bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of Water Activities of Heating and Recovery Media on Apparent Heat Resistance of
Bacillus cereus
Spores
Authors: Coroller Louis , Leguérinel Ivan , Mafart Pierre 
Published: July 2002

ABSTRACT

Spores of
Bacillus cereus
were heated and recovered in order to investigate the effect of water activity of media on the estimated heat resistance (i.e., the D value) of spores. The water activity (ranging from 0.9 to 1) of the heating medium was first successively controlled with three solutes (glycerol, glucose, and sucrose), while the water activity of the recovery medium was kept near 1. Reciprocally, the water activity of the heating medium was then kept at 1, while the water activity of the recovery medium was controlled from 0.9 to 1 with the same depressors. Lastly, in a third set of experiments, the heating medium and the recovery medium were adjusted to the same activity. As expected, added depressors caused an increase of the heat resistance of spores with a greater efficiency of sucrose with respect to glycerol and glucose. In contrast, when solutes were added to the recovery medium, under an optimal water activity close to 0.98, a decrease of water activity caused a decrease in the estimated D values. This effect was more pronounced when sucrose was used as a depressor instead of glycerol or glucose. When the heating and the recovery media were adjusted to the same water activity, a balancing effect was observed between the protective influence of the solutes during heat treatment and their negative effect during the recovery of injured cells, so that the overall effect of water activity was reduced, with an optimal value near 0.96. The difference between the efficiency of depressors was also less pronounced. It may then be concluded that the overall protective effect of a decrease in water activity is generally overestimated.
The Green Fluorescent Protein Gene Functions as a Reporter of Gene Expression in
Phanerochaete chrysosporium
Authors: Ma Biao , Mayfield Mary B. , Gold Michael H. 
Published: July 2002

ABSTRACT

The enhanced green fluorescent protein (GFP) gene (
egfp
) was used as a reporter of gene expression driven by the glyceraldehyde-
p
-dehydrogenase (
gpd
) gene promoter and the manganese peroxidase isozyme 1 (
mnp1
) gene promoter in
Phanerochaete chrysosporium
. Four different constructs were prepared. pUGGM3′ and pUGiGM3′ contain the
P. chrysosporium gpd
promoter fused upstream of the
egfp
coding region, and pUMGM3′ and pUMiGM3′ contain the
P. chrysosporium mnp1
promoter fused upstream of the
egfp
gene. In all constructs, the
egfp
gene was followed by the
mnp1
gene 3′ untranslated region. In pUGGM3′ and pUMGM3′, the promoters were fused directly with
egfp
, whereas in pUGiGM3′ and pUMiGM3′, following the promoters, the first exon (6 bp), the first intron (55 bp), and part of the second exon (9 bp) of the
gpd
gene were inserted at the 5′ end of the
egfp
gene. All constructs were ligated into a plasmid containing the
ura1
gene of
Schizophyllum commune
as a selectable marker and were used to transform a Ural1 auxotrophic strain of
P. chrysosporium
to prototrophy. Crude cell extracts were examined for GFP fluorescence, and where appropriate, the extracellular fluid was examined for MnP activity. The transformants containing a construct with an intron 5′ of the
egfp
gene (pUGiGM3′ and pUMiGM3′) exhibited maximal fluorescence under the appropriate conditions. The transformants containing constructs with no introns exhibited minimal or no fluorescence. Northern (RNA) blots indicated that the insertion of a 5′ intron resulted in more
egfp
RNA than was found in transformants carrying an intronless
egfp
. These results suggest that the presence of a 5′ intron affects the expression of the
egfp
gene in
P. chrysosporium
. The expression of GFP in the transformants carrying pUMiGM3′ paralled the expression of endogenous
mnp
with respect to nitrogen and Mn levels, suggesting that this construct will be useful in studying
cis
-acting elements in the
mnp1
gene promoter.
Specificity and Mode of Action of the Antifungal Fatty Acid
cis
-9-Heptadecenoic Acid Produced by
Pseudozyma flocculosa
Authors: Avis Tyler J. , Bélanger Richard R. 
Published: July 2002

