bluuebunny/crossref_metadata_2025 huggingface dataset:
Response surface analysis of the effects of pH and dilution rate on Ruminococcus flavefaciens FD-1 in cellulose-fed continuous culture
Authors: Shi Y , Weimer P J
Published: January 2020

The ruminal cellulolytic bacterium Ruminococcus flavefaciens FD-1 was grown in cellulose-fed continuous culture with 20 different combinations of pH and dilution rate (D); the combinations were selected according to the physiological pH range of the organism (6.0 to 7.1) and growth rate of the organism on cellulose (0.017 to 0.10 h-1). A response surface analysis was used to characterize the effects of pH and D on the extent of cellulose consumption, growth yield, soluble sugar concentration, and yields of fermentation products. The response surfaces indicate that pH and D coordinately affect cellulose digestion and growth yield in this organism. As expected, the net cellulose consumption increased with increasing D while the fraction of added cellulose that was utilized decreased with increasing D. The effect of changes in pH within the physiological range on cellulose consumption was smaller than that of changes in D. Cellulose degradation was less sensitive to low pH than to high pH. At low Ds (longer retention times), cellulose degradation did not follow first-order kinetics. This decreased rate of cellulose digestion was not due to poor mixing, limitation by other medium components, or preferential utilization of the more amorphous fraction of the cellulose. The cell yield increased from 0.13 to 0.18 mg of cells per mg of cellulose with increasing Ds from 0.02 to 0.06 h-1 and decreased when the pH was shifted from the optimum of 6.5 to 6.8. The effect of pH on cell yield increased with increasing D. The reduced cell yield at low pH appears to be due to both an increase in maintenance energy requirements and a decrease in true growth yield.
[
3
H]Thymidine Incorporation To Estimate Growth Rates of Anaerobic Bacterial Strains
Authors: Winding Anne
Published: January 2020

The incorporation of [
3
H]thymidine by axenic cultures of anaerobic bacteria was investigated as a means to measure growth. The three fermentative strains and one of the methanogenic strains tested incorporated [
3
H]thymidine, whereas the sulfate-reducing bacterium and two of the methanogenic bacteria were unable to incorporate [
3
H]thymidine during growth. It is concluded that the [
3
H]thymidine incorporation method underestimates bacterial growth in anaerobic environments.
Direct isolation of Yersinia pseudotuberculosis from fresh water in Japan
Authors: Fukushima H
Published: January 2020

Yersinia pseudotuberculosis was recovered from KOH-treated precipitates of 20.6% of 500 freshwater samples. KOH treatment of precipitates is a simple and expedient means of recovering Y. pseudotuberculosis from such samples.
Screening for microorganisms producing D-malate from maleate
Authors: van der Werf M J , van den Tweel W J , Hartmans S
Published: January 2020

More than 300 microorganisms were screened for their ability to convert maleate into D-malate as a result of the action of maleate hydratase. Accumulation of fumarate during incubation of permeabilized cells with maleate was shown to be indicative of one of the two enzymes known to transform maleate. The ratio in which fumarate and malate accumulated could be used to estimate the enantiomeric composition of the malate formed. Many strains (n = 128) were found to be capable of converting maleate to D-malate with an enantiomeric purity of more than 97%. Pseudomonas pseudoalcaligenes NCIMB 9867 was selected for more detailed studies. Although this strain was not able to grow on maleate, permeabilized cells were able to degrade maleate to undetectable levels, with a concomitant formation of D-malate. The D-malate was formed with an enantiomeric purity of more than 99.97%.
Formation of poly(hydroxybutyrate-co-hydroxyvalerate) by Azotobacter vinelandii UWD
Authors: Page W J , Manchak J , Rudy B
Published: January 2020

Azotobacter vinelandii UWD formed polyhydroxyalkanoate (PHA) copolymers containing beta-hydroxybutyrate and beta-hydroxyvalerate (HV) when grown in a medium containing glucose as the primary C source and valerate (pentanoate) as a precursor. Copolymer was not formed when propionate was added to the glucose medium but was formed when heptanoate, nonanoate, or trans-2-pentenoate was present. Optimal levels of HV were formed when valerate was added at the time of maximum PHA synthesis, although HV incorporation was not dependent on glucose catabolism. HV content in the polymer was increased from 17 to 24 mol% by adding 10 to 40 mM valerate to glucose medium, but HV insertion into the polymer occurred at a fixed rate. Similarly, the addition of valerate to a fed-batch culture of strain UWD in beet molasses in a fermentor produced 19 to 22 g of polymer per liter, containing 8.5 to 23 mol% HV after 38 to 40 h. The synthesis of HV in these cultures also occurred at a fixed rate (2.3 to 2.8 mol% h-1), while the maximum PHA production rate was 1.1 g liter-1 h-1. During synthesis of copolymer in batch or fed-batch culture, the yield from conversion of glucose into PHA (YP/S) remained at maximum theoretical efficiency (greater than or equal to 0.33 g of PHA per g of glucose consumed). Up to 45 mol% C source, but the PHA produced amounted to less than 1 g/liter. The combination of 30 mM valerate as a sole C source and 0.5 mM 4-pentenoate increased the HV content in the polymer to 52 mol%.(ABSTRACT TRUNCATED AT 250 WORDS)
Isolation and characterization of an anaerobic chlorophenol-transforming bacterium
Authors: Madsen T , Licht D
Published: January 2020

