bluuebunny/crossref_metadata_2025 huggingface dataset:
Listeria spp. found on fresh market produce
Authors: Heisick J E , Wagner D E , Nierman M L , Peeler J T
Published: January 2020

From October 1987 to August 1988, 1,000 tests were conducted on 10 types of fresh produce from two Minneapolis area supermarkets to detect Listeria spp. The produce included broccoli, cabbage, carrots, cauliflower, cucumbers, lettuce, mushrooms, potatoes, radishes, and tomatoes. The vegetables were tested by the Food and Drug Administration method for isolation of Listeria spp., with the addition of LiCl-phenylethanol-moxalactam agar in the last 280 tests; 8.6 and 11.4% of these tests were positive by modified McBride and LiCl-phenylethanol-moxalactam agars, respectively. Listeria monocytogenes was isolated from cabbage, cucumbers, potatoes, and radishes; L. innocua was isolated from cucumbers, lettuce, mushrooms, potatoes, and radishes; L. seeligeri was isolated from cabbage and radishes; and L. welshimeri was isolated from cucumbers, potatoes, and radishes. The isolates were of various serotypes; however, the L. monocytogenes isolates were predominantly serotype 1 (82%). Only potatoes (25.8% positive) and radishes (30.3% positive) showed significant amounts of L. monocytogenes contamination.
Production and characterization of antibodies against microcystins
Authors: Chu F S , Huang X , Wei R D , Carmichael W W
Published: January 2020

Antibodies against a microcystin (MCYST) leucine-arginine variant (MCYST-LR) were demonstrated 4 weeks after immunization of rabbits with either MCYST-LR-polylysine- or MCYST-LR-ethylenediamine-modified bovine serum albumin. A radioimmunoassay (RIA), a direct competitive enzyme-linked immunosorbent assay (ELISA), and an indirect competitive ELISA were developed for characterization of the antibodies. Indirect ELISA and RIA revealed that MCYST-LR-ethylenediamine-bovine serum albumin was a better immunogen. Competitive RIA and direct ELISA revealed that the antibodies had good cross-reactivities with an MCYST-arginine-arginine variant (MCYST-RR), MCYST-LR, an MCYST-tyrosine-arginine variant (MCYST-YR), and nodularin (NODLN); but they had lower reactivities with variants MCYST-leucine-tyrosine (MCYST-LY) and MCYST-leucine-alanine (MCYST-LA). The antibodies did not cross-react with ozonolyzed MCYST-LR. The concentrations causing 50% inhibition of binding of reduced MCYST-LR to the antibodies by MCYST-RR, MCYST-LR, MCYST-YR, NODLN, MCYST-LA, and MCYST-LY in the RIA were 43, 105, 112, 503, 671, and 1,920 ng/ml, respectively. The concentrations causing 50% inhibition of binding of MCYST-LR-horseradish peroxidase to the antibodies by MCYST-RR, MCYST-LR, MCYST-YR, NODLN, MCYST-LY, and MCYST-LA in the ELISA were 1.75, 2.2, 3.4, 4.6, 50, and 114 ng/ml, respectively.
Estimation of microbial densities from dilution count experiments
Authors: Haas C N
Published: January 2020

Although dilution counts have been widely used in quantitative microbiology, their interpretation has always been widely discussed both in microbiology and in applied statistics. Maximum-likelihood (most-probable-number) methods hae generally been used to estimate densities from dilution experiments. It has not been widely recognized that these methods are intrinsically and statistically biased at the sample sizes used in microbiology. This paper presents an analysis of proposed method for correction of such biases, and the method was found to be robust for moderate deviations from Poisson behavior. For analyses at greater variance with the Poisson assumptions, the use of the Spearman-Karber method is analyzed and shown to yield an estimate of density of lesser bias than that produced by the most-probable-number method. Revised methods of constructing confidence limits proposed by Loyer and Hamilton (M.W. Loyer and M.A. Hamilton, Biometrics 40:907-916, 1984) are also discussed, and charts for the three- and four-decimal dilution series with five tubes per dilution are presented.
Efficient ethanol production from glucose, lactose, and xylose by recombinant Escherichia coli
Authors: Alterthum F , Ingram L O
Published: January 2020

Lactose and all of the major sugars (glucose, xylose, arabinose, galactose, and mannose) present in cellulose and hemicellulose were converted to ethanol by recombinant Escherichia coli containing plasmid-borne genes encoding the enzymes for the ethanol pathway from Zymomonas mobilis. Environmental tolerances, plasmid stability, expression of Z. mobilis pyruvate decarboxylase, substrate range, and ethanol production (from glucose, lactose, and xylose) were compared among eight American Type Culture Collection strains. E. coli ATCC 9637(pLO1297), ATCC 11303(pLO1297), and ATCC 15224(pLO1297) were selected for further development on the basis of environmental hardiness and ethanol production. Volumetric ethanol productivities per hour in batch culture were 1.4 g/liter for glucose (12%), 1.3 g/liter for lactose (12%), and 0.64 g/liter for xylose (8%). Ethanol productivities per hour ranged from 2.1 g/g of cell dry weight with 12% glucose to 1.3 g/g of cell dry weight with 8% xylose. The ethanol yield per gram of xylose was higher for recombinant E. coli than commonly reported for Saccharomyces cerevisiae with glucose. Glucose (12%), lactose (12%), and xylose (8%) were converted to (by volume) 7.2% ethanol, 6.5% ethanol, and 5.2% ethanol, respectively.
Synthesis of poly-3-hydroxyalkanoates is a common feature of fluorescent pseudomonads
Authors: Huisman G W , de Leeuw O , Eggink G , Witholt B
Published: January 2020