ABSTRACT

cis
-9-Heptadecenoic acid (CHDA), an antifungal fatty acid produced by the biocontrol agent
Pseudozyma flocculosa
, was studied for its effects on growth and/or spore germination in fungi. Inhibition of growth and/or germination varied considerably and revealed CHDA sensitivity groups within tested fungi. Analysis of lipid composition in these fungi demonstrated that sensitivity was related primarily to a low intrinsic sterol content and that a high level of unsaturation of phospholipid fatty acids was not as involved as hypothesized previously. Our data indicate that CHDA does not act directly with membrane sterols, nor is it utilized or otherwise modified in fungi. A structural mechanism of CHDA, consistent with the other related antifungal fatty acids produced by
P. flocculosa
, is proposed in light of its activity and specificity. The probable molecular events implicated in the sensitivity of fungi to CHDA are (i) partitioning of CHDA into fungal membranes; (ii) a variable elevation in fluidity dependent on the buffering capability (sterol content) in fungi; and (iii) higher membrane disorder causing conformational changes in membrane proteins, increased membrane permeability and, eventually, cytoplasmic disintegration.
Biotransformation of
d
-Limonene to (+)
trans
-Carveol by Toluene-Grown
Rhodococcus opacus
PWD4 Cells
Authors: Duetz Wouter A. , Fjällman Ann H. M. , Ren Shuyu , Jourdat Catherine , Witholt Bernard 
Published: July 2002

ABSTRACT

The toluene-degrading strain
Rhodococcus opacus
PWD4 was found to hydroxylate
d
-limonene exclusively in the 6-position, yielding enantiomerically pure (+)
trans
-carveol and traces of (+) carvone. This biotransformation was studied using cells cultivated in chemostat culture with toluene as a carbon and energy source. The maximal specific activity of (+)
trans
-carveol formation was 14.7 U (g of cells [dry weight])
−1
, and the final yield was 94 to 97%. Toluene was found to be a strong competitive inhibitor of the
d
-limonene conversion. Glucose-grown cells did not form any
trans
-carveol from
d
-limonene. These results suggest that one of the enzymes involved in toluene degradation is responsible for this allylic monohydroxylation. Another toluene degrader (
Rhodococcus globerulus
PWD8) had a lower specific activity but was found to oxidize most of the formed
trans
-carveol to (+) carvone, allowing for the biocatalytic production of this flavor compound.
Duplication of Hemolysin Genes in a Virulent Isolate of
Vibrio harveyi
Authors: Zhang X.-H. , Meaden P. G. , Austin B. 
Published: July 2002

ABSTRACT

Vibrio harveyi
VIB 645, which is very pathogenic towards salmonids and produces extracellular product with a high titer of hemolytic activity towards fish erythrocytes, was found to contain two closely related hemolysin genes (designated
vhhA
and
vhhB
), whereas the majority of strains examined (11 of 13) carried only a single hemolysin gene. Both genes from VIB 645 were cloned and sequenced. The open reading frames (ORFs) of
vhhA
and
vhhB
shared a high level of identity (98.8%) and were predicted to encode identical polypeptides comprising 418 amino acid residues. The VHH protein shows homology to the lecithinase of
V. mimicus
and
V. cholerae
. Transformants of
Escherichia coli
containing the ORF of either
vhhA
or
vhhB
displayed weak hemolytic activity in rainbow trout blood agar. The hemolytic activity was very high when the ORF of
vhhB
was cloned in
E. coli
together with the native promoter. Surprisingly, the level of
vhh
-specific RNA transcript produced by VIB 645 was found to be very low. We conclude that the hemolytic phenotype of VIB 645 is not due to increased expression of one or both copies of the
vhh
gene.
Determination of Key Metabolites during Biodegradation of Hexahydro-1,3,5-Trinitro-1,3,5-Triazine with
Rhodococcus
sp. Strain DN22
Authors: Fournier Diane , Halasz Annamaria , Spain Jim , Fiurasek Petr , Hawari Jalal 
Published: July 2002

