bluuebunny/crossref_metadata_2025_split huggingface dataset:
Inhibition of
Streptococcus mutans
NS Adhesion to Glass with and without a Salivary Conditioning Film by Biosurfactant- Releasing
Streptococcus mitis
Strains
Authors: van Hoogmoed C. G. , van der Kuijl-Booij M. , van der Mei H. C. , Busscher H. J. 
Published: July 2002

ABSTRACT

The release of biosurfactants by adhering microorganisms as a defense mechanism against other colonizing strains on the same substratum surface has been described previously for probiotic bacteria in the urogenital tract, the intestines, and the oropharynx but not for microorganisms in the oral cavity. Two
Streptococcus mitis
strains (BA and BMS) released maximal amounts of biosurfactants when they were grown in the presence of sucrose and were harvested in the early stationary phase. The
S. mitis
biosurfactants reduced the surface tensions of aqueous solutions to about 30 to 40 mJ m
−2
. Biochemical and physicochemical analyses revealed that the biosurfactants released were glycolipids. An acid-precipitated fraction was extremely surfactive and was identified as a rhamnolipidlike compound. In a parallel-plate flow chamber, the number of
Streptococcus mutans
NS cells adhering to glass with and without a salivary conditioning film in the presence of biosurfactant-releasing
S. mitis
BA and BMS (surface coverage, 1 to 4%) was significantly reduced compared with the number of
S. mutans
NS cells adhering to glass in the absence of
S. mitis. S. mutans
NS adhesion in the presence of non-biosurfactant-releasing
S. mitis
BA and BMS was not reduced at all. In addition, preadsorption of isolated
S. mitis
biosurfactants to glass drastically reduced the adhesion of
S. mutans
NS cells and the strength of their bonds to glass, as shown by the increased percentage of
S. mutans
NS cells detached by the passage of air bubbles through the flow chamber. Preadsorption of the acid-precipitated fraction inhibited
S. mutans
adhesion up to 80% in a dose-responsive manner. These observations indicate that
S. mitis
plays a protective role in the oral cavity and protects against colonization of saliva-coated surfaces by cariogenic
S. mutans
.
Development of a Selective Medium for Isolation of
Helicobacter pylori
from Cattle and Beef Samples
Authors: Stevenson Timothy H. , Lucia Lisa M. , Acuff Gary R. 
Published: July 2002

ABSTRACT

Helicobacter pylori
has been isolated from the human stomach with media containing only minimal selective agents. However, current research on the transmission and sources of infection requires more selective media due to the higher numbers of contaminants in environmental, oral, and fecal samples. The objective of this study was to develop and evaluate detection techniques that are sufficiently selective to isolate
H. pylori
from potential animal and food sources. Since
H. pylori
survives in the acidic environment of the stomach, low pH with added urea was studied as a potential selective combination.
H. pylori
grew fairly well on
H. pylori
Special Peptone plating medium supplemented with 10 mM urea at pH 4.5, but this pH did not sufficiently inhibit the growth of contaminants. Various antibiotic combinations were then compared, and a combination consisting of 10 mg of vancomycin per liter, 5 mg of amphotericin B per liter, 10 mg of cefsulodin per liter, 62,000 IU of polymyxin B sulfate per liter, 40 mg of trimethoprim per liter, and 20 mg of sulfamethoxazole per liter proved to be highly selective but still allowed robust colonies of
H. pylori
to grow. This medium was highly selective for recovering
H. pylori
from cattle and beef samples, and it is possible that it could be used to enhance the recovery of this bacterium from human and environmental samples, which may be contaminated with large numbers of competing microorganisms.
Selected Chitinase Genes in Cultured and Uncultured Marine Bacteria in the α- and γ-Subclasses of the Proteobacteria
Authors: Cottrell Matthew T. , Wood Daniel N. , Yu Liying , Kirchman David L. 
Published: July 2002