The fluorescent pseudomonads are classified as a group, one characteristic of which is that they do not accumulate poly-3-hydroxybutyrate (PHB) during nutrient starvation in the presence of excess carbon source. In this paper we show that prototype strains from this subclass, such as Pseudomonas aeruginosa, Pseudomonas putida, and Pseudomonas fluorescens, do accumulate poly-3-hydroxyalkanoates (PHA) when grown on fatty acids. These PHAs are composed of medium-chain-length (C6 to C12) 3-hydroxy fatty acids. The ability to form these polyesters does not depend on the presence of plasmids. A specificity profile of the enzymes involved in the biosynthesis of PHA was determined by growing Pseudomonas oleovorans on fatty acids ranging from C4 to C18. In all cases, PHAs were formed which contained C6 to C12 3-hydroxy fatty acids, with a strong preference for 3-hydroxyoctanoate when Ceven fatty acids were supplied and 3-hydroxynonanoate when Codd fatty acids were the substrate. These results indicate that the formation of PHAs depends on a specific enzyme system which is distinct from that responsible for the synthesis of PHB. While the fluorescent pseudomonads are characterized by their inability to make PHB, they appear to share the capacity to produce PHAs. This characteristic may be helpful in classifying pseudomonads. It may also be useful in the optimization of PHA production for biopolymer applications.
31P nuclear magnetic resonance study of the effect of azide on xylose fermentation by Candida tropicalis
Authors: Lohmeier-Vogel E , Skoog K , Vogel H , Hahn-H�gerdal B
Published: January 2020

Maximal ethanol production by Candida tropicalis grown on xylose was obtained at an oxygen transfer rate of 5 to 7 mmol/liter per h. Addition of 0.2 mM azide increased the ethanol yield by a factor of 3 to 4, based on the cell mass produced, and decreased the formation of the by-product xylitol by 80%. In the presence of azide, ethanol was reassimilated before the carbon source was depleted. At all oxygenation levels studied, azide caused 25 to 60% of the carbon to be lost, most probably as carbon dioxide. Identical spectra were obtained with 31P nuclear magnetic resonance spectroscopy performed on extracts of C. tropicalis grown on xylose in the absence and presence of azide. Azide lowered the levels of sugar phosphates. Enzymatic analysis showed extremely low levels of fructose 1,6-diphosphate compared with the levels obtained in the absence of azide, while the level of malate, a citric acid cycle intermediate, was not influenced by azide. 31P nuclear magnetic resonance spectroscopy performed on xylose-grown whole cells of C. tropicalis showed that azide lowered the intracellular pH, inhibited the uptake of external Pi, and decreased the buildup of polyphosphate in relation to results with untreated cells. Similar results were obtained with the uncoupler of oxidative phosphorylation carbonyl cyanide m-chlorophenylhydrazone (CCCP), except that CCCP treatment led to extremely high levels of internal Pi. The dual effect of azide as a respiratory inhibitor and as an uncoupler is discussed with respect to the metabolism and product formation in xylose-assimilating C. tropicalis.
Influence of osmoregulation processes on starvation survival of Escherichia coli in seawater
Authors: Munro P M , Gauthier M J , Breittmayer V A , Bongiovanni J
Published: January 2020

The adaptation of enteric bacteria in seawater has previously been described in terms of nutrient starvation. In the present paper, we bring experimental arguments suggesting that survival of these microorganisms could also depend on their ability to overcome the effects of osmotic stress. We analyzed the influence of osmoregulatory mechanisms (potassium transport, transport and accumulation of organic osmolytes) on the survival of Escherichia coli in seawater microcosms by using mutants lacking components of the osmotic stress response. Long-term protection was afforded to cells by growth in a medium whose osmotic pressure was increased by either NaCl, LiCl, or saccharose. Achievement of the protection state depended at least partly on osmoregulatory mechanisms, but differed when these were activated or induced during prior growth or in resting cells suspended in phosphate buffer or in seawater. When achieved during growth, K+ transport, glycine-betaine (GBT) synthesis or transport, and trehalose synthesis helped increase the ability to survive in seawater. Protection by GBT was also obtained with resting cells in a phosphate buffer at high osmotic pressure. However, when added only to the seawater, GBT did not change the survival ability of cells no matter what their osmoregulation potential. These results showed that the survival of E. coli cells in seawater depends, at least partly, on whether they possess certain genes which enable them to regulate osmotic pressure and whether they can be stimulated to express those genes before or after their release into the environment. This expression requires nutrients as the substrates from which the corresponding gene products are made.
Effects of Metals on a Range of
Streptomyces
Species
Authors: Abbas Ala , Edwards Clive
Published: January 2020

A plate diffusion method was used to assess the tolerance of 28 mesophilic and 4 thermophilic species of streptomycetes to eight metals. This method allowed a qualitative screen of the effects of the metals on growth, on sporulation, and in some cases, on secondary metabolite production. Tolerant and sensitive species were identified, some of which exhibited the same response (i.e., tolerance or sensitivity) to a number of metals. Experiments in liquid culture were used to quantify the precise concentration ranges of the metals at which the most tolerant or sensitive species could grow. Distribution profiles of the sensitivities of all species examined toward different metals revealed that the order of toxicity was Hg > Cd > Co > Zn > Ni > Cu > Cr > Mn.
Mechanism of resistance to benzalkonium chloride by Pseudomonas aeruginosa
Authors: Sakagami Y , Yokoyama H , Nishimura H , Ose Y , Tashima T
Published: January 2020