ABSTRACT

Rhodococcus
sp. strain DN22 can convert hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) to nitrite, but information on degradation products or the fate of carbon is not known. The present study describes aerobic biodegradation of RDX (175 μM) when used as an N source for strain DN22. RDX was converted to nitrite (NO
2
−
) (30%), nitrous oxide (N
2
O) (3.2%), ammonia (10%), and formaldehyde (HCHO) (27%), which later converted to carbon dioxide. In experiments with ring-labeled [
15
N]-RDX, gas chromatographic/mass spectrophotometric (GC/MS) analysis revealed N
2
O with two molecular mass ions: one at 44 Da, corresponding to
14
N
14
NO, and the second at 45 Da, corresponding to
15
N
14
NO. The nonlabeled N
2
O could be formed only from -NO
2
, whereas the
15
N-labeled one was presumed to originate from a nitramine group (
15
N-
14
NO
2
) in RDX. Liquid chromatographic (LC)-MS electrospray analyses indicated the formation of a dead end product with a deprotonated molecular mass ion [M-H] at 118 Da. High-resolution MS indicated a molecular formula of C
2
H
5
N
3
O
3
. When the experiment was repeated with ring-labeled [
15
N]-RDX, the [M-H] appeared at 120 Da, indicating that two of the three N atoms in the metabolite originated from the ring in RDX. When [U-
14
C]-RDX was used in the experiment, 64% of the original radioactivity in RDX incorporated into the metabolite with a molecular weight (MW) of 119 (high-pressure LC/radioactivity) and 30% in
14
CO
2
(mineralization) after 4 days of incubation, suggesting that one of the carbon atoms in RDX was converted to CO
2
and the other two were incorporated in the ring cleavage product with an MW of 119. Based on the above stoichiometry, we propose a degradation pathway for RDX based on initial denitration followed by ring cleavage to formaldehyde and the dead end product with an MW of 119.
Identification of the 2-Methylcitrate Pathway Involved in the Catabolism of Propionate in the Polyhydroxyalkanoate-Producing Strain
Burkholderia sacchari
IPT101
T
and Analysis of a Mutant Accumulating a Copolyester with Higher 3-Hydroxyvalerate Content
Authors: Brämer C. O. , Silva L. F. , Gomez J. G. C. , Priefert H. , Steinbüchel A. 
Published: July 2002

ABSTRACT

Burkholderia sacchari
IPT101
T
induced the formation of 2-methylcitrate synthase and 2-methylisocitrate lyase when it was cultivated in the presence of propionic acid. The
prp
locus of
B. sacchari
IPT101
T
is required for utilization of propionic acid as a sole carbon source and is relevant for incorporation of 3-hydroxyvalerate (3HV) into copolyesters, and it was cloned and sequenced. Five genes (
prpR
,
prpB
,
prpC
,
acnM
, and ORF5) exhibited identity to genes located in the
prp
loci of other gram-negative bacteria.
prpC
encodes a 2-methylcitrate synthase with a calculated molecular mass of 42,691 Da.
prpB
encodes a 2-methylisocitrate lyase. The levels of PrpC and PrpB activity were much lower in propionate-negative mutant IPT189 obtained from IPT101
T
and were heterologously expressed in
Escherichia coli.
The
acnM
gene (ORF4) and ORF5, which are required for conversion of 2-methylcitric acid to 2-methylisocitric acid in
Ralstonia eutropha
HF39, are also located in the
prp
locus. The translational product of ORF1 (
prpR
) had a calculated molecular mass of 70,598 Da and is a putative regulator of the
prp
cluster. Three additional open reading frames (ORF6, ORF7, and ORF8) whose functions are not known were located adjacent to ORF5 in the
prp
locus of
B. sacchari
, and these open reading frames have not been found in any other
prp
operon yet. In summary, the organization of the
prp
genes of
B. sacchari
is similar but not identical to the organization of these genes in other bacteria investigated recently. In addition, this study provided a rationale for the previously shown increased molar contents of 3HV in copolyesters accumulated by a
B. sacchari
mutant since it was revealed in this study that the mutant is defective in
prpC
.
Nitrite as a Stimulus for Ammonia-Starved
Nitrosomonas europaea
Authors: Laanbroek Hendrikus J. , Bär-Gilissen Marie-José , Hoogveld Hans L. 
Published: July 2002

