bluuebunny/crossref_metadata_2025 huggingface dataset:
Detection of staphylococcal enterotoxins by enzyme-linked immunosorbent assays and radioimmunoassays: comparison of monoclonal and polyclonal antibody systems
Authors: Thompson N E , Razdan M , Kuntsmann G , Aschenbach J M , Evenson M L , Bergdoll M S
Published: January 2020

Murine monoclonal antibodies reactive with at least one of the serological types of staphylococcal enterotoxin were examined for use in assay systems for the detection of enterotoxin at the level of 1.0 ng of enterotoxin per ml. An antibody sandwich enzyme-linked immunosorbent assay was devised for each toxin type by identifying an effective antibody pair. One antibody (the coating antibody) was coated onto a polystyrene plate and removed the enterotoxin from the test solution; the second antibody (the probing antibody) was conjugated to horseradish peroxidase and detected the captured toxin. Enterotoxins A and E could be detected in the same system by the use of cross-reacting monoclonal antibodies. All subtypes of enterotoxin C could be detected in one assay system. Two effective systems were described for each of types B and D. Each of these systems, when compared with the homologous enterotoxin-specific polyclonal rabbit antibody systems, was found to compare favorably. The monoclonal enzyme-linked immunosorbent assay systems for the detection of enterotoxins A and C2 were examined for a variety of food extracts; no abnormal interference could be detected from these extracts. The monoclonal antibody systems were also compared with the homologous enterotoxin-specific polyclonal serum for the detection of enterotoxin by the competitive radioimmunoassay (RIA). Single monoclonal antibodies generally did not perform as well in the RIA as did the homologous toxin-specific polyclonal serum. However, pools of monoclonal antibodies were prepared that approached the sensitivity and precision of the polyclonal system for the detection of each toxin by the RIA.
Kinetics of adhesion of the oral bacterium Streptococcus sanguis CH3 to polymers with different surface free energies
Authors: Busscher H J , Uyen M H , van Pelt A W , Weerkamp A H , Arends J
Published: January 2020

The kinetics of adhesion of Streptococcus sanguis CH3 from suspension to polymers with different surface free energies were studied by using three bacterial concentrations (2.5 X 10(7), 2.5 X 10(8), and 2.5 X 10(9) cells per ml-1). Substratum surface free energies (gamma s) ranged from 18 to 120 erg cm-2. The kinetics of bacterial adhesion to these surfaces showed a typical two-step adhesion process, indicating an equilibrium in both steps. In the initial adhesion step (step 1), low equilibrium numbers of adhering bacteria were counted on substrata with surface free energies lower than 55 erg cm-2. A maximal number adhered on substrata with higher surface free energies. At the lowest bacterial concentration tested, the highest number of bacteria were found on substrata with a surface free energy around 55 erg cm-2. For each substratum, step 2 started after a characteristic time interval tau, being short (30 min) for gamma s less than 50 and long (120 min) for gamma s greater than 50 erg cm-2. The relationship between the substratum surface free energy and the number of bacteria adhering at equilibrium after step 2 was similar to, although less distinct than, that during step 1 with a slight indication of a bioadhesive minimum around gamma s = 35 erg cm-2. The results are indicative of a two-step adhesion model, in which step 1 is controlled by macroscopic substratum properties.
Effect of salinity gradients and heterotrophic microbial activity on biodegradation of nitrilotriacetic acid in laboratory simulations of the estuarine environment
Authors: Hunter M , Stephenson T , Kirk P W , Perry R , Lester J N
Published: January 2020

The biodegradation of nitrilotriacetic acid (NTA), a synthetic replacement detergent builder, in the estuarine environment was examined by using a laboratory estuarine simulation. Two interdependent microcosms were used; each of five vessels was equilibrated with a saline gradient between 1.30 and 17.17%, with the final vessel subsequently being increased to a maximum salinity of 31.6%. Each microcosm was seeded simultaneously with heterotrophic bacteria from both fresh and saline sources. Viable counts demonstrated the ability of each microcosm to sustain a mixed heterotrophic bacterial community throughout the range of salinities for 183 days after a stabilization period. Isolation studies demonstrated that both systems contained four bacterial species, representatives of the genera Vibrio and Flavobacterium and members of the coryneform group and the family Enterobacteriaceae. Total bacterial numbers and species diversity decreased with increased salinity. NTA was administered at low and high concentrations, one concentration to each microcosm, initially with the least amount of saline. Removal of both concentrations of NTA occurred and was attributed to biodegradation after a period of bacterial acclimatization. Subsequent dosing of NTA to vessels of higher salinity demonstrated that biodegradation was incomplete at observed mean salinities of greater than 9.18% at low influent NTA concentrations and greater than 5.08% at high influent NTA concentrations. Therefore, acclimatization was dose dependent. It was concluded that NTA acclimatization at the higher salinities ceased because of salinity stress-induced failure of NTA catabolism and not the disappearance of a particular bacterial species.
Microbial 7α-Hydroxylation of 3-Ketobisnorcholenol
Authors: Despreaux Carl W. , Rittweger Karen R. , Palleroni Norberto J.
Published: January 2020

The transformation of 22-hydroxy-23,24-bisnorchol-4-en-3-one to 7α-22-dihydroxy-23,24-bisnorchol-4-en-3-one by
Botryodiploida theobromae, Lasiodiplodia theobromae
, and various
Botryosphaeria
strains is described. Factors affecting the reaction were incubation temperature, sonication of the substrate, and addition of 2,2′-dipyridyl, extra carbohydrate, and Amberlite XAD-7. The enzyme responsible for the reaction appeared to be very specific and was not characteristic of all members of the genera listed above.
Effects of dissolved oxygen concentration on biodegradation of 2,4-dichlorophenoxyacetic acid
Authors: Shaler T A , Klecka G M
Published: January 2020