The mechanisms of resistance of Pseudomonas aeruginosa to benzalkonium chloride (BC) were studied. The effluence of cell components was observed in susceptible P. aeruginosa by electron microscopy, but resistant P. aeruginosa seemed to be undamaged. No marked changes in cell surface potential between Escherichia coli NIHJC-2 and a spheroplast strain were found. The contents of phospholipids (PL) and fatty and neutral lipids (FNL) in the cell walls of resistant P. aeruginosa were higher than those in the cell walls of susceptible P. aeruginosa. The amounts of BC adsorbed to PL and FNL of cell walls of BC-resistant P. aeruginosa were lower than those for BC-susceptible P. aeruginosa. Fifteen species of cellular fatty acids were identified by capillary gas chromatography and gas chromatography-mass spectrometry. The ability of BC to permeate the cell wall was reduced because of the increase in cellular fatty acids. These results suggested that the resistance of P. aeruginosa to BC is mainly a result of increased in the contents of PL and FNL. In resistant P. aeruginosa, the decrease in the amount of BC adsorbed is likely to be the result of increases in the contents of PL and FNL.
Heterotrophic nitrification by Alcaligenes faecalis: NO2-, NO3-, N2O, and NO production in exponentially growing cultures
Authors: Papen H , von Berg R , Hinkel I , Thoene B , Rennenberg H
Published: January 2020

Heterotrophic nitrification by Alcaligenes faecalis DSM 30030 was not restricted to media containing organic forms of nitrogen. In both peptone-meat extract and defined media with ammonium and citrate as the sole nitrogen and carbon sources, respectively, NO2-, NO3-, NO, and N2O were produced under aerobic growth conditions. Heterotrophic nitrification was not attributable to old or dying cell populations. Production of NO2-, NO3-, NO, and N2O was detectable shortly after cultures started growth and proceeded exponentially during the logarithmic growth phase. NO2- and NO3- production rates were higher for cultures inoculated in media with pH values below 7 than for those in media at alkaline pH. Neither assimilatory nor dissimilatory nitrate or nitrite reductase activities were detectable in aerobic cultures.
Cultivation Techniques for Hyperthermophilic Archaebacteria: Continuous Culture of
Pyrococcus furiosus
at Temperatures near 100�C
Authors: Brown S. H. , Kelly R. M.
Published: January 2020

A system which allows continuous cultivation of hyperthermophilic archaebacteria at temperatures approaching 100�C has been developed. Continuous cultivation of the hyperthermophile
Pyrococcus furiosus
was carried out with this system; the resulting dilution rate and gas production profiles are discussed.
Improved assay for quantitating adherence of ruminal bacteria to cellulose
Authors: Rasmussen M A , White B A , Hespell R B
Published: January 2020

A quantitative technique suitable for the determination of adherence of ruminal bacteria to cellulose was developed. This technique employs adherence of cells to cellulose disks and alleviates the problem of nonspecific cell entrapment within cellulose particles. By using this technique, it was demonstrated that the adherence of Ruminococcus flavefaciens FD1 to cellulose was inhibited by formaldehyde, methylcellulose, and carboxymethyl cellulose. Adherence was unaffected by acid hydrolysates of methylcellulose, glucose, and cellobiose.
Mineralization of Surfactants by Microbiota of Aquatic Plants
Authors: Federle Thomas W. , Schwab Burney S.
Published: January 2020

The biodegradation of linear alkylbenzene sulfonate (LAS) and linear alcohol ethoxylate (LAE) by the microbiota associated with duckweed (
Lemna minor
) and the roots of cattail (
Typha latifolia
) was investigated. Plants were obtained from a pristine pond and a pond receiving wastewater from a rural laundromat. Cattail roots and duckweed plants were incubated in vessels containing sterile water amended with [
14
C]LAS, [
14
C]LAE, or
14
C-labeled mixed amino acids (MAA). Evolution of
14
CO
2
was determined over time. The microbiota of cattail roots from both ponds mineralized LAS, LAE, and MAA without lag periods, and the rates and extents of mineralization were not significantly affected by the source of the plants. Mineralization of LAS and LAE was more rapid in the rhizosphere than in nearby root-free sediments, which exhibited differences as a function of pond. The microbiota of duckweed readily mineralized LAE and MAA but not LAS. The rate and extent of mineralization were not affected by the source of the duckweed.
Nitrosovibrio
spp., the Dominant Ammonia-Oxidizing Bacteria in Building Sandstone
Authors: Meincke M. , Krieg E. , Bock E.
Published: January 2020

In five historical buildings in the Federal Republic of Germany, ammonia-oxidizing bacteria of the genera
Nitrosovibrio, Nitrosospira
, and
Nitrosomonas
were detected in high cell numbers. In building stones,
Nitrosovibrio
was the most abundant ammonia-oxidizing organism. In the soil at the foot of each building,
Nitrosomonas
spp. were the most common ammonia oxidizers, whereas
Nitrosovibrio
spp. were not detected.
Growth of Aeromonas hydrophila on fresh vegetables stored under a controlled atmosphere
Authors: Berrang M E , Brackett R E , Beuchat L R
Published: January 2020

The effects of controlled-atmosphere storage (CAS) on the survival and growth of Aeromonas hydrophila on fresh asparagus, broccoli, and cauliflower were examined. Two lots of each vegetable were inoculated with A. hydrophila 1653 or K144. A third lot served as an uninoculated control. Following inoculation, vegetables were stored at 4 or 15 degrees C under a CAS system previously shown to extend the shelf life of each commodity or under ambient air. Populations of A. hydrophila were enumerated on the initial day of inoculation and at various intervals for 10 days (15 degrees C) or 21 days (4 degrees C) of storage. Direct plating of samples with selective media was used to enumerate A. hydrophila. The organism was detected on most lots of vegetables as they were received from a commercial produce supplier. Without exception, the CAS system lengthened the time vegetables were subjectively considered acceptable for consumption. However, CAS did not significantly affect populations of A. hydrophila which survived or grew on inoculated vegetables.
New modified trichothecenes accumulated in solid culture by mutant strains of Fusarium sporotrichioides
Authors: McCormick S P , Taylor S L , Plattner R D , Beremand M N
Published: January 2020