An obligately anaerobic bacterium which transforms several chlorinated phenols was isolated. Dechlorination of the substituents ortho to the phenolic OH group was preferred, while removal of a meta-substituted chlorine was observed only with 3,5-dichlorophenol. The bacterium was a gram-positive, endospore-forming, motile, slightly curved rod. Sulfate was not reduced. Nitrate was reduced via nitrite to ammonium. The bacterium is related to the genus Clostridium. The highest growth rate was obtained in a medium containing pyruvate and yeast extract. Pyruvate supported growth as the sole source of carbon, and the fermentation of pyruvate produced almost equimolar amounts of acetate.
Isolation and characterization of a fluorene-degrading bacterium: identification of ring oxidation and ring fission products
Authors: Grifoll M , Casellas M , Bayona J M , Solanas A M
Published: January 2020

An Arthrobacter sp. strain, F101, able to use fluorene as the sole source of carbon and energy, was isolated from sludge from an oil refinery wastewater treatment plant. During growth in the presence of fluorene, four major metabolites were detected and isolated by thin-layer chromatography and high-performance liquid chromatography. 9-Fluorenol, 9H-fluoren-9-one, and 3,4-dihydrocoumarin were identified by UV spectra, mass spectrometry, and 300-MHz proton nuclear magnetic resonance. The fourth metabolite has been characterized, but precise identification was not possible. Since strain F101 is not able to grow with fluorenone, two different pathways of fluorene biodegradation are suggested: one supports cell growth and produces 3,4-dihydrocoumarin as an intermediate and probably the unidentified metabolite, and the other produces 9-fluorenol and 9H-fluoren-9-one and appears to be a dead-end route.
Initial hydrogenation during catabolism of picric acid by Rhodococcus erythropolis HL 24-2
Authors: Lenke H , Knackmuss H J
Published: January 2020

Rhodococcus erythropolis HL 24-2, which was originally isolated as a 2,4-dinitrophenol-degrading bacterium, could also utilize picric acid as a nitrogen source after spontaneous mutation. During growth, the mutant HL PM-1 transiently accumulated an orange-red metabolite, which was identified as a hydride-Meisenheimer complex of picric acid. This complex was formed as the initial metabolite and further converted with concomitant liberation of nitrite. 2,4,6-Trinitrocyclohexanone was identified as a dead-end metabolite of the degradation of picric acid, indicating the addition of two hydride ions to picric acid.
DNA amplification polymorphisms of the cultivated mushroom Agaricus bisporus
Authors: Khush R S , Becker E , Wach M
Published: January 2020

Single 10-bp primers were used to generate random amplified polymorphic DNA (RAPD) markers from commercial and wild strains of the cultivated mushroom Agaricus bisporus via the polymerase chain reaction. Of 20 primers tested, 19 amplified A. bisporus DNA, each producing 5 to 15 scorable markers ranging from 0.5 to 3.0 kbp. RAPD markers identified seven distinct genotypes among eight heterokaryotic strains; two of the commercial strains were shown to be related to each other through single-spore descent. Homokaryons recovered from protoplast regenerants of heterokaryotic strains carried a subset of the RAPD markers found in the heterokaryon, and both of the haploid nuclei from two heterokaryons were distinguishable. RAPD markers also served to verify the creation of a hybrid heterokaryon and to analyze meiotic progeny from this new strain: most of the basidiospores displayed RAPD fingerprints identical to that of the parental heterokaryon, although a few selected slow growers were homoallelic at a number of loci that were heteroallelic in the parent, suggesting that they represented rare homokaryotic basidiospores; crossover events between a RAPD marker locus and its respective centromere appeared to be infrequent. These results demonstrate that RAPD markers provide an efficient alternative for strain fingerprinting and a versatile tool for genetic studies and manipulations of A. bisporus.
Assessment of
Pediococcus acidilactici
as a Potential Silage Inoculant
Authors: Fitzsimons A. , Duffner F. , Curtin D. , Brophy G. , O'Kiely P. , O'Connell M.
Published: January 2020

Eighteen
Pediococcus
strains were screened for their potential as silage inoculants.
Pediococcus acidilactici
G24 was found to be the most suitable, exhibiting a short lag phase on both glucose and fructose, a rapid rate of acid production, a high sugar-to-lactate conversion efficiency, no detectable breakdown of proteins or lactic acid, and the ability to grow within a broad range of pH and temperature. When tested in laboratory silos using grass with a water-soluble carbohydrate content of 24 g/kg of aqueous extract,
P. acidilactici
G24 stimulated the natural
Lactobacillus plantarum
population and accelerated the rates of lactic acid production and pH decrease. After 6 days of fermentation, the inoculated silage exhibited a 12% decrease in ammonia nitrogen and an 11% increase in crude protein levels compared with uninoculated controls. The use of an
L. plantarum
inoculant at a rate of 10
4
bacteria per g of grass in conjunction with
P. acidilactici
G24 produced no additional beneficial effect. Inoculation of grass with a water-soluble carbohydrate level of 8 g/kg of aqueous extract with
P. acidilactici
G24 led to no acceleration in the rate of
L. plantarum
growth or pH decrease. However, after 7 days of fermentation the inoculated silage had a 14% lower ammonia nitrogen protein content than did uninoculated controls. The results suggest that
P. acidilactici
G24 may be useful as a silage inoculant for crops with a sufficiently high water-soluble carbohydrate level.
Hexadecane mineralization in oxygen-controlled sediment-seawater cultivations with autochthonous microorganisms
Authors: Michaelsen M , Hulsch R , Höpner T , Berthe-Corti L
Published: January 2020

