bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of Sulfuroxy Anions on Degradation of Pentachlorophenol by a Methanogenic Enrichment Culture
Authors: Madsen Torben , Aamand Jens
Published: January 2020

We studied the degradation of pentachlorophenol (PCP) under methanogenic and sulfate-reducing conditions with an anaerobic mixed culture derived from sewage sludge. The consortium degraded PCP via 2,3,4,5-tetrachlorophenol, 3,4,5-trichlorophenol, and 3,5-dichlorophenol and eventually accumulated 3-chlorophenol. Dechlorination of PCP and metabolites was inhibited in the presence of sulfate, thiosulfate, and sulfite. A decrease in the rate of PCP transformation was noted when the endogenous dissolved H
2
was depleted below 0.11 μM in sulfate-reducing cultures. The effect on dechlorination observed with sulfate could be relieved by addition of molybdate, a competitive inhibitor of sulfate reduction. Addition of H
2
reduced the inhibition observed with sulfuroxy anions. The inhibitory effect of sulfuroxy anions may be due to a competition for H
2
between sulfate reduction and dechlorination. When cultured under methanogenic conditions, the consortium degraded several chlorinated and brominated phenols.
Distribution and survival of motile Aeromonas spp. in brackish water receiving sewage treatment effluent
Authors: Monfort P , Baleux B
Published: January 2020

The spatiotemporal distributions of Aeromonas spp. and fecal coliforms in a cove receiving sewage treatment effluent and draining into a brackish lagoon were studied for 34 months with sampling at six stations. A total of 452 strains of Aeromonas spp. were isolated and identified at the outflow of the treatment system and at stations in the cove. Hemolytic activity of 289 Aeromonas strains was determined. The Aeromonas spp. and fecal coliform distributions showed seasonal cycles in the pond effluent. These seasonal bacterial cycles were persistent in effluent, at the discharge point, and in the cove. However, the abundance levels of these bacterial distributions decreased gradually from the coast to the open lagoon. A dilution model showed that the Aeromonas spp. and fecal coliform distributions in the cove water were subject not only to dilution effect but also to other environmental factors, such as salinity. A. sobria is the most common species identified in the Aeromonas population present in the cove water. Survival studies confirmed that Aeromonas spp., especially A. sobria, were more sensitive to saline and/or marine stress than fecal coliforms. Among the Aeromonas hydrophila and A. sobria strains, 96 and 97%, respectively, produced hemolysin, whereas among the Aeromonas caviae strains, 95% were nonhemolytic.
Physical and chemical factors influencing transport of microorganisms through porous media
Authors: Fontes D E , Mills A L , Hornberger G M , Herman J S
Published: January 2020

Resting-cell suspensions of bacteria isolated from groundwater were added as a pulse to the tops of columns of clean quartz sand. An artificial groundwater solution (AGW) was pumped through the columns, and bacterial breakthrough curves were established and compared to test the effects of ionic strength of the AGW, cell size (by using strains of similar cell surface hydrophobicity but different size), mineral grain size, and presence of heterogeneities within the porous media on transport of the bacteria. The proportion of cells recovered in the effluent ranged from nearly 90% for AGW of a higher ionic strength (I = 0.0089 versus 0.00089 m), small cells (0.75-micron-diameter spheres versus 0.75 by 1.8-micron rods), and coarse-grained sand (1.0 versus 0.33 mm) to less than 1% for AGW of lower ionic strength, large cells, and fine-grained sand. Differences in the widths of peaks (an indicator of dispersion) were significant only for the cell size treatment. For treatments containing heterogeneities (a vein of coarse sand in the center of a bed of fine sand), doubly peaked breakthrough curves were obtained. The first peak represents movement of bacteria through the transmissive coarse-grained vein. The second peak is thought to be dominated by cells which have moved (due to dispersion) from the fine-grained matrix to the coarse-grained vein near the top of the column and thus had been retarded, but not retained, by the column. Strength of effects tests indicated that grain size was the most important factor controlling transport of bacteria over the range of values tested for all of the factors examined.(ABSTRACT TRUNCATED AT 250 WORDS)
Rapid identification of genetic variation and pathotype of Leptosphaeria maculans by random amplified polymorphic DNA assay
Authors: Goodwin P H , Annis S L
Published: January 2020

Canadian isolates of Leptosphaeria maculans, the causal agent of blackleg of crucifers, were examined for genetic relatedness by the random amplified polymorphic DNA assay. DNA polymorphisms amplified with random decamer primers were used to distinguish three groups of isolates. Group 1 contained all isolates of the virulent pathotype, group 2 contained isolates of the avirulent pathotype from western Canada, and group 3 contained avirulent pathotype isolates from Ontario. These results agreed with other reports which showed many genetic differences between pathotypes and were consistent with the hypothesis that the virulent pathotype was recently introduced into Canada and has diverged relatively little. In contrast, the avirulent pathotype has probably been present in Canada for a longer time and has diverged with geographic isolation. In addition to establishing genetic relationships, DNA fingerprints generated by the random amplified polymorphic DNA assay have potential applications in pathotype identification and blackleg disease management.
Effects of surfactant adsorption and biodegradability on the distribution of bacteria between sediments and water in a freshwater microcosm
Authors: Marchesi J R , Russell N J , White G F , House W A
Published: January 2020

