bluuebunny/crossref_metadata_2025 huggingface dataset:
Isoliquiritigenin, a strong nod gene- and glyceollin resistance-inducing flavonoid from soybean root exudate
Authors: Kape R , Parniske M , Brandt S , Werner D
Published: January 2020

Isoflavonoid signal molecules from soybean (Glycine max (L.) Merr.) seed and root exudate induce the transcription of nodulation (nod) genes in Bradyrhizobium japonicum. In this study, a new compound with symbiotic activity was isolated from soybean root exudate. The isolated 2',4',4-trihydroxychalcone (isoliquiritigenin) is characterized by its strong inducing activity for the nod genes of B. japonicum. These genes are already induced at concentrations 1 order of magnitude below those required of the previously described isoflavonoid inducers genistein and daidzein. Isoliquiritigenin is also a potent inducer of glyceollin resistance in B. japonicum, which renders this bacterium insensitive to potentially bactericidal concentrations of glyceollin, the phytoalexin of G. max. No chemotactic effect of isoliquiritigenin was observed. The highly efficient induction of nod genes and glyceollin resistance by isoliquiritigenin suggests the ecological significance of this compound, although it is not a major flavonoid constituent of the soybean root exudate in quantitative terms.
Excretion of ammonium by a nifL mutant of Azotobacter vinelandii fixing nitrogen
Authors: Bali A , Blanco G , Hill S , Kennedy C
Published: January 2020

A mutation in the gene upstream of nifA in Azotobacter vinelandii was introduced into the chromosome to replace the corresponding wild-type region. The resulting mutant, MV376, produced nitrogenase constitutively in the presence of 15 mM ammonium. When introduced into a nifH-lacZ fusion strain, the mutation permitted beta-galactosidase production in the presence of ammonium. The gene upstream of nifA is therefore designated nifL because of its similarity to the Klebsiella pneumoniae nifL gene in proximity to nifA, in mutant phenotype, and in amino acid sequence of the gene product. The A. vinelandii nifL mutant MV376 excreted significant quantities of ammonium (approximately 10 mM) during diazotrophic growth. In contrast, ammonium excretion during diazotrophy was much lower in a K. pneumoniae nifL deletion mutant (maximum, 0.15 mM) but significantly higher than in NifL+ K. pneumoniae. The expression of the A. vinelandii nifA gene, unlike that of K. pneumoniae, was not repressed by ammonium.
Inhibition of existing denitrification enzyme activity by chloramphenicol
Authors: Brooks M H , Smith R L , Macalady D L
Published: January 2020

Chloramphenicol completely inhibited the activity of existing denitrification enzymes in acetylene-block incubations with (i) sediments from a nitrate-contaminated aquifer and (ii) a continuous culture of denitrifying groundwater bacteria. Control flasks with no antibiotic produced significant amounts of nitrous oxide in the same time period. Amendment with chloramphenicol after nitrous oxide production had begun resulted in a significant decrease in the rate of nitrous oxide production. Chloramphenicol also decreased (greater than 50%) the activity of existing denitrification enzymes in pure cultures of Pseudomonas denitrificans that were harvested during log-phase growth and maintained for 2 weeks in a starvation medium lacking electron donor. Short-term time courses of nitrate consumption and nitrous oxide production in the presence of acetylene with P. denitrificans undergoing carbon starvation were performed under optimal conditions designed to mimic denitrification enzyme activity assays used with soils. Time courses were linear for both chloramphenicol and control flasks, and rate estimates for the two treatments were significantly different at the 95% confidence level. Complete or partial inhibition of existing enzyme activity is not consistent with the current understanding of the mode of action of chloramphenicol or current practice, in which the compound is frequently employed to inhibit de novo protein synthesis during the course of microbial activity assays. The results of this study demonstrate that chloramphenicol amendment can inhibit the activity of existing denitrification enzymes and suggest that caution is needed in the design and interpretation of denitrification activity assays in which chloramphenicol is used to prevent new protein synthesis.
Evidence for a correlation between auxin production and host plant species among strains of Pseudomonas syringae subsp. savastanoi
Authors: Gardan L , David C , Morel M , Glickmann E , Abu-Ghorrah M , Petit A , Dessaux Y
Published: January 2020

Auxin production by 131 strains of Pseudomonas syringae subsp. savastanoi was investigated with the aim of looking for correlations among this characteristic and the origin of the strains, the types of symptoms, and the host plant. Most of the P.syringae subsp. savastanoi strains, except those isolated from ash, produced auxin and harbored iaa genes. Among ash strains, which were pathogenic only on ash, only 2 out of 33 were found to produce auxin and to harbor iaa genes.
Use of a fluorescent redox probe for direct visualization of actively respiring bacteria
Authors: Rodriguez G G , Phipps D , Ishiguro K , Ridgway H F
Published: January 2020

