bluuebunny/crossref_metadata_2025_split huggingface dataset:
Susceptibilities of
Mycoplasma fermentans
and
Mycoplasma hyorhinis
to Membrane-Active Peptides and Enrofloxacin in Human Tissue Cell Cultures
Authors: Nir-Paz Ran , Prévost Marie-Christine , Nicolas Pierre , Blanchard Alain , Wróblewski Henri 
Published: July 2002

ABSTRACT

Mycoplasmas, which are bacteria that are devoid of a cell wall and which belong to the class
Mollicutes
, are pathogenic for humans and animals and are frequent contaminants of tissue cell cultures. Although contamination of cultures with mycoplasma can easily be monitored with fluorescent dyes that stain DNA and/or with molecular probes, protection and decontamination of cultures remain serious challenges. In the present work, we investigated the susceptibilities of
Mycoplasma fermentans
and
Mycoplasma hyorhinis
to the membrane-active peptides alamethicin, dermaseptin B2, gramicidin S, and surfactin by growth inhibition and lethality assays. In the absence of serum, the four peptides killed mycoplasmas at minimal bactericidal concentrations that ranged from 12.5 to 100 μM, but in all cases the activities were decreased by the presence of serum. As a result, under standard culture conditions (10% serum) only alamethicin and gramicidin S were able to inhibit mycoplasma growth (MICs, 50 μM), while dermaseptin B2 and surfactin were ineffective. Furthermore, 8 days of treatment of HeLa cell cultures experimentally contaminated with either mycoplasma species with 70 μM enrofloxacin cured the cultures of infection, whereas treatment with alamethicin and gramicidin S alone was not reliable because the concentrations and treatment times required were toxic to the cells. However, combination of alamethicin or gramicidin S with 70 μM enrofloxacin allowed mycoplasma eradication after 30 min or 24 h of treatment, depending on the mycoplasma and peptide considered. HeLa cell cultures experimentally infected with mycoplasmas should prove to be a useful model for study of the antimycoplasma activities of antibiotics and membrane-active peptides under conditions close to those found in vivo.
Change in Colony Morphology of
Candida lusitaniae
in Association with Development of Amphotericin B Resistance
Authors: McClenny Nancy B. , Fei Haihua , Baron Ellen J. , Gales Ana C. , Houston Allison , Hollis Richard J. , Pfaller Michael A. 
Published: July 2002

ABSTRACT

It is not uncommon to see amphotericin B treatment failure in patients with systemic infection caused by
Candida lusitaniae
. We report a patient with stage IV ovarian carcinoma and
C. lusitaniae
sepsis whose treatment with amphotericin B failed. The initial blood isolate was susceptible to amphotericin B in vitro; however, the MIC for a blood isolate recovered 7 weeks after treatment began showed a fourfold increase. Direct subculture of two positive blood samples obtained within a week of the patient's death showed the coexistence of two distinct colony color variants on CHROMagar Candida (CAC). One variant was susceptible to amphotericin B, and one was resistant. These results emphasize the importance of repeat amphotericin B susceptibility testing for patients with persistent
C. lusitaniae
infection. The presence of colony variants on CAC may signal the emergence of amphotericin B resistance in
C. lusitaniae
and should be investigated.
Mefloquine and New Related Compounds Target the F0Complex of the F0F1H+-ATPase ofStreptococcus pneumoniae
Authors: Martín-Galiano Antonio Javier , Gorgojo Begoña , Kunin Calvin M. , de la Campa Adela G. 
Published: July 2002