A microcosm containing resuspended river sediment was used to investigate the effect of anionic surfactants on the distribution of bacteria between planktonic and attached populations. Freshwater river sediment containing viable bacteria was preequilibrated in the microcosm, which was subsequently supplemented with biodegradable or recalcitrant surfactants and a non-surface-active carbon and energy source. Population dynamics of both free-living and attached bacteria were measured by epifluorescence microscopy with simultaneous analysis of the residual solution concentration of the xenobiotic carbon source. The addition of the readily biodegradable anionic surfactants sodium decyl sulfate and sodium dodecyl sulfate in separate experiments caused an increase in the number of attached bacteria and a concomitant decrease in the number of free-living bacteria. As biodegradation of the surfactants progressed, these trends reversed and the bacterial populations had returned to their preaddition values by the time when biodegradation was completed. In contrast, sodium tetradecyl sulfate or sodium dodecane sulfonate did not stimulate bacterial association with sediment, nor were they biodegraded in the microcosm. Sodium pyruvate, a non-surface-active carbon and energy source, was readily utilized but caused no bacterial attachment to the sediment. These results indicate that for an anionic surfactant to induce bacterial attachment to river sediment, it must be biodegradable. The bacterial attachment to the sediment appears to be reversible and may be dependent on the accumulation of the surfactant at the surface or as a result of alteration of the surface free energies.
Microbial populations and hydrocarbon biodegradation potentials in fertilized shoreline sediments affected by the T/V Exxon Valdez oil spill
Authors: Lindstrom J E , Prince R C , Clark J C , Grossman M J , Yeager T R , Braddock J F , Brown E J
Published: January 2020

The effort of clean up the T/V Exxon Valdez oil spill in Prince William Sound, Alaska, included the use of fertilizers to accelerate natural microbial degradation of stranded oil. A program to monitor various environmental parameters associated with this technique took place during the summer of 1990. Microbiological assays for numbers of heterotrophic and oil-degrading microbes and their hydrocarbon mineralization potentials were performed in support of this program. Fertilizer addition resulted in higher hexadecane and phenanthrene mineralization potentials on treated plots than on untreated reference plots. Microbial numbers in treated and reference surface sediments were not significantly different immediately after the first nutrient application in May 1990. However, subsurface sediments from treated plots had higher numbers of hydrocarbon degraders than did reference sediments shortly after treatment. The second application of fertilizer, later in summer, resulted in surface and subsurface increases in numbers of hydrocarbon degraders with respect to reference sediments at two of the three study sites. Elevated mineralization potentials, coupled with increased numbers of hydrocarbon degraders, indicated that natural hydrocarbon biodegradation was enhanced. However, these microbiological measurements alone are not sufficient to determine in situ rates of crude oil biodegradation.
Purification and Characterization of a Pyruvated-Mannose-Specific Xanthan Lyase from Heat-Stable, Salt-Tolerant Bacteria
Authors: Ahlgren Jeffrey A.
Published: January 2020

A xanthanase complex secreted by a consortium of heat-stable, salt-tolerant bacteria includes a lyase that specifically removes terminal pyruvated β-
d
-mannose residues from the side chains of xanthan gum. The enzyme was purified to homogeneity from the culture broth following ion-exchange chromatography and gel permeation chromatography. It consists of a single subunit of molecular weight 33,000. The enzyme is stable to 55�C for more than 6 h in 20 mM sodium phosphate buffer (pH 5.0) containing 0.25 M NaCl. Optimal enzyme activity was observed at 0.05 M NaCl and a pH of 5. The enzyme has a pI of 3.7. It does not remove unsubstituted terminal β-
d
-mannose residues from xanthan side chains nor does it hydrolyze
p
-nitrophenyl-β-
d
-mannose. Treatment of xanthan with purified lyase results in a polysaccharide containing side chains terminating in an unsaturated 4,5-
ene
-glucuronic acid.
Isolation and Characterization of Microorganisms Associated with the Traditional Sorghum Fermentation for Production of Sudanese Kisra
Authors: Mohammed Sulma I. , Steenson Larry R. , Kirleis Allen W.
Published: January 2020

Sorghum flour obtained from Sudan was mixed with water in a 1:2 (wt/vol) ratio and fermented at 30°C for 24 h. The bacterial populations increased with fermentation time and reached a plateau at approximately 18 h. At the end of 24 h, sorghum batter pH had dropped from 5.95 to 3.95 and the batter had a lactic acid content of 0.80%. The microbial population during the 24 h of fermentation consisted of bacteria (
Pediococcus pentosaceus, Lactobacillus confusus, Lactobacillus brevis, Lactobacillus
sp.,
Erwinia ananas, Klebsiella pneumoniae
, and
Enterobacter cloacae
), yeasts (
Candida intermedia
and
Debaryomyces hansenii
), and molds (
Aspergillus
sp.,
Penicillium
sp.,
Fusarium
sp., and
Rhizopus
sp.).
P. pentosaceus
was the dominant microorganism at the end of the 24-h fermentation. When three consecutive fermentations using an inoculum from the previous fermentation were carried out, the bacterial population increase plateaued at 9 h. The microbial populations in these fermentations were dominated by
P. pentosaceus.
Production and characterization of N-acyl-D-glutamate amidohydrolase from Pseudomonas sp. strain 5f-1
Authors: Sakai K , Oshima K , Moriguchi M
Published: January 2020