The redox dye 5-cyano-2,3-ditolyl tetrazolium chloride (CTC) was employed for direct epifluorescent microscopic enumeration of respiring bacteria in environmental samples. Oxidized CTC is nearly colorless and is nonfluorescent; however, the compound is readily reduced via electron transport activity to fluorescent, insoluble CTC-formazan, which accumulates intracellularly. Bacteria containing CTC-formazan were visualized by epifluorescence microscopy in wet-mount preparations, on polycarbonate membrane filter surfaces, or in biofilms associated with optically opaque surfaces. Counterstaining of CTC-treated samples with the DNA-specific fluorochrome 4',6-diamidino-2-phenylindole allowed enumeration of active and total bacterial subpopulations within the same preparation. Municipal wastewater, groundwater, and seawater samples supplied with exogenous nutrients yielded CTC counts that were generally lower than total 4',6-diamidino-2-phenylindole counts but typically equal to or greater than standard heterotrophic (aerobic) plate counts. In unsupplemented water samples, CTC counts were typically lower than those obtained with the heterotrophic plate count method. Reduction of CTC by planktonic or biofilm-associated bacteria was suppressed by formaldehyde, presumably because of inhibition of electron transport activity and other metabolic processes. Because of their bright red fluorescence (emission maximum, 602 nm), actively respiring bacteria were readily distinguishable from abiotic particles and other background substances, which typically fluoresced at shorter wavelengths. The use of CTC greatly facilitated microscopic detection and enumeration of metabolically active (i.e., respiring) bacteria in environmental samples.
Oxidative degradation of phenanthrene by the ligninolytic fungus Phanerochaete chrysosporium
Authors: Hammel K E , Gai W Z , Green B , Moen M A
Published: January 2020

The ligninolytic fungus Phanerochaete chrysosporium oxidized phenanthrene and phenanthrene-9,10-quinone (PQ) at their C-9 and C-10 positions to give a ring-fission product, 2,2'-diphenic acid (DPA), which was identified in chromatographic and isotope dilution experiments. DPA formation from phenanthrene was somewhat greater in low-nitrogen (ligninolytic) cultures than in high-nitrogen (nonligninolytic) cultures and did not occur in uninoculated cultures. The oxidation of PQ to DPA involved both fungal and abiotic mechanisms, was unaffected by the level of nitrogen added, and was significantly faster than the cleavage of phenanthrene to DPA. Phenanthrene-trans-9,10-dihydrodiol, which was previously shown to be the principal phenanthrene metabolite in nonligninolytic P. chrysosporium cultures, was not formed in the ligninolytic cultures employed here. These results suggest that phenanthrene degradation by ligninolytic P. chrysosporium proceeds in order from phenanthrene----PQ----DPA, involves both ligninolytic and nonligninolytic enzymes, and is not initiated by a classical microsomal cytochrome P-450. The extracellular lignin peroxidases of P. chrysosporium were not able to oxidize phenanthrene in vitro and therefore are also unlikely to catalyze the first step of phenanthrene degradation in vivo. Both phenanthrene and PQ were mineralized to similar extents by the fungus, which supports the intermediacy of PQ in phenanthrene degradation, but both compounds were mineralized significantly less than the structurally related lignin peroxidase substrate pyrene was.
Leaching of Pyrites of Various Reactivities by
Thiobacillus ferrooxidans
Authors: Baldi Franco , Clark Thomas , Pollack S. S. , Olson Gregory J.
Published: January 2020

Wide variations were found in the rate of chemical and microbiological leaching of iron from pyritic materials from various sources.
Thiobacillus ferrooxidans
accelerated leaching of iron from all of the pyritic materials tested in shake flask suspensions at loadings of 0.4% (wt/vol) pulp density. The most chemically reactive pyrites exhibited the fastest bioleaching rates. However, at 2.0% pulp density, a delay in onset of bioleaching occurred with two of the pyrites derived from coal sources.
T. ferrooxidans
was unable to oxidize the most chemically reactive pyrite at 2.0% pulp density. No inhibition of pyrite oxidation by
T. ferrooxidans
occurred with mineral pyrite at 2.0% pulp density. Experiments with the most chemically reactive pyrite indicated that the leachates from the material were not inhibitory to iron oxidation by
T. ferrooxidans
.
Characterization of a methane-utilizing bacterium from a bacterial consortium that rapidly degrades trichloroethylene and chloroform
Authors: Alvarez-Cohen L , McCarty P L , Boulygina E , Hanson R S , Brusseau G A , Tsien H C
Published: January 2020

A mixed culture of bacteria grown in a bioreactor with methane as a carbon and energy source rapidly oxidized trichloroethylene and chloroform. The most abundant organism was a crescent-shaped bacterium that bound the fluorescent oligonucleotide signature probes that specifically hybridize to serine pathway methylotrophs. The 5S rRNA from this bacterium was found to be 93.5% homologous to the Methylosinus trichosporium OB3b 5S RNA sequence. A type II methanotrophic bacterium, isolated in pure culture from the bioreactor, synthesized soluble methane monooxygenase during growth in a copper-limited medium and was also capable of rapid trichloroethylene oxidation. The bacterium contained the gene that encodes the soluble methane monooxygenase B component on an AseI restriction fragment identical in size to a restriction fragment present in AseI digests of DNA from bacteria in the mixed culture. The sequence of the 16S rRNA from the pure culture was found to be 92 and 94% homologous to the 16S rRNAs of M. trichosporium OB3b and M. sporium, respectively. Both the pure and mixed cultures oxidized naphthalene to naphthol, indicating the presence of soluble methane monooxygenase. The mixed culture also synthesized soluble methane monooxygenase, as evidenced by the presence of proteins that cross-reacted with antibodies prepared against purified soluble methane monooxygenase components from M. trichosporium OB3b on Western blots (immunoblots). It was concluded that a type II methanotrophic bacterium phylogenetically related to Methylosinus species synthesizes soluble methane monooxygenase and is responsible for trichloroethylene oxidation in the bioreactor.
Application of ribotyping for differentiating aeromonads isolated from clinical and environmental sources
Authors: Moyer N P , Luccini G M , Holcomb L A , Hall N H , Altwegg M
Published: January 2020