ABSTRACTThe activities of mefloquine (MFL) and related compounds against previously characterizedStreptococcus pneumoniaestrains carrying defined amino acid substitutions in thecsubunit of the F0F1H+-ATPase were studied. In addition, a series of MFL-resistant (Mflr) strains were isolated and characterized. A good correlation was observed between inhibition of growth and inhibition of the membrane-associated F0F1H+-ATPase activity. MFL was about 10-fold more active than optochin and about 200-fold more active than quinine in inhibiting both the growth and the ATPase activities of laboratory pneumococcal strain R6. Mutant strains were inhibited by the different compounds to different degrees, depending on their specific mutations in thecsubunit. The resistant strains studied had point mutations that changed amino acid residues in either thecsubunit or theasubunit of the F0complex. Changes in thecsubunit were located in one of the two transmembrane α helices: residues M13, G14, G20, M23, and N24 of helix 1 and residues M44, G47, V48, A49, and V57 of helix 2. Changes in theasubunit were also found in either of the transmembrane α helices, helix 5 or 6: residue L186 of helix 5 and residues W206, F209, and S214 of helix 6. These results suggest that the transmembrane helices of thecandasubunits interact and that the mutated residues are important for the structure of the F0complex and proton translocation.
In Vitro Activities of Pentamidine, Pyrimethamine, Trimethoprim, and Sulfonamides against
Aspergillus
Species
Authors: Afeltra Javier , Meis Jacques F. G. M. , Vitale Roxana G. , Mouton Johan W. , Verweij Paul E. 
Published: July 2002

ABSTRACT

The susceptibilities of 70 strains of
Aspergillus
species were tested against seven different sulfa drugs and pentamidine by a microdilution method with RPMI 1640 and yeast nitrogen base media. Sulfamethoxazole, sulfadiazine, and pentamidine were active in vitro. The MICs obtained with RPMI 1640 were significantly higher than those with yeast nitrogen base. More studies are needed to further elucidate the action of these drugs.
Lentivirus Lytic Peptide 1 Perturbs both Outer and Inner Membranes of
Serratia marcescens
Authors: Phadke Shruti M. , Lazarevic Vanja , Bahr Caroline C. , Islam Kazi , Stolz Donna Beer , Watkins Simon , Tencza Sarah B. , Vogel Hans J. , Montelaro Ronald C. , Mietzner Timothy A. 
Published: July 2002

ABSTRACT

Bis-lentivirus lytic protein 1 (Bis-LLP1) and polymyxin B exhibited similar killing activities against
Serratia marcescens
. By electron microscopy, bis-LLP1 interacted with the outer and cytoplasmic bacterial membranes, while polymyxin B affected only the outer membrane. The results of standard biochemical probes supported the findings of the electron microscopy studies, suggesting that these antimicrobial peptides have different mechanisms of action.
Characterization of
Cryptosporidium parvum
by Matrix-Assisted Laser Desorption Ionization–Time of Flight Mass Spectrometry
Authors: Magnuson Matthew L. , Owens James H. , Kelty Catherine A. 
Published: July 2002

ABSTRACT

Matrix-assisted laser desorption ionization–time of flight mass spectrometry (MALDI-TOF MS) was used to investigate whole and freeze-thawed
Cryptosporidium parvum
oocysts. Whole oocysts revealed some mass spectral features. Reproducible patterns of spectral markers and increased sensitivity were obtained after the oocysts were lysed with a freeze-thaw procedure. Spectral-marker patterns for
C. parvum
were distinguishable from those obtained for
Cryptosporidium muris
. One spectral marker appears specific for the genus, while others appear specific at the species level. Three different
C. parvum
lots were investigated, and similar spectral markers were observed in each. Disinfection of the oocysts reduced and/or eliminated the patterns of spectral markers.
Anaerobic Degradation of 2-Methylnaphthalene by a Sulfate-Reducing Enrichment Culture
Authors: Annweiler Eva , Materna Arne , Safinowski Michael , Kappler Andreas , Richnow Hans H. , Michaelis Walter , Meckenstock Rainer U. 
Published: July 2002