N-Acyl-D-glutamate amidohydrolase from Pseudomonas sp. strain 5f-1 was inducibly produced by D isomers of N-acetylglutamate, glutamate, aspartate, and asparagine. The enzyme has been purified to homogeneity by DEAE-cellulose, (NH4)2SO4 fractionation, and chromatofocusing followed by gel filtration on a Sephadex G-100 column. The enzyme was a monomer with molecular weight of 55,000. The enzyme activity was optimal at pH 6.5 to 7.5 and 45 degrees C. The isoelectric point and the pH stability were 8.8 and 9.0, respectively. N-Formyl, N-acetyl, N-butyryl, N-propionyl, N-chloroacetyl derivatives of D-glutamate and glycyl-D-glutamate were substrates for the enzyme. At pH 6.5 in 100 mM N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid (HEPES) buffer at 30 degrees C, a Km of 6.67 mM and a Vmax of 662 mumol/min/mg of protein for N-acetyl-D-glutamate were obtained. None of the metal ions stimulated the enzyme activity. Na+, K+, Mg2+, and Ba2+ acted as stabilizers. Hg2+, Cu2+, Zn2+, Fe3+, and EDTA were strongly inhibitory.
Isolation and characterization of Clostridium acetobutylicum mutants with enhanced amylolytic activity
Authors: Annous B A , Blaschek H P
Published: January 2020

Clostridium acetobutylicum mutants BA 101 (hyperamylolytic) and BA 105 (catabolite depressed) were isolated by using N-methyl-N'-nitro-N-nitrosoguanidine together with selective enrichment on the glucose analog 2-deoxyglucose. Amylolytic enzyme production by C. acetobutylicum BA 101 was 1.8- and 2.5-fold higher than that of the ATCC 824 strain grown in starch and glucose, respectively. C. acetobutylicum BA 105 produced 6.5-fold more amylolytic activity on glucose relative to that of the wild-type strain. The addition of glucose at time zero to starch-based P2 medium reduced the total amylolytic activities of C. acetobutylicum BA 101 and BA 105 by 82 and 25%, respectively, as compared with the activities of the same strains grown on starch alone. Localization studies demonstrated that the amylolytic activities of C. acetobutylicum BA 101 and BA 105 were primarily extracellular on all carbohydrates tested.
Autoproteolysis of the Extracellular Serine Proteinase of
Lactococcus lactis
subsp.
cremoris
Wg2
Authors: Laan Harry , Konings Wil N.
Published: January 2020

The molecular masses of purified extracellular serine proteinase of a number of
Lactococcus lactis
strains vary significantly, and these molecular mass values do not correspond to the values estimated on the basis of genetic data. The discrepancies can only partially be explained by N-terminal processing during maturation of the precursor enzyme and by C-terminal cleaving during the release from the cell envelope. With a monoclonal antibody that binds in the active site region of the
L. lactis
proteinase, the processing of the released proteinase was followed. At 30�C the proteinase was degraded with a concomitant loss of β-casein hydrolytic activity. In the presence of CaCl
2
, proteinase degradation was inhibited, and new degradation products were detected. The specific serine proteinase inhibitors phenylmethylsulfonyl fluoride and diisopropylfluorophosphate also inhibited proteinase degradation. Two major high-molecular-mass proteinase fragments (165 and 90 kDa) were found to have the same N-terminal amino acid sequence as the mature proteinase, i.e., [Asp-1-Ala-2-Lys-3-Ala-4-Asn-5-Ser-6, indicating that both fragments were formed by cleavage at the C terminus. The N terminus of a proteinase fragment with low molecular mass (58 kDa) started with Gln-215. In this fragment part of the active site region was eliminated, suggesting that it is proteolytically inactive. Unlike larger fragments, this 58-kDa fragment remained intact after prolonged incubations. These results indicate that autoproteolysis of the
L. lactis
subsp.
cremoris
Wg2 proteinase ultimately leads to inactivation of the proteinase by deletion of the active site region.
Overproduction of lignin-degrading enzymes by an isolate of Phanerochaete chrysosporium
Authors: Orth A B , Denny M , Tien M
Published: January 2020

Phanerochaete chrysosporium is a white rot fungus which secretes a family of lignin-degrading enzymes under nutrient limitation. PSBL-1 is a mutant of this organism that generates the ligninolytic system under nonlimiting conditions during primary metabolism. Lignin peroxidase, manganese peroxidase, and glyoxal oxidase activities for PSBL-1 under nonlimiting conditions were 4- to 10-fold higher than those of the wild type (WT) under nitrogen-limiting conditions. PSBL-1 was still in the log phase of growth while secreting the enzymes, whereas the WT had ceased to grow by this time. As in the WT, manganese(II) increased manganese peroxidase activity in the mutant. However, manganese also caused an increase in lignin peroxidase and glyoxal oxidase activities in PSBL-1. Addition of veratryl alcohol to the culture medium stimulated lignin peroxidase activity, inhibited glyoxal oxidase activity, and had little effect on manganese peroxidase activity in PSBL-1, as in the WT. Fast protein liquid chromatography (FPLC) analysis shows production of larger amounts of isozyme H2 in PSBL-1 than in the WT. These properties make PSBL-1 very useful for isolation of large amounts of all ligninolytic enzymes for biochemical study, and they open the possibility of scale-up production for pratical use.
Utility of phenomenological models for describing temperature dependence of bacterial growth
Authors: Heitzer A , Kohler H P , Reichert P , Hamer G
Published: January 2020

We compared three unstructured mathematical models, the master reaction, the square root, and the damage/repair models, for describing the relationship between temperature and the specific growth rates of bacteria. The models were evaluated on the basis of several criteria: applicability, ease of use, simple interpretation of model parameters, problem-free determination of model parameters, statistical evaluation of goodness of fit (chi 2 test), and biological relevance. Best-fit parameters for the master reaction model could be obtained by using two consecutive nonlinear least-square fits. The damage/repair model proved to be unsuited for the data sets considered and was judged markedly overparameterized. The square root model allowed nonproblematical parameter estimation by a nonlinear least-square procedure and, together with the master reaction model, was able to describe the temperature dependence of the specific growth rates of Klebsiella pneumoniae NCIB 418, Escherichia coli NC3, Bacillus sp. strain NCIB 12522, and the thermotolerant coccobacillus strain NA17. The square root and master reaction models were judged to be equally valid and superior to the damage/repair model, even though the square root model is devoid of a conceptual basis.
Genomic Relatedness of
Xanthomonas campestris
Strains Causing Diseases of Citrus
Authors: Egel D. S. , Graham J. H. , Stall R. E.
Published: January 2020