Mutant strains of Fusarium sporotrichioides NRRL 3299 deficient in the ability to synthesize T-2 toxin were examined on solid rice medium. Five novel alicyclic trichothecenes were isolated: 11 alpha-hydroxytrichodiene; tricho-9-ene-2 alpha,3 alpha,11 alpha-triol; tricho-9-ene-2 alpha,3 alpha,8 alpha,11 alpha-tetraol; tricho-9-ene-2 alpha,3 alpha,8 beta,11 alpha-tetraol; and tricho-9-ene-2 alpha,3 alpha,11 alpha,16-tetraol.
Modification of Lignins by Growing Cells of the Sulfate-Reducing Anaerobe
Desulfovibrio desulfuricans
Authors: Ziomek E. , Williams R. E.
Published: January 2020

The anaerobic sulfate-reducing bacterium
Desulfovibrio desulfuricans
was grown on medium supplemented with either Kraft lignin or lignosulfonate. Only lignosulfonate contributed to the growth of
D. desulfuricans
cells, by replacing sulfate, a natural electron acceptor for this microorganism. Kraft lignin added to the culture medium could not substitute for lactate or sulfate, both necessary culture medium components. However, it was found to enhance the viability of
D. desulfuricans
cells. When changes occurring in lignin during growth of
Desulfovibrio
cultures were monitored, it was found that both lignin preparations could be partially depolymerized. Spectrophotometric and elemental analysis of biologically treated lignins suggested that both the polyphenolic backbone and lignin functional groups were affected by
D. desulfuricans.
After treatment, a twofold increase in the sulfur content of Kraft lignin and a minor decrease (14%) in the sulfur content of lignosulfonate were observed. After biological treatment, Kraft lignin and lignosulfonate both bound larger quantities of heavy metals.
Colloidal Gold Cytochemistry of Endo-1,4-β-Glucanase, 1,4-β-
D
-Glucan Cellobiohydrolase, and Endo-1,4-β-Xylanase: Ultrastructure of Sound and Decayed Birch Wood
Authors: Blanchette Robert A. , Abad André R. , Cease Kory R. , Lovrien Rex E. , Leathers Timothy D.
Published: January 2020

Colloidal gold coupled to endo-1,4-β-glucanase II (EG II) and 1,4-β-
D
-glucan cellobiohydrolase I (CBH I), isolated from
Trichoderma reesei
(QM9414), and endo-1,4-β-xylanase from
Aureobasium pullulans
(NRRLY-2311-1) was used successfully to determine the ultrastructural localization of cellulose and xylan in sound birch wood. In addition, these enzyme-gold complexes demonstrated the distribution of cellulose and xylan after decay by three white rot fungi,
Phanerochaete chrysosporium, Phellinus pini
, and
Trametes versicolor
, and one brown rot fungus,
Fomitopis pinicola.
Transverse sections of sound wood showed that EG II was localized primarily on the S
1
layer of the secondary wall, whereas CBH I labeled all layers of the secondary wall. Oblique sections showed a high concentration of gold labeling, using EG II or CBH I. Preference for the sides of the microfibrillar structure was observed for both EG II and CBH I, whereas only CBH I had a specificity for the cut ends of microfibrils. Labeling with the xylanase-gold complex occurred primarily in the inner regions of the S
2
layer, S
1
, and the middle lamella. In contrast, little labeling occurred in the middle lamella with EG II or CBH I. Intercellular regions within the cell corners of the middle lamella were less electron dense and labeled positively when EG II- and xylanase-gold were used. Wood decayed by
P. chrysosporium
or
P. pini
was delignified, and extensive degradation of the middle lamella was evident. The remaining secondary walls labeled with EG II and CBH I, but little labeling was found with the xylanase-gold complex. Wood decayed by
T. versicolor
was nonselective, and erosion of all cell wall layers was apparent. Remaining wall layers near sites of erosion labeled with both EG II and CBH I. Erosion troughs that reached the S
1
layer or the middle lamella had less xylanase-gold labeling in the adjacent cell wall that remained. Brown-rotted wood had very low levels of gold particles present in sections treated with EG II or xylanase. Labeling with CBH I had the lowest concentrations in the S
2
layer near cell lumina and corresponded to sites with the most extensive degradation.
Purification and Characterization of an Aminopeptidase from
Lactococcus lactis
subsp.
cremoris
AM2
Authors: Neviani E. , Boquien C. Y. , Monnet V. , Thanh L. Phan , Gripon J.-C.
Published: January 2020

An aminopeptidase was purified from cell extracts of
Lactococcus lactis
subsp.
cremoris
AM2 by ion-exchange chromatography. After electrophoresis of the purified enzyme in the presence or absence of sodium dodecyl sulfate, one protein band was detected. The enzyme was a 300-kilodalton hexamer composed of identical subunits not linked by disulfide bridges. Activity was optimal at 40°C and pH 7 and was inhibited by classical thiol group inhibitors. The aminopeptidase hydrolyzed naphthylamide-substituted amino acids, as well as dipeptides and tripeptides. Longer protein chains such as the B chain of insulin were hydrolyzed, but at a much slower rate. The Michaelis constant (
K

m

) and the maximal rate of hydrolysis (
V
max
) were, respectively, 4.5 mM and 3,600 pkat/mg for the substrate
l
-histidyl-β-naphthylamide. Amino acid analysis showed that the enzyme contained low levels of hydrophobic residues. The partial N-terminal sequence of the first 19 residues of the mature enzyme was determined. Polyclonal antibodies were obtained from the purified enzyme, and after immunoblotting, there was no cross-reaction between these antibodies and other proteins in the crude extract.
Fungal Growth Stimulation by CO
2
and Root Exudates in Vesicular-Arbuscular Mycorrhizal Symbiosis
Authors: Bécard G. , Piché Y.
Published: January 2020