Laboratory studies investigated the influence of dissolved oxygen tension (DOT) on microbial degradation of hexadecane in cultures with sediment-seawater suspensions. With a fermentor system, it was possible to adjust and regulate different oxic conditions (DOTs between 0.4 and 80% of oxygen saturation) as well as anoxia. The effects of DOT reduction on the amount and rate of hexadecane degraded and on the degree of mineralization and on the production of biomass were investigated. When the DOT was reduced from 80% to 5%, no dependence of the investigated parameters on the oxygen concentration was found. The amount of hexadecane degraded was constant, with an average value of 86% of the initially applied amount. The degradation rate was constant even down to 1% DOT, with an average value of 0.15 mg of hexadecane per g of sediment per h (16.2 mg liter-1 h-1). The mean degree of mineralization was 70% of the initially applied hexadecane, and biomass production reached a value of about 1.5 g per g of hexadecane consumed. A significant influence on the degradation process was detected only with DOTs below 1%. The degree of mineralization and the amount of degraded hexadecane decreased, whereas the degradation rate was still unaffected. Under anoxic conditions, no hexadecane degradation occurred within 190 h. The fact that the hexadecane biodegradation rate was constant down to at least 0.04% DOT shows that the actual oxygen concentration is of minor importance as long as the oxygen supply is high enough to guarantee the oxygen-dependent degradation step.
Vibrio cholerae non-O1 isolated from ayu fish (Plecoglossus altivelis) in Japan
Authors: Kiiyukia C , Nakajima A , Nakai T , Muroga K , Kawakami H , Hashimoto H
Published: January 2020

A fish pathogen, Vibrio cholerae non-O1, was isolated from diseased ayu fish (Plecoglossus altivelis) collected from rivers in eight prefectural districts of Japan. This organism was found to have biochemical characteristics similar to those of V. cholerae non-O1, except that our isolates were negative for ornithine decarboxylase. Antiserum against an ayu isolate did not agglutinate with the majority of environmental V. cholerae non-O1 isolates, but a major O antigen was common among the ayu isolates. All strains were hemolytic to sheep erythrocytes, and oral administration of culture supernatants induced fluid accumulation in suckling mice. However, the crude toxin was not lethal to adult mice, and no cholera toxin-like enterotoxins were detected.
Enhanced biodegradation of phenanthrene in oil tar-contaminated soils supplemented with Phanerochaete chrysosporium
Authors: Brodkorb T S , Legge R L
Published: January 2020

In recent years, the white rot fungus Phanerochaete chrysosporium has shown promise as an organism suitable for the breakdown of a broad spectrum of environmental pollutants, including polynuclear aromatic hydrocarbons (PAHs). The focus of this study was to determine whether P. chrysosporium could effectively operate in an actual field sample of oil tar-contaminated soil. The soil was loaded with [14C]phenanthrene to serve as a model compound representative of the PAHs. Soil with the native flora present under static, aerobic conditions with buffering (pH 5.0 to 5.5) displayed full mineralization on the order of 20% in 21 days. The addition of P. chrysosporium was synergistic, with full mineralization on the order of 38% in 21 days. In addition to full mineralization, there was an increase in the proportion of radiolabelled polar extractives, both soluble and bound, in the presence of P. chrysosporium. From this study, it is apparent that the native soil microflora can be prompted into full mineralization of PAHs in some contaminated soils and that this mineralization can be enhanced when supplemented with the white rot fungus P. chrysosporium. With further refinement, this system may prove an effective bioremediation technology for soils contaminated with PAHs.
Metal-based formulations with high microbicidal activity
Authors: Sagripanti J L
Published: January 2020

Substances were evaluated for their relative potencies in inactivating Junin virus, Escherichia coli, and spores of Bacillus subtilis. Under the conditions of our test, glutaraldehyde was the most efficient agent among all substances currently recommended for disinfecting and sterilizing medical devices. Either copper or iron ions by themselves were able to inactivate virus with an efficiency similar to that of substances currently used for disinfection and sterilization. The microbicidal effect of metals, however, was enhanced further by the addition of peroxide. The mixtures of copper and peroxide described here were more efficient than glutaraldehyde in inactivating viruses and bacteria. The addition of a metal chelator to metal-peroxide mixtures further increased the microbicidal potency of the reagent. The formulations described in this study should be harmless to people but able to quickly and efficiently inactivate microorganisms, particularly viruses.
Evidence of hydrolytic route for anaerobic cyanide degradation
Authors: Fallon R D
Published: January 2020

Products observed during anaerobic cyanide transformation are consistent with a hydrolytic pathway (HCN + H2O <--> HCONH2 + H2O <--> HCOOH + NH3). Formate, the most frequently observed product, was generally converted to bicarbonate. Formamide was rapidly hydrolyzed to formate upon exposure to the anaerobic consortium but was not detected as an intermediate of cyanide transformation.
Organization and nucleotide sequence of the glutamine synthetase (glnA) gene from Lactobacillus delbrueckii subsp. bulgaricus
Authors: Ishino Y , Morgenthaler P , Hottinger H , Söll D
Published: January 2020