Xanthomonas campestris
strains that cause disease in citrus were compared by restriction endonuclease analysis of DNA fragments separated by pulsed-field gel electrophoresis and by DNA reassociation. Strains of
X. campestris
pv. citrumelo, which cause citrus bacterial spot, were, on average, 88% related to each other by DNA reassociation, although these strains exhibited diverse restriction digest patterns. In contrast, strains of
X. campestris
pv. citri groups A and B, which cause canker A and canker B, respectively, had relatively homogeneous restriction digest patterns. The groups of strains causing these three different citrus diseases were examined by DNA reassociation and were found to be from 55 to 63% related to one another. Several pathovars of
X. campestris
, previously shown to cause weakly aggressive symptoms on citrus, ranged from 83 to 90% similar to
X. campestris
pv. citrumelo by DNA reassociation. The type strain of
X. campestris
pv. campestris ranged from 30 to 40% similar in DNA reassociation experiments to strains of
X. campestris
pv. citrumelo and
X. campestris
pv. citri groups A and B. Whereas DNA reassociation quantified the difference between relatively unrelated groups of bacterial strains, restriction endonuclease analysis distinguished between closely related strains.

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Complementation of the inability of Lactobacillus strains to utilize D-xylose with D-xylose catabolism-encoding genes of Lactobacillus pentosus
Authors: Posno M , Heuvelmans P T , van Giezen M J , Lokman B C , Leer R J , Pouwels P H
Published: January 2020

The inability of two Lactobacillus strains to ferment D-xylose was complemented by the introduction of Lactobacillus pentosus genes encoding D-xylose isomerase, D-xylulose kinase, and a D-xylose catabolism regulatory protein. This result opens the possibility of using D-xylose fermentation as a food-grade selection marker for Lactobacillus spp.
Enhancement of soybean nodulation by Bacillus cereus UW85 in the field and in a growth chamber
Authors: Halverson L J , Handelsman J
Published: January 2020

Seed treatments with Bacillus cereus UW85 increased nodulation of soybeans in three field seasons and in three different sterilized soils in the growth chamber. In the field, 28 and 35 days after planting, UW85-treated plants had 31 to 133% more nodules than untreated plants. From 49 days after planting until seed harvest, there were no significant differences between nodulation of UW85-treated plants and untreated control plants. In the growth chamber, in sterilized soil-vermiculite mixtures, at 28 days after planting, UW85 seed treatments enhanced nodulation by 34 to 61%, indicating that the increase in nodulation was not dependent on the soil flora.
Identification of the Proton Source for the Microbial Reductive Dechlorination of 2,3,4,5,6-Pentachlorobiphenyl
Authors: Nies Loring , Vogel Timothy M.
Published: January 2020

Microbially mediated reductive dechlorination of polychlorinated biphenyls (PCBs) in anaerobic sediments has been observed during laboratory experiments. Reductive dechlorination is a two-electron transfer reaction which involves the release of chlorine as a chloride ion and its replacement on the aromatic ring by hydrogen. The exact mechanism of the electron transfer for PCBs is unknown; however, this work shows that the source of the hydrogen atom is the proton (H
+
) from water.
Dyes as fungal inhibitors: effect on colony diameter
Authors: Bragulat M R , Abarca M L , Bruguera M T , Caba�es F J
Published: January 2020

The effects of a wide range of concentrations of 13 dyes on the colony diameters of nine fungal strains (including members of the Deuteromycetes and Zygomycetes) were evaluated. Auramine at a concentration of 50 ppm (50 micrograms/ml), methylene blue at a concentration of 500 ppm, gentian violet at a concentration of 5 ppm, and phenol red at a concentration of 50 ppm performed as well as the commonly used dyes dichloran at a concentration of 2 ppm and rose bengal at a concentration of 50 ppm in that they allowed adequate colony development of the Deuteromycetes strains tested and controlled rapidly spreading fungi.
Differential Siderophore Utilization and Iron Uptake by Soil and Rhizosphere Bacteria
Authors: Jurkevitch Edouard , Hadar Yitzhak , Chen Yona
Published: January 2020

The differential availabilities of the hydroxamate siderophores ferrioxamine B (FOB) and ferrichrome (FC) and the pseudobactin siderophores St3, 7NSK
2
, and WCS 358 as sources of Fe for soil and rhizosphere bacteria were studied. About 20% of the total bacterial CFU from the rhizospheres of four plant species were able to use FOB as the sole Fe source in an Fe-deficient medium, while about 12, 10, 2, and > 1% were able to use FC and pseudobactins 7NSK
2
, St3, and WCS 358, respectively. Of the 165 colonies isolated from plates containing pseudobactins, 64 were able to use the pseudobactin on which they were isolated as the sole Fe source in pure culture. Cross-feeding tests showed that almost all of these 64 strains were also able to use at least one of the other siderophores studied (pseudobactin, FOB, or FC).
Pseudomonas putida
StS2,
Pseudomonas maltophilia
7NM1, and
Vibrio fluvialis
WS1, which were originally isolated on pseudobactins St3, 7NSK
2
, and WCS 358, respectively, were selected for their ability to grow with pseudobactin St3 as the sole Fe source. They incorporated
55
Fe
3+
mediated by pseudobactin St3 at various rates (71.5, 4, and 23 pmol/min/mg [dry weight] of cells, respectively). Similarly,
P. putida
St3 was shown to incorporate
55
Fe
3+
mediated by FOB and FC. We suggest that the ability of bacteria to utilize a large variety of siderophores confers an ecological advantage.
Molecular characterization of the integration of the lactose plasmid from Lactococcus lactis subsp. cremoris SK11 into the chromosome of L. lactis subsp. lactis
Authors: Petzel J P , McKay L L
Published: January 2020