Transformed roots of carrot were used to determine the effects of root metabolites on hyphal development from spores of the vesicular-arbuscular mycorrhizal fungus
Gigaspora margarita.
Hyphal growth of this obligately biotrophic symbiont was greatly stimulated by a synergistic interaction between volatile and exudated factors produced by roots. Root volatiles alone provided little stimulation, and root exudates alone had no effect. For the first time, carbon dioxide was demonstrated to be a critical root volatile involved in the enhancement of hyphal growth.
14
C-labeled root volatiles were fixed by the fungus and thus strongly suggested that CO
2
served as an essential carbon source.
Simulation of Airborne Microbial Droplet Transport
Authors: Lighthart Bruce , Kim Jinwon
Published: January 2020

The framework for a simulation model which describes the dispersion of individual droplets of water containing viable microbes is presented. The model accounts for physical, chemical, biological, and measured meteorological parameters of each droplet at each of many short time steps. Repeating the modeling process for many droplets will simulate a cloud of droplets. The model is compared with the Tulelake, Calif., release in 1988 and found to show very similar patterns of deposition within 30 m (the maximum observation distance of the source. A hypothesis for the survival sequence in the microbe-containing droplets is discussed.
Cloning of an endo-1,4-beta-D-glucanase gene from Clostridium josui and its expression in Escherichia coli
Authors: Ohmiya K , Fujino T , Sukhumavasi J , Shimizu S
Published: January 2020

The gene for carboxymethyl cellulose-degrading enzyme (endoglucanase) from Clostridium josui (FERM P-9684) was cloned in Escherichia coli HB101 with pBR322. A 5.6-kilobase-pair HindIII fragment encoding an endoglucanase was hybridized with C. josui chromosomal DNA. The size of the cloned DNA fragment was reduced with PvuII, and the resulting active fragment (2 kilobase pairs, with restriction sites of EcoRI and PstI) was ligated into pUC118 at the SmaI sites (pUCJ1). The endoglucanase production by E. coli JM103(pUCJ1) in Luria-Bertani broth was enhanced up to approximately three times by maintaining the pH at 6.5 and using 80 mM NaCl.
Biosynthesis of 130-kilodalton mosquito larvicide in the cyanobacterium Agmenellum quadruplicatum PR-6
Authors: Angsuthanasombat C , Panyim S
Published: January 2020

The 130-kilodalton mosquito larvicidal gene, cloned from Bacillus thuringiensis var. israelensis, was introduced into the cyanobacterium Agmenellum quadruplicatum PR-6 by plasmid transformation. Transformed cells synthesized 130-kilodalton delta-endotoxin protein and showed mosquito larvicidal activity. Results demonstrate a potential use of a cyanobacterium for biological control of mosquitoes.
Stereospecific production of the herbicide phosphinothricin (glufosinate) by transamination: isolation and characterization of a phosphinothricin-specific transaminase from Escherichia coli
Authors: Schulz A , Taggeselle P , Tripier D , Bartsch K
Published: January 2020

An aminotransferase capable of transaminating 2-oxo-4-[(hydroxy)(methyl)phosphinoyl]butyric acid to L-phosphinothricin [L-homoalanine-4-yl-(methyl)phosphinic acid], the active ingredient of the herbicide Basta (Hoechst AG), was purified to apparent homogeneity from Escherichia coli K-12. The enzyme catalyzes the transamination of L-phosphinothricin and various analogs with 2-ketoglutarate as the amino group acceptor. The transaminase has a molecular mass of 43 kilodaltons by sodium dodecyl sulfate-gel analysis and an isoelectric point of 4.35. The enzyme was most active in the high-pH region, with a maximum at pH 8.0 to 9.5, and had a temperature optimum of 55 degrees C. Heat stability was observed up to 70 degrees C. Substrate specificity studies suggested that the enzyme is identical with the 4-aminobutyrate:2-ketoglutarate transaminase (EC 2.6.1.19). The first 30 amino acids of the N terminus of the protein were determined by gas phase sequencing. The transaminase was immobilized by coupling to the epoxy-activated carrier VA-Biosynth (Riedel de Haen) and used in a column reactor for the continuous production of L-phosphinothricin. The enzyme reactor was operated for 7 weeks with only a slight loss of catalytic capacity. Production rates of more than 50 g of L-phosphinothricin per liter of column per h were obtained.
Plasmid-Determined Copper Resistance in
Pseudomonas syringae
from Impatiens
Authors: Cooksey Donald A.
Published: January 2020

A strain of
Pseudomonas syringae
was recently identified as the cause of a new foliar blight of impatiens. The bacterium was resistant to copper compounds, which are used on a variety of crops for bacterial and fungal disease control. The bacterium contained a single 47-kilobase plasmid (pPSI1) that showed homology to a copper resistance operon previously cloned and characterized from
P. syringae
pv.
tomato
plasmid pPT23D (D. Cooksey, Appl. Environ. Microbiol. 53:454-456, 1987). pPSI1 was transformed by electroporation into a copper-sensitive
P. syringae
strain, and the resulting transformants were copper resistant. A physical map of pPSI1 was constructed, and the extent of homology to pPT23D outside the copper resistance operon was determined in Southern hybridizations. The two plasmids shared approximately 20 kilobases of homologous DNA, with the remainder of each plasmid showing no detectable homology. The homologous regions hybridized strongly, but there was little or no conservation of restriction enzyme recognition sites.
Biodegradation of Dinoseb (2-
sec
-Butyl-4,6-Dinitrophenol) in Several Idaho Soils with Various Dinoseb Exposure Histories
Authors: Stevens Todd O. , Crawford Ronald L. , Crawford Don L.
Published: January 2020