A 3.3-kb BamHI fragment of Lactobacillus delbrueckii subsp. bulgaricus DNA was cloned and sequenced. It complements an Escherichia coli glnA deletion strain and hybridizes strongly to a DNA containing the Bacillus subtilis glnA gene. DNA sequence analysis of the L. delbrueckii subsp. bulgaricus DNA showed it to contain the glnA gene encoding class I glutamine synthetase, as judged by extensive homology with other prokaryotic glnA genes. The sequence suggests that the enzyme encoded in this gene is not controlled by adenylylation. Based on a comparison of glutamine synthetase sequences, L. delbrueckii subsp. bulgaricus is much closer to gram-positive eubacteria, especially Clostridium acetobutylicum, than to gram-negative eubacteria and archaebacteria. The fragment contains another open reading frame encoding a protein of unknown function consisting of 306 amino acids (ORF306), which is also present upstream of glnA of Bacillus cereus. In B. cereus, a repressor gene, glnR, is found between the open reading frame and glnA. Two proteins encoded by the L. delbrueckii subsp. bulgaricus gene were identified by the maxicell method; the sizes of these proteins are consistent with those of the open reading frames of ORF306 and glnA. The lack of a glnR gene in the L. delbrueckii subsp. bulgaricus DNA in this position may indicate a gene rearrangement or a different mechanism of glnA gene expression.
Occurrence of Fumonisin in Forage Grass in New Zealand
Authors: Mirocha C. J. , Mackintosh C. G. , Mirza U. A. , Xie W. , Xu Y. , Chen J.
Published: January 2020

Fumonisin B
1
(FB
1
) was isolated from samples of forage grass originating in paddocks associated with an idiopathic disease of Canadian wapiti and wapiti-red deer hybrids characterized by “ill thrift” and liver dysfunction. Four of 40 samples contained 1, 3, 6, and 9 ppm (micrograms per gram) of FB
1
and 4, 0.5, 2, and 0.5 ppm, respectively, of the methyl ester of FB
1
. Analyses were done by ion spray mass spectrometry and confirmed by both fast atom bombardment (solids probe) and mass spectral analysis by electron impact ionization of the trifluoroacetate derivative of the base hydrolyzed product (pentolamine) of FB
1
. This article contains the first report of the presence of fumonisin B
1
in grass.
Identification and enumeration of Listeria monocytogenes by nonradioactive DNA probe colony hybridization
Authors: Datta A R , Moore M A , Wentz B A , Lane J
Published: January 2020

A plasmid containing the cloned listeriolysin gene of Listeria monocytogenes was used as a probe to identify Listeria strains by DNA colony hybridization. The probe DNA was labeled with horseradish peroxidase in the presence of glutaraldehyde. After the hybridization and wash procedures, the hybrid molecules were detected by luminescence, which resulted from the oxidation of luminol by a horseradish peroxidase-hydrogen peroxide-coupled reaction. Of the 150 Listeria strains and 16 non-Listeria strains examined, the probe hybridized only with L. monocytogenes. The technique was also used to enumerate L. monocytogenes in artificially contaminated foods.
Administration of different Lactobacillus strains in fermented oatmeal soup: in vivo colonization of human intestinal mucosa and effect on the indigenous flora
Authors: Johansson M L , Molin G , Jeppsson B , Nobaek S , Ahrné S , Bengmark S
Published: January 2020

In vivo colonization by different Lactobacillus strains on human intestinal mucosa of healthy volunteers was studied together with the effect of Lactobacillus administration on different groups of indigenous bacteria. A total of 19 test strains were administered in fermented oatmeal soup containing 5 x 10(6) CFU of each strain per ml by using a dose of 100 ml of soup per day for 10 days. Biopsies were taken from both the upper jejunum and the rectum 1 day before administration was started and 1 and 11 days after administration was terminated. The administration significantly increased the Lactobacillus counts on the jejunum mucosa, and high levels remained 11 days after administration was terminated. The levels of streptococci increased by 10- to 100-fold in two persons, and the levels of sulfite-reducing clostridia in the jejunum decreased by 10- to 100-fold in three of the volunteers 1 day after administration was terminated. In recta, the anaerobic bacterium counts and the gram-negative anaerobic bacterium counts decreased significantly by the end of administration. Furthermore, a decrease in the number of members of the Enterobacteriaceae by 1,000-fold was observed on the rectal mucosa of two persons. Randomly picked Lactobacillus isolates were identified phenotypically by API 50CH tests and genotypically by the plasmid profiles of strains and by restriction endonuclease analysis of chromosomal DNAs.(ABSTRACT TRUNCATED AT 250 WORDS)
Cloning of the afl-2 gene involved in aflatoxin biosynthesis from Aspergillus flavus
Authors: Payne G A , Nystrom G J , Bhatnagar D , Cleveland T E , Woloshuk C P
Published: January 2020

Aflatoxins are extremely potent carcinogens produced by Aspergillus flavus and Aspergillus parasiticus. Cloning of genes in the aflatoxin pathway provides a specific approach to understanding the regulation of aflatoxin biosynthesis and, subsequently, to the control of aflatoxin contamination of food and feed. This paper reports the isolation of a gene involved in aflatoxin biosynthesis by complementation of an aflatoxin-nonproducing mutant with a wild-type genomic cosmid library of A. flavus. Strain 650-33, blocked in aflatoxin biosynthesis at the afl-2 allele, was complemented by a 32-kb cosmid clone (B9), resulting in the production of aflatoxin. The onset and profile of aflatoxin accumulation was similar for the transformed strain and the wild-type strain (NRRL 3357) of the fungus, indicating that the integrated gene is under the same control as in wild-type strains. Complementation analyses with DNA fragments from B9 indicated that the gene resides within a 2.2-kb fragment. Because this gene complements the mutated afl-2 allele, it was designated afl-2. Genetic evidence obtained from a double mutant showed that afl-2 is involved in aflatoxin biosynthesis before the formation of norsolorinic acid, the first stable intermediate identified in the pathway. Further, metabolite feeding studies with the mutant, transformed, and wild-type cultures and enzymatic activity measurements in cell extracts of these cultures suggest that afl-2 regulates gene expression or the activity of other aflatoxin pathway enzymes. This is the first reported isolation of a gene for aflatoxin biosynthesis in A. flavus.
Occurrence of UV-Absorbing, Mycosporine-Like Compounds among Cyanobacterial Isolates and an Estimate of Their Screening Capacity
Authors: Garcia-Pichel Ferran , Castenholz Richard W.
Published: January 2020