Batch experiments were conducted to examine the effects of dissolved oxygen concentration on the degradation of 2,4-dichlorophenoxyacetic acid (2,4-D) by an enrichment culture of 2,4-D-utilizing bacteria. A modified Monod equation was found to describe the relationship between the specific growth rate and the concentrations of both the organic substrate and dissolved oxygen. Values for the maximum specific growth rate, yield, and Monod coefficient for growth on 2,4-D were 0.09 h-1, 0.14 g/g, and 0.6 mg/liter, respectively. The half-saturation constant for dissolved oxygen was estimated to be 1.2 mg/liter. These results suggest that dissolved oxygen concentrations below 1 mg/liter may be rate limiting for the biodegradation of chlorinated aromatic compounds such as 2,4-D, which have a requirement for molecular oxygen as a cosubstrate for metabolism.
Two approaches to modeling kinetics of biodegradation by growing cells and application of a two-compartment model for mineralization kinetics in sewage
Authors: Simkins S , Mukherjee R , Alexander M
Published: January 2020

The patterns of microbial mineralization of 0.3 to 30 ng of glucose, benzoate, and phenol per ml of sewage collected in late fall and winter were analyzed with the integrated Monod equation and a model in which growth of active organisms occurs at the expense of organic compounds other than the test substrate. Either model could be closely fit by nonlinear regression to the data from individual tests with one concentration of substrate added to one dilution of sewage. However, neither model accounted satisfactorily for differences in patterns of mineralization resulting from differences in substrate concentration and cell density between different tests. It is suggested that both the added substrates and other organics present in sewage contributed to the growth of the active organisms. The mineralization of glucose in sewage collected in summer was better described by a two-compartment model than by any other model tested.
Temporal Variation of Denitrification Activity in Plant-Covered, Littoral Sediment from Lake Hampen, Denmark
Authors: Christensen Peter Bondo , Sørensen Jan
Published: January 2020

Diel and seasonal variations in denitrification were determined in a littoral lake sediment colonized by the perennial macrophyte
Littorella uniflora
(L.) Aschers. In the winter, the activity was low (5 μmol of N m
−2
h
−1
) and was restricted to the uppermost debris layer at a depth of 0 to 1 cm. By midsummer, the activity increased to 50 μmol of N m
−2
h
−1
and was found throughout the root zone to a depth of 10 cm. The root zone accounted for as much as 50 to 70% of the annual denitrification. A significant release of organic substrates from the roots seemed to determine the high activities of root zone denitrification in the summer. The denitrification in the surface layer and in the root zone formed two distinct activity zones in the summer, when the root zone also contained nitrification activity, as indicated from the accumulations of NO
3
−
. Light conditions inhibited denitrification in both the surface layer and the upper part of the root zone, suggesting that a release of O
2
by benthic algae and from the roots of
L. uniflora
controlled a diel variation of denitrification. In midsummer, the rate of denitrification in both the surface layer and the upper part of the root zone was limited by NO
3
−
. In the growth season, there was evidence for a significant population of denitrifiers closely associated with the root surface.
Isolation of non-O1 Vibrio cholerae serovars from surface waters in western Colorado
Authors: Rhodes J B , Smith H L , Ogg J E
Published: January 2020

Non-O1 Vibrio cholerae was isolated from rivers, creeks, washes, irrigation canals, and ditches in western Colorado during the summer of 1985. The organism occurred in fresh water (less than or equal to 5 mmol of Na+ per liter) as well as in water of higher salinity (approximately equal to 17 mmol per liter). Sixteen serovars of non-O1 V. cholerae were Sixteen serovars of non-O1 V. cholerae were identified among the environmental isolates. All of the isolates were cytotoxic to Y-1 mouse adrenal cells.
Influence of External pH and Fermentation Products on
Clostridium acetobutylicum
Intracellular pH and Cellular Distribution of Fermentation Products
Authors: Huang Li , Forsberg Cecil W. , Gibbins L. N.
Published: January 2020

Clostridium acetobutylicum
ATCC 824 cells harvested from a phosphate-limited chemostat culture maintained at pH 4.5 had intracellular concentrations of acetate, butyrate, and butanol which were 13-, 7-, and 1.3-fold higher, respectively, than the corresponding extracellular concentrations. Cells from a culture grown at pH 6.5 had intracellular concentrations of acetate and butyrate which were only 2.2-fold higher than the respective external concentrations. The highest intracellular concentrations of these acids were attained at ca. pH 5.5. When cells were suspended in anaerobic citrate-phosphate buffer at pH 4.5, exogenous acetate and butyrate caused a concentration-dependent decrease in the intracellular pH, while butanol had relatively little effect until the external concentration reached 150 mM. Acetone had no effect at concentrations up to 200 mM. These data demonstrate that acetate and butyrate are concentrated within the cell under acidic conditions and thus tend to lower the intracellular pH. The high intracellular butyrate concentration presumably leads to induction of solvent production, thereby circumventing a decrease in the intracellular pH great enough to be deleterious to the cell.
Stimulation of Methanogenesis by Aldicarb and Several Other
N
-Methyl Carbamate Pesticides
Authors: Kiene Ronald P. , Capone Douglas G.
Published: January 2020

