An assembly of R27-encoded proteins was previously visualized by use of a TrhC-green fluorescent protein fusion, which appeared as discrete membrane-associated fluorescent foci. We have utilized this experimental system to determine the requirements for assembly of this TrhC-associated protein complex, and we found that 12 of the other 18 R27 transfer proteins are required for focus formation. An individual focus possibly represents a subassembly comprised of some or all of these transfer proteins. These data support the notion that the transfer apparatus is a multicomponent structure. In contrast, substitutions and deletions within TrhC NTP-binding motifs had minor effects on focus formation, but these mutations did affect plasmid transfer and bacteriophage susceptibility. These results indicate that TrhC requires intact NTP-binding motifs to function during conjugative transfer but that these motifs are not essential for the assembly of TrhC into a complex with other transfer proteins.
Molybdenum-Containing Arsenite Oxidase of the Chemolithoautotrophic Arsenite Oxidizer NT-26
Authors: Santini Joanne M. , vanden Hoven Rachel N. 
Published: March 2004

ABSTRACT

The chemolithoautotroph NT-26 oxidizes arsenite to arsenate by using a periplasmic arsenite oxidase. Purification and preliminary characterization of the enzyme revealed that it (i) contains two heterologous subunits, AroA (98 kDa) and AroB (14 kDa); (ii) has a native molecular mass of 219 kDa, suggesting an α
2
β
2
configuration; and (iii) contains two molybdenum and 9 or 10 iron atoms per α
2
β
2
unit. The genes that encode the enzyme have been cloned and sequenced. Sequence analyses revealed similarities to the arsenite oxidase of
Alcaligenes faecalis
, the putative arsenite oxidase of the beta-proteobacterium ULPAs1, and putative proteins of
Aeropyrum pernix
,
Sulfolobus tokodaii
, and
Chloroflexus aurantiacus
. Interestingly, the AroA subunit was found to be similar to the molybdenum-containing subunits of enzymes in the dimethyl sulfoxide reductase family, whereas the AroB subunit was found to be similar to the Rieske iron-sulfur proteins of cytochrome
bc
1
and
b
6
f
complexes. The NT-26 arsenite oxidase is probably exported to the periplasm via the Tat secretory pathway, with the AroB leader sequence used for export. Confirmation that NT-26 obtains energy from the oxidation of arsenite was obtained, as an
aroA
mutant was unable to grow chemolithoautotrophically with arsenite. This mutant could grow heterotrophically in the presence of arsenite; however, the arsenite was not oxidized to arsenate.
The Tricarballylate Utilization (
tcuRABC
) Genes of
Salmonella enterica
Serovar Typhimurium LT2
Authors: Lewis Jeffrey A. , Horswill Alexander R. , Schwem Brian E. , Escalante-Semerena Jorge C. 
Published: March 2004

ABSTRACT

The genes of
Salmonella enterica
serovar Typhimurium LT2 encoding functions needed for the utilization of tricarballylate as a carbon and energy source were identified and their locations in the chromosome were established. Three of the tricarballylate utilization (
tcu
) genes,
tcuABC
, are organized as an operon; a fourth gene,
tcuR
, is located immediately 5′ to the
tcuABC
operon. The
tcuABC
operon and
tcuR
gene share the same direction of transcription but are independently transcribed. The
tcuRABC
genes are missing in the
Escherichia coli
K-12 chromosome. The
tcuR
gene is proposed to encode a regulatory protein needed for the expression of
tcuABC
. The
tcuC
gene is proposed to encode an integral membrane protein whose role is to transport tricarballylate across the cell membrane.
tcuC
function was sufficient to allow
E. coli
K-12 to grow on citrate (a tricarballylate analog) but not to allow growth of this bacterium on tricarballylate.
E. coli
K-12 carrying a plasmid with wild-type alleles of
tcuABC
grew on tricarballylate, suggesting that the functions of the TcuABC proteins were the only ones unique to
S. enterica
needed to catabolize tricarballylate. Analyses of the predicted amino acid sequences of the TcuAB proteins suggest that TcuA is a flavoprotein, and TcuB is likely anchored to the cell membrane and probably contains one or more Fe-S centers. The TcuB protein is proposed to work in concert with TcuA to oxidize tricarballylate to
cis-
aconitate, which is further catabolized via the Krebs cycle. The glyoxylate shunt is not required for growth of
S. enterica
on tricarballylate. A model for tricarballylate catabolism in
S. enterica is
proposed.
Temperature Regulation of the Hemin Storage (Hms
+
) Phenotype of
Yersinia pestis
Is Posttranscriptional
Authors: Perry Robert D. , Bobrov Alexander G. , Kirillina Olga , Jones Heather A. , Pedersen Lisa , Abney Jennifer , Fetherston Jacqueline D. 
Published: March 2004