We have investigated the usefulness of ribotyping for the differentiation of aeromonads isolated from five patients with gastroenteritis and from the source water, treatment plant, and distribution system of a small public water supply. Aeromonas hydrophila and Aeromonas caviae were isolated from fecal specimens preserved in Cary-Blair transport medium by using blood ampicillin agar or alkaline peptone water (pH 8.4) subcultured to blood ampicillin agar plates. A. hydrophila, Aeromonas sobria, and A. caviae were isolated from duplicate 100-ml water samples by the membrane filter technique by using ampicillin dextrin agar for quantitative determination of growth and alkaline peptone water enrichment for detection of the presence or absence of aeromonads below the detection limit of the membrane filter method. In addition, free chlorine residuals and pH values were determined for all water samples and heterotrophic plate counts and total and fecal coliform analyses were performed on them. Ribotyping patterns of aeromonads recovered from well 1, detention basin, sand filter, softener, and distribution samples were compared with those of the five clinical isolates. All patient strains were unique; however, identical ribotypes of A. hydrophila and A. sobria isolated from multiple sites in the water system indicated colonization of a well, sand filters, and the softener, with the potential for sporadic contamination of distribution water. Plant operational deficiencies were noted and corrected. Ribotyping can effectively differentiate otherwise indistinguishable strains of bacteria, thus providing a powerful tool for investigation of waterborne diseases and bacteriological problems within water treatment plants and distribution systems.
Characterization of form variants of Xenorhabdus luminescens
Authors: Gerritsen L J , de Raay G , Smits P H
Published: January 2020

From Xenorhabdus luminescens XE-87.3 four variants were isolated. One, which produced a red pigment and antibiotics, was luminescent, and could take up dye from culture media, was considered the primary form (XE-red). A pink-pigmented variant (XE-pink) differed from the primary form only in pigmentation and uptake of dye. Of the two other variants, one produced a yellow pigment and fewer antibiotics (XE-yellow), while the other did not produce a pigment or antibiotics (XE-white). Both were less luminescent, did not take up dye, and had small cell and colony sizes. These two variants were very unstable and shifted to the primary form after 3 to 5 days. It was not possible to separate the primary form and the white variant completely; subcultures of one colony always contained a few colonies of the other variant. The white variant was also found in several other X. luminescens strains. DNA fingerprints showed that all four variants are genetically identical and are therefore derivatives of the same parent. Protein patterns revealed a few differences among the four variants. None of the variants could be considered the secondary form. The pathogenicity of the variants decreased in the following order: XE-red, XE-pink, XE-yellow, and XE-white. The mechanism and function of this variability are discussed.
Growth phase, cellular hydrophobicity, and adhesion in vitro of lactobacilli colonizing the keratinizing gastric epithelium in the mouse
Authors: Savage D C
Published: January 2020

Lactobacillus strains of numerous species isolated from several animal sources exhibited cellular hydrophobicities that differed from those expected on the basis of their abilities to colonize the keratinizing stratified squamous epithelium in the mouse stomach. Cells of Lactobacillus fermentum 100-33, grown to either exponential or stationary phase, were strongly hydrophilic. By contrast, cells of L. fermentum RI and six transformant derivatives of strain RI and 100-33, strains DM101 through DM106, were hydrophobic to various degrees in either growth phase. Most of them were less hydrophobic, however, when in the stationary phase than in the exponential phase. Cells of strains RI and 100-33 in the exponential phase adhered in the same number in vitro to disks of keratinized mouse gastric mucosa. By contrast, when in stationary phase, strain RI and two transformants, DM103 and DM104, adhered to the surface in higher numbers than 100-33. In contrast to their cellular progenitor, 100-33, the transformant strains share with their DNA donor, RI, the capacity to colonize the keratinizing gastric epithelium in mice. These findings indicate that lactobacilli able to colonize the surface of the keratinocytes in the murine stomach can adhere to that surface by either hydrophilic or hydrophobic molecules.
Complete biological reductive transformation of tetrachloroethene to ethane
Authors: de Bruin W P , Kotterman M J , Posthumus M A , Schraa G , Zehnder A J
Published: January 2020

Reductive dechlorination of tetrachloroethene (perchloroethylene; PCE) was observed at 20 degrees C in a fixed-bed column, filled with a mixture (3:1) of anaerobic sediment from the Rhine river and anaerobic granular sludge. In the presence of lactate (1 mM) as an electron donor, 9 microM PCE was dechlorinated to ethene. Ethene was further reduced to ethane. Mass balances demonstrated an almost complete conversion (95 to 98%), with no chlorinated compounds remaining (less than 0.5 micrograms/liter). When the temperature was lowered to 10 degrees C, an adaptation of 2 weeks was necessary to obtain the same performance as at 20 degrees C. Dechlorination by column material to ethene, followed by a slow ethane production, could also be achieved in batch cultures. Ethane was not formed in the presence of bromoethanesulfonic acid, an inhibitor of methanogenesis. The high dechlorination rate (3.7 mumol.l-1.h-1), even at low temperatures and considerable PCE concentrations, together with the absence of chlorinated end products, makes reductive dechlorination an attractive method for removal of PCE in bioremediation processes.
Inactivation of poliovirus type 1 in mixed human and swine wastes and by bacteria from swine manure
Authors: Deng M Y , Cliver D O
Published: January 2020