Aldicarb and several other
N
-methyl carbamate pesticides stimulated methane production in anaerobic salt marsh soils and organic-rich aquifer soils. Stimulation was biological and linearly related to the amount of carbamate added. Of the four carbamates studied, methomyl gave the greatest stimulation followed by carbaryl, aldicarb, and baygon. The percent conversions [(moles of CH
4
in excess of control/mole of carbamate added) × 100] for methomyl, carbaryl, aldicarb, and baygon were 88, 57, 40, and 11, respectively. Using aldicarb as a model carbamate, we found that monomethylamine (MA) accumulated in sediments as a result of aldicarb addition. MA arises from the
N
-methyl carbamoyl portion of the carbamates as a result of presumptive biological hydrolysis. MA levels decreased as CH
4
production was stimulated, and 2-bromoethane sulfonic acid (a specific inhibitor of mathanogenesis) partially inhibited the loss of MA. These findings suggest that
N
-methyl carbamates are readily hydrolyzed to MA in the presence of an active microbial population under anaerobic conditions and that methanogenesis is stimulated as a result of the consumption of MA by methanogenic bacteria.
Conjugal Transfer of Bacteriophage Resistance Determinants on pTR2030 into
Streptococcus cremoris
Strains
Authors: Sing Wesley D. , Klaenhammer Todd R.
Published: January 2020

Agar surface conjugal matings were used to introduce heat-sensitive phage resistance (Hsp
+
) determinants carried on the conjugal plasmid pTR2030 into
Streptococcus cremoris
KH, HP, 924, and TDM1. Lactose-fermenting (Lac
+
) transconjugants were selected from matings of Lac
−
variants of
S. cremoris
KH, HP, 924, and TDM1 with
Streptococcus lactis
ME2 or a high-frequency donor,
S. lactis
T-EK1 (pTR1040, Lac
+
; pTR2030, Hsp
+
). For all of the
S. cremoris
strains examined, select Lac
+
transconjugants were completely resistant to plaquing by their homologous lytic phages. In all cases the plaquing efficiencies were less than 10
−9
. Acquisition of a 30-megadalton plasmid (pTR2030) in the
S. cremoris
phage-resistant transconjugants was demonstrated by direct plasmid analysis, by hybridization with
32
P-labeled probes, or by conjugal transfer of pTR2030 out of the phage-resistant transconjugants into a plasmid-cured recipient,
S. lactis
LM2302. Acid production, coagulation ability, and proteolytic activity of phage-resistant transconjugants in milk were comparable to those of their phage-sensitive parents. Further,
S. cremoris
phage-resistant transconjugants were not attacked by phage in starter culture activity tests, which included a 40°C incubation period. The results demonstrated that phage resistance determinants on pTR2030 could be conjugally transferred to a variety of
S. cremoris
strains and confer resistance to phage under conditions encountered during cheese manufacture. Phage-resistant transconjugants of
S. cremoris
M43 and HP were also constructed without the use of antiblotic markers to select conjugal recipients from mating mixtures.
Bacteriophage Resistance Conferred on Lactic Streptococci by the Conjugative Plasmid pTR2030: Effects on Small Isometric-, Large Isometric-, and Prolate-Headed Phages
Authors: Jarvis Audrey W. , Klaenhammer Todd R.
Published: January 2020

A series of reactions between phages, sensitive hosts, and transconjugants where the sensitivity of small isometric-, large isometric-, and prolate-headed phages to pTR2030-induced phage resistance was evaluated in
Streptococcus lactis
and
Streptococcus cremoris
strains. Phage-resistant transconjugants were constructed in the desired host by conjugal transfer of lactose-fermenting ability (Lac
+
, pTR1040) and phage resistance (Hsp
+
, pTR2030) from
S. lactis
TEK1.
S. lactis
and
S. cremoris
transconjugants harboring pTR2030 were resistant to all small isometric-headed phages examined. In contrast, prolate- and large isometric-headed phages were either not inhibited in the pTR2030 transconjugants or exhibited a reduction in plaque size without a reduction in the efficiency of plaquing. Small isometric-headed phages subject to pTR2030 induced inhibition shared no significant DNA homology with pTR2030, suggesting that phage immunity genes are not harbored on the plasmid or responsible for resistance. The general effectiveness of pTR2030 against small isometric-headed phages was highly significant since these are the phages which have been isolated most commonly from dairy fermentation plants.
Thermal Tolerance of
Zymomonas mobilis
: Temperature-Induced Changes in Membrane Composition
Authors: Benschoter A. S. , Ingram L. O.
Published: January 2020

The membrane composition of
Zymomonas mobilis
changed dramatically in response to growth temperature. With increasing temperature, the proportion of vaccenic acid declined with an increase in myristic acid, the proportion of phosphatidylcholine and cardiolipin increased with decreases in phosphatidylethanolamine and phosphatidylglycerol, and the phospholipid/protein ratio of the membrane declined. These changes in membrane composition were correlated with changes in thermal tolerance and with changes in membrane fluidity. Cells grown at 20°C were more sensitive to inactivation at 45°C than were cells grown at 30°C, as expected. However, cells grown at 41°C (near the maximal growth temperature for
Z. mobilis
) were hypersensitive to thermal inactivation, suggesting that cells may be damaged during growth at this temperature. When cells were held at 45°C, soluble proteins from cells grown at 41°C were rapidly lost into the surrounding buffer in contrast to cells grown at lower temperatures. The synthesis of phospholipid-deficient membranes during growth at 41°C was proposed as being responsible for this increased thermal sensitivity.
Coincident plasmids and antimicrobial resistance in marine bacteria isolated from polluted and unpolluted Atlantic Ocean samples
Authors: Baya A M , Brayton P R , Brown V L , Grimes D J , Russek-Cohen E , Colwell R R
Published: January 2020