ABSTRACT

Anaerobic degradation of 2-methylnaphthalene was investigated with a sulfate-reducing enrichment culture. Metabolite analyses revealed two groups of degradation products. The first group comprised two succinic acid adducts which were identified as naphthyl-2-methyl-succinic acid and naphthyl-2-methylene-succinic acid by comparison with chemically synthesized reference compounds. Naphthyl-2-methyl-succinic acid accumulated to 0.5 μM in culture supernatants. Production of naphthyl-2-methyl-succinic acid was analyzed in enzyme assays with dense cell suspensions. The conversion of 2-methylnaphthalene to naphthyl-2-methyl-succinic acid was detected at a specific activity of 0.020 ± 0.003 nmol min
−1
mg of protein
−1
only in the presence of cells and fumarate. We conclude that under anaerobic conditions 2-methylnaphthalene is activated by fumarate addition to the methyl group, as is the case in anaerobic toluene degradation. The second group of metabolites comprised 2-naphthoic acid and reduced 2-naphthoic acid derivatives, including 5,6,7,8-tetrahydro-2-naphthoic acid, octahydro-2-naphthoic acid, and decahydro-2-naphthoic acid. These compounds were also identified in an earlier study as products of anaerobic naphthalene degradation with the same enrichment culture. A pathway for anaerobic degradation of 2-methylnaphthalene analogous to that for anaerobic toluene degradation is proposed.
Application of Neural Computing Methods for Interpreting Phospholipid Fatty Acid Profiles of Natural Microbial Communities
Authors: Noble Peter A. , Almeida Jonas S. , Lovell Charles R. 
Published: July 2002

ABSTRACT

The microbial community compositions of surface and subsurface marine sediments and sediments lining burrows of marine polychaetes and hemichordates from the North Inlet estuary (near Georgetown, S.C.) were analyzed by comparing ester-linked phospholipid fatty acid (PLFA) profiles with a back-propagating neural network (NN). The NNs were trained to relate PLFA inputs to sediment type outputs (e.g., surface, subsurface, and burrow lining) and worm species (e.g.,
Notomastus lobatus
,
Balanoglossus aurantiacus
, and
Branchyoasychus americana
). Sensitivity analysis was used to determine which of the 60 PLFAs significantly contributed to training the NN. The NN architecture was optimized by changing the number of hidden neurons and calculating the cross-validation error between predicted and actual outputs of training and test data. The optimal NN architecture was found to be four hidden neurons with 60-input neurons representing the 60 PLFAs, and four output neurons coding for both sediment types and worm species. Comparison of cross-validation results using NNs and linear discriminant analysis (LDA) revealed that NNs had significantly fewer incorrect classifications (2.7%) than LDA (8.4%). For the NN cross-validation, both sediment type and worm species had 3 incorrect classifications out of 112. For the LDA cross-validation, sediment type and worm species had 7 and 12 incorrect classifications out of 112, respectively. Sensitivity analysis of the trained NNs revealed that 17 fatty acids explained 50% of variability in the data set. These PLFAs were highly different among sediments and burrow types, indicating significant differences in the microbiota.
Reactivation of Insertionally Inactivated Shiga Toxin 2 Genes of
Escherichia coli
O157:H7 Caused by Nonreplicative Transposition of the Insertion Sequence
Authors: Kusumoto Masahiro , Nishiya Yoshiaki , Kawamura Yoshihisa 
Published: July 2002

ABSTRACT

IS
1203
v is an insertion sequence which has been found in inactivated Shiga toxin 2 genes of
Escherichia coli
O157:H7. We analyzed the transpositional mechanism of IS
1203
v in order to investigate whether the Shiga toxin 2 genes inactivated by IS
1203
v could revert to the wild type. When the transposase activity of IS
1203
v was enhanced by artificial frameshifting, IS
1203
v was obviously excised from the Shiga toxin 2 gene in a circular form. The IS
1203
v circle consisted of the entire IS
1203
v, but an extra 3-bp sequence (ATC) intervened between the 5′ and 3′ ends of IS
1203
v. The extra 3-bp sequence was identical to a direct repeat which was probably generated upon insertion. Moreover, we detected the Shiga toxin 2 gene with a precise excision of IS
1203
v. In the wild-type situation, the transposition products of IS
1203
v could be observed by PCR amplification. These results show that IS
1203
v can transpose in a nonreplicative manner and that the Shiga toxin gene inactivated by this insertion sequence can revert to the wild type.
The Secondary Endosymbiotic Bacterium of the Pea AphidAcyrthosiphon pisum(Insecta: Homoptera)
Authors: Fukatsu Takema , Nikoh Naruo , Kawai Rena , Koga Ryuichi 
Published: July 2002

