bluuebunny/crossref_metadata_2025 huggingface dataset:
Identification of a specific manganese peroxidase among ligninolytic enzymes secreted by Phanerochaete chrysosporium during wood decay
Authors: Datta A , Bettermann A , Kirk T K
Published: January 2020

The specific enzymes associated with lignin degradation in solid lignocellulosic substrates have not been identified. Therefore, we examined extracts of cultures of Phanerochaete chrysosporium that were degrading a mechanical pulp of aspen wood. Western blot (immunoblot) analyses of the partially purified protein revealed lignin peroxidase, manganese-dependent peroxidase (MnP), and glyoxal oxidase. The dominant peroxidase, an isoenzyme of MnP (pI 4.9), was isolated, and its N-terminal amino acid sequence and amino acid composition were determined. The results reveal both similarities to and differences from the deduced amino acid sequences from cDNA clones of dominant MnP isoenzymes from liquid cultures. Our results suggest, therefore, that the ligninolytic-enzyme-encoding genes that are expressed during solid substrate degradation differ from those expressed in liquid culture or are allelic variants of their liquid culture counterparts. In addition to lignin peroxidase, MnP, and glyoxal oxidase, xylanase and protease activities were present in the extracts of the degrading pulp.
Production of Cell Wall-Degrading Enzymes by the Phytopathogenic Fungus
Sclerotinia sclerotiorum
Authors: Riou Christine , Freyssinet Georges , Fevre Michel
Published: January 2020

The range of polysaccharide-degrading enzymes and glycosidases formed by the phytopathogenic fungus
Sclerotinia sclerotiorum
was monitored following growth on 16 carbohydrate substrates. Endo- and exoenzymes capable of degrading cellulosic, hemicellulosic, and pectinolytic polysaccharides were secreted. Pectinolytic activities were produced constitutively on all of the substrates tested. Cellulolytic enzymes were not induced in simple sugar (i.e., glucose or xylose) media. Polysaccharide growth substrates and cellulase inducers increased all of the enzyme activities tested. Gel filtration analysis revealed the appearance of new molecular forms of pectinase, β-xylosidase, and cellobiosidase during induction on pectin and carboxymethyl cellulose media.
Ultrastructural Changes in an Obligately Barophilic Marine Bacterium after Decompression
Authors: Chastain Roger A. , Yayanos A. Aristides
Published: January 2020

The bacterial isolate MT-41 from 10,476 m, nearly the greatest ocean depth, is obligately barophilic. The purpose of this study was to describe the morphological changes in MT-41 due to nearly isothermal decompression followed by incubation at atmospheric pressure. Two cultures were grown at 103.5 MPa and 2°C and then decompressed to atmospheric pressure (0.101 MPa). One of the cultures was fixed just before decompression. The other culture, kept at 0°C, was sampled immediately and four more times over 168 h. The number of CFU (assayed at 103.5 MPa and 2°C) declined with incubation time at atmospheric pressure. Decompression itself did not lead to immediate morphological changes. The ultrastructure, however, was altered with increasing time at atmospheric pressure. The first aberrations were intracellular vesicles and membrane fragments in the medium. After these changes were plasmolysis, cell lysis, the formation of extracellular vesicles, and the formation of ghost cells. Intact cells in the longest incubation at atmospheric pressure had the normal cytoplasmic granularity suggestive of ribosomes but had few and poorly stained fibrils in the bacterial nucleoids. From the practical standpoint, samples of hadal deep-sea regions need to be fixed either in situ or shortly after arrival at the sea surface even when recovered in insulated sampling gear. This should prevent drastic structural degradation of sampled cells, thus allowing both accurate estimates of deep-sea benthic standing stock and realistic morphological descriptions.
Quantitative assessment of the effects of metals on microbial degradation of organic chemicals
Authors: Said W A , Lewis D L
Published: January 2020