A survey of 20 strains of cyanobacteria (belonging to 13 genera) isolated from habitats exposed to strong insolation revealed that 13 strains contained one or more water-soluble, UV-absorbing, mycosporine amino acid (MAA)-like compounds. Some of the compounds were identical in several strains. In all, 13 distinct compounds were found. The UV absorption spectra of MAAs complemented well that of the extracellular sunscreen pigment scytonemin, which many of the strains also produced. Even though the specific MAA contents were variable among strains, they were invariably higher when the cultures were grown with UV radiation than when it was absent. In five strains tested, the MAA complement accumulated as a solute in the cytoplasmic cell fraction. The sunscreen capacities of MAA and scytonemin and their combined capacity were estimated for each strain and condition on the basis of the specific contents, cell size, and cellular location of the compounds. The estimates suggested that significant, albeit not complete, protection from UV photodamage could be gained from the possession of either MAA or scytonemin but especially from simultaneous screening by both types of compounds.
Regulation and cloning of the gene encoding amylase activity of the ruminal bacterium Streptococcus bovis
Authors: Cotta M A , Whitehead T R
Published: January 2020

Streptococcus bovis is an important starch-degrading ruminal bacterium that has been implicated as being important in the etiology of a number of ruminal pathologies associated with diets high in grains. Previous studies with S. bovis have shown that amylase production was influenced by the growth substrate, but the nature of this regulation was not determined. The current study was conducted to better describe the regulatory phenomena and gain a better understanding of the molecular characteristics of this activity. Nutritional experiments demonstrated that the presence of starch or the starch-derived disaccharide maltose was required for maximum amylase production. Subsequent time-course experiments showed that amylase synthesis was induced by maltose and repressed by glucose, cellobiose, and fructose, while inulin and lactose had little effect on enzyme accumulation. The effects of the added antibiotics rifampin and tetracycline were consistent with transcriptional control of amylase synthesis. Analysis of S. bovis cells grown on glucose or maltose showed that they contained similar low levels of cyclic AMP, indicating that it was unlikely that regulation of amylase synthesis was mediated through a mechanism involving this nucleotide. The amylase gene from S. bovis JB1 was cloned and expressed in Escherichia coli. The amylase produced in E. coli was of lower molecular weight than that synthesized by S. bovis and had catalytic characteristics different from those of S. bovis amylase. When the gene was introduced back into S. bovis JB1, only one form of amylase activity was detected, indicating that the entire gene was present on this insert. The use of the amylase gene as a genetic probe for identification of S. bovis strains is discussed.
Restriction/Modification Systems and Restriction Endonucleases Are More Effective on Lactococcal Bacteriophages That Have Emerged Recently in the Dairy Industry
Authors: Moineau Sylvain , Pandian Sithian , Klaenhammer Todd R.
Published: January 2020

Recently, eight lytic small isometric-headed bacteriophages were isolated from cheese-manufacturing plants throughout North America. The eight phages were different, but all propagated on one strain,
Lactococcus lactis
NCK203. On the basis of DNA homology, they were classified in the P335 species. Digestion of their genomes in vitro with restriction enzymes resulted in an unusually high number of type II endonuclease sites compared with the more common lytic phages of the 936 (small isometric-headed) and c2 (prolate-headed) species. In vivo, the P335 phages were more sensitive to four distinct lactococcal restriction and modification (R/M) systems than phages belonging to the 936 and c2 species. A significant correlation was found between the number of restriction sites for endonucleases (purified from other bacterial genera) and the relative susceptibility of phages to lactococcal R/M systems. Comparisons among these three phage species indicate that the P335 species may have emerged most recently in the dairy industry.
Properties of nisin Z and distribution of its gene, nisZ, in Lactococcus lactis
Authors: de Vos W M , Mulders J W , Siezen R J , Hugenholtz J , Kuipers O P
Published: January 2020

Two natural variants of the lantibiotic nisin that are produced by Lactococcus lactis are known. They have a similar structure but differ in a single amino acid residue at position 27; histidine in nisin A and asparagine in nisin Z (J.W.M. Mulders, I.J. Boerrigter, H.S. Rollema, R.J. Siezen, and W.M. de Vos, Eur. J. Biochem, 201:581-584, 1991). The nisin variants were purified to apparent homogeneity, and their biological activities were compared. Identical MICs of nisin A and nisin Z were found with all tested indicator strains of six different species of gram-positive bacteria. However, at concentrations above the MICs, with nisin Z the inhibition zones obtained in agar diffusion assays were invariably larger than those obtained with nisin A. This was observed with all tested indicator strains. These results suggest that nisin Z has better diffusion properties than nisin A in agar. The distribution of the nisin variants in various lactococcal strains was determined by amplification of the nisin structural gene by polymerase chain reaction followed by direct sequencing of the amplification product. In this way, it was established that the nisZ gene for nisin Z production is widely distributed, having been found in 14 of the 26 L. lactis strains analyzed.
Microbial degradation of dibenzofuran, fluorene, and dibenzo-p-dioxin by Staphylococcus auriculans DBF63
Authors: Monna L , Omori T , Kodama T
Published: January 2020