The persistence of poliovirus type 1 (PO1) in mixed septic tank effluent and swine manure slurry was determined, and the antiviral effects of several bacterial cultures isolated from swine manure slurry were demonstrated. In two field experiments, PO1 was consistently inactivated more rapidly in the mixed waste than in the control Dulbecco's phosphate-buffered saline (D-PBS). D values (time [in days] for a 90% reduction of virus titer) were 18.7 and 29.9 for the mixed waste and 56.5 and 51.8 for the D-PBS control, respectively. The virus inactivation in the mixed waste was temperature dependent. A comparison of PO1 inactivation in raw mixed waste, autoclaved mixed waste, and bacterium-free filtrate of raw mixed waste at the same pH and temperatures provided an initial demonstration that the virus inactivation in the mixed waste is related, at least in part, to microbial activity. At 25 degrees C, the D value was 6.8 for the mixed waste, 11.2 for the autoclaved mixed waste, and 10.5 for the bacterium-free filtrate of raw mixed waste. At 37 degrees C, D values were 1.3, 3.9, and 3.1 for these three suspending media, respectively. Three bacterial isolates which had shown antiviral effects in a screening test each caused virus inactivation in autoclaved mixed waste, in which the effect of other microorganisms was excluded. Inhibition of PO1 inactivation by protease inhibitors suggests that the virus inactivation in the mixed waste was due in part to proteolytic enzymes produced by bacteria in the waste.
Thermotolerance of heat-shocked Listeria monocytogenes in milk exposed to high-temperature, short-time pasteurization
Authors: Bunning V K , Crawford R G , Tierney J T , Peeler J T
Published: January 2020

The effect of prior heat shock (48 degrees C for 15 min) on the thermotolerance of Listeria monocytogenes at the minimal high-temperature, short-time (71.7 degrees C for 15 s) parameters required by the Pasteurized Milk Ordinance was examined. The mean D71.7 degrees C value for heat-shocked L. monocytogenes was 4.6 +/- 0.5 s (control D = 3.0 +/- 1.0 s); the ratio of D to control D was 1.5. The increased thermotolerance of heat-shocked Listeria cells was not significant and appeared unlikely to have practical implications, in terms of risk assessment, for the safety of pasteurized milk.
Microbial oxidation of oleic acid
Authors: el-Sharkawy S H , Yang W , Dostal L , Rosazza J P
Published: January 2020

Resting cells of Saccharomyces cerevisiae (baker's yeast, type II; Sigma) were used to convert oleic acid into 10-hydroxyoctadecanoic acid with a 45% yield. Nocardia aurantia (ATCC 12674), Nocardia sp. (NRRL 5646), and Mycobacterium fortuitum (UI 53378) all converted oleic acid into 10-oxo-octadecanoic acid with 65, 55, and 80% yields, respectively. Structures of all metabolites were suggested by 1H and 13C nuclear magnetic resonance and by infrared and mass spectrometry. Structures of isomeric hydroxystearate and oxostearate derivatives and the stereochemical purity of hydroxystearates are difficult to prove unambiguously unless authentic standard compounds are available for spectral comparison. We describe the use of the chemical Baeyer-Villiger oxidation technique with 10-oxo-octadecanoic acid followed by mass spectral analysis of neutral extracts as a simple method to confirm the position of oxo-functional groups in the structures of fatty acid ketones. We further introduce a simple method based on 1H nuclear magnetic resonance analysis of diastereomeric S-(+)-O-acetylmandelate esters of hydroxystearates as a means of ascertaining stereochemical purities of hydroxy fatty acids.
Screening of Nonfilamentous Bacteria for Production of Cutin-Degrading Enzymes
Authors: Fett W. F. , Gerard H. C. , Moreau R. A. , Osman S. F. , Jones L. E.
Published: January 2020

Two hundred thirty-two nonfilamentous bacterial strains, including saprophytes, plant pathogens, and opportunistic plant and human pathogens, were screened for the ability to produce cutinases (cutin-degrading esterases). Initially, esterase activity of culture filtrates of strains grown in nutrient broth-yeast extract medium supplemented with 0.4% apple or tomato cutin was determined by a spectrophotometric assay utilizing the model substrate
p
-nitrophenyl butyrate. The culture filtrates of the 10
Pseudomonas aeruginosa
strains tested exhibited the highest esterase activity, with values of >500 nmol/min/ml. Of these 10 strains, 3 (K799, 1499A, and DAR41352) demonstrated significant induction (10-fold or above) of esterase activity by addition of cutin to nutrient broth-yeast extract medium. The ability of culture filtrates of the three strains to cause release of apple cutin monomers was confirmed by a novel high-performance liquid chromatography technique. Monomer identification was confirmed by gas chromatography-mass spectroscopy analyses. Addition of the nonionic detergent
n
-octylglucoside stimulated cutinase activity of culture filtrates from strains K799 and DAR41352, but not that of filtrates from strain 1499A. Time course studies in nutrient broth-yeast extract medium supplemented with apple cutin indicated maximal levels of cutinase in the culture fluids after cultures entered stationary phase. Incubation temperatures below the optimal temperature for growth (37°C) led to maximal production of cutinase.
Diversity among Rhizobia Effective with
Robinia pseudoacacia
L
Authors: McCray Batzli Janet , Graves William R. , van Berkum Peter
Published: January 2020

The diversity of rhizobia that form symbioses with roots of black locust (
Robinia pseudoacacia
L.), an economically important leguminous tree species, was examined by inoculating seedling root zones with samples of soil collected from the United States, Canada, and China. Bacteria were isolated from nodules, subcultured, and verified to be rhizobia. The 186 isolates varied significantly in their resistance to antibiotics and NaCl, their growth on different carbohydrates, and their effect on the pH of culture media. Most isolates showed intermediate antibiotic resistance, the capacity to use numerous carbohydrates, and a neutral to acid pH response. Isolates had greater similarity within sampling locations than among sampling locations. The isolates were grouped by using numerical taxonomy techniques, and representative strains of 37 groups were selected. The mean generation times of these isolates ranged from 3 to 9 h, and the protein profile of each of the 37 isolates was unique. Nitrogen fixation, total nitrogen accumulation, and plant growth varied significantly among black locust seedlings inoculated with the representative isolates. We conclude that great variation exists among
Rhizobium
spp. that nodulate black locust, and selection of strains for efficiency of the symbiotic association appears possible.
Structure, organization, and transcription of a cellobiohydrolase gene cluster from Phanerochaete chrysosporium
Authors: Covert S F , Vanden Wymelenberg A , Cullen D
Published: January 2020