ABSTRACT

PCR primers were patterned after chitinase genes in four γ-proteobacteria in the families
Alteromonadaceae
and
Enterobacteriaceae
(group I chitinases) and used to explore the occurrence and diversity of these chitinase genes in cultured and uncultured marine bacteria. The PCR results from 104 bacterial strains indicated that this type of chitinase gene occurs in two major groups of marine bacteria, α- and γ-proteobacteria, but not the
Cytophaga-Flavobacter
group. Group I chitinase genes also occur in some viruses infecting arthropods. Phylogenetic analysis indicated that similar group I chitinase genes occur in taxonomically related bacteria. However, the overall phylogeny of chitinase genes did not correspond to the phylogeny of 16S rRNA genes, possibly due to lateral transfer of chitinase genes between groups of bacteria, but other mechanisms, such as gene duplication, cannot be ruled out. Clone libraries of chitinase gene fragments amplified from coastal Pacific Ocean and estuarine Delaware Bay bacterioplankton revealed similarities and differences between cultured and uncultured bacteria. We had hypothesized that cultured and uncultured chitin-degrading bacteria would be very different, but in fact, clones having nucleotide sequences identical to those of chitinase genes of cultured α-proteobacteria dominated both libraries. The other clones were similar but not identical to genes in cultured γ-proteobacteria, including vibrios and alteromonads. Our results suggest that a closer examination of chitin degradation by α-proteobacteria will lead to a better understanding of chitin degradation in the ocean.
Copper Induction of Laccase Isoenzymes in the Ligninolytic Fungus
Pleurotus ostreatus
Authors: Palmieri Gianna , Giardina Paola , Bianco Carmen , Fontanella Bianca , Sannia Giovanni 
Published: July 2002

ABSTRACT

Pleurotus ostreatus
is a white rot basidiomycete that produces several extracellular laccase isoenzymes, including phenol oxidase A1b (POXA1b), POXA2, and POXC. POXC was the most abundant isoenzyme produced under all of the growth conditions examined in this study. Copper was the most efficient inducer of laccase activity among the putative inducers tested. The amounts of all of the previously described laccase isoenzymes increased substantially in copper-supplemented cultures. Under these conditions expression of POX isoenzymes was regulated at the level of gene transcription. It is worth noting that
poxa1b
mRNA was the most abundant induced transcript at all of the growth times analyzed, and the amount of this mRNA increased until day 7. The discrepancy between the
poxa1b
transcript and protein amounts can be explained by the presence of a high level of the protein in
P. ostreatus
cellular extract, which indicated that the POXA1b isoenzyme could be inefficiently secreted and/or that its physiological activity could occur inside the cell or on the cell wall. Moreover, the POXA1b isoenzyme behaved uniquely, as its activity was maximal on the second day of growth and then decreased. An analysis performed with protease inhibitors revealed that the loss of extracellular POXA1b activity could have been due to the presence of specific proteases secreted into the copper-containing culture medium that affected the extracellular POXA1b isoenzyme.
Molecular Analysis of the
pmo
(Particulate Methane Monooxygenase) Operons from Two Type II Methanotrophs
Authors: Gilbert Bettina , McDonald Ian R. , Finch Ruth , Stafford Graham P. , Nielsen Allan K. , Murrell J. Colin 
Published: July 2002

ABSTRACT

The particulate methane monooxygenase gene clusters,
pmoCAB
, from two representative type II methanotrophs of the α-
Proteobacteria
,
Methylosinus trichosporium
OB3b and
Methylocystis
sp. strain M, have been cloned and sequenced. Primer extension experiments revealed that the
pmo
cluster is probably transcribed from a single transcriptional start site located 300 bp upstream of the start of the first gene,
pmoC
, for
Methylocystis
sp. strain M. Immediately upstream of the putative start site, consensus sequences for ς
70
promoters were identified, suggesting that these
pmo
genes are recognized by ς
70
and negatively regulated under low-copper conditions. The
pmo
genes were cloned in several overlapping fragments, since parts of these genes appeared to be toxic to the
Escherichia coli
host. Methanotrophs contain two virtually identical copies of
pmo
genes, and it was necessary to use Southern blotting and probing with
pmo
gene fragments in order to differentiate between the two
pmoCAB
clusters in both methanotrophs. The complete DNA sequence of one copy of
pmo
genes from each organism is reported here. The gene sequences are 84% similar to each other and 75% similar to that of a type I methanotroph of the γ-
Proteobacteria
,
Methylococcus capsulatus
Bath. The derived proteins PmoC and PmoA are predicted to be highly hydrophobic and consist mainly of transmembrane-spanning regions, whereas PmoB has only two putative transmembrane-spanning helices. Hybridization experiments showed that there are two copies of
pmoC
in both
M. trichosporium
OB3b and
Methylocystis
sp. strain M, and not three copies as found in
M. capsulatus
Bath.
Carbon Monoxide Dehydrogenase Activity in
Bradyrhizobium japonicum
Authors: Lorite María J. , Tachil Jörg , Sanjuán Juán , Meyer Ortwin , Bedmar Eulogio J. 
Published: July 2002