ABSTRACT

In
Yersinia pestis
, the Congo red (and hemin) binding that is characteristic of the Hms
+
phenotype occurs at temperatures up to 34°C but not at higher temperatures. Manifestation of the Hms
+
phenotype requires at least five proteins (HmsH, -F, -R, -S, and -T) that are organized into two separate operons:
hmsHFRS
and
hmsT.
HmsH and HmsF are outer membrane proteins, while HmsR, HmsS, and HmsT are predicted to be inner membrane proteins. We have used transcriptional reporter constructs, RNA dot blots, and Western blots to examine the expression of
hms
operons and proteins. Our studies indicate that transcription from the
hmsHFRS
and
hmsT
promoters is not regulated by the iron status of the cells, growth temperature, or any of the Hms proteins. In addition, the level of mRNA for both operons is not significantly affected by growth temperature. However, protein levels of HmsH, HmsR, and HmsT in cells grown at 37°C are very low compared to those in cells grown at 26°C, while the amounts of HmsF and HmsS show only a moderate reduction at the higher growth temperature. Neither the Pla protease nor a putative endopeptidase (Y2360) encoded upstream of
hmsH
is essential for temperature regulation of the Hms
+
phenotype. However, HmsT at 37°C is sensitive to degradation by Lon and/or ClpPX. Thus, the stability of HmsH, HmsR, and HmsT proteins likely plays a role in temperature regulation of the Hms
+
phenotype of
Y. pestis
.
Proteome Analyses of Heme-Dependent Respiration inLactococcus lactis: Involvement of the Proteolytic System
Authors: Vido Karin , le Bars Dominique , Mistou Michel-Yves , Anglade Patricia , Gruss Alexandra , Gaudu Philippe 
Published: March 2004

ABSTRACTSugar fermentation was long considered the sole means of energy metabolism available to lactic acid bacteria. We recently showed that metabolism ofLactococcus lactisshifts progressively from fermentation to respiration during growth when oxygen and heme are available. To provide insights into this phenomenon, we compared the proteomic profiles ofL. lactisunder fermentative and respiratory growth conditions in rich medium. We identified 21 proteins whose levels differed significantly between these conditions. Two major groups of proteins were distinguished, one involved in carbon metabolism and the second in nitrogen metabolism. Unexpectedly, enzymes of the proteolytic system (PepO1 and PepC) which are repressed in rich medium in fermentation growth were induced under respiratory conditions despite the availability of free amino acids. A triple mutant (dtpT dtpP oppA) deficient in oligopeptide transport displayed normal respiration, showing that increased proteolytic activity is not an absolute requirement for respiratory metabolism. Transcriptional analysis confirmed thatpepO1is induced under respiration-permissive conditions. This induction was independent of CodY, the major regulator of proteolytic functions inL. lactis. We also observed thatpepO1induction is redox sensitive. In acodYmutant,pepO1expression was increased twofold in aeration and eightfold in respiration-permissive conditions compared to static conditions. These observations suggest that new regulators activate proteolysis inL. lactis, which help to maintain the energetic needs ofL. lactisduring respiration.
The
Legionella pneumophila
PilT Homologue DotB Exhibits ATPase Activity That Is Critical for Intracellular Growth
Authors: Sexton Jessica A. , Pinkner Jerome S. , Roth Robyn , Heuser John E. , Hultgren Scott J. , Vogel Joseph P. 
Published: March 2004