Restriction mapping and sequence analysis of cosmid clones revealed a cluster of three cellobiohydrolase genes in Phanerochaete chrysosporium. P. chrysosporium cbh1-1 and cbh1-2 are separated by only 750 bp and are located approximately 14 kb upstream from a cellulase gene previously cloned from P. chrysosporium (P. Sims, C. James, and P. Broda, Gene 74:411-422, 1988). Within a well-conserved region, the deduced amino acid sequences of P. chrysosporium cbh1-1 and cbh1-2 are, respectively, 80 and 69% homologous to that of the Trichoderma reesei cellobiohydrolase I gene. The conserved cellulose-binding domain typical of microbial cellulases is absent from cbh1-1. Transcript levels of the three P. chrysosporium genes varied substantially, depending on culture conditions. cbh1-1 and cbh1-2 were not induced in the presence of cellulose, nor did they appear to be subject to glucose repression. Therefore, aspects of the chromosomal organization, structure, and transcription of these genes are unlike those of any previously described cellulase genes.
Production of Dihomo-γ-Linolenic Acid by a Δ5-Desaturase-Defective Mutant of
Mortierella alpina
1S-4
Authors: Jareonkitmongkol Saeree , Kawashima Hiroshi , Shirasaka Norifumi , Shimizu Sakayu , Yamada Hideaki
Published: January 2020

A mutant, which has low Δ5-desaturase activity, of an arachidonic acid-producing fungus,
Mortierella alpina
1S-4, was shown to be a novel potent producer of dihomo-γ-linolenic acid (DHGA). On submerged culture under optimal conditions for 6 days at 28°C in a 10-liter fermentor, the mutant produced 3.2 g of DHGA per liter of culture broth (123 mg/g of dry mycelia), which accounted for 23.4% of the total mycelial fatty acids. Mycelial arachidonic acid amounted to only 19 mg/g of dry mycelia (0.5 g/liter of culture broth), which accounted for 3.7% of the total mycelial fatty acids. The other major mycelial fatty acids were palmitic acid (11.0%), stearic acid (12.8%), oleic acid (22.7%), linoleic acid (8.9%), γ-linolenic acid (6.5%), and lignoceric acid (7.8%). More than 97 mol% of the DHGA produced was found in the triglyceride fraction irrespective of the growth temperature employed (12 to 28°C).
Biosorption of dichlorodiphenyltrichloroethane and hexachlorobenzene in groundwater and its implications for facilitated transport
Authors: Lindqvist R , Enfield C G
Published: January 2020

The potential for enhanced mobility of hydrophobic pollutants by cotransport with bacteria in saturated soils was evaluated from measurements of biosorption of 14C-labeled hexachlorobenzene and dichlorodiphenyltrichloroethane (DDT) to five strains of soil and sewage bacteria. The sorption process could be described by a linear partition equation and appeared to be reversible, but desorption kinetics were slow and/or partly irreversible. The DDT partition coefficients varied with equilibration time, possibly reflecting DDT-induced changes in the physiology of the bacteria. The partition coefficients, normalized to the masses of the bacteria, ranged from 250 to 14,000 for live cells, but the largest coefficients were associated with autoclaved cells of a Pseudomonas sp. The sorptive capacity of the bacterial biomass was greater for DDT than for hexachlorobenzene but was not correlated to overall bacterial hydrophobicity, measured by hydrophobic interaction chromatography. In a column study, 1.2 x 10(9) cells of a Bacillus sp. strain per ml enhanced DDT transport about 8-fold, whereas an advective-dispersive-sorptive equilibrium model for two mobile phases, water and free-living bacteria, suggested a 14-fold enhancement, based on the DDT partition coefficient. The disagreement was in part due to a retarded nonequilibrium movement of the bacteria. Model calculations based on literature data covering a wide range of organisms and compounds suggested that 10(6) cells ml-1 would increase the mobility of very hydrophobic compounds (log octanol-water partition coefficient [K(ow) of greater than or equal to 6), whereas higher densities of bacteria (10(8) cells ml-1) would have a significant impact on compounds with a log K(ow) of greater than or equal to 4.(ABSTRACT TRUNCATED AT 250 WORDS)
Biodegradation of mixtures of substituted benzenes by Pseudomonas sp. strain JS150
Authors: Haigler B E , Pettigrew C A , Spain J C
Published: January 2020