ABSTRACT

Bradyrhizobium japonicum
strain 110
spc
4 was capable of chemolithoautotrophic growth with carbon monoxide (CO) as a sole energy and carbon source under aerobic conditions. The enzyme carbon monoxide dehydrogenase (CODH; EC
1.2.99.2
) has been purified 21-fold, with a yield of 16% and a specific activity of 58 nmol of CO oxidized/min/mg of protein, by a procedure that involved differential ultracentrifugation, anion-exchange chromatography, hydrophobic interaction chromatography, and gel filtration. The purified enzyme gave a single protein and activity band on nondenaturing polyacrylamide gel electrophoresis and had a molecular mass of 230,000 Da. The 230-kDa enzyme was composed of large (L; 75-kDa), medium (M; 28.4-kDa), and small (S; 17.2-kDa) subunits occurring in heterohexameric (LMS)
2
subunit composition. The 75-kDa polypeptide exhibited immunological cross-reactivity with the large subunit of the CODH of
Oligotropha carboxidovorans
. The
B. japonicum
enzyme contained, per mole, 2.29 atoms of Mo, 7.96 atoms of Fe, 7.60 atoms of labile S, and 1.99 mol of flavin. Treatment of the enzyme with iodoacetamide yielded di(carboxamidomethyl)molybdopterin cytosine dinucleotide, identifying molybdopterin cytosine dinucleotide as the organic portion of the
B. japonicum
CODH molybdenum cofactor. The absorption spectrum of the purified enzyme was characteristic of a molybdenum-containing iron-sulfur flavoprotein.
Investigation of the Relationship between Lysogeny and Lysis of
Lactococcus lactis
in Cheese Using Prophage-Targeted PCR
Authors: O'Sullivan David , Ross R. Paul , Fitzgerald Gerald F. , Coffey Aidan 
Published: July 2002

ABSTRACT

The ability of lactococcal strains to lyse (and release intracellular enzymes) during cheese manufacture can be a very desirable trait and has been associated with improvement in flavor and acceleration of cheese ripening. Using a laboratory-scale cheese manufacturing assay, the autolytic behavior of 31 strains of
Lactococcus lactis
was assessed. In general, marked variation was observed between strains with a 20-fold difference between the best and worst lysing strains based on the release of the intracellular enzyme lactate dehydrogenase. In a parallel experiment, the genomes of these strains were examined for the presence of prophage integrase (
int
) sequences by using conserved primer sequences from known lysogenic phage. Results demonstrated that the lytic behavior of lactococcal starter strains significantly correlates with the presence of prophage sequences. These results highlight not only the contribution of prophage to starter cell lysis but also the potential of PCR as a useful initial screen to assess strains for this important industrial trait.
Detection of
Pseudomonas savastanoi
pv. savastanoi in Olive Plants by Enrichment and PCR
Authors: Penyalver Ramón , García Amparo , Ferrer Amparo , Bertolini Edson , López María M. 
Published: July 2002

ABSTRACT

The sequence of the gene
iaaL
of
Pseudomonas savastanoi
EW2009 was used to design primers for PCR amplification. The
iaaL
-derived primers directed the amplification of a 454-bp fragment from genomic DNA isolated from 70 strains of
P. savastanoi
, whereas genomic DNA from 93 non-
P. savastanoi
isolates did not yield this amplified product. A previous bacterial enrichment in the semiselective liquid medium PVF-1 improved the PCR sensitivity level, allowing detection of 10 to 100 CFU/ml of plant extract.
P. savastanoi
was detected by the developed enrichment-PCR method in knots from different varieties of inoculated and naturally infected olive trees. Moreover,
P. savastanoi
was detected in symptomless stem tissues from naturally infected olive plants. This enrichment-PCR method is more sensitive and less cumbersome than the conventional isolation methods for detection of
P. savastanoi
.
Characterization ofS-Triazine Herbicide Metabolism by aNocardioidessp. Isolated from Agricultural Soils
Authors: Topp Edward , Mulbry Walter M. , Zhu Hong , Nour Sarah M. , Cuppels Diane 
Published: July 2002

