bluuebunny/crossref_metadata_2025 huggingface dataset:
Transposon Mutagenesis and Excision of R′ Plasmids by Conjugative, Chimeric Plasmid pUW942 in Extra-Slow-Growing
Rhizobium japonicum
Strains
Authors: Arunakumari Alahari , Vidaver Anne K.
Published: January 2020

Transposons Tn
501
(specifying mercury resistance) and Tn
7
(specifying resistance to trimethoprim and streptomycin) were introduced into extra-slow-growing
Rhizobium japonicum
by conjugal transfer of the 82 kilobase chimeric plasmid pUW942. Mercury-resistant transconjugants were obtained at a frequency of 10
−7
to 10
−9
. The transfer frequency of streptomycin resistance was lower than that of mercury resistance, and Tn
7
was relatively unstable. pUW942 was not maintained as an autonomously replicating plasmid in
R. japonicum
strains. However, some of the Hg
r
transconjugants from the RJ19FY, RJ17W, and RJ12S strains acquired antibiotic markers of the vector plasmid pUW942. Southern hybridization of plasmid and chromosomal DNA of
R. japonicum
strains with
32
P-labeled pUW942 and pAS8Rep-1, the same plasmid as pUW942 except that it does not contain Tn
501
, revealed the formation of cointegrates between pUW942 and the chromosome of
R. japonicum.
More transconjugants with only Tn
501
insertions in plasmids or the chromosome were obtained in crosses with strains RJ19FY and RJ17W than with RJ12S. These retained stable Hg
r
both in plant nodules and under nonselective in vitro growth conditions. One of the RJ19FY and two of the RJ12S Hg
r
transconjugants with vector plasmid-chromosome cointegrates conjugally transferred plasmids of 82, 84 or 86, and 90 kilobases, respectively, into plasmidless
Escherichia coli
C. These plasmids strongly hybridized to pUW942 and
Eco
RI digests of total DNA of each respective
R. japonicum
strain but not to indigenous plasmid DNA of the
R. japonicum
strains. These R′ plasmids consisted of pUW942-specific
Eco
RI fragments and an additional one or two new fragments derived from the
R. japonicum
chromosome.
Evaluation of carriers used in the test methods of the Association of Official Analytical Chemists
Authors: Ascenzi J M , Ezzell R J , Wendt T M
Published: January 2020

Revision of the official test method for the determination of the tuberculocidal activity of disinfectants is being undertaken. The current procedure lacks precision and accuracy and is not quantitative. Variability associated with carriers and the lack of temperature control were evaluated in this paper. The use of porcelain versus stainless steel carriers was also evaluated. When carriers of either type were contaminated with Mycobacterium bovis BCG, the number of organisms on the carriers varied by as much as 1.0 on the log10 scale. The average number of organisms attached to each porcelain carried was 1.10 x 10(5) CFU (range, 2.7 x 10(4) to 2.7 x 10(5) CFU), whereas the average number of organisms attached to each stainless steel carrier was 1.38 x 10(5) CFU (range, 2.9 x 10(4) to 4.0 x 10(5) CFU). The average number of cells attached to the carrier was directly proportional to the number of cells in the contaminating cell suspension. Variations in drying time did not alter the number of cells attached to the carrier. When porcelain carriers were placed in a test solution, the average number of organisms washed from the carriers was 55% of the total, with a range of 19 to 80%, whereas for stainless steel carriers, the average number was 82% of the total, with a range of 52 to 96%. Data for B. subtilis spores were similar to those for M. bovis BCG, suggesting that there may be similar problems with the Association of Official Analytical Chemists sporicidal test, which uses carriers. It was also found that the lack of an exacting temperature control could influence the outcome of the test. Changes in temperature as little as 1 degree C could influence the rate of killing of M. bovis BCG.
Cloning in Streptococcus lactis of plasmid-mediated UV resistance and effect on prophage stability
Authors: Chopin M C , Chopin A , Rouault A , Simon D
Published: January 2020

Plasmid pIL7 (33 kilobases) from Streptococcus lactis enhances UV resistance and prophage stability. A 5.4-kilobase pIL7 fragment carrying genes coding for both characters was cloned into S. lactis, using plasmid pHV1301 as the cloning vector. The recombinant plasmid was subsequently transferred to three other S. lactis strains by transformation or protoplast fusion. Cloned genes were expressed in all tested strains.
Semicontinuous and Continuous Production of Chloroperoxidase by
Caldariomyces fumago
Immobilized in
k
-Carrageenan
Authors: Carmichael Robert D. , Jones Alan , Pickard Michael A.
Published: January 2020

Three strains of
Caldariomyces fumago
were immobilized in 4%
k
-carrageenan and tested for semicontinuous production of chloroperoxidase (CPO). Over an 80-day period, growing in defined medium,
C. fumago
strains CMI 89362 and ATCC 11925 produced enzyme concentrations of 99 and 71 mg/liter, respectively, during six production periods of 12 to 14 days, while
C. fumago
DAOM 137632 produced only 24 mg of CPO per liter during six growth periods of 10 days. CPO production was unaffected by various regimens of washing between transfers. Mycelial growth was primarily restricted to the head surface, and bead size increased linearly with time. Attempts to restrict growth but maintain CPO production were unsuccessful. Pigment production, fructose utilization, and pH change in the immobilized cell cultures compared closely with the growth characteristics of free cell cultures. By using an airlift tower fermentor with an external loop run with continuous medium replacement of 20 ml/h (
D
= 0.016), strain CMI 89362 in bead form produced CPO at 40 mg/liter for 11 days.
Influence of Macrophyte Decomposition on Growth Rate and Community Structure of Okefenokee Swamp Bacterioplankton
Authors: Murray Robert E. , Hodson Robert E.
Published: January 2020