Pseudomonas sp. strain JS150 was isolated as a nonencapsulated variant of Pseudomonas sp. strain JS1 that contains the genes for the degradative pathways of a wide range of substituted aromatic compounds. Pseudomonas sp. strain JS150 grew on phenol, ethylbenzene, toluene, benzene, naphthalene, benzoate, p-hydroxybenzoate, salicylate, chlorobenzene, and several 1,4-dihalogenated benzenes. We designed experiments to determine the conditions required for induction of the individual pathways and to determine whether multiple substrates could be biodegraded simultaneously. Oxygen consumption studies with whole cells and enzyme assays with cell extracts showed that the enzymes of the meta, ortho, and modified ortho cleavage pathways can be induced in strain JS150. Strain JS150 contains a nonspecific toluene dioxygenase with a substrate range similar to that found in strains of Pseudomonas putida. The presence of the dioxygenase along with multiple pathways for metabolism of substituted catechols allows facile extension of the growth range by spontaneous mutation and degradation of mixtures of substituted benzenes and phenols. Chlorobenzene-grown cells of strain JS150 degraded mixtures of chlorobenzene, benzene, toluene, naphthalene, trichloroethylene, and 1,2- and 1,4-dichlorobenzenes in continuous culture. Under similar conditions, phenol-grown cells degraded a mixture of phenol, 2-chloro-, 3-chloro, and 2,5-dichlorophenol and 2-methyl- and 3-methylphenol. These results indicate that induction of appropriate biodegradative pathways in strain JS150 permits the biodegradation of complex mixtures of aromatic compounds.
Long-Term Dosimetry of Solar UV Radiation in Antarctica with Spores of
Bacillus subtilis
Authors: Puskeppeleit Monika , Quintern Lothar E. , el Naggar Saad , Schott Jobst-Ulrich , Eschweiler Ute , Horneck Gerda , Bücker Horst
Published: January 2020

The main objective was to assess the influence of the seasonal stratospheric ozone depletion on the UV climate in Antarctica by using a biological test system. This method is based on the UV sensitivity of a DNA repair-deficient strain of
Bacillus subtilis
(TKJ 6321). In our field experiment, dried layers of
B. subtilis
spores on quartz discs were exposed in different seasons in an exposure box open to solar radiation at the German Antarctic Georg von Neumayer Station (70°37′S, 8°22′W). The UV-induced loss of the colony-forming ability was chosen as the biological end point and taken as a measure for the absorbed biologically harmful UV radiation. Inactivation constants were calculated from the resulting dose-response curves. The results of field experiments performed in different seasons indicate a strongly season-dependent trend of the daily UV-B level. Exposures performed at extremely depleted ozone concentrations (October 1990) gave higher biologically harmful UV-B levels than expected from the calculated season-dependent trend, which was determined at normal ozone values. These values were similar to values which were measured during the Antarctic summer, indicating that the depleted ozone column thickness has an extreme influence on the biologically harmful UV climate on ground.
Cloning, expression, and nucleotide sequence of genes involved in production of pediocin PA-1, and bacteriocin from Pediococcus acidilactici PAC1.0
Authors: Marugg J D , Gonzalez C F , Kunka B S , Ledeboer A M , Pucci M J , Toonen M Y , Walker S A , Zoetmulder L C , Vandenbergh P A
Published: January 2020

The production of pediocin PA-1, a small heat-stable bacteriocin, is associated with the presence of the 9.4-kbp plasmid pSRQ11 in Pediococcus acidilactici PAC1.0. It was shown by subcloning of pSRQ11 in Escherichia coli cloning vectors that pediocin PA-1 is produced and, most probably, secreted by E. coli cells. Deletion analysis showed that a 5.6-kbp SalI-EcoRI fragment derived from pSRQ11 is required for pediocin PA-1 production. Nucleotide sequence analysis of this 5.6-kbp fragment indicated the presence of four clustered open reading frames (pedA, pedB, pedC, and pedD). The pedA gene encodes a 62-amino-acid precursor of pediocin PA-1, as the predicted amino acid residues 19 to 62 correspond entirely to the amino acid sequence of the purified pediocin PA-1. Introduction of a mutation in pedA resulted in a complete loss of pediocin production. The pedB and pedC genes, encoding proteins of 112 and 174 amino acid residues, respectively, are located directly downstream of the pediocin structural gene. Functions could not be assigned to their gene products; mutation analysis showed that the PedB protein is not involved in pediocin PA-1 production. The mutation analysis further revealed that the fourth gene, pedD, specifying a relatively large protein of 724 amino acids, is required for pediocin PA-1 production in E. coli. The predicted pedD protein shows strong similarities to several ATP-dependent transport proteins, including the E. coli hemolysin secretion protein HlyB and the ComA protein, which is required for competence induction for genetic transformation in Streptococcus pneumoniae.(ABSTRACT TRUNCATED AT 250 WORDS)
Effect of Protistan Grazing on the Frequency of Dividing Cells in Bacterioplankton Assemblages
Authors: Sherr Barry F. , Sherr Evelyn B. , McDaniel Julie
Published: January 2020

Grazing by phagotrophic flagellates and ciliates is a major source of mortality for bacterioplankton in both marine and freshwater systems. Recent studies have demonstrated a positive relationship between clearance rate and prey size for bacterivorous protists. We tested the idea that, by selectively grazing the larger (more actively growing or dividing) cells in a bacterial assemblage, protists control bacterial standing stock abundances by directly cropping bacterial production. Samples of estuarine water were passed through 0.8-μm-pore-size filters (bacteria only) or 20-μm-mesh screens (bacteria and bacterivorous protists) and placed in dialysis tubing suspended in 7 liters of unfiltered water. Changes in total bacterial biovolume per milliliter (bacterial biomass), frequency of dividing cells (FDC), and average per cell biovolume were followed over a period of 24 h. In three experiments, the FDC increased more rapidly and attained higher values in water passed through 0.8-μm-pore-size filters (average, 5.1 to 8.9%; maximum, 15.5%) compared with FDC values in water passed through 20-μm-mesh screens (average, 2.7 to 5.3%; maximum, 6.7%). Increases in bacterial biomass per milliliter lagged behind increases in FDC by about 4 to 6 h. Grazed bacterial assemblages were characterized by lower total biomasses and smaller average cell sizes compared with those of cells in nongrazed assemblages. We conclude that bacterivorous protists control bacterial standing stock abundances partly by preferentially removing dividing cells. Selective grazing of the more actively growing cells may also explain, in part, the ability of slow-growing cells to persist in bacterioplankton assemblages.
Bradyrhizobium Populations Occur in Deep Soil under the Leguminous Tree Acacia albida
Authors: Dupuy Nicolas C. , Dreyfus Bernard L.
Published: January 2020