ABSTRACTAtrazine, a herbicide widely used in corn production, is a frequently detected groundwater contaminant. Nine gram-positive bacterial strains able to use this herbicide as a sole source of nitrogen were isolated from four farms in central Canada. The strains were divided into two groups based on repetitive extragenic palindromic (rep)-PCR genomic fingerprinting with ERIC and BOXA1R primers. Based on 16S ribosomal DNA sequence analysis, both groups were identified asNocardioidessp. strains. None of the isolates mineralized [ring-U-14C]atrazine. There was no hybridization to genomic DNA from these strains usingatzABCcloned fromPseudomonassp. strain ADP ortrzAcloned fromRhodococcus corallinus. S-Triazine degradation was studied in detail inNocardioidessp. strain C190. Oxygen was not required for atrazine degradation by whole cells or cell extracts. Based on high-pressure liquid chromatography and mass spectrometric analyses of products formed from atrazine in incubations of whole cells with H218O, sequential hydrolytic reactions converted atrazine to hydroxyatrazine and then to the end productN-ethylammelide. Isopropylamine, the putative product of the second hydrolytic reaction, supported growth as the sole carbon and nitrogen source. The triazine hydrolase from strain C190 was isolated and purified and found to have aKmfor atrazine of 25 μM and aVmaxof 31 μmol/min/mg of protein. The subunit molecular mass of the protein was 52 kDa. Atrazine hydrolysis was not inhibited by 500 μM EDTA but was inhibited by 100 μM Mg, Cu, Co, or Zn. Whole cells and purified triazine hydrolase converted a range of chlorine or methylthio-substituted herbicides to the corresponding hydroxy derivatives. In summary, an atrazine-metabolizingNocardioidessp. widely distributed in agricultural soils degrades a range ofs-triazine herbicides by means of a novels-triazine hydrolase.
Comparison of 2,4-Dichlorophenoxyacetic Acid Degradation and Plasmid Transfer in Soil Resulting from Bioaugmentation with Two Different pJP4 Donors
Authors: Newby D. T. , Gentry T. J. , Pepper I. L. 
Published: July 2002

ABSTRACT

A pilot field study was conducted to assess the impact of bioaugmentation with two plasmid pJP4-bearing microorganisms: the natural host,
Ralstonia eutropha
JMP134, and a laboratory-generated strain amenable to donor counterselection,
Escherichia coli
D11. The
R. eutropha
strain contained chromosomal genes necessary for mineralization of 2,4-dichlorophenoxyacetic acid (2,4-D), while the
E. coli
strain did not. The soil system was contaminated with 2,4-D alone or was cocontaminated with 2,4-D and Cd. Plasmid transfer to indigenous populations, plasmid persistence in soil, and degradation of 2,4-D were monitored over a 63-day period in the bioreactors. To assess the impact of contaminant reexposure, aliquots of bioreactor soil were reamended with additional 2,4-D. Both introduced donors remained culturable and transferred plasmid pJP4 to indigenous recipients, although to different extents. Isolated transconjugants were members of the
Burkholderia
and
Ralstonia
genera, suggesting multiple, if not successive, plasmid transfers. Upon a second exposure to 2,4-D, enhanced degradation was observed for all treatments, suggesting microbial adaptation to 2,4-D. Upon reexposure, degradation was most rapid for the
E. coli
D11-inoculated treatments. Cd did not significantly impact 2,4-D degradation or transconjugant formation. This study demonstrated that the choice of donor microorganism might be a key factor to consider for bioaugmentation efforts. In addition, the establishment of an array of stable indigenous plasmid hosts at sites with potential for reexposure or long-term contamination may be particularly useful.
Characterization of an Isolate That Uses Vinyl Chloride as a Growth Substrate under Aerobic Conditions
Authors: Verce Matthew F. , Ulrich Ricky L. , Freedman David L. 
Published: July 2002