Sewage effluent and outfall confluence samples were collected at the Barceloneta Regional Treatment Plant in Barceloneta, Puerto Rico; outfall confluence samples at Ocean City, Md., were also collected. Samples from uncontaminated open ocean areas served as clean-water controls. Bacteria were enriched in marine broth 2216 amended with 1 microgram of one of a set of chemicals selected for study per ml: nitrobenzene, dibutyl phthalate, m-cresol, o-cresol, 4-nitroaniline, bis(tributyltin) oxide, and quinone. MICs of the chemicals were determined individually for all isolates. Bacterial isolates were evaluated for resistance to nine different antibiotics and for the presence of plasmid DNA. Treated sewage was found to contain large numbers of bacteria simultaneously possessing antibiotic resistance, chemical resistance, and multiple bands of plasmid DNA. Bacteria resistant to penicillin, erythromycin, nalidixic acid, ampicillin, m-cresol, quinone, and bis(tributyltin) oxide were detected in nearly all samples, but only sewage outfall confluence samples yielded bacterial isolates that were resistant to streptomycin. Bacteria resistant to a combination of antibiotics, including kanamycin, chloramphenicol, gentamicin, and tetracycline, were isolated only from sewage effluent samples. It is concluded that bacterial isolates derived from toxic chemical wastes more frequently contain plasmid DNA and demonstrate antimicrobial resistance than do bacterial isolates from domestic sewage-impacted waters or from uncontaminated open ocean sites.
Reduction of digoxin to 20R-dihydrodigoxin by cultures of Eubacterium lentum
Authors: Robertson L W , Chandrasekaran A , Reuning R H , Hui J , Rawal B D
Published: January 2020

The anaerobic bacterium Eubacterium lentum, a common constituent of the intestinal microflora, inactivates digoxin by reducing the unsaturated lactone ring. Reduction of the cardiac glycoside by growing cultures of E. lentum ATCC 25559 proceeded in a stereospecific manner, with the 20R-dihydrodigoxin constituting more than 99% of the product formed. This is in contrast to the 3:1 ratio of 20R and 20S epimers formed in the chemical catalytic hydrogenation. Formation of the reduced glycosides proceeded quantitatively when an overall concentration of 10 micrograms/ml was added to the cultures. E. lentum did not hydrolyze the digitoxose sugars from C-3 of the parent glycoside. However, the synthetically prepared sugar-hydrolyzed metabolites (digoxigenin, digoxigenin monodigitoxoside, and digoxigenin bisdigitoxoside) were reduced to the corresponding dihydro metabolites. Repetition of the experiments with a feces sample from a volunteer who was known to be a converter of digoxin to dihydrodigoxin gave results identical to those obtained with pure E. lentum cultures.
Electrostatic mechanism of survival of virulent Aeromonas salmonicida strains in river water
Authors: Sakai D K
Published: January 2020

The ecological mechanism of survival of Aeromonas salmonicida, the bacterial pathogen of fish furunculosis, in river water was investigated by laboratory-based experiments with two virulent strains (which were autoagglutinating) and two virulent strains (which were nonagglutinating). A difference in net electrical charge of A. salmonicida cells was detected by electrophoresis; cells of the virulent strains were negative, whereas cells of the avirulent strains were positive. Despite the loss of viable cells within a week in distilled water and physiological saline (0.85% sodium chloride), the cells of the virulent strains survived for more than 15 weeks in the presence of diluted humic acid (10 micrograms/ml), tryptone (10 micrograms/ml), and cleaned river sand (100 g/100 ml of medium), but loss of viable cells occurred within 5 weeks in the absence of sand. The cells of the avirulent strains lost viability within 2 weeks with no relation to the presence of sand. Using ion-exchange columns, humic acid and the amino acids of tryptone were found to be anionic and cationic in water (pH 7.0), respectively. Sand particles had a high capacity to adsorb humic acid alone and amino acid-humic acid complexes. Thirty to fifty times the environmental concentration of amino acids (10 micrograms/ml) were accumulated on the surface of sand particles, thereby permitting only bacterial cells carrying net negative electrical charges (virulent cells) to survive for a long period on the surface of the sand particles. These electrostatic interrelationships among river sand, humic acid, and bacterial cells are closely implicated in the mechanism of long-term survival of virulent A. salmonicida in river sediments.
Sensitivity of the Entomogenous Fungus
Beauveria bassiana
to Selected Plant Growth Regulators and Spray Additives
Authors: Storey Greggory K. , Gardner Wayne A.
Published: January 2020

Mefluidide was the only one of four plant growth regulators that caused little to no significant inhibition of in vitro germination and growth of the entomogenous fungus
Beauveria bassiana
. Silaid, paclobutrazol, and flurprimidol significantly inhibited germination and growth. Mortality of fall armyworm,
Spodoptera frugiperda
, resulting from
B. bassiana
was significantly reduced when larvae were exposed to conidia plus soil treated with paclobutrazol. Larval mortality resulting from conidia plus soil treated with mefluidide did not differ significantly from mortality resulting from untreated conidia. Triton CS-7 was the only one of eight spray adjuvants that significantly inhibited germination of
B. bassiana
conidia.
Tight coupling of root-associated nitrogen fixation and plant photosynthesis in the salt marsh grass Spartina alterniflora and carbon dioxide enhancement of nitrogenase activity
Authors: Whiting G J , Gandy E L , Yoch D C
Published: January 2020

The coupling of root-associated nitrogen fixation and plant photosynthesis was examined in the salt marsh grass Spartina alterniflora. In both field experiments and hydroponic assay chambers, nitrogen fixation associated with the roots was rapidly enhanced by stimulating plant photosynthesis. A kinetic analysis of acetylene reduction activity (ARA) showed that a five-to sixfold stimulation occurred within 10 to 60 min after the plant leaves were exposed to light or increased CO2 concentrations (with the light held constant). In field experiments, CO2 enrichment increased plant-associated ARA by 27%. Further evidence of the dependence of ARA on plant photosynthate was obtained when activity in excised roots was shown to decrease after young greenhouse plants were placed in the dark. Seasonal variation in the ARA of excised plant roots from field cores appears to be related to the annual cycle of net photosynthesis in S. alterniflora.
Role of Pili (Fimbriae) in Attachment of
Bradyrhizobium japonicum
to Soybean Roots
Authors: Vesper Stephen J. , Bauer Wolfgang D.
Published: January 2020