Staphylococcus auriculans DBF63, which can grow on dibenzofuran (DBF) or fluorene (FN) as the sole source of carbon and energy, was isolated. Salicylic acid and gentisic acid accumulated in the culture broth of this strain when DBF was supplied as a growth substrate. Also, the formation of 9-fluorenol, 9-fluorenone, 4-hydroxy-9-fluorenone, and 1-hydroxy-9-fluorenone was demonstrated, and accumulation of 1,1a-dihydroxy-1-hydro-9-fluorenone was observed when this strain grew on FN. On the basis of these results, the degradation pathways of DBF and FN were proposed. The analogous oxidation products of dibenzo-p-dioxin were obtained by incubation with DBF-grown S. auriculans DBF63 cells.
Differentiation of Listeria monocytogenes and Listeria innocua by 16S rRNA genes and intraspecies discrimination of Listeria monocytogenes strains by random amplified polymorphic DNA polymorphisms
Authors: Czajka J , Bsat N , Piani M , Russ W , Sultana K , Wiedmann M , Whitaker R , Batt C A
Published: January 2020

Differences in the 16S rRNA genes (16S rDNA) which can be used to discriminate Listeria monocytogenes from Listeria innocua have been detected. The 16S rDNA were amplified by polymerase chain reaction with a set of oligonucleotide primers which flank a 1.5-kb fragment. Sequence differences were observed in the V2 region of the 16S rDNA both between L. monocytogenes Scott A and L. innocua and between different L. monocytogenes serotypes. Although L. monocytogenes SLCC2371 had the same V2 region sequence as L. innocua, the two species were different within the V9 region at nucleotides 1259 and 1292, in agreement with previous studies (R.-F. Wang, W.-W. Cao, and M.G. Johnson, Appl. Environ. Microbiol. 57:3666-3670, 1991). Intraspecies discrimination of L. monocytogenes strains was achieved by using the patterns generated by random amplified polymorphic DNA primers. Although some distinction can be made within the L. monocytogenes species by their 16S rDNA sequence, a far greater discrimination within species could be made by generating random amplified polymorphic DNA patterns from chromosomal DNA. By using a number of 10-bp primers, unique patterns for each isolate which in all cases examined differentiate between various L. monocytogenes serotypes, even though they may have the same 16S rRNA sequences, could be generated.
Chromosomal rearrangements during vegetative growth of a wild strain of Saccharomyces cerevisiae
Authors: Longo E , Vezinhet F
Published: January 2020

Electrophoretic karyotypes of two strains of Saccharomyces cerevisiae, a haploid laboratory strain and a wild strain known to be at least diploid, have been checked during vegetative growth. The karyotype of the haploid strain was very stable; however, the diploid strain underwent frequent modifications. In most cases the number of bands was reduced, but occasionally we observed one band splitting into two. In one case, chromosomal rearrangements took place between differently sized copies of chromosomes I and VI. We concluded that the chromosome length polymorphism observed among wild strains of S. cerevisiae could be explained partly by chromosomal structure reorganization occurring during mitosis.
Comparison of membrane filters for recovery of legionellae from water samples
Authors: Smith L , Carroll K , Mottice S
Published: January 2020

The procedure currently used for isolating legionellae from environmental samples recommend filtration through a 0.2-microns-pore-size polycarbonate filter. In this study we evaluated the performance of 23 other filters composed of various materials and having various pore sizes. We prefer the 0.2-micron-pore-size Gelman Supor filter because of its high level of recovery, faster filtration rate, and ease of handling.
Waterborne Giardia cysts and Cryptosporidium oocysts in the Yukon, Canada
Authors: Roach P D , Olson M E , Whitley G , Wallis P M
Published: January 2020

Several outbreaks of waterborne giardiasis have occurred in southern Canada, but nothing has been reported from the Canadian North. The objective of this study was to collect information relevant to waterborne giardiasis and cryptosporidiosis in the Yukon including epidemiological data and analyses of water, sewage, and animal fecal samples. Remote, pristine water samples were found to be contaminated with Giardia cysts (7 of 22 or 32%) but not with Cryptosporidium oocysts. Giardia cysts were found in 21% (13 of 61) of animal scats, but no Cryptosporidium oocysts were observed (small sample size). Whitehorse's drinking water was episodically contaminated with Giardia cysts (7 of 42 or 17%) and Cryptosporidium oocysts (2 of 42 or 5%). Neither were found in Dawson City's water supply. The only water treatment in the Yukon is chlorination, but contact times and free chlorine residuals are often too low to provide adequate protection by disinfection. Raw sewage samples from the five largest population centers in the Yukon contained 26 to 3,022 Giardia cysts and 0 to 74 Cryptosporidium oocysts per liter. Treated sewage from Whitehorse contained fewer Giardia cysts but more Cryptosporidium oocysts on average. Both were detected in Lake Laberge, downstream of Whitehorse, which has a history of fecal coliform contamination. Daily monitoring of raw sewage from the suburbs of Whitehorse showed a summertime peak of Giardia cysts and occasional Cryptosporidium oocysts after springtime contamination of drinking water. Despite this evidence, epidemiological data for the Yukon showed an endemic infection rate of only 0.1% for giardiasis (cryptosporidiosis is not notifiable).(ABSTRACT TRUNCATED AT 250 WORDS)
Precipitation of cadmium by Clostridium thermoaceticum
Authors: Cunningham D P , Lundie L L
Published: January 2020