Dissolved substances released during decomposition of the white water lily (
Nymphaea odorata
) can alter the growth rate of Okefenokee Swamp bacterioplankton. In microcosm experiments dissolved compounds released from senescent
Nymphaea
leaves caused a transient reduction in the abundance and activity of water column bacterioplankton, followed by a period of intense bacterial growth. Rates of [
3
H]thymidine incorporation and turnover of dissolved
d
-glucose were depressed by over 85%, 3 h after the addition of
Nymphaea
leachates to microcosms containing Okefenokee Swamp water. Bacterial activity subsequently recovered; after 20 h [
3
H]thymidine incorporation in leachate-treated microcosms was 10-fold greater than that in control microcosms. The recovery of activity was due to a shift in the composition of the bacterial population toward resistance to the inhibitory compounds present in
Nymphaea
leachates. Inhibitory compounds released during the decomposition of aquatic macrophytes thus act as selective agents which alter the community structure of the bacterial population with respect to leachate resistance. Soluble compounds derived from macrophyte decomposition influence the rate of bacterial secondary production and the availability of microbial biomass to microconsumers.
Methods for quantitative and qualitative evaluation of vaginal microflora during menstruation
Authors: Onderdonk A B , Zamarchi G R , Walsh J A , Mellor R D , Muñoz A , Kass E H
Published: January 2020

The quantitative and qualitative changes in the bacterial flora of the vagina during menstruation have received inadequate study. Similarly, the effect of vaginal tampons on the microbial flora as well as the relationship between the microbial flora of the vagina and that of the tampon has not been adequately evaluated. The purposes of the present study were (i) to develop quantitative methods for studying the vaginal flora and the flora of tampons obtained during menstruation and (ii) to determine whether there were differences between the microflora of the tampon and that of the vaginal vault. Tampon and swab samples were obtained at various times from eight young healthy volunteers for 8 to 10 menstrual cycles. Samples consisted of swabs from women wearing menstrual pads compared with swab and tampon samples taken at various times during the menstrual cycle. Samples were analyzed for total facultative and anaerobic bacterial counts, and the six dominant bacterial species in each culture were identified. Statistical evaluation of the results indicates that total bacterial counts decreased during menstruation and that swab and tampon samples yielded similar total counts per unit weight of sample. The numbers of bacteria in tampons tended to be lower than in swabs taken at the same time. Overall, during menstruation, the concentrations of lactobacilli declined, but otherwise there was little difference among the species found during menstruation compared with those found in intermenstrual samples. Cotton tampons had little discernible effect on the microbial flora.
Rumen microbial changes in cattle fed diets with or without salinomycin
Authors: Olumeyan D B , Nagaraja T G , Miller G W , Frey R A , Boyer J E
Published: January 2020

Four rumen-fistulated steers, randomly assigned to two groups (control and salinomycin fed) were used to monitor the changes in rumen microbial populations and volatile fatty acids (VFA) concentrations associated with feeding salinomycin (0.22 mg X kg-1 X day-1). Steers were adapted to an alfalfa hay and grain (80:20) diet before supplementing the diet with salinomycin, and then the diet was changed to 50:50 and 20:80 ratios of alfalfa hay to grain at 2-week intervals. Rumen samples for total and selective enumeration of anaerobic bacteria. VFA analysis, and enumeration of protozoa were collected during the 80:20 alfalfa hay-to-grain diet before salinomycin feeding, and during the 80:20, 50:50, and 20:80 hay-to-grain diets with salinomycin. At each sampling period, rumen samples were collected at 3 h after feeding on three consecutive days. Salinomycin feeding had no effect on rumen pH and total VFA concentration. The acetate-to-propionate ratio was significantly lower in salinomycin-fed steers than in the control. The molar proportion of butyrate increased in both control and salinomycin-fed steers. Total anaerobic bacterial counts were lower in salinomycin-fed steers than in the control steers after 8 weeks of salinomycin feeding. Salinomycin-resistant bacteria increased from 7.6 to 15.6% in salinomycin-fed steers but remained unchanged in control steers. Salinomycin had no effect on cellulolytic and lactate-utilizing bacteria, but the proportion of amylolytic bacteria was higher in salinomycin-fed steers than in control steers. The total number of protozoa decreased initially in salinomycin-fed steers. The initial reduction was due to reduced numbers of Entodinium species. Holotrichs were unaffected by salinomycin feeding.
Stimulation of Tentoxin Synthesis by Aged-Culture Filtrates and Continued Synthesis in the Presence of Protein Inhibitors
Authors: Sheu Jyh-Tsing , Talburt Dwight E.
Published: January 2020

Tentoxin, a cyclic tetrapeptide produced by
Alternaria alternata
(Fries) Keissler, induces chlorosis in certain seedling plants. It can be extracted from culture filtrates of the fungus. Tentoxin production is stimulated and increased by using a mixture of aged culture filtrates and modified Richards solution. Aged culture filtrates can be obtained from 3-week-old or older cultures of
A. alternata
in modified Richards solution or Pratts solution. A mixture of aged culture filtrate and fresh medium in the ratio 2:3 gives the maximal enhancement of tentoxin production. This growth system provided us with a model for studying the effects of protein synthesis inhibitors on tentoxin production. Two antibiotics which inhibit protein synthesis at the ribosomal level were tested on growth, protein synthesis, and tentoxin production in
A. alternata
cultures. Cycloheximide at concentrations of 500 μg/ml or emetine at concentrations of 250 μg/ml did not inhibit tentoxin synthesis, although they stopped mycelial growth and protein synthesis of the fungus at the logarithmic growth stage in the enhancement medium. These results led us to conclude that tentoxin, like certain other bioactive cyclic peptides, is synthesized by a nonribosomal peptide synthesis mechanism.
Glyphosate-Degrading Microorganisms from Industrial Activated Sludge
Authors: Balthazor Terry M. , Hallas Laurence E.
Published: January 2020