When Lactococcus lactis subsp. lactis LM0230 is transformed by the lactose plasmid (pSK11L) from Lactococcus lactis subsp. cremoris SK11, variants with pSK11L in the integrated state can be derived (J. M. Feirtag, J. P. Petzel, E. Pasalodos, K. A. Baldwin, and L. L. McKay, Appl. Environ. Microbiol. 57:539-548, 1991). In the present study, a 1.65-kb XbaI-XhoI fragment of pSK11L was subcloned for use as a probe in Southern hybridization analyses of the mechanism of integration, which was shown to proceed via a Campbell-like, single-crossover event. Furthermore, the presence of the XbaI-XhoI fragment in a nonreplicating vector facilitated the stable, Rec-dependent integration of the vector into the chromosome of L. lactis subsp. lactis LM0230 and other lactococci. DNA sequence analysis of the fragment revealed an open reading frame of 885 bp with lactococcal expression sequences. The putative gene did not have significant homology with other genes in computer data bases. The XbaI-XhoI fragment is a naturally occurring piece of lactococcal DNA that can be used as a recombinogenic cassette in the construction of integration vectors for the industrially important lactococci.
Analysis of genes involved in biosynthesis of the lantibiotic subtilin
Authors: Klein C , Kaletta C , Schnell N , Entian K D
Published: January 2020

Lantibiotics are peptide-derived antibiotics with high antimicrobial activity against pathogenic gram-positive bacteria. They are ribosomally synthesized and posttranslationally modified (N. Schnell, K.-D. Entian, U. Schneider, F. Götz, H. Zähner, R. Kellner, and G. Jung, Nature [London] 333:276-278, 1988). The most important lantibiotics are subtilin and the food preservative nisin, which both have a very similar structure. By using a hybridization probe specific for the structural gene of subtilin, spaS, the DNA region adjacent to spaS was isolated from Bacillus subtilis. Sequence analysis of a 4.9-kb fragment revealed several open reading frames with the same orientation as spaS. Downstream of spaS, no reading frames were present on the isolated XbaI fragment. Upstream of spaS, three reading frames, spaB, spaC, and spaT, were identified which showed strong homology to genes identified near the structural gene of the lantibiotic epidermin. The SpaT protein derived from the spaT sequence was homologous to hemolysin B of Escherichia coli, which indicated its possible function in subtilin transport. Gene deletions within spaB and spaC revealed subtilin-negative mutants, whereas spaT gene disruption mutants still produced subtilin. Remarkably, the spaT mutant colonies revealed a clumpy surface morphology on solid media. After growth on liquid media, spaT mutant cells agglutinated in the mid-logarithmic growth phase, forming longitudinal 3- to 10-fold-enlarged cells which aggregated. Aggregate formation preceded subtilin production and cells lost their viability, possibly as a result of intracellular subtilin accumulation. Our results clearly proved that reading frames spaB and spaC are essential for subtilin biosynthesis whereas spaT mutants are probably deficient in subtilin transport.
Production, purification, and properties of a lipase from a bacterium (Pseudomonas aeruginosa YS-7) capable of growing in water-restricted environments
Authors: Shabtai Y , Daya-Mishne N
Published: January 2020

An extracellular lipase from the low-water-tolerant bacterium P. aeruginosa YS-7 was produced, purified, and characterized with respect to its functional properties in aqueous solutions and organic solvents. The enzyme was partially released from the cells during fermentation in defined medium with 5% (wt/vol) soybean oil. Approximately one-half of the total culture activity remained in solution after removal of cells. More than 95% of the activity was found in culture supernatant after mild detergent treatment (10 mM sodium deoxycholate) or after shifting the carbon source during the fermentation from triglyceride to a free fatty acid. The enzyme was recovered from an acetone precipitate of the whole culture and purified by hydrophobic interaction chromatography, yielding a preparation having a specific activity of about 1,300 mumol of fatty acid mg-1 h-1. The lipase (molecular size, approximately 40 kDa) hydrolyzes a variety of fatty acid esters and has an optimum pH of about 7. The enzyme retained its full activity at 20 to 55 degrees C, even after prolonged exposure (more than 30 days) to different concentrations of water-miscible organic solvents such as alcohols, glycols, pyridine, acetonitrile, dimethyl formamide, and dimethyl sulfoxide. The hydrolysis of 4-nitrophenyl laurate ester and of triglyceride emulsified in water was slightly accelerated with increasing concentrations of alcohols and glycols up to about 20% but was abolished with a further increase in alcohol concentration or in the presence of acetonitrile. In contrast, the rate of hydrolysis of these substrates in concentrated solutions of dimethyl formamide or dimethyl sulfoxide was markedly increased, by more than twofold and more than fivefold, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)
Examination of fungi in domestic interiors by using factor analysis: correlations and associations with home factors
Authors: Su H J , Rotnitzky A , Burge H A , Spengler J D
Published: January 2020