Cadmium at an initial concentration of 1 mM was completely precipitated by cultures of Clostridium thermoaceticum in complex medium. The precipitation was energy dependent and required cysteine, although cysteine alone did not act as a growth substrate. Electron microscopic analysis revealed localized areas of precipitation at the surfaces of nonstarved cells as well as precipitate in the surrounding medium. The addition of cadmium had no apparent effect on growth or acetogenesis. However, nickel and cadmium were synergistically toxic at a concentration (1 mM) at which neither alone was toxic. The amount of protein extracted from cadmium-treated cultures was twofold higher than that in control extracts, and the amount of total sulfide was fourfold higher in cultures containing cadmium than in control cultures. Comparable levels of cysteine desulfhydrase activity were observed in extracts of both cadmium-treated and control cultures, but the enzyme activity was expressed maximally about 24 h earlier in the cadmium-treated cultures than in the untreated controls.
Organic Thiols as Organolithotrophic Substrates for Growth of Phototrophic Bacteria
Authors: Visscher Pieter T. , Taylor Barrie F.
Published: January 2020

Rhodopseudomonas
sp. strain BB1, isolated from a coastal marine sediment, immediately metabolized mercaptomalate when grown on mercaptomalate. Sulfide was detected as an intermediate. Extracts of cells grown on mercaptomalate converted mercaptomalate or 3-mercaptopropionate to equimolar amounts of sulfide and either fumarate or acrylate, respectively.
Rhodopseudomonas
sp. strain BB1 gave higher growth yields on mercaptomalate than on sulfide or malate, consistent with metabolism of the carbon chain of the thiol and the liberated sulfide; i.e., the organic thiol was an organolithotrophic substrate. In contrast,
Thiocapsa roseopersicina
, isolated previously from a marine microbial mat, had similar growth yields on sulfide, mercaptomalate, or 3-mercaptopropionate, with fumarate or acrylate accumulation from the thiols.
T. roseopersicina
did not grow photoorganotrophically on fumarate or acrylate, and the thiols were only a source of sulfide for photolithoautotrophic growth.
Nuclear Ribosomal DNA as a Probe for Genetic Variability in the Japanese Pear Pathotype of
Alternaria alternata
Authors: Adachi Yoshihiko , Watanabe Hiroyuki , Tanabe Kentaro , Doke Noriyuki , Nishimura Syoyo , Tsuge Takashi
Published: January 2020

A restriction fragment length polymorphism analysis of nuclear ribosomal RNA genes (rDNA) was used to measure the amount and distribution of genetic variability in populations of the Japanese pear pathotype of
Alternaria alternata
on both micro- and macrogeographical scales. A total of 322 isolates were obtained from 13 areas in Aichi, Gifu, and Tottori Prefectures in central and western Japan. The restriction fragment length polymorphism analysis revealed that the pathogen populations contained at least eight rDNA variants. The eight variant types differed in the lengths and in the presence of the restriction sites in spacer DNA outside the coding regions for rRNAs. A total of 271 isolates were classified into the eight types. The remaining 51 isolates were determined to have mixed rDNA types. Single pear fields typically contained two to five types of rDNA variants. The frequencies of rDNA variants in 11 populations in Tottori Prefecture were compared; in this prefecture orchards containing the susceptible pear are common. Except for one collection site, there were no significant differences in the composition of the rDNA variants among the populations. This suggests that dispersal of inocula has occurred frequently in Tottori Prefecture. In contrast, significantly different distributions were observed in the three prefectures, indicating that gene flow between prefectures might be limited by geographical isolation. DNA fingerprints resulting from hybridization with a moderately repetitive DNA sequence of the fungus revealed greater genetic variability and geographical differences in genetic population structure even within the same rDNA type.
Bacterial Adhesion under Static and Dynamic Conditions
Authors: Rijnaarts Huub H. M. , Norde Willem , Bouwer Edward J. , Lyklema Johannes , Zehnder Alexander J. B.
Published: January 2020

The deposition of various pseudomonads and coryneform bacteria with different hydrophobicities (water contact angles) and negative cell surface charges on negatively charged Teflon and glass surfaces was investigated. The levels of deposition varied between 5.0 × 10
4
and 1.6 × 10
7
cells cm
-2
and between 5.0 × 10
4
and 3.6 × 10
7
cells cm
-2
for dynamic column and static batch systems, respectively, indicating that there was a wide variation in physicochemical interactions. Batch and column results were compared in order to better distinguish between hydrodynamic and other system-dependent influences and method-independent physicochemical interactions. Despite the shorter suspension-solid contact time in columns (1 h) than in batch systems (4 h), the level of deposition (expressed as the number of cells that adhered) divided by the applied ambient cell concentration was 4.12 ± 1.63 times higher in columns than in batch sytems for 15 of 22 strain-surface combinations studied. This demonstrates that transport of microbial particles from bulk liquid to surfaces is more efficient in dynamic columns (transport dominated by convection and diffusion) than in static batch systems (transport by diffusion only). The relative constancy of this ratio for the 15 combinations shows that physicochemical interactions affect adhesion similarly in the two systems. The deviating deposition behavior of the other seven strain-surface combinations could be attributed to method-dependent effects resulting from specific cell characteristics (e.g., to the presence of capsular polymers, to an ability to aggregate, to large cell sizes, or to a tendency to desorb after passage through an air-liquid interface).
Cloning of the Aspergillus parasiticus apa-2 gene associated with the regulation of aflatoxin biosynthesis
Authors: Chang P K , Cary J W , Bhatnagar D , Cleveland T E , Bennett J W , Linz J E , Woloshuk C P , Payne G A
Published: January 2020