Biodegradation inhibition of a benchmark chemical, 2,4-dichloro-phenoxyacetic acid methyl ester (2,4-DME), was used to quantify the inhibitory effects of heavy metals on aerobic microbial degradation rates of organic chemicals. This procedure used lake sediments and aufwuchs (floating mats) collected in the field or from laboratory microcosms. Effects of CuCl2, HgCl2, ZnCl2, Cd(NO3)2, and Cr(NO3)3 at initial concentrations ranging from 0.3 microM to 73 mM (approximately 0.1 to 10,000 mg liter-1) were investigated. In general, such metallic compounds appeared to be considerably more inhibitory to the biodegradation of an organic chemical than high concentrations of microbially toxic organics studied previously. Effects of various metal concentrations were evaluated based on the following: (i) estimated MICs, (ii) concentrations that caused a significant effect on biodegradation parameters (both a greater than 10% decrease in Vmax and a greater than 10% increase in t1/2 for 2,4-DME degradation), and (iii) concentrations that caused biodegradation half-life doublings (HLDs). The MICs of metals in sediment were lowest for Zn2+ (0.10 microM) and highest for Cd2+ and Cu2+ (0.9 and 1.2 microM, respectively). The MICs of metals in aufwuchs were lowest for Hg2+ (0.01 microM), intermediate for Cu2+ and Zn2+ (0.42 and 0.62 microM, respectively), and highest for Cr3+ and Cd2+ (3.4 and 5.6 microM, respectively). Compared with Cu2+ on aufwuchs, 70 times more Zn2+, 250 times more Cr3+, and 1,000 times more Cd2+ was required to significantly affect aufwuchs biodegradation rate parameters and coefficients (Vmax and t1/2). Aufwuchs was significantly affected by the lowest Hg2+ concentration tested (5 microM).(ABSTRACT TRUNCATED AT 250 WORDS)
Comparative study of commercial 4-methylumbelliferyl-beta-D-glucuronide preparations with the Standard Methods membrane filtration fecal coliform test for the detection of Escherichia coli in water samples
Authors: Clark D L , Milner B B , Stewart M H , Wolfe R L , Olson B H
Published: January 2020

The performance capabilities of two commercial 4-methylumbelliferyl-beta-D-glucuronide preparations were evaluated for the detection of Escherichia coli from water samples. Eighty-three water samples were collected from a treated water reservoir, and 32 samples were collected from untreated surface water. There was a statistically significant difference between the two commercial preparations compared with the Standard Methods membrane filtration fecal coliform (MFC) method for the detection of E. coli from treated water samples. However, there was no difference between the two methods and the MFC test for E. coli detection from the untreated surface water samples. The disagreement between the two commercial products and the MFC method was primarily due to the occurrence of false-negative results with the two commercial products. The data indicate that the occurrence of false-negative samples could be attributed to impaired substrate specificity and sensitivity of the two tests for E. coli detection. There was no apparent relationship between the occurrence of false-negative results and heterotrophic plate counts in samples.
Subgroups of the Cowpea Miscellany: Symbiotic Specificity within
Bradyrhizobium
spp. for
Vigna unguiculata, Phaseolus lunatus, Arachis hypogaea
, and
Macroptilium atropurpureum
Authors: Thies Janice E. , Bohlool B. Ben , Singleton Paul W.
Published: January 2020

Rhizobia classified as
Bradyrhizobium
spp. comprise a highly heterogeneous group of bacteria that exhibit differential symbiotic characteristics on hosts in the cowpea miscellany cross-inoculation group. To delineate the degree of specificity exhibited by four legumes in the cowpea miscellany, we tested the symbiotic characteristics of indigenous cowpea bradyrhizobia on cowpea (
Vigna unguiculata
), siratro (
Macroptilium atropurpureum
), lima bean (
Phaseolus lunatus
), and peanut (
Arachis hypogaea
). The most-probable-number counts of indigenous bradyrhizobia at three sites on Maui, Hawaii, were substantially different on the four hosts: highest on siratro, intermediate on cowpea, and significantly lower on both lima bean and peanut. Bradyrhizobia from single cowpea nodules from the most-probable-number assays were inoculated onto the four hosts. Effectiveness patterns of these rhizobia on cowpea followed a normal distribution but were strikingly different on the other legumes. The effectiveness profiles on siratro and cowpea were similar but not identical. The indigenous cowpea-derived bradyrhizobia were of only moderate effectiveness on siratro and were in all cases lower than the inoculant-quality reference strain. Between 5 and 51% of the bradyrhizobia, depending on site, failed to nodulate peanut, whereas 0 to 32% failed to nodulate lima bean. No significant correlation was observed between the relative effectiveness of the bradyrhizobia on cowpea and their corresponding effectiveness on either lima bean or peanut. At all sites, bradyrhizobia that were ineffective on cowpea but that effectively nodulated lima bean, peanut, or both were found. Eighteen percent or fewer of the bradyrhizobia were as effective on lima bean as the reference inoculant strain; 44% or fewer were as effective on peanut as the reference strain. Only 18% of all cowpea-derived bradyrhizobia tested were able to form N
2
-fixing nodules on both lima bean and peanut. These results indicate the need to measure indigenous bradyrhizobial population characteristics directly with the crop of interest to obtain an accurate assessment of the need to inoculate.
Transfer and Expression of the Catabolic Plasmid pBRC60 in Wild Bacterial Recipients in a Freshwater Ecosystem
Authors: Fulthorpe Roberta R. , Wyndham R. Campbell
Published: January 2020