Pili (fimbriae) were observed on cells of each of the five strains of
Bradyrhizobium japonicum
and the one strain of
Rhizobium trifolii
examined. Pili on
B. japonicum
were about 4 nm in diameter and polarly expressed. Piliated cells were estimated by transmission electron microscopy and hydrophobic attachment to polystyrene to constitute only a small percentage of the total population. The proportion of piliated cells in these populations was dependent on culture age in some strains. Piliated
B. japonicum
cells were selectively and quantitatively removed from suspension when cultures were incubated with either soybean roots or hydrophobic plastic surfaces, indicating that pili were involved in the attachment of the bacteria to these surfaces. Pili from
B. japonicum
110 ARS were purified and found to have a subunit molecular weight of approximately 21,000. Treatment of
B. japonicum
suspensions with antiserum against the isolated pili reduced attachment to soybean roots by about 90% and nodulation by about 80%. Pili appear to be important mediators of attachment of
B. japonicum
to soybean roots under the conditions examined.
Chitinase determinants of Vibrio vulnificus: gene cloning and applications of a chitinase probe
Authors: Wortman A T , Somerville C C , Colwell R R
Published: January 2020

To initiate study of the genetic control of chitinolytic activity in vibrios, the chitobiase gene was isolated by cloning chromosomal DNA prepared from Vibrio vulnificus. Chimeric plasmids were constructed from Sau3A I partial digests of chromosomal DNA by ligating 5 to 15-kilobase fragments into the BamHI site, i.e., in the Tcr gene, of pBR322 (Amr Tcr). The resulting plasmids were transformed into Escherichia coli DH1. Chitobiase activity of the insert-bearing clones was detected by using a chromogenic substrate, p-nitrophenyl-N-acetyl-beta, D-glucosaminide, and confirmed by the appearance of a fluorescent end product from the hydrolysis of 4-methylumbelliferyl-beta,D-N-N'-diacetylchitobiose. Endochitinase activity was demonstrated by liberation of water-soluble products produced by the degradation of [3H]chitin. Transformation of E. coli Y10R (lacY) with plasmids from chitinase-positive clones restored the lactose-positive phenotype, suggesting the presence of a permease associated with chitinase activity. Physical mapping of plasmids containing the chitinase determinants indicate that transcription of these genes in E. coli may be initiated at a V. vulnificus promoter.
Use of a Nylon Manufacturing Waste as an Industrial Fermentation Substrate
Authors: Ramsay Bruce A. , Znoj George M. , Cooper David G.
Published: January 2020

Nonvolatile residue (NVR), a waste stream from the manufacture of nylon 6′6′, contains mainly small carboxylic acids and alcohols, making it a potential fermentation substrate. Above a concentration of 1.3% (wt/vol), NVR inhibited the growth of all microorganisms tested. The most inhibitory of the major NVR components were the monocarboxylic acids (C
4
to C
6
) and ε-caprolactone. The inhibitory effects of NVR could be avoided by using a carbon-limited chemostat. Microorganisms were found that could use all of the major NVR components as carbon and energy sources. One such organism,
Pseudomonas cepacia
, was grown in a carbon-limited chemostat with a medium feed concentration of 20.5 g of NVR liter
−1
. At a dilution rate of 0.14 h
−1
the yield of biomass (

Y
x/s

, where
x
is biomass produced and
s
is substrate used) from NVR was 18% (neglecting the water content of NVR). It was concluded that NVR would be a suitable carbon source for certain industrial fermentation processes such as the production of poly-β-hydroxybutyric acid.
Microoxic-Anoxic Niche of
Beggiatoa
spp.: Microelectrode Survey of Marine and Freshwater Strains
Authors: Nelson Douglas C. , Revsbech Niels Peter , Jørgensen Bo Barker
Published: January 2020

Beggiatoa
spp. grow optimally in media containing opposed gradients of oxygen and soluble sulfide, although some strains also require an organic substrate. By using microelectrodes, we characterized oxygen and sulfide gradients during their initial development in uninoculated media and in cultures of marine and freshwater strains. In gradient media,
Beggiatoa
strains always grew some distance below the air/agar interface as a dense “plate” of constantly gliding filaments with sharply demarcated upper and lower boundaries. Within established plates, the maximum oxygen partial pressure was 0.6 to 6.0% of air saturation and not significantly lower if filaments were fixing nitrogen. Oxygen penetrated only 100 to 300 μm into the plate, and the anoxic fraction increased from less than 10% to approximately 90% during later stages of growth. For lithoautotrophically grown marine strains, the linearity of the oxygen profile above the plate plus its drop to zero therein indicated that oxygen uptake for the entire tube occurred only within the
Beggiatoa
plate. Consequently, oxygen consumption could be predicted solely from the distance between the air/agar interface and the top of a plate, given the diffusion coefficient for oxygen. By contrast, for freshwater strains grown heterotrophically (with sulfide also in the medium), oxygen profiles were frequently nonlinear because of nonbiological reaction with sulfide which had diffused past the aggregated filaments. For all strains tested, microoxic aggregation also occurred in the absence of sulfide, apparently reflecting a step-up phobic response to oxygen.
Modified plasmid isolation method for Clostridium perfringens and Clostridium absonum
Authors: Roberts I , Holmes W M , Hylemon P B
Published: January 2020