Soil cores were drilled under the leguminous tree
Acacia albida
growing in two different ecoclimatic zones of West Africa: the Sahelian area (100 to 500 mm of annual rainfall) and the Sudano-Guinean area (1,000 to 1,500 mm of annual rainfall). Soil samples were collected at different depths from the surface down to the water table level and analyzed for the presence of rhizobia able to nodulate
A. albida.
In both areas, population densities of rhizobia were substantially greater near the water table than near the surface. In the Sahelian area, rhizobia were present as deep as 34 m at a concentration of 1.3 × 10
3
/g of soil. In the Sudano-Guinean area, population densities at 0.5 to 4.5 m depth were higher than in the Sahelian area and, at several depths, comparable to that of temperate soils supporting legume crops (10
4
rhizobia per g of soil). Surface and deep soil isolates from all four sites were found to be slow-growing rhizobia (
Bradyrhizobium
sp.). The proportion of effective isolates was almost the same within surface and deep soils.
Relationship between Legionella pneumophila and Acanthamoeba polyphaga: physiological status and susceptibility to chemical inactivation
Authors: Barker J , Brown M R , Collier P J , Farrell I , Gilbert P
Published: January 2020

Survival studies were conducted on Legionella pneumophila cells that had been grown intracellularly in Acanthamoeba polyphaga and then exposed to polyhexamethylene biguanide (PHMB), benzisothiazolone (BIT), and 5-chloro-N-methylisothiazolone (CMIT). Susceptibilities were also determined for L. pneumophila grown under iron-sufficient and iron-depleted conditions. BIT was relatively ineffective against cells grown under iron depletion; in contrast, iron-depleted conditions increased the susceptibilities of cells to PHMB and CMIT. The activities of all three biocides were greatly reduced against L. pneumophila grown in amoebae. PHMB (1 x MIC) gave 99.99% reductions in viability for cultures grown in broth within 6 h and no detectable survivors at 24 h but only 90 and 99.9% killing at 6 h and 24 h, respectively, for cells grown in amoebae. The antimicrobial properties of the three biocides against A. polyphaga were also determined. The majority of amoebae recovered from BIT treatment, but few, if any, survived CMIT treatment or exposure to PHMB. This study not only shows the profound effect that intra-amoebal growth has on the physiological status and antimicrobial susceptibility of L. pneumophila but also reveals PHMB to be a potential biocide for effective water treatment. In this respect, PHMB has significant activity, below its recommended use concentrations, against both the host amoeba and L. pneumophila.
Composition, Variation, and Dynamics of Major Osmotic Solutes in
Methanohalophilus
Strain FDF1
Authors: Robertson Diane E. , Lai Mei-Chin , Gunsalus Robert P. , Roberts Mary F.
Published: January 2020

Methanohalophilus
strain FDF1, a member of the halophilic genus of methanogens, can grow over a range of external NaCl concentrations from 1.2 to 2.9 M and utilize methanol, trimethylamine, and dimethyl sulfide as substrates for methanogenesis. It produces the osmolytes glycine betaine, β-glutamine, and
N
ε
-acetyl-β-lysine with increasing external NaCl, but the relative ratio of these zwitterions depends primarily on the methanogenic substrate and less on the external osmolarity. When the cells are grown on methanol in defined medium, accumulation of glycine betaine predominates over the other zwitterionic solutes. The cells also synthesized a carbohydrate which was not detected in cells grown on trimethylamine. This negatively charged compound, identified as α-glucosylglycerate from the
13
C and
1
H chemical shifts, does not act as an osmoregulatory solute in the salt range 1.4 to 2.7 M in this methanogen as evidenced by its invariant intracellular concentration.
13
CH
3
OH-pulse/
12
CH
3
OH-chase experiments were used to determine half-lifes for these organic solute pools in the cells.
l
-α-Glutamate showed a rapid loss of heavy isotope, indicating that
l
-α-glutamate functions as a biosynthetic intermediate in these cells. Measurable turnover rates for both β-glutamine, which acts as an osmolyte, and α-glucosylglycerate suggest that they function as metabolic intermediates as well. Molecules which function solely as osmolytes (glycine betaine and
N
ε
-acetyl-β-lysine) showed a slower turnover consistent with their roles as osmotic solutes in
Methanohalophilus
strain FDF1.
Development and Application of a New Method To Extract Bacterial DNA from Soil Based on Separation of Bacteria from Soil with Cation-Exchange Resin
Authors: Jacobsen Carsten S. , Rasmussen Ole F.
Published: January 2020

A new method for the extraction of bacterial DNA from soil has been developed. Soil samples of 50 g were dispersed, and bacteria were released by use of a cation-exchange resin; subsequently, bacteria were separated from soil particles by low-speed centrifugation and lysed with lysozyme and ionic detergent, and the DNA was then purified by CsCl-ethidium bromide equilibrium density centrifugation. The extracted DNA was of high molecular weight and sufficiently pure for restriction enzyme digestion, DNA-DNA hybridization, and amplification by the polymerase chain reaction. The advantages of the new method are that the separation of bacteria from soil is considerably faster than by repeated blending, more samples can be handled, and furthermore no aerosols are formed during separation. Also, we investigated whether the CsCl-ethidium bromide equilibrium density centrifugation could be replaced by purification using Gene-Clean. However, this method produced DNAs which were insufficiently pure for several types of analysis. The new method was used to study survival of a 2,4-dichlorophenoxyacetic acid (2,4-D)-degrading
Pseudomonas cepacia
DBO1 (pRO101) in unamended soil and in soil amended with 2,4-D. We found that the degrading strain, irrespective of inoculation level, was able to grow to the same high numbers in soil amended with 2,4-D, while the strain in nonamended soil were maintained at the inoculation level. Detection based on DNA extraction and subsequent dot blot DNA-DNA hybridization was in accordance with detection by plating on selective medium.
Nisin dissipates the proton motive force of the obligate anaerobe Clostridium sporogenes PA 3679
Authors: Okereke A , Montville T J
Published: January 2020