ABSTRACT

Ammonia-starved cells of
Nitrosomonas europaea
are able to preserve a high level of ammonia-oxidizing activity in the absence of ammonium. However, when the nitrite-oxidizing cells that form part of the natural nitrifying community do not keep pace with the ammonia-oxidizing cells, nitrite accumulates and may subsequently inhibit ammonia oxidation. The maintenance of a high ammonia-oxidizing capacity during starvation is then nullified. In this study we demonstrated that cells of
N. europaea
starved for ammonia were not sensitive to nitrite, either when they were starved in the presence of nitrite or when nitrite was supplied simultaneously with fresh ammonium. In the latter case, the initial ammonia-oxidizing activity of starved cells was stimulated at least fivefold.
Photosynthetic Apparatus in
Roseateles depolymerans
61A Is Transcriptionally Induced by Carbon Limitation
Authors: Suyama Tetsushi , Shigematsu Toru , Suzuki Toshihiko , Tokiwa Yutaka , Kanagawa Takahiro , Nagashima Kenji V. P. , Hanada Satoshi 
Published: July 2002

ABSTRACT

Production of a photosynthetic apparatus in
Roseateles depolymerans
61A, a recently discovered freshwater β-
Proteobacterium
showing characteristics of aerobic phototrophic bacteria, was observed when the cells were subjected to a sudden decrease in carbon sources (e.g., when cells grown with 0.1 to 0.4% Casamino Acids were diluted or transferred into medium containing ≤0.04% Casamino Acids). Accumulation of bacteriochlorophyll (BChl)
a
was observed in the presence of oxygen and was enhanced under semiaerobic conditions (2% oxygen) but was reduced in the presence of light. Similarly to what has been reported regarding some aerobic phototrophic bacteria belonging to the α subclass of the
Proteobacteria
, viability of the cells in the carbon source-free medium was prolonged under aerobic-light (10 W m
−2
) conditions, possibly due to photosynthetic energy conversion, but was not prolonged under aerobic-dark conditions. The
puf
operon, which encodes most of the apoproteins of light-harvesting and reaction center complexes, was sequenced, and the effect of changes in Casamino Acids concentrations, oxygen, and light on its expression was estimated by the accumulation of its mRNA. The expression of the
puf
operon was induced by the decrease in carbon sources, similarly to what was observed for the accumulation of BChl
a
under aerobic and semiaerobic conditions (≥0.2% O
2
), and was reduced in the presence of light. Transcription of the
R. depolymerans puf
operon is considered to be controlled by changes in carbon nutrients in addition to oxygen tension and light intensity.
Use of Recombinant Cellulose-Binding Domains of
Trichoderma reesei
Cellulase as a Selective Immunocytochemical Marker for Cellulose in Protozoa
Authors: Linder Markus , Winiecka-Krusnell Jadwiga , Linder Ewert 
Published: July 2002