A plating medium was developed to isolate
N
-phosphonomethylglycine (glyphosate)-degrading microorganisms, with glyphosate as the sole phosphorus source. Two industrial biosystems treating glyphosate wastes contained elevated microbial counts on the medium. One purified isolate metabolized glyphosate to aminomethylphosphonic acid, mineralizing this accumulating intermediate during log growth. This microorganism has been identified as a
Flavobacterium
species.
Isolation of Listeria monocytogenes from raw milk
Authors: Hayes P S , Feeley J C , Graves L M , Ajello G W , Fleming D W
Published: January 2020

During a recent outbreak of listeriosis, we examined 121 raw milk samples and 14 milk socks (filters). Listeria monocytogenes was recovered from 15 (12%) of 121 milk specimens and 2 (14%) of 14 milk socks. The optimal processing method consisted of cold enriching diluted milk for 1 month with culture to selective broth, followed by plating.
Improved Flotation Technique for Microscopy of In Situ Soil and Sediment Microorganisms
Authors: Bone T. L. , Balkwill D. L.
Published: January 2020

An improved flotation method for microscopy of in situ soil and sediment microorganisms was developed. Microbial cells were released into gellike flotation films that were stripped from soil and sediment aggregates as these aggregates were submerged in 0.5% solutions of polyvinylpyrrolidone. The use of polyvinylpyrrolidone solutions instead of water facilitated the release of films from saturated samples such as aquifer sediments as well as from typical surface soils. In situ microbial morphological characteristics could then be surveyed rapidly by light microscopy of films stained with acridine orange. This method effectively determined the ranges of morphological diversity in a variety of sample types. It also detected microcolonies and other spatial relationships among microbial cells. Only a small fraction (3.4 to 10.1%) of the microflora was released into the flotation films, but plating and direct evaluations by microscopy showed that this fraction was representative of the total population.
Isolation and Characterization of Coproporphyrin Produced by Four Subspecies of
Bacillus thuringiensis
Authors: Harms R. L. , Martinez D. R. , Griego V. M.
Published: January 2020

It was found by using spectrophotometric, spectrofluorometric, and high-pressure liquid chromatography that four subspecies of
Bacillus thuringiensis
produce coproporphyrin. The porphyrin isomer was identified as coproporphyrin I for
B. thuringiensis
subsp.
kurstaki
(HD1). The porphyrin was isolated both from spores and from a variety of spent growth media. The quantity of porphyrin released by each
Bacillus
subspecies differed. The rank order of porphyrin production follows:
B. thuringiensis
subsp.
kurstaki
HD1 >
B. thuringiensis
subsp.
thuringiensis
HD27 >
B. thuringiensis
subsp.
thuringiensis
HD41 >
B. thuringiensis
subsp.
darmstadiensis
HD199.
Optimized Batch Fermentation of Cheese Whey-Supplemented Feedlot Waste Filtrate to Produce a Nitrogen-Rich Feed Supplement for Ruminants
Authors: Erdman M. D. , Reddy C. Adinarayana
Published: January 2020

An optimized batch fermentation process for the conversion of cattle feedlot waste filtrate, supplemented with cheese whey, into a nitrogenous feed supplement for ruminants is described. Feedlot waste filtrate supplemented with cheese whey (5 g of whey per 100 ml) was fermented by the indigenous microbial flora in the feedlot waste filtrate. Ammonium hydroxide was added to the fermentation not only to maintain a constant pH but also to produce ammonium salts of organic acids, which have been shown to be valuable as nitrogenous feed supplements for ruminants. The utilization of substrate carbohydrate at pH 7.0 and 43°C was >94% within 8 h, and the crude protein (total N × 6.25) content of the product was 70 to 78% (dry weight basis). About 66 to 69% of the crude protein was in the form of ammonia nitrogen. Lactate and acetate were the predominant acids during the first 6 to 8 h of fermentation, but after 24 h, appreciable levels of propionate and butyrate were also present. The rate of fermentation and the crude protein content of the product were optimal at pH 7.0 and decreased at a lower pH. For example, fermentation did not go to completion even after 24 h at pH 4.5. Fermentation proceeded optimally at 43°C, less so at 37°C, and considerably more slowly at 23 and 50°C. Concentrations of up to 15 g of cheese whey per 100 ml of feedlot waste filtrate were fermented efficiently. Fermentation of feedlot waste filtrate obtained from animals fed low silage-high grain, high silage-low grain, or dairy rations resulted in similar products in terms of total nitrogen and organic acid composition.
Investigation of cadmium resistance in an Alcaligenes sp
Authors: McEntee J D , Woodrow J R , Quirk A V
Published: January 2020