ABSTRACT

The ability of
Legionella pneumophila
to grow and cause disease in the host is completely dependent on a type IV secretion system known as the Dot/Icm complex. This membrane-spanning apparatus translocates effector molecules into host cells in a process that is poorly understood but that is known to require the putative ATPase DotB. One possible role for DotB is suggested by its similarity to the PilT family of proteins, which mediate pilus retraction. To better understand the molecular behavior of DotB, we have purified the protein and shown that it forms stable homohexameric rings and hydrolyzes ATP with a specific activity of 6.4 nmol of ATP/min/mg of protein. ATPase activity is critical to the function of DotB, as alteration of the conserved Walker box lysine residue resulted in a mutant protein, DotB K162Q, which failed to bind or hydrolyze ATP and which could not complement a Δ
dotB
strain for intracellular growth in macrophages. Consistent with the ability of DotB to interact with itself, the
dotBK162Q
allele exhibited transdominance over wild-type
dotB
, providing the first example of such a mutation in
L. pneumophila
. Finally, the DotB K162Q mutant protein had a significantly enhanced membrane localization in
L. pneumophila
compared to wild-type DotB, suggesting a relationship between nucleotide binding and membrane association. These results are consistent with a model in which DotB cycles between the cytoplasm and the Dot/Icm complex at the membrane, where it hydrolyzes nucleotides to provide energy to the complex.
Thermoprotection of
Bacillus subtilis
by Exogenously Provided Glycine Betaine and Structurally Related Compatible Solutes: Involvement of Opu Transporters
Authors: Holtmann Gudrun , Bremer Erhard 
Published: March 2004

ABSTRACT

Bacillus subtilis
possesses five osmotically regulated transporters (Opu) for the uptake of various compatible solutes for osmoprotective purposes. We have now found that compatible solutes also function as thermoprotectants for
B. subtilis
. Low concentrations of glycine betaine enhanced the growth of the
B. subtilis
wild-type strain JH642 at its maximal growth temperature (52°C) but did not allow an extension of the upper growth limit. A similar enhancement in the growth of
B. subtilis
was also observed by the addition of several other compatible solutes that are structurally related to glycine betaine or by the addition of proline. Each of these compatible solutes was taken up under heat stress by the cell through the same Opu transporters that are used for their acquisition under osmostress conditions. Northern blot analysis revealed a moderate increase in transcription of the structural genes for each of the Opu transport systems in cells that were propagated at 52°C. In contrast, the uptake level of radiolabeled glycine betaine was very low under high-temperature growth conditions but nevertheless allowed the buildup of an intracellular glycine betaine pool comparable to that found in cells grown at 37°C in the absence of salt stress. Although exogenously added glutamate has only a limited osmoprotective potential for
B. subtilis
, it was found to be a very effective thermoprotectant. Collectively, our data demonstrate thermoprotection by a variety of compatible solutes in
B. subtilis
, thus ascribing a new physiological function for this class of compounds in this microorganism and broadening the physiological role of the known osmoprotectant uptake systems (Opu).
Role of
murE
in the Expression of β-Lactam Antibiotic Resistance in
Staphylococcus aureus
Authors: Gardete S. , Ludovice A. M. , Sobral R. G. , Filipe S. R. , de Lencastre H. , Tomasz A. 
Published: March 2004