Factor analysis was utilized to investigate correlations among airborne microorganisms collected with Andersen samplers from homes in Topeka, Kans., during the winter of 1987 to 1988. The factors derived were used to relate microbial concentrations with categorical, questionnaire-derived descriptions of housing conditions. This approach successfully identified groups of common aboveground decay fungi including Cladosporium, Alternaria, Epicoccum, and Aureobasidium spp. The common soil fungi Aspergillus and Penicillium spp. were also separated as a group. These previously known ecological groupings were confirmed with air sampling data by a quantitative evaluation technique. The aboveground decay fungi sampled indoors in winter were present at relatively high concentrations in homes with gas stoves for cooking, suggesting a possible association between these fungi and increased humidity from the combustion process. Elevated concentrations of the soil fungi were significantly (P = 0.05) associated with the dirt floor, crawl-space type of basement. Elevated concentrations of water-requiring fungi, such as Fusarium spp., were shown to be associated with water collection in domestic interiors. Also, elevated mean concentrations for the group of fungi including Cladosporium, Epicoccum, Aureobasidium, and yeast spp. were found to be associated (P = 0.03) with symptoms reported on a health questionnaire. This finding was consistent with our previous study of associations between respiratory health and airborne microorganisms by univariate logistic regression analysis.
High-Frequency Plasmid Transduction by
Lactobacillus gasseri
Bacteriophage φadh
Authors: Raya R. R. , Klaenhammer T. R.
Published: January 2020

The temperate bacteriophage φadh mediates plasmid DNA transduction in
Lactobacillus gasseri
ADH at frequencies in the range of 10
-8
to 10
-10
transductants per PFU.
Bgl
II-generated DNA fragments from phage φadh were cloned into the
Bcl
I site of the transducible plasmid vector pGK12 (4.4 kb). Phage φadh lysates induced from
Lactobacillus
lysogens harboring pGK12 or the recombinant plasmids were used to transduce strain ADH to chloramphenicol resistance. The transduction frequencies of recombinant plasmids were 10
2
- to 10
5
-fold higher than that of native pGK12. The increase in frequency generally correlated with the extent of DNA-DNA homology between plasmid and phage DNAs. The highest transduction frequency was obtained with plasmid pTRK170 (6.6 kb), a pGK12 derivative containing the 1.4- and 0.8-kb
Bgl
II DNA fragments of φadh. DNA hybridization analysis of pTRK170-transducing phage particles revealed that pTRK170 had integrated into the φadh genome, suggesting that recombination between homologous sequences present in phage and plasmid DNAs was responsible for the formation of high-frequency transducing phage particles. Plasmid DNA analysis of 13 transductants containing pTRK170 showed that each had acquired intact plasmids, indicating that in the process of transduction a further recombination step was involved in the resolution of plasmid DNA monomers from the recombinant pTRK170::φadh molecule. In addition to strain ADH, pTRK170 could be transduced via φadh to eight different
L. gasseri
strains, including the neotype strain, F. Gasser 63 AM (ATCC 33323).
Variations in rRNA content of marine Vibrio spp. during starvation-survival and recovery
Authors: Kramer J G , Singleton F L
Published: January 2020

The degree and temporal context of variations in ribosome content during nutrient starvation of two copiotrophic marine bacteria, Vibrio alginolyticus and Vibrio furnissii, have been examined. The organisms were starved either by nutritional shift-down or by consumption of limiting nutrients resulting from growth into stationary phase. Measurements of the amount of hybridization to 16S rRNA-specific probes revealed that the cells retained between 10 and 26% of their original rRNA content after 15 days of starvation. In V. alginolyticus, losses in stationary-phase cells occurred rapidly (1 to 2 days), whereas cells shifted into starvation remained larger and retained considerably more rRNA. The ability of V. alginolyticus to recover from starvation was assessed after cells were maintained for 2, 8, and 15 days in nutrient-depleted medium. The pattern of recovery at the level of rRNA accumulation depended upon the duration of nutrient deprivation and the manner in which it was imposed. Stationary-phase cells starved for 2 days had only slight relative increases in rRNA levels after excess nutrients were added. As the duration of starvation lengthened to 8 and 15 days, increasingly greater amounts of rRNA (30 and 70 times preenrichment values, respectively) were transcribed after nutrient enrichment. Shift-down cells recovered from 2 and 8 days of starvation without extensive rRNA production. After 15 days, nutrient enrichment caused 16S rRNA levels to increase 30-fold. The results indicate that the mechanisms controlling starvation-survival in these marine bacterial species are linked to the physiological state at the onset of starvation and that the subsequent pattern of recovery will depend upon how starvation was initiated.
Jenseniin G, a heat-stable bacteriocin produced by Propionibacterium jensenii P126
Authors: Grinstead D A , Barefoot S F
Published: January 2020

The genus Propionibacterium includes cutaneous species typically found on human skin and the dairy or classical species (Propionibacterium freudenreichii, P. jensenii, P. thoenii, and P. acidipropionici) used industrially for the production of Swiss cheese and propionic acid. Grinstead (1989, M.S. thesis, Iowa State University, Ames) has previously observed that some dairy propionibacteria inhibit other species in the classical grouping. We further investigated the inhibitor(s) produced by P. jensenii P126 (ATCC 4872). An antagonist(s) from anaerobic agar cultures of P126 strongly inhibited two closely related strains of propionibacteria, P. acidipropionici P5 and P. jensenii P54, and Lactobacillus bulgaricus NCDO 1489, Lactobacillus delbrueckii subsp. lactis ATCC 4797, Lactococcus cremoris NCDO 799, and Lactococcus lactis subsp. lactis C2. The inhibitor, designated jenseniin G, was active at pH 7.0; inactivated by treatment with pronase E, proteinase K, and type 14 protease; insensitive to catalase; and stable to freezing, cold storage (4 degrees C, 3 days), and heat (100 degrees C, 15 min). Classification of the inhibitor as a bacteriocin is supported by its proteinaceous nature and its bactericidal activity against L. delbrueckii subsp. lactis ATCC 4797. The lack of detectable plasmids suggests a chromosomal location for the determinant(s) of jenseniin G.
Degradation of 2,4-dinitrotoluene by the lignin-degrading fungus Phanerochaete chrysosporium
Authors: Valli K , Brock B J , Joshi D K , Gold M H
Published: January 2020