The mechanisms of metal resistance of a cadmium-resistant Alcaligenes sp. were studied. Growth in a defined medium was unaffected by cadmium at concentrations up to 0.1 mM, while at concentrations up to 2.5 mM, growth occurred after an extended lag phase. The increase in length of the lag phase was abolished by repeated subculturing at these higher concentrations. However, subculture in the absence of cadmium reversed the adaptation process. Plasmid DNA was not detected in adapted cells, suggesting that adaptation is not plasmid mediated. Increased sulfide production in response to cadmium was observed, although the levels were too low to account fully for cadmium resistance. Adaptation of cells to cadmium resulted in the appearance of a major new membrane protein (molecular weight, 34,500) whose presence was not dependent upon the method of membrane preparation. This protein was induced at cadmium concentrations of 0.1 mM and above, but below this level the protein was absent. The onset of growth at concentrations above 0.1 mM was coincident with the appearance of this protein, which was also induced by zinc (0.4 mM) but not by manganese or nickel. The protein was only solubilized by a sodium dodecyl sulfate-2-mercaptoethanol mixture. Similar solubility properties were shown by a second major membrane protein (molecular weight, 33,000). These two proteins proved to be similar by peptide-mapping experiments and amino acid analysis. The appearance of the 34,500-molecular-weight protein and its possible role in cadmium resistance are discussed.
Rapid extraction of plasmids from Clostridium perfringens
Authors: Mahony D E , Clark G A , Stringer M F , MacDonald M C , Duchesne D R , Mader J A
Published: January 2020

Two rapid methods were evaluated for their extraction of plasmids from Clostridium perfringens. The first method involved lysis of 1 to 2 ml of C. perfringens culture by treatment with hyaluronidase, lysozyme, and sarcosyl. DNA, extracted with phenol-chloroform, was treated with RNase, boiled, and electrophoresed in a 1.2% agarose gel. The second method involved lysis of 2 ml of culture by lysozyme treatment and extraction with alkaline sodium dodecyl sulfate (SDS). Extracted DNA was treated with RNase, boiled, and electrophoresed in a 0.7% agarose gel. Of 57 strains of C. perfringens analyzed by both extraction procedures, 11 were shown to have plasmids by the alkaline SDS method which were missed by the phenol-chloroform extraction method. These new plasmids were of higher molecular mass and ranged up to 68 megadaltons. Use of the DNase inhibitor diethyl pyrocarbonate did not further improve the yield of plasmid DNA. An additional 159 isolates of C. perfringens screened by the alkaline SDS method revealed plasmids up to 80 megadaltons in mass and an overall plasmid carriage rate of 69%.
Biotransformations of Chloroguaiacols, Chlorocatechols, and Chloroveratroles in Sediments
Authors: Remberger Mikael , Allard Ann-Sofie , Neilson Alasdair H.
Published: January 2020

The occurrence of trichloro- and tetrachloroguaiacols, -catechols, and -veratroles and their transformation was studied in freshwater and brackish water sediments putatively exposed to bleachery discharge. The samples contained both chloroguaiacols and chlorocatechols, of which >90% could not be removed by simple extraction. The bound concentrations varied and ranged from 550 μg kg of organic C
−1
for 3,4,5-trichloroguaiacol to 8,250 μg kg of organic C
−1
for tetrachlorocatechol. Chlorinated substrates added to the aqueous phase were rapidly bound to the sediment with

K
p

values between 1.3 and 2.8 ml kg of organic C
−1
for the chloroguaiacols and chloroveratroles and 22 to 36 ml kg of organic C
−1
for the chlorocatechols. Sediment samples incubated aerobically brought about O-methylation of 4,5,6-trichloroguaiacol to 3,4,5-trichloroveratrole in a yield of ca. 25%. Under anaerobic conditions, however, de-O-methylation of both the chloroguaiacols and chloroveratroles took place with synthesis of the corresponding chlorocatechols. In separate experiments, the chlorocatechols were not completely stable under anaerobic conditions, but their ultimate fate has not yet been resolved. Sediment which had been autoclaved twice at 121°C for 20 min was unable to bring about any of these transformations; we therefore conclude that they were mediated by biological processes. These results emphasize that, in determining the fate of chloroguaiacols and related compounds discharged into the aquatic environment, the cardinal roles of sorption to the sediment phase and of the oxygen tension must be taken into account. We propose a hypothetical guaiacol cycle to accommodate our observations.
Quantitative determination of infinite inhibition concentrations of antimicrobial agents
Authors: Marwan A G , Nagel C W
Published: January 2020

We developed a method to determine the infinite inhibition concentrations (IICs) of antimicrobial agents. This method was based on finding the relative effectiveness of an inhibitor at various concentrations. Benzoic acid and parabens were tested on Saccharomyces bayanus, Hansenula sp., and Pseudomonas fluorescens. The relative effectiveness values of these compounds were established. A plot of the inhibitor concentration versus the reciprocal of relative effectiveness was linear. The chi-axis intercept was the concentration of the inhibitor which gave infinite microbial inhibition. For S. bayanus the IICs were 330, 930, 480, and 220 ppm (330, 930, 480, and 220 ml/liter) for benzoic acid and methyl-, ethyl-, and propylparabens, respectively. For Hansenula sp. the IIC was 180 ppm for benzoic acid. For P. fluorescens the IICs were 1,310, 960, and 670 ppm for methyl-, ethyl-, and propylparabens, respectively. Our results indicated that the IIC is affected by the growth medium. The advantages and applications of this method are discussed.
Bacteria Associated with the Ectoperitrophic Space in the Midgut of the Larva of the Midge
Xylotopus par
(Diptera: Chironomidae)
Authors: Kaufman Michael G. , Pankratz H. Stuart , Klug Michael J.
Published: January 2020