We examined the ability of native microorganisms in various Idaho soils to degrade dinoseb and studied some physical and chemical soil characteristics which might affect the biodegradation process. Dinoseb biodegradation rates were higher in silt-loam soils than in loamy-sand soils. Biodegradation rates were not influenced by previous exposure of the soils to dinoseb. Bacterial numbers, measured by standard plate counts on soil extract agar, were the best predictors of biodegradation rates, accounting for 53% of the variability between soils. Soil nitrate-N inhibited dinoseb biodegradation and accounted for 39% of the variability. Sorption of dinoseb to soil surfaces also appeared to influence biodegradation rates. No other soil parameter contributed significantly to the variability in biodegradation rates. Persistence of dinoseb in one soil was due to inhibition of biodegradation by nitrate, while in another soil persistence appeared to be due to lack of native degradative microorganisms.
Simple medium that preserves low concentrations of Escherichia coli for use in the water bacteriology proficiency test
Authors: Chen M
Published: January 2020

A medium containing (per liter) 6.8 g of sodium acetate trihydrate, 3.4 g of potassium dihydrogen phosphate, and 0.1 g of magnesium sulfate heptahydrate (medium pH, 5.85 plus/minus 0.05) was developed for use in a water bacteriology proficiency test. The medium maintained 80 to 100 % viability of inoculated Escherichia coli at temperatures up to 31 degrees C for at least 12 days, while the concentrations of bacteria in the medium were as low as 20 bacteria per 100 ml. The medium remained stable after a year of storage. It has been used successfully to preserve bacteria in nine statewide bacteriology proficiency tests for potable and nonpotable water and has also been used in a nationwide pilot test. This report presents the results of these tests.
Odorous Sulfur Compounds Emitted during Production of Compost Used as a Substrate in Mushroom Cultivation
Authors: Derikx P. J. L. , Op Den Camp H. J. M. , van der Drift C. , van Griensven L. J. L. D. , Vogels G. D.
Published: January 2020

Large-scale composting facilities are known to cause environmental problems, mainly through pungent air emitted by composting material. In air samples taken above stacks set up to prepare compost used as a substrate in mushroom cultivation, several volatile compounds were identified by means of the coupled techniques of gas chromatography and mass spectrography. Among the compounds identified, sulfur-containing compounds [H
2
S, COS, CH
3
SH, CS
2
, (CH
3
)
2
S, (CH
3
)
2
S
2
, and (CH
3
)
2
S
3
] are the most conspicuous in causing a nuisance. Quantification of these compounds was performed by concentrating a relatively small air sample on Tenax GC. The sampling method appeared to be very useful under field conditions. During the composting process, the concentration of the volatile sulfur compounds in emitted air ranged from 1 to 35 μmol/m
3
. The highest concentrations were obtained at the end of the outdoor process. Total sulfur emission amounted to 8.3 mg of sulfur per kg (fresh weight) of compost. The end product still contained 2.58 g of sulfur per kg (fresh weight) of compost. Suggestions about the origin of the volatile sulfur compounds are made.
Genetic structure of natural populations of the nitrogen-fixing bacterium Rhizobium meliloti
Authors: Eardly B D , Materon L A , Smith N H , Johnson D A , Rumbaugh M D , Selander R K
Published: January 2020

The genetic structure of populations of the symbiotic nitrogen-fixing soil bacterium Rhizobium meliloti was examined by analysis of electrophoretically demonstrable allelic variation in 14 metabolic, presumably chromosomal, enzyme genes. A total of 232 strains were examined, most of which were isolated from southwest Asia, where there is an unsurpassed number of indigenous host species for R. meliloti. The collection consisted of 115 isolates recovered from annual species of Medicago in Syria, Turkey, and Jordan; 85 isolates cultured from two perennial species of Medicago (M. sativa [alfalfa] and M. falcata) in northern Pakistan and Nepal; and 32 isolates collected at various localities in North and South America, Europe, South Africa, New Zealand, and Australia, largely from M. sativa. Fifty distinctive multilocus genotypes (electrophoretic types [ETs]) were identified, and cluster analysis revealed two primary phylogenetic divisions separated at a genetic distance of 0.83. By the criterion of genetic differentiation conventionally applied in defining species limits among members of the family Enterobacteriaceae and certain other bacteria, the two primary divisions of R. meliloti represent distinct evolutionary species. Division A included 35 ETs represented by 209 strains from the eastern Mediterranean basin, northern Pakistan, Nepal, and various other localities worldwide. This division contained the nine commercial alfalfa inoculant strains examined. Division B included 15 ETs represented by 23 isolates, 21 of which were isolated from annual medic species growing in previously uninoculated soils in the eastern Mediterranean basin. The two remaining strains in division B, both representing the same ET, were isolated in the United States and Australia.(ABSTRACT TRUNCATED AT 250 WORDS)
Mn(II) Regulation of Lignin Peroxidases and Manganese-Dependent Peroxidases from Lignin-Degrading White Rot Fungi
Authors: Bonnarme P. , Jeffries T. W.
Published: January 2020