ABSTRACT

Some unicellular organisms are able to encyst as a protective response to a harmful environment. The cyst wall usually contains chitin as its main structural constituent, but in some cases, as in
Acanthamoeba
, it consists of cellulose instead. Specific cytochemical differentiation between cellulose and chitin by microscopy has not been possible, due to the similarity of their constituent β-1,4-linked hexose backbones. Thus, various fluorescent brightening agents and lectins bind to both cellulose and chitin. We have used a recombinant cellulose-binding protein consisting of two cellulose-binding domains (CBDs) from
Trichoderma reesei
cellulases linked together in combination with monoclonal anticellulase antibodies and anti-mouse immunoglobulin fluorescein conjugate to specifically stain cellulose in the cysts of
Acanthamoeba
strains for fluorescence microscopy imaging. Staining was observed in ruptured cysts and frozen sections of cysts but not in intact mature cysts. No staining reaction was observed with the chitin-containing cyst walls of
Giardia intestinalis
,
Entamoeba dispar
, or
Pneumocystis carinii
. Thus, the recombinant CBD can be used as a marker to distinguish between cellulose and chitin. Thirteen of 25 environmental or clinical isolates of amoebae reacted in the CBD binding assay. All 13 isolates were identified as
Acanthamoeba
spp. Five isolates of
Hartmannella
and seven isolates of
Naegleria
tested negative in the CBD binding assay. Whether cyst wall cellulose really is a unique property of
Acanthamoeba
spp. among free-living amoebae, as suggested by our findings, remains to be shown in more extensive studies.
Negative Effect of High pH on Biocidal Efficacy of Copper and Silver Ions in Controlling
Legionella pneumophila
Authors: Lin Yu-sen E. , Vidic Radisav D. , Stout Janet E. , Yu Victor L. 
Published: July 2002

ABSTRACT

Copper-silver (Cu-Ag) ionization has effectively controlled
Legionella
spp. in the hot water systems of numerous hospitals. However, it was ineffective at controlling
Legionella
in one Ohio hospital despite the confirmation of adequate total concentrations of copper and silver ions. The pH of the water at this hospital was found to be 8.5 to 9.0. The purpose of this study was to investigate the impact of pH and other water quality parameters, including alkalinity (HCO
3
−
), hardness (Ca
2+
and Mg
2+
), and amount of dissolved organic carbon (DOC), on the control of
Legionella
by Cu-Ag ionization. Initial concentrations of
Legionella
and copper and silver ions used in batch experiments were 3 × 10
6
CFU/ml and 0.4 and 0.08 mg/liter, respectively. Changes in bicarbonate ion concentration (50, 100, and 150 mg/liter), water hardness (Ca
2+
at 50 and 100 mg/liter; Mg
2+
at 40 and 80 mg/liter), and level of DOC (0.5 and 2 mg/liter) had no significant impact on the efficacy of copper and silver ions in killing
Legionella
at a neutral pH. When the pH was elevated to 9 in these experiments, copper ions achieved only a 10-fold reduction in the number of
Legionella
organisms in 24 h, compared to a millionfold decrease at pH 7.0. Silver ions were able to achieve a millionfold reduction in 24 h at all ranges of water quality parameters tested. Precipitation of insoluble copper complexes was observed at a pH above 6.0. These results suggest that pH may be an important factor in the efficacy of copper-silver ionization in controlling
Legionella
in water systems.
Functional Analysis of
Sinorhizobium meliloti
Genes Involved in Biotin Synthesis and Transport
Authors: Entcheva Plamena , Phillips Donald A. , Streit Wolfgang R. 
Published: July 2002

ABSTRACT

External biotin greatly stimulates bacterial growth and alfalfa root colonization by
Sinorhizobium meliloti
strain 1021. Several genes involved in responses to plant-derived biotin have been identified in this bacterium, but no genes required for biotin transport are known, and not all loci required for biotin synthesis have been assigned. Searches of the
S. meliloti
genome database in combination with complementation tests of
Escherichia coli
biotin auxotrophs indicate that biotin synthesis probably is limited in
S. meliloti
1021 by the poor functioning or complete absence of several key genes. Although several open reading frames with significant similarities to genes required for synthesis of biotin in gram-positive and gram-negative bacteria were found, only
bioB
,
bioF
, and
bioH
were demonstrably functional in complementation tests with known
E. coli
mutants. No sequence or complementation evidence was found for
bioA
,
bioC
,
bioD
, or
bioZ
. In contrast to other microorganisms, the
S. meliloti bioB
and
bioF
genes are not localized in a biotin synthesis operon, but
bioB
is cotranscribed with two genes coding for ABC transporter-like proteins, designated here
bioM
and
bioN.
Mutations in
bioM
and
bioN
eliminated growth on alfalfa roots and reduced bacterial capacity to maintain normal intracellular levels of biotin. Taken together, these data suggest that
S. meliloti
normally grows on exogenous biotin using
bioM
and
bioN
to conserve biotin assimilated from external sources.
Variations in the Membrane Fatty Acid Composition of Resistant or Susceptible
Leuconostoc
or
Weissella
Strains in the Presence or Absence of Mesenterocin 52A and Mesenterocin 52B Produced by
Leuconostoc mesenteroides
subsp.
mesenteroides
FR52
Authors: Limonet Maxime , Revol-Junelles Anne-Marie , Millière Jean-Bernard 
Published: July 2002