An ectoperitrophic association of bacteria with the midgut of
Xylotopus par
larvae was investigated by scanning electron microscopy and transmission electron microscopy. The bacteria attached to the epithelium as a well-defined band in the posterior midgut. They were morphotypically uniform and formed short filaments with endosporelike structures. The consistent presence and well-defined location of the bacteria in a region of the insect digestive tract usually void of microbes indicates a highly evolved symbiotic association, the nature of which is unknown at present.
Organic Matter Mineralization with Reduction of Ferric Iron in Anaerobic Sediments
Authors: Lovley Derek R. , Phillips Elizabeth J. P.
Published: January 2020

The potential for ferric iron reduction with fermentable substrates, fermentation products, and complex organic matter as electron donors was investigated with sediments from freshwater and brackish water sites in the Potomac River Estuary. In enrichments with glucose and hematite, iron reduction was a minor pathway for electron flow, and fermentation products accumulated. The substitution of amorphous ferric oxyhydroxide for hematite in glucose enrichments increased iron reduction 50-fold because the fermentation products could also be metabolized with concomitant iron reduction. Acetate, hydrogen, propionate, butyrate, ethanol, methanol, and trimethylamine stimulated the reduction of amorphous ferric oxyhydroxide in enrichments inoculated with sediments but not in uninoculated or heat-killed controls. The addition of ferric iron inhibited methane production in sediments. The degree of inhibition of methane production by various forms of ferric iron was related to the effectiveness of these ferric compounds as electron acceptors for the metabolism of acetate. The addition of acetate or hydrogen relieved the inhibition of methane production by ferric iron. The decrease of electron equivalents proceeding to methane in sediments supplemented with amorphous ferric oxyhydroxides was compensated for by a corresponding increase of electron equivalents in ferrous iron. These results indicate that iron reduction can outcompete methanogenic food chains for sediment organic matter. Thus, when amorphous ferric oxyhydroxides are available in anaerobic sediments, the transfer of electrons from organic matter to ferric iron can be a major pathway for organic matter decomposition.
Biodegradation of chlorinated ethenes by a methane-utilizing mixed culture
Authors: Fogel M M , Taddeo A R , Fogel S
Published: January 2020

Chlorinated ethenes are toxic substances which are widely distributed groundwater contaminants and are persistent in the subsurface environment. Reports on the biodegradation of these compounds under anaerobic conditions which might occur naturally in groundwater show that these substances degrade very slowly, if at all. Previous attempts to degrade chlorinated ethenes aerobically have produced conflicting results. A mixed culture containing methane-utilizing bacteria was obtained by methane enrichment of a sediment sample. Biodegradation experiments carried out in sealed culture bottles with radioactively labeled trichloroethylene (TCE) showed that approximately half of the radioactive carbon had been converted to 14CO2 and bacterial biomass. In addition to TCE, vinyl chloride and vinylidene chloride could be degraded to products which are not volatile chlorinated substances and are therefore likely to be further degraded to CO2. Two other chlorinated ethenes, cis and trans-1,2-dichloroethylene, were shown to degrade to chlorinated products, which appeared to degrade further. A sixth chlorinated ethene, tetrachloroethylene, was not degraded by the methane-utilizing culture under these conditions. The biodegradation of TCE was inhibited by acetylene, a specific inhibitor of methane oxidation by methanotrophs. This observation supported the hypothesis that a methanotroph is responsible for the observed biodegradations.
Effect of lectin on nodulation by wild-type Bradyrhizobium japonicum and a nodulation-defective mutant
Authors: Halverson L J , Stacey G
Published: January 2020

The nodulation characteristics of wild-type Bradyrhizobium japonicum USDA 110 and mutant strain HS111 were examined. Mutant strain HS111 exhibits a delayed-nodulation phenotype, a result of its inability to initiate successful nodulation promptly following inoculation of the soybean root. Previously, we showed that the defect in initiation of infection leading to subsequent nodulation which is found in HS111 can be phenotypically reversed by pretreatment with soybean root exudate or soybean seed lectin. This effect is not seen after pretreatment with root exudates and lectins obtained from other plant species. Treatment of strain HS111 with as little as 10 soybean seed lectin molecules per bacterium (3.3 X 10 (-12) M) resulted in enhancement of nodule formation. Pretreatment of wild-type B. japonicum USDA 110 with soybean root exudate or seed lectin increased nodule numbers twofold on 6-week-old plants. Wild-type strain USDA 110 cells inoculated at 10(4) cells per seedling exhibited a delay in initiation of infection leading to subsequent nodulation. Wild-type cells pretreated in soybean root exudates or seed lectin did not exhibit a delay in nodulation at this cell concentration. Mutant strain HS111 pretreated in seed lectin for 0 or 1 h, followed by washing with the hapten D-galactose to remove the lectin, exhibited a delay in initiation of nodulation. Phenotypic reversal of the delayed-nodulation phenotype exhibited by strain HS111 was seen if incubation was continued for an additional 71 h in plant nutrient solution following 1 h of lectin pretreatment. Reversal of the delayed-nodulation phenotype of HS111 through lectin pretreatment was prevented by chloramphenicol or rifampin.(ABSTRACT TRUNCATED AT 250 WORDS)
Rapid assay for screening and characterizing microorganisms for the ability to degrade polychlorinated biphenyls
Authors: Bedard D L , Unterman R , Bopp L H , Brennan M J , Haberl M L , Johnson C
Published: January 2020