ABSTRACTThe secondary intracellular symbiotic bacterium (S-symbiont) of the pea aphidAcyrthosiphon pisumwas investigated to determine its prevalence among strains, its phylogenetic position, its localization in the host insect, its ultrastructure, and the cytology of the endosymbiotic system. A total of 14 aphid strains were examined, and the S-symbiont was detected in 4 Japanese strains by diagnostic PCR. Two types of eubacterial 16S ribosomal DNA sequences were identified in disymbiotic strains; one of these types was obtained from the primary symbiontBuchnerasp., and the other was obtained from the S-symbiont. In situ hybridization and electron microscopy revealed that the S-symbiont was localized not only in the sheath cells but also in a novel type of cells, the secondary mycetocytes (S-mycetocytes), which have not been found previously inA. pisum. The size and shape of the S-symbiont cells were different when we compared the symbionts in the sheath cells and the symbionts in the S-mycetocytes, indicating that the S-symbiont is pleomorphic under different endosymbiotic conditions. Light microscopy, electron microscopy, and diagnostic PCR revealed unequivocally that the hemocoel is also a normal location for the S-symbiont. Occasional disordered localization of S-symbionts was also observed in adult aphids, suggesting that there has been imperfect host-symbiont coadaptation over the short history of coevolution of these organisms.
Fate of Nitrate Acquired by the Tubeworm
Riftia pachyptila
Authors: Girguis Peter R. , Lee Raymond W. , Desaulniers Nicole , Childress James J. , Pospesel Mark , Felbeck Horst , Zal Franck 
Published: July 2002

ABSTRACT

The hydrothermal vent tubeworm
Riftia pachyptila
lacks a mouth and gut and lives in association with intracellular, sulfide-oxidizing chemoautotrophic bacteria. Growth of this tubeworm requires an exogenous source of nitrogen for biosynthesis, and, as determined in previous studies, environmental ammonia and free amino acids appear to be unlikely sources of nitrogen. Nitrate, however, is present in situ (K. Johnson, J. Childress, R. Hessler, C. Sakamoto-Arnold, and C. Beehler, Deep-Sea Res. 35:1723–1744, 1988), is taken up by the host, and can be chemically reduced by the symbionts (U. Hentschel and H. Felbeck, Nature 366:338–340, 1993). Here we report that at an in situ concentration of 40 μM, nitrate is acquired by
R. pachyptila
at a rate of 3.54 μmol g
−1
h
−1
, while elimination of nitrite and elimination of ammonia occur at much lower rates (0.017 and 0.21 μmol g
−1
h
−1
, respectively). We also observed reduction of nitrite (and accordingly nitrate) to ammonia in the trophosome tissue. When
R. pachyptila
tubeworms are exposed to constant in situ conditions for 60 h, there is a difference between the amount of nitrogen acquired via nitrate uptake and the amount of nitrogen lost via nitrite and ammonia elimination, which indicates that there is a nitrogen “sink.” Our results demonstrate that storage of nitrate does not account for the observed stoichiometric differences in the amounts of nitrogen. Nitrate uptake was not correlated with sulfide or inorganic carbon flux, suggesting that nitrate is probably not an important oxidant in metabolism of the symbionts. Accordingly, we describe a nitrogen flux model for this association, in which the product of symbiont nitrate reduction, ammonia, is the primary source of nitrogen for the host and the symbionts and fulfills the association's nitrogen needs via incorporation of ammonia into amino acids.
Polyamine Composition and Expression of Genes Related to Polyamine Biosynthesis in an Aphid Endosymbiont,
Buchnera
Authors: Nakabachi Atsushi , Ishikawa Hajime 
Published: July 2002