A rapid plasmid isolation procedure for Clostridium perfringens and C. absonum is described. The ratio of culture volume to lysis buffer volume was found to be crucial for efficient plasmid isolation. The method can be scaled up, without difficulty, for large-scale plasmid preparation.
Incorporation of Oxygen from Water into Toluene and Benzene during Anaerobic Fermentative Transformation
Authors: Vogel Timothy M. , Grbìc-Galìc Dunja
Published: January 2020

Toluene and benzene were anaerobically transformed and eventually mineralized in mixed methanogenic cultures. However, the source of oxygen for the initial oxidation step had been unknown, owing to the presence of both methanol and water. No exogenous electron acceptors other than carbon dioxide, toluene, and benzene were present in the defined mineral medium. Through the use of
18
O-labeled water, the oxygen incorporated into the monoaromatic compounds was shown to come from water. The cresol from the toluene and the phenol from the benzene contained up to 8%
18
O label after incubation in 9%
18
O-labeled medium. Gas chromatography-mass spectrometry was used to detect the
18
O-labeled aromatic metabolites.
Mobilization of Tn5 insertions from Rhizobium fredii by pJB3JI
Authors: Thomas P M , Kuykendall L D , Angle J S
Published: January 2020

Techniques for in vivo cloning were used with the fast-growing nitrogen-fixing soybean microsymbiont R. fredii USDA 191. Selection for transfer of Tn5 insertions from R. fredii USDA 191 containing the gene-mobilizing plasmid pJB3JI provided recombinants at up to 400 times the background mutation level. These techniques may be useful for future genetic analysis of R. fredii.
Effect of 3-Phenylpropanoic Acid on Growth of and Cellulose Utilization by Cellulolytic Ruminal Bacteria
Authors: Stack Robert J. , Cotta Michael A.
Published: January 2020

The growth of several cellulolytic species of ruminal bacteria was measured in media containing either cellobiose or cellulose as the energy source and with or without added 3-phenylpropanoic acid (PPA). With
Ruminoccoccus albus
7 and 8, the addition of PPA greatly enhanced the rate of cellulose utilization but had little effect on the rate of growth when cellobiose was the energy source. Comparative rates of growth obtained on either cellobiose or cellulose for
Ruminococcus flavefaciens
FD1 or C94 and
Butyrivibrio fibrisolvens
12, 49, or A38 were similar regardless of the PPA content of the growth medium.
Hydrophobic Interactions Involved in Attachment of a Baculovirus to Hydrophobic Surfaces
Authors: Small Deirdre A. , Moore Norman F. , Entwistle Philip F.
Published: January 2020

The hydrophobic interactions of
Trichoplusia ni
nuclear polyhedrosis virus were characterized by hydrophobic interaction chromatography. The determination of the hydrophobic force and some of the factors that influence its size is discussed in relation to the attachment to leaf surfaces of polyhedra during their use as biological control agents against insect pests.
Purification and Properties of a Novel Xanthan Depolymerase from a Salt-Tolerant Bacterial Culture, HD1
Authors: Hou Ching T. , Barnabe Nancy , Greaney Kathy
Published: January 2020

A novel xanthan depolymerase (endo-β-1,4-glucanase) was isolated from a salt-tolerant bacteria culture (HD1) grown on xanthan. The depolymerase was purified 55-fold through chromatography on ion-exchange and molecular sieve columns, including high-performance liquid chromatography. The purified enzyme fraction was homogeneous as judged by polyacrylamide gel electrophoresis. The molecular weight of this enzyme is 60,000. Optimum pH and temperature for xanthan depolymerase activity were around 5 and 30 to 35°C, respectively. The enzyme was not stable at a temperature higher than 45°C. The activation energy calculated from an Arrhenius plot was 6.40 kcal (26.78 kJ). The enzyme molecule contains no sugar moiety. The amino acid composition of the enzyme protein was determined. Xanthan depolymerase cleaves the endo-β-1,4-glucosidic linkage of the xanthan molecule, freeing reducing groups of some sugars and decreasing viscosity of the polymer solution. Only the backbones of β-1,4-linked glucans with side chains or other substituents were cleaved. No monosaccharide was produced by the action of this enzyme. The oligosac-charide(s) in the low-molecular weight fraction consisted of 15 to 58 monosaccharide units. The enzymic reaction resulted in the decrease in weight-average molecular weight of xanthan from 6.5 × 10
6
to 8.0 × 10
5
in 0.5 h. This enzyme alone could not degrade xanthan to a single or multiple pentasaccharide unit(s). Results suggest that there may be regions inside the xanthan molecule that are susceptible to the attack of this enzyme. Xanthan depolymerase activity was not inhibited by many chemicals, including thiols, antioxidants, chlorinated hydrocarbons, metal-chelating agents, and inorganic compounds, except ferric chloride and arsenomolybdate. Many biocides were tested and found not to be inhibitory. Conditions used in enhanced oil recovery operations, i.e., the presence of formaldehyde, Na
2
S
2
O
4
, 2,2-dibromo-3-nitrilopropionamide, and an anaerobic environment, did not inhibit xanthan depolymerase activity.
Use of Genetically Marked Minicells as a Probe in Measurement of Predation on Bacteria in Aquatic Environments
Authors: Wikner Johan , Andersson Agneta , Normark Staffan , Hagström Åke
Published: January 2020

Minicells produced by
Escherichia coli
M2141 were used as probes to measure predation on pelagic bacteria in situ. The minicells, labeled with [
35
S]methionine in one specific protein, were shown to disappear in the presence of a microflagellate (
Ochromonas
sp.), as seen by a decrease in the amount of labeled marker protein with time. Incubation in filtered (pore size, 0.2 μm) and autoclaved seawater did not affect the amount of labeled marker protein in the minicell. The generation time of flagellates feeding on minicells was determined to be similar to that found for flagellates grown on seawater bacteria or living
E. coli
NC3. Data indicate that minicells are seen as true food particles by the flagellates. The minicell probe was used in recapture experiments, in which predation in situ on pelagic bacteria was demonstrated. The rate of bacterial production showed a clear covariation with the rate of predation, both in different sea areas and in depth profiles. The obtained results (11 field experiments) showed that the rate of predation, on average, accounts for the consumption of 62% of the bacteria produced.
Cloning and expression of the beta-D-galactosidase gene from Streptococcus thermophilus in Escherichia coli
Authors: Herman R E , McKay L L
Published: January 2020