We designed a rapid assay that assesses the polychlorinated biphenyl (PCB)-degradative competence and congener specificity of aerobic microorganisms, identifies strains capable of degrading highly chlorinated biphenyls, and distinguishes among those that degrade PCBs by alternative pathways. Prior attempts to assay PCB-degradative competence by measuring disappearance of Aroclors (commercial PCB mixtures) have frequently produced false-positive findings because of volatilization, adsorption, or absorption losses. Furthermore, these assays have generally left the chemical nature of the competence obscure because of incomplete gas chromatographic resolution and uncertain identification of Aroclor peaks. We avoided these problems by using defined mixtures of PCB congeners and by adopting incubation and extraction methods that prevent physical loss of PCBs. Our assay mixtures include PCB congeners ranging from dichloro- to hexachlorobiphenyls and representing various structural classes, e.g., congeners chlorinated on a single ring (2,3-dichlorobiphenyl), blocked at 2,3 sites (2,5,2'5'-tetrachlorobiphenyl), blocked at 3,4 sites (4,4'-dichlorobiphenyl), and lacking adjacent unchlorinated sites (2,4,5,2',4',5'-hexachlorobiphenyl). The PCB-degrative ability of microorganisms is assessed by packed-column gas chromatographic analysis of these defined congener mixtures following 24-h incubation with resting cells. When tested with 25 environmental isolates, this assay revealed a broad range of PCB-degradative competence, highlighted differences in congener specificity and in the extent of degradation of individual congeners, predicted degradative competence on commercial PCBs, and (iv) identified strains with superior PCB-degradative ability.
Natural occurrence of deoxynivalenol, 15-acetyl-deoxynivalenol, and zearalenone in refusal factor corn stored since 1972
Authors: Abbas H K , Mirocha C J , Tuite J
Published: January 2020

Two samples of "refusal factor" corn, one stored frozen in Minnesota and one stored dry in Indiana since 1972 or 1973, were analyzed for the presence of Fusarium spp. and Fusarium toxins. Both samples were from corn refused by swine in Indiana from 1972 to 1973. Sample FS 808 (stored in Indiana) contained 20 ppm of deoxynivalenol (20 micrograms/g), 16 ppm of 15-acetyl-deoxynivalenol, 5 ppm of zearalenone, and 0.2 ppm of alpha-zearalenol. Sample FS 362 (stored in Minnesota) contained 3 ppm of deoxynivalenol, 1 ppm of 15-acetyldeoxynivalenol, and 0.3 ppm of zearalenone. The presence of 15-acetyl-deoxynivalenol is significant because it is the first report of it occurring naturally in refusal factor corn, and it may account in part for the refusal that could not be solely attributed to deoxynivalenol.
Cloning and Expression in
Escherichia coli
of the Polysaccharide Depolymerase Associated with Bacteriophage-Infected
Erwinia amylovora
Authors: Vandenbergh Peter A. , Cole Ronald L.
Published: January 2020

The bacteriophage-encoded polysaccharide depolymerase produced in
Erwinia amylovora
has been cloned and expressed in
Escherichia coli
. The bacteriophage ERA103 genome was observed to consist of five
EcoR
I fragments, labeled as follows: A, 7.5 kilobases (kb); B, 5.0 kb; C, 2.7 kb; D, 2.1 kb; and E, 1.8 kb. A restriction map for ERA103 was also prepared. Each of the fragments were cloned into the positive-selection vector pOP203(A
2
+
) and pBR322.
Incidence of antibodies reactive with toxic shock syndrome toxin 1 in bovine milk
Authors: Thompson N E , Gomez-Lucia E , Bergdoll M S
Published: January 2020

Fourteen samples of bovine milk, purchased in six states, were found to contain significant antibody titers to toxic shock syndrome toxin 1. This reactivity seems to have been due primarily to antibodies of the immunoglobulin A class. Some of these antibodies survived the cheese-making process.
Enhancement of Wheat Root Colonization and Plant Development by
Azospirillum brasilense
Cd. Following Temporary Depression of Rhizosphere Microflora
Authors: Bashan Yoav
Published: January 2020

Inoculation of wheat with
Azospirillum brasilense
, combined with the application of four fungal and bacterium-inhibiting substances to which
A. brasilense
is resistant in the soil, decreased the rhizosphere population, while it increased wheat root colonization by
A. brasilense
, even in cases of poor inoculation. The inoculation significantly increased the following wheat plant parameters as well: plant dry weight, number of tillers per plant, spikelet fertility, harvest index, and grain yield. This model may provide a new approach to improve control of root colonization by beneficial bacteria.
Fermentation of Aqueous Plant Seed Extracts by Lactic Acid Bacteria
Authors: Schaffner Donald W. , Beuchat Larry R.
Published: January 2020

The effects of lactic acid bacterial fermentation on chemical and physical changes in aqueous extracts of cowpea (
Vigna unguiculata
), peanut (
Arachis hypogea
), soybean (
Glycine max
), and sorghum (
Sorghum vulgare
) were studied. The bacteria investigated were
Lactobacillus helveticus, L. delbrueckii, L. casei, L. bulgaricus, L. acidophilus
, and
Streptococcus thermophilus
. Organisms were inoculated individually into all of the seed extracts;
L. bulgaricus
and
S. thermophilus
were also evaluated together as inocula for fermenting the legume extracts. During fermentation, bacterial population and changes in titratable acidity, pH, viscosity, and color were measured over a 72-h period at 37°C. Maximum bacterial populations, titratable acidity, pH, and viscosity varied depending upon the type of extract and bacterial strain. The maximum population of each organism was influenced by fermentable carbohydrates, which, in turn, influenced acid production and change in pH. Change in viscosity was correlated with the amount of protein and titratable acidity of products. Color was affected by pasteurization treatment and fermentation as well as the source of extract. In the extracts inoculated simultaneously with
L. bulgaricus
and
S. thermophilus
, a synergistic effect resulted in increased bacterial populations, titratable acidity, and viscosity, and decreased pH in all the legume extracts when compared to the extracts fermented with either of these organisms individually. Fermented extracts offer potential as substitutes for cultured dairy products.
Symbiotic Effectiveness and Host-Strain Interactions of
Rhizobium fredii
USDA 191 on Different Soybean Cultivars
Authors: Israel Daniel W. , Mathis James N. , Barbour W. Mark , Elkan Gerald H.
Published: January 2020