An Aspergillus parasiticus gene, designated apa-2, was identified as a regulatory gene associated with aflatoxin biosynthesis. The apa-2 gene was cloned on the basis of overproduction of pathway intermediates following transformation of fungal strains with cosmid DNA containing the aflatoxin biosynthetic genes nor-1 and ver-1. Transformation of an O-methylsterigmatocystin-accumulating strain, A. parasiticus SRRC 2043, with a 5.5-kb HindIII-XbaI DNA fragment containing apa-2 resulted in overproduction of all aflatoxin pathway intermediates analyzed. Specific enzyme activities associated with the conversion of norsolorinic acid and sterigmatocystin were increased approximately twofold. The apa-2 gene was found to complement an A. flavus afl-2 mutant strain for aflatoxin production, suggesting that apa-2 is functionally homologous to afl-2. Comparison of the A. parasiticus apa-2 gene DNA sequence with that of the A. flavus afl-2 gene (G. A. Payne, G. J. Nystorm, D. Bhatnagar, T. E. Cleveland, and C. P. Woloshuk, Appl. Environ. Microbiol. 59:156-162, 1993) showed that they shared > 95% DNA homology. Physical mapping of cosmid subclones placed apa-2 approximately 8 kb from ver-1.
Attachment Stimulates Exopolysaccharide Synthesis by a Bacterium
Authors: Vandevivere Philippe , Kirchman David L.
Published: January 2020

This study examined the hypothesis that solid surfaces may stimulate attached bacteria to produce exopolymers. Addition of sand to shake-flask cultures seemed to induce exopolymer synthesis by a number of subsurface isolates, as revealed by optical microscopy. Several additional lines of evidence indicated that exopolymer production by attached cells (in continuous-flow sand-packed columns) was greater than by their free-living counterparts. Total carbohydrates and extracellular polysaccharides, both normalized to cell protein, were greater (2.5- and 5-fold, respectively) for attached cells than for free-living cells. Also, adsorption of a polyanion-binding dye to the exopolymer fraction was sixfold greater for attached cells than for unattached cells. When surface-grown cells were resuspended in fresh medium, exopolymer production decreased to the level characteristic of unattached cells, which ruled out the possibility that attached cells comprised a subpopulation of sticky mucoid variants. The mechanism by which attachment stimulated exopolymer synthesis did not involve changes of the specific growth rate, growth stage, or limiting nutrient.
Rapid, automated separation of specific bacteria from lake water and sewage by flow cytometry and cell sorting
Authors: Porter J , Edwards C , Morgan J A , Pickup R W
Published: January 2020

The use of fluorescence-activated flow cytometric cell sorting to obtain highly enriched populations of viable target bacteria was investigated. Preliminary studies employed mixtures of Staphylococcus aureus and Escherichia coli. Cells of S. aureus, when mixed in different proportions with E. coli, could be selectively recovered at a purity in excess of 90%. This was possible even when S. aureus composed only approximately 0.4% of the total cells. Cell sorting was also tested for the ability to recover E. coli from natural lake water populations and sewage. The environmental samples were challenged with fluorescently labelled antibodies specific for E. coli prior to cell sorting. Final sample purities of greater than 70% were routinely achieved, as determined by CFU. Populations of E. coli released into environmental samples were recovered at greater than 90% purity. The use of flow cytometry and cell sorting to detect and recover viable target bacteria present at levels of less than 1% within an indigenous microflora was also demonstrated.
Fusarium poae
and
Fusarium crookwellense
, Fungi Responsible for the Natural Occurrence of Nivalenol in Hokkaido
Authors: Sugiura Yoshitsugu , Fukasaku Kazuaki , Tanaka Toshitsugu , Matsui Yukio , Ueno Yoshio
Published: January 2020

To determine the reasons for the natural occurrence of nivalenol in the northernmost area of Japan, scabby wheat was harvested from 19 crop fields in Hokkaido. Mycological surveys and analysis for mycotoxin contamination were performed. Among 13 wheat grain samples harvested in seven locations, 9, 2, and 6 samples were positive for deoxynivalenol, nivalenol, and zearalenone, respectively, at levels ranging from 0.03 to 1.28 μg/g, 0.04 to 1.22 μg/g, and 2 to 25 ng/g, respectively. The predominant
Fusarium
species of the scabby wheat examined were
F. sporotrichioides, F. avenaceum, F. poae
, and
F. crookwellense.
Fifteen of 48
F. poae
isolates and all four
F. crookwellense
isolates were screened for the production of seven derivatives of trichothecenes and zearalenone respectively, on rice culture. One isolate of
F. poae
produced diacetoxyscirpenol alone (4.3 μg/g); seven produced nivalenol (1.3 to 23.8 μg/g), 4-acetylnivalenol (0.1 to 4.6 μg/g), and diacetoxyscirpenol (0.9 to 99.5 μg/g); and five produced nivalenol alone (0.4 to 3.5 μg/g). The remaining two isolates produced no trichothecenes. Zearalenone production was not found in any isolate of
F. poae
tested. All isolates of
F. crookwellense
produced nivalenol (0.9 to 22.5 μg/g), 4-acetylnivalenol (0.5 to 25.0 μg/g), and zearalenone (1.4 to 162.5 μg/g). From these results, it is apparent that deoxynivalenol and zearalenone, and occasionally nivalenol, occur naturally throughout Hokkaido, and it is suggested that nivalenol-producing
F. poae
and
F. crookwellense
strains are responsible for the natural contamination with nivalenol found in the northernmost area of Japan. Furthermore, it was found for the first time that several isolates of
F. poae
distributed in Hokkaido possessed the ability to produce both type A and type B trichothecenes.