3-Chlorobenzoate (3Cba)-degrading bacteria were isolated from the waters and sediments of flowthrough mesocosms dosed with various concentrations of 3Cba and inoculated with a 3Cba-degrading
Alcaligenes
sp., strain BR60. Bacteria capable of 3Cba degradation which were distinct from BR60 were isolated. They carried pBRC60, a plasmid introduced with
Alcaligenes
sp. strain BR60 that carries a transposable element (Tn
5271
) encoding 3Cba degradation. The isolates expressed these genes in different ways. The majority of pBRC60 recipients were motile, yellow-pigmented, gram-negative rods related to the group III pseudomonads and to BR60 by substrate utilization pattern. They were capable of complete 3Cba degradation at both millimolar and micromolar concentrations. Two isolates,
Pseudomonas fluorescens
PR24B(pBRC60) and
Pseudomonas
sp. strain PR120(pBRC60), are more distantly related to BR60 and both produced chlorocatechol when exposed to 3Cba at millimolar concentrations in the presence of yeast extract. These species showed poor growth in liquid 3Cba minimal medium but could degrade 3Cba in continuous cultures dosed with micromolar levels of the chemical. Laboratory matings confirm that pBRC60 can transfer from BR60 to species in both the beta and gamma subgroups of the proteobacteria and that 3Cba gene expression is variable between species. Selection pressures acting on pBRC60 recipients are discussed.
Reductive
ortho
and
meta
Dechlorination of a Polychlorinated Biphenyl Congener by Anaerobic Microorganisms
Authors: Van Dort Heidi M. , Bedard Donna L.
Published: January 2020

We used gas chromatography-mass spectrometry to study the metabolic fate of 2,3,5,6-tetrachlorobiphenyl (2356-CB) (350 μM) incubated with unacclimated methanogenic pond sediment. The 2356-CB was dechlorinated to 25-CB (21%), 26-CB (63%), and 236-CB (16%) in 37 weeks. This is the first experimental demonstration of
ortho
dechlorination of a polychlorinated biphenyl by anaerobic microorganisms.
Distribution of DNA Sequences Encoding Narrow- and Broad-Spectrum Mercury Resistance
Authors: Rochelle Paul A. , Wetherbee Mary K. , Olson Betty H.
Published: January 2020

The distribution of DNA sequences homologous with three
mer
genes was determined in unselected and mercury-resistant water and sediment isolates. The maximum proportions of unselected bacterial isolates containing DNA hybridizing with the 358
merA
, 358
merB
, and 501
merR
probes, derived from gram-negative organisms, were 93.8, 21, and 100%, respectively. Up to 53.3% of mercury chloride-resistant isolates and 54% of methylmercury hydroxide-resistant isolates did not contain DNA homologous with 358
merA
or 358
merB
, respectively. Hybridizations performed at high and low stringencies demonstrated that divergence of the
merA
gene accounted for many of the mercury-resistant but probe-negative isolates. Sixteen mercury-resistant
Bacillus
spp. isolated from the least contaminated site all contained DNA homologous with 258
merA
, originally from a gram-positive organism, but only four hybridized weakly with 358
merA
. The results demonstrate the wide distribution of mercury resistance genes but, because of the diversity of genetic determinants, highlight the importance of using multiple detection techniques and gene probes derived from a variety of origins for such studies.
Procedure for Obtaining Efficient Root Nodulation of a Pea Cultivar by a Desired
Rhizobium
Strain and Preempting Nodulation by Other Strains
Authors: Fobert P. R. , Roy N. , Nash J. H. E. , Iyer V. N.
Published: January 2020

The specificity between the
sym-2
gene bred into certain cultivars of pea (
Pisum sativum
L.) and the
nodX
gene, present only rarely in isolates of
Rhizobium leguminosarum
, can be exploited to preempt competition or nodulation blocking by a
Rhizobium
strain indigenous to a soil environment. The principle is to isolate an
R. leguminosarum
strain prevalent in a locale, convert it into a strain that will nodulate a desirable pea cultivar carrying
sym-2
by establishing
nodX
in it, and then use the resulting
Rhizobium
strain with the pea cultivar carrying
sym-2
. To accomplish this, we first constructed a transposon Tn
5
derivative called Tn
5nodX
and an efficient delivery vehicle that is suicidal in
R. leguminosarum
. We tested the potential utility of the system in greenhouse experiments. The results are encouraging enough to warrant extensive experiments under field conditions.
Role of sodium in the growth of a ruminal selenomonad
Authors: Strobel H J , Russell J B
Published: January 2020