ABSTRACT

Mesenterocins 52A (Mes52A) and 52B (Mes52B) are antimicrobial peptides produced by
Leuconostoc mesenteroides
subsp.
mesenteroides
FR 52. Mes52A is a class IIa bacteriocin of lactic acid bacteria with a broad spectrum of activity. Mes52B is an atypical class II bacteriocin with a narrow spectrum of activity. Four
Leuconostoc
and
Weissella
wild-type strains were selected for their susceptibility or insensitivity to these mesenterocins. Four strains resistant to Mes52A or Mes52B were generated from the three susceptible wild-type strains by increasing bacteriocin concentrations in culture media. These resistant strains were at least 30 times more resistant than the wild-type strains. No cross-resistance to Mes52A and Mes52B was observed in these strains. No significant differences in membrane fatty acid composition were observed among the three susceptible wild-type strains and the four resistant strains cultured in MRS broth. Thus, the mesenterocin resistance is unlikely to be due to changes in membrane fatty acid composition. When cultured with Mes52A or Mes52B, the membranes of insensitive and resistant strains contained more saturated fatty acids (1 to 10% more) and less unsaturated fatty acids (3 to 6% less), resulting in a more rigid membrane. Thus, the presence of mesenterocin in the culture media of insensitive or resistant strains induced a significant increase in saturated fatty acid contents and a decrease in unsaturated fatty acid contents.
Weissella paramesenteroides
DSM 20288BR, resistant to Mes52B, responded atypically, probably due to the production of an inhibitor.
Genetic and Biochemical Characterization of Glycerol Uptake in
Mycoplasma mycoides
subsp.
mycoides
SC: Its Impact on H
2
O
2
Production and Virulence
Authors: Vilei Edy M. , Frey Joachim 
Published: July 2002

ABSTRACT

Highly virulent strains of
Mycoplasma mycoides
subsp.
mycoides
SC belonging to the African cluster contain an operon with the genes
gtsA
,
gtsB
, and
gtsC
, encoding membrane ATP binding cassette transporter proteins GtsA, GtsB, and GtsC, which are involved in glycerol transport. Strain Afadé from the African cluster incorporated [U-
14
C]glycerol with a time-dependent increase. The less virulent strain L2 of the European cluster, which lacks
gtsB
and
gtsC
, failed to incorporate glycerol. Antibodies against GtsB noncompetitively inhibited glycerol uptake.
l
-α-Glycerophosphate was not transported by
M. mycoides
subsp.
mycoides
SC. It is postulated to be synthesized by phosphorylation of glycerol during transport and subsequently metabolized further to dihydroxyacetone phosphate accompanied by release of H
2
O
2
. Peroxide production in glycerol-containing growth medium was high for the African strain Afadé but very low for the European strain L2. Virtually no H
2
O
2
was produced by both strains without glycerol. Hence, the efficient glycerol uptake system found in the virulent strain of the African cluster leads to a strong release of peroxide, a potential virulence factor which is lacking in the less virulent European strains.
M. mycoides
subsp.
mycoides
SC might have adopted, as a strategy for virulence, a highly efficient uptake system for glycerol which allows the production of an active metabolic intermediate that damages host cells.