Under ligninolytic conditions, the white rot basidiomycete Phanerochaete chrysosporium mineralizes 2,4-dinitrotoluene (I). The pathway for the degradation of I was elucidated by the characterization of fungal metabolites and oxidation products generated by lignin peroxidase (LiP), manganese peroxidase (MnP), and crude intracellular cell extracts. The multistep pathway involves the initial reduction of I to yield 2-amino-4-nitrotoluene (II). II is oxidized by MnP to yield 4-nitro-1,2-benzoquinone (XII) and methanol. XII is then reduced to 4-nitro-1,2-hydroquinone (V), and the latter is methylated to 1,2-dimethoxy-4-nitrobenzene (X). 4-Nitro-1,2-hydroquinone (V) is also oxidized by MnP to yield nitrite and 2-hydroxybenzoquinone, which is reduced to form 1,2,4-trihydroxybenzene (VII). 1,2-Dimethoxy-4-nitrobenzene (X) is oxidized by LiP to yield nitrite, methanol, and 2-methoxy-1,4-benzoquinone (VI), which is reduced to form 2-methoxy-1,4-hydroquinone (IX). The latter is oxidized by LiP and MnP to 4-hydroxy-1,2-benzoquinone, which is reduced to 1,2,4-trihydroxybenzene (VII). The key intermediate 1,2,4-trihydroxybenzene is ring cleaved by intracellular cell extracts to produce, after reduction, beta-ketoadipic acid. In this pathway, initial reduction of a nitroaromatic group generates the peroxidase substrate II. Oxidation of II releases methanol and generates 4-nitro-1,2-benzoquinone (XII), which is recycled by reduction and methylation reactions to regenerate intermediates which are in turn substrates for peroxidase-catalyzed oxidation leading to removal of the second nitro group. Thus, this unique pathway apparently results in the removal of both aromatic nitro groups before ring cleavage takes place.
Sheared-Root Inocula of Vesicular-Arbuscular Mycorrhizal Fungi
Authors: Sylvia D. M. , Jarstfer A. G.
Published: January 2020

For efficient handling, vesicular-arbuscular mycorrhizal fungi should be processed into small and uniform inocula; however, processing can reduce the inoculum density. In this article we describe the preparation and use of sheared-root inocula of
Glomus
spp. in which inoculum densities were increased during processing. Our objectives were to determine inoculum viability and density after shearing and to ascertain if the sheared inocula could be pelletized or used with a gel carrier. Root samples were harvested from aeroponic cultures, blotted dry, cut into 1-cm lengths, and sheared in a food processor for up to 80 s. After shearing, the inoculum was washed over sieves, and the propagule density in each fraction was determined. Sheared inocula were also encapsulated in carrageenan or used in a gel carrier. Shearing aeroponically produced root inocula reduced particle size. Propagule density increased with decreasing size fraction down to a size of 63 μm, after which propagule density decreased. The weighted-average propagule density of the inoculum was 135,380 propagules g (dry weight) of sheared root material
-1
. Sheared roots were encapsulated successfully in carrageenan, and the gel served as an effective carrier. Aeroponic root inoculum was stored dry at 4°C for 23 months without significant reduction in propagule density; however, this material was not appropriate for shearing. Moist roots, useful for shearing, began to lose propagule density after 1 month of storage. Shearing proved to be an excellent method to prepare viable root inocula of small and uniform size, allowing for more efficient and effective use of limited inoculum supplies.
Fate of Fumonisin B
1
in Naturally Contaminated Corn during Ethanol Fermentation
Authors: Bothast R. J. , Bennett G. A. , Vancauwenberge J. E. , Richard J. L.
Published: January 2020

Two lots of corn naturally contaminated with fumonisin B
1
(15 and 36 ppm) and a control lot (no fumonisin B
1
detected) were used as substrates for ethanol production in replicate 8.5-liter yeast fermentations. Ethanol yields were 8.8% for both the control and low-fumonisin corn, while the high-fumonisin corn contained less starch and produced 7.2% ethanol. Little degradation of fumonisin occurred during fermentation, and most was recovered in the distillers' grains, thin stillage, and distillers' solubles fractions. No toxin was detected in the distilled alcohol or centrifuge solids. Ethanol fermentation of fumonisin-contaminated corn coupled with effective detoxification of distillers' grains and aqueous stillage is suggested as a practical process strategy for salvaging contaminated corn.
Specific amplification of 18S fungal ribosomal genes from vesicular-arbuscular endomycorrhizal fungi colonizing roots
Authors: Simon L , Lalonde M , Bruns T D
Published: January 2020

The first DNA sequences obtained from arbuscular endomycorrhizal fungi are reported. They were obtained by directly sequencing overlapping amplified fragments of the nuclear genes coding for the small subunit rRNA. These sequences were used to develop a polymerase chain reaction primer (VANS1) that enables the specific amplification of a portion of the vesicular-arbuscular endomycorrhizal fungus small subunit rRNA directly from a mixture of plant and fungal tissues. The specificity of this primer for arbuscular endomycorrhizal fungi was demonstrated by testing it on a number of organisms and by sequencing the fragment amplified from colonized leek (Allium porum) roots. This approach, coupled with other molecular techniques, will facilitate rapid detection, identification, and possibly quantitation of arbuscular endomycorrhizal fungi.
Isolation and characterization of a nitrite reductase gene and its use as a probe for denitrifying bacteria
Authors: Smith G B , Tiedje J M
Published: January 2020