Nodulation, acetylene reduction activity, dry matter accumulation, and total nitrogen accumulation by nodulated plants growing in a nitrogen-free culture system were used to compare the symbiotic effectiveness of the fast-growing
Rhizobium fredii
USDA 191 with that of the slow-growing
Bradyrhizobium japonicum
USDA 110 in symbiosis with five soybean (
Glycine max
(L.) Merr.) cultivars. Measurement of the amount of nitrogen accumulated during a 20-day period of vegetative growth (28 to 48 days after transplanting) showed that USDA 110 fixed 3.7, 39.1, 4.6, and 57.3 times more N
2
than did USDA 191 with cultivars Pickett 71, Harosoy 63, Lee, and Ransom as host plants, respectively. With the unimproved Peking cultivar as the host plant, USDA 191 fixed 3.3 times more N
2
than did the USDA 110 during the 20-day period. The superior N
2
fixation capability of USDA 110 with the four North American cultivars as hosts resulted primarily from higher nitrogenase activity per unit nodule mass (specific acetylene reduction activity) and higher nodule mass per plant. The higher N
2
-fixation capability of USDA 191 with the Peking cultivar as host resulted primarily from higher nodule mass per plant, which was associated with higher nodule numbers. There was significant variation in the N
2
-fixation capabilities of the four North American cultivar-USDA 191 symbioses. Pickett 71 and Lee cultivars fixed significantly more N
2
in symbiosis with USDA 191 than did the Harosoy 63 and Ransom cultivars. This quantitative variation in N
2
-fixation capability suggests that the total incompatibility (effectiveness of nodulation and efficiency of N
2
fixation) of host soybean plants and
R. fredii
strains is regulated by more than one host plant gene. These results indicate that it would not be prudent to introduce
R. fredii
strains into North American agricultural systems until more efficient N
2
-fixing symbioses between North American cultivars and these fast-growing strains can be developed. When inoculum containing equal numbers of USDA 191 and of strain USDA 110 was applied to the unimproved Peking cultivar in Perlite pot culture, 85% of the 160 nodules tested were occupied by USDA 191. With Lee and Ransom cultivars, 99 and 85% of 140 and 96 nodules tested, respectively, were occupied by USDA 110.
Isolation of indigenous wastewater bacterial strains capable of mobilizing plasmid pBR325
Authors: McPherson P , Gealt M A
Published: January 2020

Members of the family Enterobacteriaceae have been isolated from raw wastewater, identified, and characterized with respect to their plasmid content and antibiotic resistance. Several strains possessing both antibiotic resistance and high-molecular-weight plasmid(s) transferred their resistance characteristics to recipient cells during a 25 h coincubation. Eight were characterized (six Escherichia coli and two Klebsiella pneumoniae); each produced 10(2) to 10(7) transconjugants per ml by the end of the incubation period. They were also able to mobilize pBR325 from a laboratory E. coli strain into plasmid-free recipients to yield 10(2) to 10(7) transconjugants per ml. These transconjugants possessed phenotypic characteristics specified by pBR325, the R plasmid, and the chromosome of the recipient. Many transconjugants exhibited recombinational rearrangements of the acquired plasmid material.
Comparison of proteins involved in chondroitin sulfate utilization by three colonic Bacteroides species
Authors: Lipeski L , Guthrie E P , O'Brien M , Kotarski S F , Salyers A A
Published: January 2020

Three species of colonic bacteria can ferment the mucopolysaccharide chondroitin sulfate: Bacteroides ovatus, Bacteroides sp. strain 3452A (an unnamed DNA homology group), and B. thetaiotaomicron. Proteins associated with the utilization of chondroitin sulfate by B. thetaiotaomicron have been characterized previously. In this report we compare chondroitin lyases and chondroitin sulfate-associated outer membrane polypeptides of B. ovatus and Bacteroides sp. strain 3452A with those of B. thetaiotaomicron. All three species produce two soluble cell-associated chondroitin lyases, chondroitin lyase I and II. Purified enzymes from the three species have similar pH optima, Km values, and molecular weights. However, peptide mapping experiments show that the chondroitin lyases from B. ovatus and Bacteroides sp. strain 3452A are not identical to those of B. thetaiotaomicron. A cloned gene that codes for the chondroitin lyase II from B. thetaiotaomicron hybridized on a Southern blot with DNA from B. ovatus or Bacteroides sp. strain 3452A only when low-stringency conditions were used. Antibody to chondroitin lyase II from B. thetaiotaomicron did not cross-react with chondroitin lyase II from B. ovatus or Bacteroides sp. strain 3452A. Chondroitin lyase activity in all three species was inducible by chondroitin sulfate. B. ovatus and Bacteroides sp. strain 3452A, like B. thetaiotaomicron, have outer membrane polypeptides that appear to be regulated by chondroitin sulfate, but the chondroitin sulfate-associated outer membrane polypeptides differ in molecular weight. Despite these differences, the ability of intact bacteria to utilize chondroitin sulfate, as indicated by growth yields in carbohydrate-limited continuous culture and the rate at which the chondroitin lyases were induced, was the same for all three species.
Bradyrhizobium japonicum
Serocluster 123 and Diversity among Member Isolates
Authors: Schmidt E. L. , Zidwick Mary Jo , Abebe H. M.
Published: January 2020