The ruminal selenomonad strain H18 grew rapidly (mu = 0.50 h-1) in a defined medium containing glucose, ammonia, purified amino acids, and sodium (95 mM); little if any ammonia was utilized as a nitrogen source. When the sodium salts were replaced by potassium salts (0.13 mM sodium), there was a small reduction in growth rate (mu = 0.34 h-1), and under these conditions greater than 95% of the cell nitrogen was derived from ammonia. No growth was observed when the medium lacked sodium (less than 0.35 mM) and amino acids were the only nitrogen source. At least six amino acid transport systems (aspartate, glutamine, lysine, phenylalanine, serine, and valine) were sodium dependent, and these systems could be driven by an electrical potential (delta psi) or a chemical gradient of sodium. H18 utilized lactate as an energy source for growth, but only when sodium and aspartate were added to the medium. Malate or fumarate was able to replace aspartate, and when these acids were added, sodium was no longer required. Glucose-grown cells accumulated large amounts of polysaccharide (64% of dry weight), and when the exogenous glucose was depleted, this material was converted to acetate and propionate as long as sodium was present. When the cells were incubated in buffers lacking sodium, succinate accumulated and exogenous succinate could not be decarboxylated. Because sodium had little effect on the transmembrane pH gradient at pH 6.7 to 4.5, it did not appear that sodium was required for intracellular pH regulation.
Phylogenetic analysis of a natural marine bacterioplankton population by rRNA gene cloning and sequencing
Authors: Britschgi T B , Giovannoni S J
Published: January 2020

The identification of the prokaryotic species which constitute marine bacterioplankton communities has been a long-standing problem in marine microbiology. To address this question, we used the polymerase chain reaction to construct and analyze a library of 51 small-subunit (16S) rRNA genes cloned from Sargasso Sea bacterioplankton genomic DNA. Oligonucleotides complementary to conserved regions in the 16S rDNAs of eubacteria were used to direct the synthesis of polymerase chain reaction products, which were then cloned by blunt-end ligation into the phagemid vector pBluescript. Restriction fragment length polymorphisms and hybridizations to oligonucleotide probes for the SAR11 and marine Synechococcus phylogenetic groups indicated the presence of at least seven classes of genes. The sequences of five unique rDNAs were determined completely. In addition to 16S rRNA genes from the marine Synechococcus cluster and the previously identified but uncultivated microbial group, the SAR11 cluster [S. J. Giovannoni, T. B. Britschgi, C. L. Moyer, and K. G. Field. Nature (London) 345:60-63], two new gene classes were observed. Phylogenetic comparisons indicated that these belonged to unknown species of alpha- and gamma-proteobacteria. The data confirm the earlier conclusion that a majority of planktonic bacteria are new species previously unrecognized by bacteriologists.
Degradation of the Herbicide Glyphosate by Members of the Family
Rhizobiaceae
Authors: Liu C.-M. , McLean P. A. , Sookdeo C. C. , Cannon F. C.
Published: January 2020

Several strains of the family
Rhizobiaceae
were tested for their ability to degrade the phosphonate herbicide glyphosate (isopropylamine salt of
N
-phosphonomethylglycine). All organisms tested (seven
Rhizobium meliloti
strains,
Rhizobium leguminosarum, Rhizobium galega, Rhizobium trifolii, Agrobacterium rhizogenes
, and
Agrobacterium tumefaciens
) were able to grow on glyphosate as the sole source of phosphorus in the presence of the aromatic amino acids, although growth on glyphosate was not as fast as on P
i
. These results suggest that glyphosate degradation ability is widespread in the family
Rhizobiaceae.
Uptake and metabolism of glyphosate were studied by using
R. meliloti
1021. Sarcosine was found to be the immediate breakdown product, indicating that the initial cleavage of glyphosate was at the C—P bond. Therefore, glyphosate breakdown in
R. meliloti
1021 is achieved by a C—P lyase activity.
Genetic Variation of
Lactobacillus delbrueckii
subsp.
lactis
Bacteriophages Isolated from Cheese Processing Plants in Finland
Authors: Forsman Päivi , Alatossava Tapani
Published: January 2020