The influence of nisin on the proton motive force (delta p) generated by glucose-energized cells of the obligate putrefactive anaerobe Clostridium sporogenes PA 3679 was determined. The components of delta p, the transmembrane potential (delta psi) and the pH gradient (delta pH), were determined from the distributions of the lipophilic cation [3H]TPP+ ([3H]tetraphenylphosphonium bromide) and [14C]salicylic acid, respectively. The cells maintained a constant delta p of -111 mV, consisting of a delta pH of 0.4 to 1.0 pH units at an external pH of 5 to 7 and a delta psi of -60 to -88 mV. Nisin, carbonyl cyanide m-chlorophenylhydrazone (CCCP), and N,N'-dicyclohexylcarbodiimide (DCCD) at pH 6.0 elicited the complete release of preaccumulated [3H]tetraphenylphosphonium bromide and [14C]salicylic acid, with a concomitant depletion of delta psi and delta pH. Nisin and DCCD caused rapid drops in intracellular ATP levels from 1.2 to 0.01 and 0.06 nmol/mg of cells (dry weight), respectively. Cells exposed to nisin and DCCD lost the ability to form colonies, thus suggesting that delta psi and delta pH are necessary for cell viability. The data suggest that depletion of delta p and exhaustion of cellular ATP reserves are the basis for nisin inhibition of C. sporogenes PA 3679.
Multiple periplasmic catalases in phytopathogenic strains of Pseudomonas syringae
Authors: Klotz M G , Hutcheson S W
Published: January 2020

Phytopathogenic strains of Pseudomonas syringae are exposed to plant-produced, detrimental levels of hydrogen peroxide during invasion and colonization of host plant tissue. When P. syringae strains were investigated for their capacity to resist H2O2, they were found to contain 10- to 100-fold-higher levels of total catalase activity than selected strains belonging to nonpathogenic related taxa (Pseudomonas fluorescens and Pseudomonas putida) or Escherichia coli. Multiple catalase activities were identified in both periplasmic and cytoplasmic fluids of exponential- and stationary-phase P. syringae cells. Two of these activities were unique to the periplasm of P. syringae pv. glycinea. During the stationary growth phase, the specific activity of cytoplasmic catalases increased four- to eightfold. The specific activities of catalases in both fluids from exponential-phase cells increased in response to treatment with 0.25 to 10 mM H2O2 but decreased when higher H2O2 concentrations were used. In stationary-growth phase cultures, the specific activities of cytoplasmic catalases increased remarkably after treatment with 0.25 to 50 mM H2O2. The growth of P. syringae into stationary phase and H2O2 treatment did not induce synthesis of additional catalase isozymes. Only the stationary-phase cultures of all of the P. syringae strains which we tested were capable of surviving high H2O2 stress at concentrations up to 50 mM. Our results are consistent with the involvement of multiple catalase isozymes in the reduction of oxidative stress during plant pathogenesis by these bacteria.
Two types of bacterial alginate lyases
Authors: Kitamikado M , Tseng C H , Yamaguchi K , Nakamura T
Published: January 2020

The extracellular alginate lyases were purified from Vibrio harveyi AL-128 and V. alginolyticus ATCC 17749. The former enzyme appears to be specific for alpha-1,4 bonds involving L-guluronate units in alginate, whereas the latter exhibits specificity for beta-1,4 bonds involving D-mannuronate units. The molecular weights of the enzymes were estimated to be 57,000 and 47,000, and they had isoelectric points of 4.3 and 4.6, respectively. The enzyme from strain AL-128 was most active at NaCl concentrations of 0.3 to 1.0 M. Optimum activity of the enzyme from strain ATCC 17749 was found in the presence of 5 to 10 mM CaCl2.
Fate of Escherichia coli O157:H7 as affected by pH or sodium chloride and in fermented, dry sausage
Authors: Glass K A , Loeffelholz J M , Ford J P , Doyle M P
Published: January 2020

The influence of pH adjusted with lactic acid or HCl or sodium chloride concentration on survival or growth of Escherichia coli O157:H7 in Trypticase soy broth (TSB) was determined. Studies also determined the fate of E. coli O157:H7 during the production and storage of fermented, dry sausage. The organism grew in TSB containing less than or equal to 6.5% NaCl or at a pH of 4.5 to 9.0, adjusted with HCl. When TSB was acidified with lactic acid, the organism grew at pH 4.6 but not at pH 4.5. A commercial sausage batter inoculated with 4.8 x 10(4) E. coli O157:H7 per g was fermented to pH 4.8 and dried until the moisture/protein ratio was less than or equal to 1.9:1. The sausage chubs were then vacuum packaged and stored at 4 degrees C for 2 months. The organism survived but did not grow during fermentation, drying, or subsequent storage at 4 degrees C and decreased by about 2 log10 CFU/g by the end of storage. These studies reveal the importance of using beef containing low populations or no E. coli O157:H7 in sausage batter, because when initially present at 10(4) CFU/g, this organism can survive fermentation, drying, and storage of fermented sausage regardless of whether an added starter culture was used.