Diversity was examined within a group of 79 isolates of
Bradyrhizobium japonicum
reactive to fluorescent antibodies (FAs) prepared against
B. japonicum
USDA 123. Analyses were by means of cross-adsorbed FAs, bacteriophage typing, and endonuclease restriction digest patterns. Serogroups 127 and 129 shared antigenic determinants with serogroup 123 but not with each other. Bacteriophage and DNA digest patterns reflected more common features between serogroups 123 and 127 than between 123 and 129. Serogroups 129 and 122 showed FA cross-reactivity. The term serocluster was proposed to reflect interrelationships observed among the serogroups.
Mutants of
Pachysolen tannophilus
with Improved Production of Ethanol from
d
-Xylose
Authors: Lee Hung , James Allen P. , Zahab Diana M. , Mahmourides George , Maleszka Ryszard , Schneider Henry
Published: January 2020

The conversion of
d
-xylose to ethanol by the yeast
Pachysolen tannophilus
is relatively inefficient in batch culture. The inefficiency has been attributed in part to concurrent utilization of ethanol in the presence of appreciable concentrations of
d
-xylose and to the formation of xylitol and other by-products. To increase the concentration of ethanol accumulated in batch cultures, UV-induced mutants of
P. tannophilus
were selected on the basis of diminished growth on ethanol. Eleven independent mutant loci that conferred the ethanol-defective phenotype were identified. Three led to a greater yield and volumetric rate of production of ethanol than the wild type. One also produced less xylitol and was characterized by a deficiency in activity for malate dehydrogenase.
Impact of Storms on Heterotrophic Activity of Epilimnetic Bacteria in a Southwestern Reservoir
Authors: Hubbard James G. , Chrzanowski Thomas H.
Published: January 2020

The impact of storm conditions on the heterotrophic activity of planktonic bacteria in a southwestern reservoir was investigated. Storm events were considered as rainfall in excess of 2.5 cm in a 24-h period before sampling. Storm conditions stimulated heterotrophic activities and resulted in increased uptake rates and decreased turnover times of glutamate and acetate. Uptake rates were 45 to 75% faster immediately after storm conditions than they were during calm conditions. Activity levels appeared to return to prestorm levels within 48 h. Bacterial cell numbers did not change substantially during storm events. Cell-specific activity indicated that increases in heterotrophic activity were the result of increased activity of individual cells. Light penetration, levels of particulate organic carbon,
K

t

+
S

n

values, and population levels of attached bacteria suggest that immediate sediment loading of the reservoir or increased substrate levels could not account for abrupt increases in heterotrophic activities.
Variation in composition and yield of exopolysaccharides produced by Klebsiella sp. strain K32 and Acinetobacter calcoaceticus BD4
Authors: Bryan B A , Linhardt R J , Daniels L
Published: January 2020

The exopolysaccharides produced by Klebsiella sp. strain K32 and Acinetobacter calcoaceticus BD4 under different growth conditions have been analyzed for sugar composition. The first use of ion chromatography for the quantitative determination of microbial exopolysaccharide composition is reported. Klebsiella sp. strain K32 produced a polymer composed of rhamnose, galactose, and mannose early in its fermentation. The composition of the polymer varied markedly depending on the growth stage of the organism. Klebsiella sp. strain K32 grown in a fermentor produced a polymer which was rich in mannose during early exponential growth in a complex medium, but in the late stationary phase it did not contain detectable levels of mannose. The rhamnose present in the polymer increased from 12 to 55% over the course of growth, whereas galactose decreased from 63 to 45%. A. calcoaceticus BD4 produced a polymer containing rhamnose, glucose, mannose throughout its growth and stationary phase. Klebsiella sp. strain K32 and A. calcoaceticus BD4 were grown on various carbon sources in shake flasks. The polymer yield and composition from both organisms were found to vary with the carbon source. The exopolysaccharide with the highest mannose composition was obtained by using rhamnose as a carbon source for both organisms. These and other data suggest that regulatory changes caused by growth on different substrates result in either the production of a different distribution of polymers or a change in exopolysaccharide structure.
Differential partition of virulent Aeromonas salmonicida and attenuated derivatives possessing specific cell surface alterations in polymer aqueous-phase systems
Authors: Van Alstine J M , Trust T J , Brooks D E
Published: January 2020

Two-polymer aqueous-phase systems were used to compare via partitioning the surface properties of strains of the fish pathogen Aeromonas salmonicida which differed in their ability to produce the surface protein array known as the A layer and in their ability to produce smooth lipopolysaccharide. In these two-phase systems, biological particles are known to partition between the phases in a manner related to a variety of surface properties, including hydrophobicity, charge, and lipid composition. Both the presence of the superficial protein layer and the O polysaccharide chains of lipopolysaccharide were shown to play an important role in the partitioning behavior of A. salmonicida cells. The presence of the A layer, which is crucial to the virulence of A. salmonicida, appeared to decrease the surface hydrophilicity of this pathogen and to increase, in a somewhat specific manner, its surface affinity for fatty acid esters of polyethylene glycol. The ability of two-polymer aqueous-phase systems to differentially partition A. salmonicida cells on the basis of differences in surface architecture suggests their general usefulness for the analysis of surface properties important in bacterial virulence and should permit their use in the selection of strains and mutants exhibiting specific surface characteristics.