ABSTRACT

An aerobic enrichment culture was developed by using vinyl chloride (VC) as the sole organic carbon and electron donor source. VC concentrations as high as 7.3 mM were biodegraded without apparent inhibition. VC use did not occur when nitrate was provided as the electron acceptor. A gram-negative, rod-shaped, motile isolate was obtained from the enrichment culture and identified based on biochemical characteristics and the sequence of its 16S rRNA gene as
Pseudomonas aeruginosa
, designated strain MF1. The observed yield of MF1 when it was grown on VC was 0.20 mg of total suspended solids (TSS)/mg of VC. Ethene, acetate, glyoxylate, and glycolate also served as growth substrates, while ethane, chloroacetate, glycolaldehyde, and phenol did not. Stoichiometric release of chloride and minimal accumulation of soluble metabolites following VC consumption indicated that the predominant fate for VC is mineralization and incorporation into cell material. MF1 resumed consumption of VC after at least 24 days when none was provided, unlike various mycobacteria that lost their VC-degrading ability after brief periods in the absence of VC. When deprived of oxygen for 2.5 days, MF1 did not regain the ability to grow on VC, and a portion of the VC was transformed into VC-epoxide. Acetylene inhibited VC consumption by MF1, suggesting the involvement of a monooxygenase in the initial step of VC metabolism. The maximum specific VC utilization rate for MF1 was 0.41 μmol of VC/mg of TSS/day, the maximum specific growth rate was 0.0048/day, and the Monod half-saturation coefficient was 0.26 μM. A higher yield and faster kinetics occurred when MF1 grew on ethene. When grown on ethene, MF1 was able to switch to VC as a substrate without a lag. It therefore appears feasible to grow MF1 on a nontoxic substrate and then apply it to environments that do not exhibit a capacity for aerobic biodegradation of VC.
Heterologous Coproduction of Enterocin A and Pediocin PA-1 by
Lactococcus lactis
: Detection by Specific Peptide-Directed Antibodies
Authors: Martínez José M. , Kok Jan , Sanders Jan W. , Hernández Pablo E. 
Published: July 2002

ABSTRACT

Antibodies against enterocin A were obtained by immunization of rabbits with synthetic peptides PH4 and PH5 designed, respectively, on the N- and C-terminal amino acid sequences of enterocin A and conjugated to the carrier protein KLH. Anti-PH4-KLH antibodies not only recognized enterocin A but also pediocin PA-1, enterocin P, and sakacin A, three bacteriocins which share the N-terminal class IIa consensus motif (YGNGVXC) that is contained in the sequence of the peptide PH4. In contrast, anti-PH5-KLH antibodies only reacted with enterocin A because the amino acid sequences of the C-terminal parts of class IIa bacteriocins are highly variable. Enterocin A and/or pediocin PA-1 structural and immunity genes were introduced in
Lactococcus lactis
IL1403 to achieve (co)production of the bacteriocins. The level of production of the two bacteriocins was significantly lower than that obtained by the wild-type producers, a fact that suggests a low efficiency of transport and/or maturation of these bacteriocins by the chromosomally encoded bacteriocin translocation machinery of IL1403. Despite the low production levels, both bacteriocins could be specifically detected and quantified with the anti-PH5-KLH (anti-enterocin A) antibodies isolated in this study and the anti-PH2-KLH (anti-pediocin PA-1) antibodies previously generated (J. M. Martı́nez, M. I. Martı́nez, A. M. Suárez, C. Herranz, P. Casaus, L. M. Cintas, J. M. Rodrı́guez, and P. E. Hernández, Appl. Environ. Microbiol. 64:4536–4545, 1998). In this work, the availability of antibodies for the specific detection and quantification of enterocin A and pediocin PA-1 was crucial to demonstrate coproduction of both bacteriocins by
L. lactis
IL1403(pJM04), because indicator strains that are selectively inhibited by each bacteriocin are not available.
Germination-Induced Bioluminescence, a Route To Determine the Inhibitory Effect of a Combination Preservation Treatment on Bacterial Spores
Authors: Ciarciaglini Gianni , Hill Philip J. , Davies Ken , McClure Peter J. , Kilsby Derrick , Brown Martyn H. , Coote Peter J. 
Published: July 2002

ABSTRACT

In this work, we have used spores of
Bacillus subtilis
that specifically induce bioluminescence upon initiation of germination as a rapid, real-time monitor of the effects of preservative treatments on germination. Using this tool, we have demonstrated that the combination of mild acidity (pH 5.5 to 5.0), lactic acid (0.5%), and a pasteurization step (90°C for 5 min) results in enhanced inhibition of spore germination compared with the effects of the individual treatments alone. Inhibition by the combination treatment occurred as a result of both direct but reversible inhibition, entirely dependent on the physical presence of the preservative factors, and permanent, nonreversible damage to the
l
-alanine germination apparatus of the spore. However, we were able to restore germination of the preservative-damaged spores unable to germinate on
l
-alanine by supplementing the medium with the nonnutrient germinant calcium dipicolinic acid. The demonstration that simple combinations of preservative factors inhibit spore germination indicates that food preservation systems providing ambient stability could be designed which do not adhere to the strict limits set by commonly accepted processes and which are based on precise understanding of their inhibitory action.