The beta-D-galactosidase (beta-gal) gene from Streptococcus thermophilus was cloned to isolate and characterize it for potential use as a selection marker in a food-grade cloning vector. Chromosomal DNA from S. thermophilus 19258 was cleaved with the restriction enzyme PstI and ligated to pBR322 for transformation into Escherichia coli JM108. A beta-galactosidase-positive clone was detected by its blue color on a medium supplemented with 5-bromo-4-chloro-3-indolyl-beta-D-galactoside. This transformant possessed a single plasmid, designated pRH116, which contained, in addition to the vector DNA, a 7.0-kilobase (kb) PstI insertion fragment coding for beta-gal activity. An extract from JM108(pRH116) contained a beta-gal protein with the same electrophoretic mobility as the beta-gal from S. thermophilus 19258. Compared with the beta-gal from E. coli HB101, the S. thermophilus beta-gal was of lower molecular weight. A restriction map of pRH116 was constructed from cleavage of both the plasmid and the purified insert. The construction of deletion derivatives of pRH116 with BglII, BstEII, and HindIII revealed the approximate location of the gene on the 7.0-kb fragment. The beta-gal gene was further localized to a 3.85-kb region.
Effect of temperature, sodium chloride, and pH on growth of Listeria monocytogenes in cabbage juice
Authors: Conner D E , Brackett R E , Beuchat L R
Published: January 2020

Human illness and death have resulted from the consumption of milk, cheese, and cole slaw contaminated with Listeria monocytogenes. Since the effects of temperature, NaCl, and pH on the growth of the organism in cabbage were unknown, a series of experiments was designed to investigate these factors. Two strains (LCDC 81-861 and Scott A, both serotype 4b) were examined. At 30 degrees C, the viable population of the LCDC 81-861 strain increased in sterile unclarified cabbage juice (CJ) containing 0 to 1.5% NaCl; a decrease in the population of both strains occurred in juice containing greater than or equal to 2% NaCl. At 5 degrees C, the population of the Scott A strain in CJ containing up to 5% NaCl was reduced by about 90% over a 70-day period; the LCDC 81-861 strain was more sensitive to refrigeration but remained viable in CJ containing less than or equal to 3.5% NaCl for 70 days. Growth in CJ at 30 degrees C resulted in a decrease in pH from 5.6 to 4.1 within 8 days. Death of L. monocytogenes occurred at 30 degrees C when the organism was inoculated into sterile CJ adjusted to pH less than or equal to 4.6 with lactic acid. No viable cells were detected after 3 days at pH less than or equal to 4.2. At 5 degrees C, the rate of death at pH less than or equal to 4.8 was slower than at 30 degrees C.(ABSTRACT TRUNCATED AT 250 WORDS)
Analysis of the Symbiotic Performance of
Bradyrhizobium japonicum
USDA 110 and Its Derivative I-110 and Discovery of a New Mannitol-Utilizing, Nitrogen-Fixing USDA 110 Derivative
Authors: Mathis James N. , Israel Daniel W. , Barbour W. Mark , Jarvis Brion D. W. , Elkan Gerald H.
Published: January 2020

Previously,
Bradyrhizobium japonicum
USDA 110 was shown to contain colony morphology variants which differed in nitrogen-fixing ability. Mannitol-utilizing derivatives L1-110 and L2-110 have been shown to be devoid of symbiotic nitrogen fixation ability, and non-mannitol-utilizing derivatives I-110 and S-110 have been shown to be efficient at nitrogen fixation. The objectives of this study were to determine the effect of media carbon sources on the symbiotic N
2
-fixing ability of strain USDA 110 and to compare the effectiveness of strain USDA 110 and derivative I-110. Based on acetylene reduction activity and the nitrogen content of 41-day-old soybean plants, neither derivative I-110 nor cultures of USDA 110 grown in media favoring non-mannitol-using derivatives had symbiotic nitrogen fixation that was statistically superior to that of cultures of USDA 110 grown in media favoring mannitol-using derivatives. In another experiment 200 individual nodules formed by strain USDA 110 grown in yeast extract gluconate were screened for colony morphology of occupying variant(s) and acetylene reduction activity. Nodules occupied by mannitol-using derivatives (large colony type on 0.1% yeast extract-0.05% K
2
HPO
4
-0.08% MgSO
4
· 7H
2
O-0.02% NaCl-0.001% FeCl
3
· 6H
2
O [pH 6.7] with 1% mannitol [YEM] plates) had a mean acetylene reduction activity equal to that of nodules occupied by non-mannitol-using derivatives (small colony type on YEM plates). A total of 20 large colonial derivatives and 10 small colonial derivatives (I-110-like) were isolated and purified by repeated culture in YEM and YEG (same as YEM except 1% gluconate instead of 1% mannitol) media, respectively, followed by dilution in solutions containing 0.05% Tween 40. After 25 days of growth, soybean plants inoculated with the large colony isolates had mean whole-plant acetylene reduction activity, whole-plant dry weight, and whole-plant nitrogen contents equal to or better than those of plants inoculated with either the small colony isolates (I-110-like) or the I-110 (non-mannitol-using) derivative. Hence, the existence of a mannitol-utilizing derivative that fixes nitrogen in a culture of strain USDA 110 obtained from the U.S. Department of Agriculture, Beltsville, Md., was established. This new USDA 110 derivative was designated as MN-110 because it was a mannitol-utilizing nitrogen-fixing USDA 110 derivative. This derivative was morphologically indistinguishable from the non-nitrogen-fixing derivative L2-110 found in cultures obtained earlier from the U.S. Department of Agriculture, Beltsville. DNA-DNA homology and restriction enzyme analyses indicated that MN-110 is genetically related to other USDA 110 derivatives that have been characterized previously.
Susceptibility of
Agrobacterium tumefaciens
Strains to Two Agrocin-Producing
Agrobacterium
Strains
Authors: van Zyl Frederik G. H. , Strijdom Barend W. , Staphorst Johannes L.
Published: January 2020