Two families of peroxidases—lignin peroxidase (LiP) and manganese-dependent lignin peroxidase (MnP)—are formed by the lignin-degrading white rot basidiomycete
Phanerochaete chrysosporium
and other white rot fungi. Isoenzymes of these enzyme families carry out reactions important to the biodegradation of lignin. This research investigated the regulation of LiP and MnP production by Mn(II). In liquid culture, LiP titers varied as an inverse function of and MnP titers varied as a direct function of the Mn(II) concentration. The extracellular isoenzyme profiles differed radically at low and high Mn(II) levels, whereas other fermentation parameters, including extracellular protein concentrations, the glucose consumption rate, and the accumulation of cell dry weight, did not change significantly with the Mn(II) concentration. In the absence of Mn(II), extracellular LiP isoenzymes predominated, whereas in the presence of Mn(II), MnP isoenzymes were dominant. The release of
14
CO
2
from
14
C-labeled dehydrogenative polymerizate lignin was likewise affected by Mn(II). The rate of
14
CO
2
release increased at low Mn(II) and decreased at high Mn(II) concentrations. This regulatory effect of Mn(II) occurred with five strains of
P. chrysosporium
, two other species of
Phanerochaete
, three species of
Phlebia, Lentinula edodes
, and
Phellinus pini
.
Symbiotic Effectiveness of Indigenous Soybean Bradyrhizobia as Related to Serological, Morphological, Rhizobitoxine, and Hydrogenase Phenotypes
Authors: Fuhrmann J.
Published: January 2020

A Collection of 360 isolates of
Bradyrhizobium japonicum
was developed from soybean (
Glycine max
[L.] Merrill) nodules taken from 18 locations in Delaware. The isolates were characterized serologically with an enzyme-linked immunosorbent assay, morphologically by colony type on yeast extract-mannitol agar, and for production of rhizobitoxine symptoms with soybean plants. These analyses revealed 12 and 3 groups based on serology and morphology, respectively. The more common identifiable isolates were in serogroups 94, 6, 122, and 76. Nearly 33% of the isolates were rated nonreactive with all of the antisera tested. Overall, 18% of the isolates produced rhizobitoxine symptoms, and these were associated with five known serogroups (31, 46, 76, 94, and 130) and the nonreactive grouping, but with only one colony type. A subsample of 92 isolates was rated for N
2
-fixing ability in the greenhouse and for hydrogenase phenotype in the laboratory. The nitrogen content of plant shoots was strongly and comparably related to both the serological and morphological groupings. Rhizobitoxine and hydrogenase phenotypes were relatively poor predictors of symbiotic effectiveness. Among the serologically reactive isolates, those in serogroups 38-115, 122, and 110 fixed the most N
2
, whereas one colony type (that containing isolates producing rhizobitoxine) was clearly inferior to the remaining two morphological groupings. Isolates displaying hydrogenase activity (approximately 15% of the isolates tested) correlated with three serologically reactive groupings (serogroups 110 and 122 and a 122/123 cross-reactive group) and two colony types, none of which coincided with groupings containing bradyrhizobia rated positive for rhizobitoxine production.
Identification of Salmonella somatic and flagellar antigens by modified serological methods
Authors: Gruenewald R , Dixon D P , Brun M , Yappow S , Henderson R , Douglas J E , Backer M H
Published: January 2020

This report describes two modified methods for the identification of Salmonella somatic (O) and flagellar (H) antigens. Over a period of 2 years, both modified methods were found to be approximately three times less labor intensive than the standard methods while requiring no more technical skill. The modified methods were as accurate as the standard methods in identifying the O and H antigens of 350 Salmonella isolates. Furthermore, 43 O antisera reacted exclusively with organisms possessing homologous O antigens when the modified and two standard methods were used. At the antiserum dilutions used for H antigen identification, H antisera did not react with O antigens or heterologous H antigens by either the modified or the standard method. Compared with the standard method for H antigen identification, the modified method was approximately 20 times more economical with respect to antisera and usually generated a 1.5- to 4-fold higher titer. Since the antisera stored for use in the modified method for H antigen identification were usually 100-fold more dilute than the antisera stored for the standard method, an antibody-stabilizing buffer was incorporated in the diluted antisera, allowing these reagents to be used for at least 9 to 16 months.
Construction and applications of DNA probes for detection of polychlorinated biphenyl-degrading genotypes in toxic organic-contaminated soil environments
Authors: Walia S , Khan A , Rosenthal N
Published: January 2020

Several DNA probes for polychlorinated biphenyl (PCB)-degrading genotypes were constructed from PCB-degrading bacteria. These laboratory-engineered DNA probes were used for the detection, enumeration, and isolation of specific bacteria degrading PCBs. Dot blot analysis of purified DNA from toxic organic chemical-contaminated soil bacterial communities showed positive DNA-DNA hybridization with a 32P-labeled DNA probe (pAW6194, cbpABCD). Less than 1% of bacterial colonies isolated from garden topsoil and greater than 80% of bacteria isolated from PCB-contaminated soils showed DNA homologies with 32P-labeled DNA probes. Some of the PCB-degrading bacterial isolates detected by the DNA probe method did not show biphenyl clearance. The DNA probe method was found to detect additional organisms with greater genetic potential to degrade PCBs than the biphenyl clearance method did. Results from this study demonstrate the usefulness of DNA probes in detecting specific PCB-degrading bacteria, abundance of PCB-degrading genotypes, and genotypic diversity among PCB-degrading bacteria in toxic chemical-polluted soil environments. We suggest that the DNA probe should be used with caution for accurate assessment of PCB-degradative capacity within soils and further recommend that a combination of DNA probe and biodegradation assay be used to determine the abundance of PCB-degrading bacteria in the soil bacterial community.
Prevalence of Giardia spp. in beaver and muskrat populations in northeastern states and Minnesota: detection of intestinal trophozoites at necropsy provides greater sensitivity than detection of cysts in fecal samples
Authors: Erlandsen S L , Sherlock L A , Bemrick W J , Ghobrial H , Jakubowski W
Published: January 2020