ABSTRACT

It was shown earlier that Tn
551
inserted into the C-terminal region of
murE
of parental methicillin-resistant
Staphylococcus aureus
strain COL causes a drastic reduction in methicillin resistance, accompanied by accumulation of UDP-MurNAc dipeptide in the cell wall precursor pool and incorporation of these abnormal muropeptides into the peptidoglycan of the mutant. Methicillin resistance was recovered in a suppressor mutant. The
murE
gene of the same strain was then put under the control of the isopropyl-β-
d
-thiogalactopyranoside (IPTG)-inducible promoter P

spac

. Bacteria grown in the presence of suboptimal concentrations of IPTG accumulated UDP-MurNAc dipeptide in the cell wall precursor pool. Both growth rates and methicillin resistance levels (but not resistance to other antibiotics) were a function of the IPTG concentration. Northern analysis showed a gradual increase in the transcription of
murE
and also in the transcription of
pbpB
and
mecA
, parallel with the increasing concentrations of IPTG in the medium. A similar increase in the transcription of
pbpB
and
mecA
, the structural genes of penicillin-binding protein 2 (PBP2) and PBP2A, was also detected in the suppressor mutant. The expression of these two proteins, which are known to play critical roles in the mechanism of staphylococcal methicillin resistance, appears to be—directly or indirectly—under the control of the
murE
gene. Our data suggest that the drastic reduction of the methicillin MIC seen in the
murE
mutant may be caused by the insufficient cellular amounts of these two PBPs.
A −1 Ribosomal Frameshift in the Transcript That Encodes the Major Head Protein of Bacteriophage A2 Mediates Biosynthesis of a Second Essential Component of the Capsid
Authors: García Pilar , Rodríguez Isabel , Suárez Juan E. 
Published: March 2004

ABSTRACTThe two major capsid proteins ofLactobacillusbacteriophage A2 share their amino termini. The smaller of these (gp5A) results from translation oforf5and proteolytic processing after residue 123. The larger form (gp5B) originates through a −1 ribosomal frameshift at the penultimate codon oforf5mRNA, resulting in a product that is 85 amino acids longer than gp5A. Frameshifting needs twocis-acting elements: a slippery region with the sequence C CCA AAA (0 frame), and a stem-loop that begins 9 nucleotides after the end of the slippery sequence. Mutations introduced in the slippery sequence suppress the frameshift. Similarly, deletion of the second half of the stem-loop results in drastic reduction of frameshifting. Both gp5A and gp5B appear to be essential for phage viability, since lysogens harboring prophages that produce only one or the other protein become lysed upon induction with mitomycin C, though no viable phage progeny are observed.
Light Control ofhliATranscription and Transcript Stability in the CyanobacteriumSynechococcus elongatusStrain PCC 7942
Authors: Salem Kavitha , van Waasbergen Lorraine G. 
Published: March 2004

ABSTRACTThe high-light-inducible proteins (HLIPs) of cyanobacteria are polypeptides involved in protecting the cells from high-intensity light (HL). ThehliAgene encoding the HLIP fromSynechococcus elongatusstrain PCC 7942 is expressed in response to HL or low-intensity blue or UV-A light. In this study, we explore via Northern analysis details of the transcriptional regulation and transcript stability of thehliAgene under various light conditions. Transcript levels of thehliAgene increased dramatically upon a shift to HL or UV-A light to similar levels, followed by a rapid decrease in UV-A light, but not in HL, consistent with blue/UV-A light involvement in early stages of HL-mediated expression. A 3-min pulse of low-intensity UV-A light was enough to triggerhliAmRNA accumulation, indicating that a blue/UV-A photoreceptor is involved in upregulation of the gene. Low-intensity red light was found to cause a slight, transient increase in transcript levels (raising the possibility of red-light photoreceptor involvement), while light of other qualities had no apparent effect. No evidence was found for wavelength-specific attenuation ofhliAtranscript levels induced by HL or UV-A light. Transcript decay was slowed somewhat in darkness, and when photosynthetic electron transport was inhibited by darkness or treatment with DCMU, there appeared a smaller mRNA species that may represent a decay intermediate that accumulates when mRNA decay is slowed. Evidence suggests that upregulation ofhliAby light is primarily a transcriptional response but conditions that cause ribosomes to stall on the transcript (e.g., a shift to darkness) can help stabilizehliAmRNA and affect expression levels.