The dissimilatory nitrite reductase gene (nir) from denitrifying bacterium Pseudomonas stutzeri JM300 was isolated and sequenced. In agreement with recent sequence information from another strain of P. stutzeri (strain ZoBell), strain JM300 nir is the first gene in an operon and is followed immediately by a gene which codes for a tetraheme protein; 2.5 kb downstream from the nitrite reductase carboxyl terminus is the cytochrome c551 gene. P. stutzeri JM300 nir is 67% homologous to P. aeruginosa nir and 88% homologous to P. stutzeri ZoBell nir. Within the nitrite reductase promoter region is an fnr-like operator very similar to an operator upstream of a separate anaerobic pathway, that for arginine catabolism in P. aeruginosa. The denitrification genes in P. stutzeri thus may be under the same regulatory control as that found for other anaerobic pathways of pseudomonads. We have generated gene probes from restriction fragments within the nitrite reductase operon to evaluate their usefulness in ecology studies of denitrification. Probes generated from the carboxyl terminus region hybridized to denitrifying bacteria from five separate genera and did not cross-hybridize to any nondenitrifying bacteria among six genera tested. The denitrifier probes were successful in detecting denitrifying bacteria from samples such as a bioreactor consortium, aquifer microcosms, and denitrifying toluene-degrading enrichments. The probes also were used to reveal restriction fragment length polymorphism patterns indicating the diversity of denitrifiers present in these mixed communities.
Influence of Calcium, Iron, and pH on Phosphate Availability for Microbial Mineralization of Organic Chemicals
Authors: Robertson B. K. , Alexander Martin
Published: January 2020

A study was conducted to determine some of the factors affecting the P requirement for the biodegradation of
p
-nitrophenol, phenol, and glucose by
Pseudomonas
and
Corynebacterium
strains. Mineralization of glucose was rapid and the
Pseudomonas
sp. grew extensively in solutions with 5 and 10 mM phosphate, but the rate and extent of degradation were low and the bacterial population never became abundant in media with 0.2 mM phosphate. Similar results were obtained with the
Corynebacterium
sp. growing in media containing
p
-nitrophenol or phenol and in solutions with a purified phosphate salt. The extent of growth of the
Corynebacterium
sp. was reduced with 2 or 10 mM phosphate in media containing high Fe concentrations. Ca at 5 mM but not 0.5 mM inhibited
p
-nitrophenol mineralization by the
Corynebacterium
sp. with phosphate concentrations from 0.2 to 5.0 mM. Phenol mineralization by the
Pseudomonas
sp. in medium with 0.2 mM phosphate was rapid at pH 5.2, but the bacteria had little or no activity at pH 8.0. In contrast, the activity was greater at pH 8.0 than at pH 5.2 when the culture contained 10 mM phosphate. These effects of pH were similar in media with 5 mM Ca or no added Ca. We conclude that the effect of P on bacterial degradation can be influenced by the pH and the concentrations of Fe and Ca.
Lack of virulence factors in Escherichia coli strains of enteropathogenic serogroups isolated from water
Authors: Valentini S R , Gomes T A , Falcão D P
Published: January 2020

Thirty-eight Escherichia coli strains belonging to 14 human enteropathogenic serogroups were isolated from 33 of 208 water samples studied. No virulence factor or virulence-related gene sequences were found in any of the 38 strains analyzed. The results point out the importance of detecting specific virulence factors before incriminating water as a source of human diarrhea.
Characterization of lactoferrin binding by Aeromonas hydrophila
Authors: Ascencio F , Ljungh A , Wadstrom T
Published: January 2020

Various lactoferrin preparations (iron-saturated and iron-depleted human milk lactoferrins and bovine milk and colostrum lactoferrins) were bound by Aeromonas hydrophila. Binding was (i) reversible (65% of bound lactoferrin was displaced by unlabeled lactoferrin), (ii) specific (lactoferrin but not other iron-containing glycoproteins such as ferritin, transferrin, hemoglobin, and myoglobin inhibited binding), and (iii) significantly reduced by pepsin and neuraminidase treatment of the bacteria. The glycosidic domains of the lactoferrin molecule seem to be involved in binding since precursor monosaccharides of the lactoferrin oligosaccharides (mannose, fucose, and galactose) and glycoproteins which have homologous glycosidic moieties similar to those of the lactoferrin oligosaccharides (asialofetuin or fetuin) strongly inhibited lactoferrin binding. A. hydrophila also binds transferrin, ferritin, cytochrome c, hemin, and Congo red. However, binding of these iron-containing compounds seems to involve bacterial surface components different from those required for lactoferrin binding. Expression of lactoferrin binding by A. hydrophila was influenced by culture conditions. In addition, there was an inverse relationship between lactoferrin binding and siderophore production by the bacterium.
Transfer of IncP Plasmids to Extremely Acidophilic
Thiobacillus thiooxidans
Authors: Jin S. M. , Yan W. M. , Wang Z. N.
Published: January 2020

The broad-host-range IncP plasmids RP4, R68.45, RP1::Tn
501
, and and pUB307 were transferred directly to extremely acidophilic
Thiobacillus thiooxidans
from
Escherichia coli
by conjugation at frequencies of 10
-5
to 10
-7
per recipient. The ability of
T. thiooxidans
to receive and express the antibiotic resistance markers was examined. The plasmid RP4 was transferred back to
E. coli
from
T. thiooxidans
at a frequency of 1.0 × 10
-3
per recipient.