ABSTRACT

Polyamine composition in an aphid endosymbiotic bacterium,
Buchnera
sp., was determined by high-performance liquid chromatographic analysis. We found that
Buchnera
contained virtually only a single polyamine, spermidine. The spermidine content of
Buchnera
was considerably higher in young aphids and tended to decrease with the age of the host. Expression of
speD
and
speE
, whose gene products are key enzymes in the synthesis of spermidine, was analyzed by real-time quantitative reverse transcription-PCR. It was shown that the levels of their mRNAs fluctuated in line with the spermidine content.
Chlamydophila abortus
in a Brown Skua (
Catharacta antarctica lonnbergi
) from a Subantarctic Island
Authors: Herrmann Björn , Rahman Rubaiyat , Bergström Sven , Bonnedahl Jonas , Olsen Björn 
Published: July 2002

ABSTRACT

On Bird Island, South Georgia, a new strain of
Chlamydophila abortus
was detected in one Brown skua out of 37 specimens from six different seabird species. Phylogenetic analysis of the
rnpB
and
omp1
genes indicated the strain to be more closely related to
C. abortus
than to 6BC, the type strain of
Chlamydophila psittaci
.
Starvation Alters the Apparent Half-Saturation Constant for Methane in the Type II Methanotroph
Methylocystis
Strain LR1
Authors: Dunfield Peter F. , Conrad Ralf 
Published: July 2002

ABSTRACT

When cells of a type II methanotrophic bacterium (
Methylocystis
strain LR1) were starved of methane, both the
K

m
(app)

and the
V
max(app)
for methane decreased. The specific affinity (

a
o
s

) remained nearly constant. Therefore, the decreased
K

m
(app)

in starved cells was probably not an adjustment to better utilize low-methane concentrations.
Detection of Indigenous
Halobacillus
Populations in Damaged Ancient Wall Paintings and Building Materials: Molecular Monitoring and Cultivation
Authors: Piñar Guadalupe , Ramos Cayo , Rölleke Sabine , Schabereiter-Gurtner Claudia , Vybiral Dietmar , Lubitz Werner , Denner Ewald B. M. 
Published: July 2002

ABSTRACT

Several moderately halophilic gram-positive, spore-forming bacteria have been isolated by conventional enrichment cultures from damaged medieval wall paintings and building materials. Enrichment and isolation were monitored by denaturing gradient gel electrophoresis and fluorescent in situ hybridization. 16S ribosomal DNA analysis showed that the bacteria are most closely related to
Halobacillus litoralis
. DNA-DNA reassociation experiments identified the isolates as a population of hitherto unknown
Halobacillus
species.
Oral Toxicity of
Photorhabdus
luminescens
W14 Toxin Complexes in
Escherichia
coli
Authors: Waterfield Nicholas , Dowling Andrea , Sharma Sadhana , Daborn Phillip J. , Potter Ursula , Ffrench-Constant Richard H. 
Published: July 2002

ABSTRACT

Previous attempts to express the toxin complex genes of
Photorhabdus
luminescens
W14 in
Escherichia
coli
have failed to reconstitute their oral toxicity to the model insect
Manduca
sexta
. Here we show that the combination of three genes,
tcdA
,
tcdB
, and
tccC
, is essential for oral toxicity to
M
.
sexta
when expression in
E
.
coli
is used. Further, when transcription from native toxin complex gene promoters is used, maximal toxicity in
E
.
coli
cultures is associated with the addition of mitomycin C to the growth medium. In contrast, the expression of
tcdAB
(or the homologous
tcaABC
operon) with no recombinant
tccC
homolog in a different
P
.
luminescens
strain, K122, is sufficient to confer oral toxicity on this strain, which is otherwise not orally toxic. We therefore infer that
P
.
luminescens
K122 carries a functional
tccC
-like homolog within its own genome, a hypothesis supported by Southern analysis. Recombinant toxins from both
P
.
luminescens
K122 and
E
.
coli
were purified as high-molecular-weight particulate preparations. Transmission electron micrograph (TEM) images of these particulate preparations showed that the expression of
tcdAB
(either with or without
tccC
) in
E
.
coli
produces visible ∼25-nm-long complexes with a head and tail-like substructure. These data are consistent with a model whereby TcdAB constitutes the majority of the complex visible under TEM and TccC either is a toxin itself or is an activator of the complex. The implications for the potential mode of action of the toxin complex genes are discussed.
Regulation of the Packaging of
Bacillus thuringiensis
δ-Endotoxins into Inclusions
Authors: Chang Lily , Grant Rian , Aronson Arthur 
Published: July 2002