Surveys of the prevalence of the intestinal protozoan Giardia spp. in animal populations have relied almost exclusively on the detection of cysts in fecal samples. We have determined the prevalence of Giardia spp. in beaver and muskrat populations in four northeastern states and Minnesota by using both the detection of trophozoites in mucosal scrapings from live-trapped animals at necropsy and the detection of cysts in fecal samples collected from kill-trapped animals. In muskrats the prevalence of Giardia infection was 36.6% by cyst detection in fecal samples (n = 790) from kill-trapped animals and 95.9% in live-trapped muskrats when the intestinal contents were analyzed for the presence of trophozoites (n = 219). Similarly, in beavers, Giardia infection was 9.2% by cyst detection in fecal samples (n = 662) from kill-trapped beavers and 13.7% in live-trapped animals examined for the presence of intestinal trophozoites (n = 302). The detection of trophozoites in mucosal scrapings from live-trapped animals consistently yielded a significantly higher prevalence for both muskrats and beavers than did the method based on detection of cysts in the fecal samples. The prevalence of Giardia infection in juvenile and adult live-trapped muskrats was similar (92.5 and 94.4%, respectively), but the prevalence in juvenile live-trapped beavers (23.2%) was significantly greater than that seen in the adult animals (12.6%). No difference in Giardia prevalence on the basis of sex was seen in either animal species. Regional variation, often statistically significant, was seen in the prevalence of Giardia in beavers in the northeastern states and Minnesota, but was not detected for muskrats.
Supernatant protein and cellulase activities of the anaerobic ruminal fungus Neocallimastix frontalis EB188
Authors: Barichievich E M , Calza R E
Published: January 2020

Protein and cellulose activities were measured in culture supernatants of the anaerobic ruminal fungus Neocallimastix frontalis EB188 established in glucose medium and switched to either glucose, cellobiose, or cellulose media. Polyacrylamide gel electrophoresis was used to show differences caused by changing medium carbon source. Culture supernatants contained proteins with molecular weights ranging from greater than 116,000 to about 19,000. Low levels of cellulose activity were evident in glucose-grown cultures. Increased amounts of slowly migrating cellulase activities appeared in the supernatants of glucose-grown cultures switched to cellulose. Cellulase activities which reacted differentially during colorimetric and in situ assays were produced. Isoelectric points of cellulase activities varied from 3.7 to 8.3, and activities possessed optimal pHs of between 5.9 and 6.5.
Stereospecific production of the herbicide phosphinothricin (glufosinate) by transamination: cloning, characterization, and overexpression of the gene encoding a phosphinothricin-specific transaminase from Escherichia coli
Authors: Bartsch K , Dichmann R , Schmitt P , Uhlmann E , Schulz A
Published: January 2020

We have cloned the gene encoding a 43-kilodalton transaminase from Escherichia coli K-12 with a specificity for L-phosphinothricin [L-homoalanine-4-yl-(methyl)phosphinic acid], the active ingredient of the herbicide Basta (Hoechst AG). The structural gene was isolated, together with its own promoter, and shown to be localized on a 1.6-kilobase DraI-BamHI fragment. The gene is subject to catabolite repression by glucose; however, repression could be relieved completely when 4-aminobutyrate (GABA) served as the sole nitrogen source. The regulation pattern obtained and a comparison of the restriction map of the initially cloned 15-kilobase SalI fragment with the physical map of the E. coli K-12 genome suggest that the cloned gene is identical with gabT, a locus on the gab gene cluster of E. coli K-12 which codes for the GABA:2-ketoglutartate transaminase (EC 2.6.1.19). A number of expression plasmids carrying the isolated transaminase gene were constructed. With these constructs, the transaminase expression in transformants of E. coli could be increased up to 80-fold compared with that in a wild-type control, and the transaminase constituted up to 20% of the total soluble protein of the bacteria. Thus, the protein crude extracts of the transformants could be used, after a simple heat precipitation step, for the biotechnological production of L-phosphinothricin in an enzyme reactor.
Effects of Toxic Substances on Natural Bacterial Assemblages Determined by Means of [
3
H]Thymidine Incorporation
Authors: Riemann Bo , Lindgaard-Jørgensen Palle
Published: January 2020

The effects of 3,5-dichlorophenol, 2,4-dinitrophenol, and potassium dichromate on natural bacterial assemblages were examined by means of [
3
H]thymidine incorporation into trichloroacetic acid-insoluble material. Results from a large number of coastal marine and freshwater samples suggest the following. (i) The effects of the three toxicants included reductions in the bacterial cell number as well as changes in rates of [
3
H]thymidine incorporation and in [
3
H]thymidine incorporation per cell. The concentrations that inhibited [
3
H]thymidine incorporation by 50% ranged from 3 to 11 mg liter
−1
for 3,5-dichlorophenol, 6 to 10 mg liter
−1
for 2,4-dinitrophenol, and 21 to 123 mg liter
−1
for potassium dichromate, with a tendency to higher values in bacterial assemblages from more eutrophic environments. (ii) The effects of 3,5-dichlorophenol and potassium dichromate determined by [
3
H]leucine incorporation into bacterial protein were similar or larger than those obtained from [
3
H]thymidine incorporation. (iii) Two to four hours of exposure to the toxicants was necessary before stable maximum effects were found in [
3
H]thymidine incorporation. (iv) Storage of natural environmental samples should be avoided, since tests with water stored for 1 to 3 days sometimes produced results different from results obtained from in situ tests. (v) The effects of 3,5-dichlorophenol, 2,4-dinitrophenol, and potassium dichromate on natural bacterial assemblages were relatively constant during periods with different growth rates in the assemblages, during various periods of the year, and between samples from freshwater and marine localities. With some precautions, [
3
H]thymidine incorporation can be used as a quick and sensitive method for determining the effects of toxicants on aquatic bacterial assemblages from natural environmental samples.