Sixty-five strains and isolates of
Agrobacterium tumefaciens
representing each of the known biotypes, were tested for in vitro and in vivo susceptibility to the agrocin-producing strains
Agrobacterium radiobacter
84 and
A. tumefaciens
D286. No biotype 3 strain was susceptible to the effects of either of the agrocinogenic strains in vitro. On datura and tobacco, the best inhibition of tumor formation was obtained when the agrocinogenic strains were applied to wounds 24 h before the pathogens and by the concomitant application of agrocin producer and pathogen at cell ratios of 10:1 or 3:1; inhibition of infection tended to decrease progressively as the cell ratio decreased from 10:1 to 3:1 to 1:1. Generally, strain 84 was superior to D286 in inhibiting tumor formation. A combined cell suspension of 84 and D286 was as effective as 84 alone. The overall pattern of inhibition of tumor formation by biotype 1 and 2 pathogens resistant to the agrocinogenic strains in vitro was similar to that obtained with strains that were susceptible in vitro.
Effects of pH on Lignin and Cellulose Degradation by
Streptomyces viridosporus
Authors: Pometto Anthony L. , Crawford Don L.
Published: January 2020

Lignocellulose degradation by
Streptomyces viridosporus
results in the oxidative depolymerization of lignin and the production of a water-soluble lignin polymer, acid-precipitable polymeric lignin (APPL). The effects of the culture pH on lignin and cellulose metabolism and APPL production by
S. viridosporus
are reported. Dry, ground, hot-water-extracted corn (
Zea mays
) lignocellulose was autoclaved in 1-liter reagent bottles (5 g per bottle) and inoculated with 50-ml volumes of
S. viridosporus
cells suspended in buffers of specific pH (pH 6.0 to 9.2 at 0.4 pH unit intervals). Four replicates of inoculated cultures and of uninoculated controls at each pH were incubated as solid-state fermentations at 37°C. After 6 weeks of incubation the percent loss of lignocellulose, lignin, and carbohydrate and the amount of APPL produced were determined for each replicate. Optimal lignocellulose degradation, as shown by substrate weight loss, was observed in the pH range of 8.4 to 8.8. Only minor differences were seen in the Klason lignin, carbohydrate, protein, and ash contents of the APPLS produced by cultures at each pH. The effects of pH on the degradation of a spruce (
Picea pungens
) [
14
C-lignin]lignocellulose and a Douglas fir (
Pseudotsuga menziesii
) [
14
C-glucan]-lignocellulose were also determined at pH values between 6.5 and 9.5 (0.5 pH unit intervals). The incubations were carried out for 3 weeks at 37°C with bubbler-tube cultures. The percentage of initial
14
C recovered as
14
CO
2
,
14
C-labeled water-soluble products, and [
14
C]APPL was then determined. The mineralization of lignin and cellulose to CO
2
was optimal at pHs 6.5 and 7.0, respectively. However, the optimum for lignin and cellulose solubilization was pH 8.5, which correlated with the pH 8.5 optimum for APPL production. Overall, the data show that, whereas lignin mineralization is optimal at neutral to slightly acidic pHs, lignocellulose degradation with lignin solubilization and APPL production is promoted by alkaline pHs. These findings indicate that lignin-solubilizing actinomycetes may play an important role in the metabolism of lignin in neutral to alkaline soils in which ligninolytic fungi are not highly competitive.
Inhibitor studies of dissimilative Fe(III) reduction by Pseudomonas sp. strain 200 ("Pseudomonas ferrireductans")
Authors: Arnold R G , DiChristina T J , Hoffmann M R
Published: January 2020

Aerobic respiration and dissimilative iron reduction were studied in pure, batch cultures of Pseudomonas sp. strain 200 ("Pseudomonas ferrireductans"). Specific respiratory inhibitors were used to identify elements of electron transport chains involved in the reduction of molecular oxygen and Fe(III). When cells were grown at a high oxygen concentration, dissimilative iron reduction occurred via an abbreviated electron transport chain. The induction of alternative respiratory pathways resulted from growth at low oxygen tension (less than 0.01 atm [1 atm = 101.29 kPa]). Induced cells were capable of O2 utilization at moderately increased rates; dissimilative iron reduction was accelerated by a factor of 6 to 8. In cells grown at low oxygen tension, dissimilative iron reduction appeared to be uncoupled from oxidative phosphorylation. Models of induced and uninduced electron transport chains, including a mathematical treatment of chemical inhibition within the uninduced, aerobic electron transport system, are presented. In uninduced cells respiring anaerobically, electron transport was limited by ferrireductase activity. This limitation may disappear among induced cells.
Occurrence of Trichothecin in Wheat
Authors: Ishii Kenji , Kobayashi Jun , Ueno Yoshio , Ichinoe Masakatsu
Published: January 2020

Trichothecin, a toxic metabolite of
Trichothecium roseum,
was detected in 3 of 13 wheat samples examined at levels of 560, 290, and 270 ng/g. In addition, all the
T. roseum
isolates from the wheat produced the toxin on wheat.