ABSTRACT

During sporulation, many
Bacillus thuringiensis
subspecies synthesize several related δ-endotoxins which are packaged into bipyramidal intracellular inclusions. These inclusions are solubilized in the alkaline, reducing conditions of the midguts of susceptible insect larvae and are converted by proteolysis to active toxins. The toxins insert into the membranes of cells lining the midgut and form cation-selective channels, which results in lethality. There are three δ-endotoxins, Cry1Ab3, Cry1Ca1, and Cry1Da1, present in the inclusions produced by a
B. thuringiensis
subsp.
aizawai
cell. While the ratio of the steady-state mRNAs for these three protoxins has been shown to differ (
cry1Ab3/cry1Ca1/cry1Da1
mRNA ratio, 4:2:1), the half-lives of the
cry1Da1
and
cry1Ab3
mRNAs were found to be similar, indicating that there were differences in the transcription rates. The relative contents of these δ-endotoxins in purified inclusions from
B. thuringiensis
subsp.
aizawai
have been measured previously, and an even greater relative deficiency of the Cry1Da1 protoxin (ratio, 20:12:1) was found. In order to account for this deficiency, other steps which could be involved in inclusion formation, such as translation and packaging, were examined. The three
cry
genes have the same dual overlapping promoters, but the ribosome binding sequence for the
cry1Da1
gene was not the consensus sequence. Translation was enhanced about fourfold by changing to the consensus sequence. In addition, the relative amount of Cry1Da1 protoxin in inclusions was twofold lower when cells were sporulated in Luria-Bertani (LB) medium than when cells were sporulated in a glucose-yeast extract medium. This difference was attributable to packaging since the relative amounts of Cry1Da1 antigen in cells sporulating in the two media were the same. Some factor(s) required for packaging of the Cry1Da1 protoxin in inclusions is apparently limiting in LB medium. Differences in the initial transcription rates, translation efficiencies, and packaging all contribute to the δ-endotoxin composition of an inclusion.
Detection and Quantification of Methyl
tert
-Butyl Ether-Degrading Strain PM1 by Real-Time TaqMan PCR
Authors: Hristova Krassimira R. , Lutenegger Christian M. , Scow Kate M. 
Published: July 2002

ABSTRACT

The fuel oxygenate methyl
tert
-butyl ether (MTBE), a widely distributed groundwater contaminant, shows potential for treatment by in situ bioremediation. The bacterial strain PM1 rapidly mineralizes and grows on MTBE in laboratory cultures and can degrade the contaminant when inoculated into groundwater or soil microcosms. We applied the TaqMan quantitative PCR method to detect and quantify strain PM1 in laboratory and field samples. Specific primers and probes were designed for the 16S ribosomal DNA region, and specificity of the primers was confirmed with DNA from 15 related bacterial strains. A linear relationship was measured between the threshold fluorescence (
C

T

) value and the quantity of PM1 DNA or PM1 cell density. The detection limit for PM1 TaqMan assay was 2 PM1 cells/ml in pure culture or 180 PM1 cells/ml in a mixture of PM1 with
Escherichia coli
cells. We could measure PM1 densities in solution culture, groundwater, and sediment samples spiked with PM1 as well as in groundwater collected from an MTBE bioaugmentation field study. In a microcosm biodegradation study, increases in the population density of PM1 corresponded to the rate of removal of MTBE.