The genomes of four
Lactobacillus delbrueckii
subsp.
lactis
bacteriophages were characterized by restriction endonuclease mapping, Southern hybridization, and heteroduplex analysis. The phages were isolated from different cheese processing plants in Finland between 1950 and 1972. All four phages had a small isometric head and a long noncontractile tail. Two different types of genome (double-stranded DNA) organization existed among the different phages, the
pac
type and the
cos
type, corresponding to alternative types of phage DNA packaging. Three phages belonged to the
pac
type, and a fourth was a
cos
-type phage. The
pac
-type phages were genetically closely related. In the genomes of the
pac
-type phages, three putative insertion/deletions (0.7 to 0.8 kb, 1.0 kb, and 1.5 kb) and one other region (0.9 kb) containing clustered base substitutions were discovered and localized. At the phenotype level, three main differences were observed among the
pac
-type phages. These concerned two minor structural proteins and the efficiency of phage DNA packaging. The genomes of the
pac
-type phages showed only weak homology with that of the
cos
-type phage. Phage-related DNA, probably a defective prophage, was located in the chromosome of the host strain sensitive to the
cos
-type phage. This DNA exhibited homology under stringent conditions to the
pac
-type phages.
Production of beta-carotene in Zymomonas mobilis and Agrobacterium tumefaciens by introduction of the biosynthesis genes from Erwinia uredovora
Authors: Misawa N , Yamano S , Ikenaga H
Published: January 2020

The Erwinia uredovora crtB, crtE, crtI, and crtY genes required for beta-carotene biosynthesis were introduced by conjugal transfer into an ethanol-producing bacterium, Zymomonas mobilis, and a phytopathogenic bacterium, Agrobacterium tumefaciens, in which no carotenoid is synthesized. The transconjugants of Z. mobilis and A. tumefaciens carrying these genes appeared as yellow colonies and produced 220 and 350 micrograms of beta-carotene per g of dry weight, respectively, in the stationary phase in liquid culture.
New version of the negative stain
Authors: Woeste S , Demchick P
Published: January 2020

We have developed a new version of the negative stain which is very quick, reliable, and easy to perform and which uses a waterproof marking pen instead of nigrosin. It is ideal for teaching the negative staining technique to beginning student microbiologists.
Unexpected Errors in Gas Chromatographic Analysis of Methane Production by Thermophilic Bacteria
Authors: Kim Byoung-Kwan , Daniels Lacy
Published: January 2020

Unexpected errors in methane measurement by gas chromatography occurred when samples at thermophilic temperatures were analyzed. With a standard curve prepared at room temperature (25°C), stoppered bottles incubated and sampled at 37 to 85°C showed more methane upon analysis than bottles incubated at 25°C: values at 50, 63, and 85°C were 109, 126, and 125%, respectively, of the 25°C value. All variation between 4 and 50°C can be explained by the temperature difference between culture bottle and sampling syringe, and the variation of methane concentration can be predicted by the gas law. Between 50 and 63°C, there was a more dramatic rise than predicted by theory. These variations are important to consider if thermophilic methane production is to be measured accurately. Methods to avoid errors are discussed.
Use of a xylE marker gene to monitor survival of recombinant Pseudomonas putida populations in lake water by culture on nonselective media
Authors: Winstanley C , Morgan J A , Pickup R W , Saunders J R
Published: January 2020

IncQ marker plasmids were previously constructed to enable the analysis of the survival of populations of Pseudomonas putida released into lake water (C. Winstanley, J. A. W. Morgan, R. W. Pickup, J. G. Jones, and J. R. Saunders, Appl. Environ. Microbiol. 55:771-777, 1989). We constructed equivalent IncP plasmids, pLV1016 and pLV1017, to provide conjugative alternative systems. Detection of the xylE gene carried by marker plasmids was found to be a valid indicator to use for studying the survival of released populations by culturing on nonselective media. These plasmids were used to study the survival of populations of Pseudomonas putida in both sterile and untreated lake water. The effects of inoculum size, the metabolic burden imposed on the cell by the unregulated expression of xylE, and an auxotrophic mutation carried by the host strain were studied. We also assessed the reproducibility and hence the predictability of the survival of released populations. Model systems with a single lake water sample and model systems with three different lake water samples, taken from the same site in consecutive months, were used to analyze variability between replicates and to assess differences caused by host strain or water sample. A large variability was found depending on which water sample was used. These findings imply that it will be difficult to predict accurately the survival of released populations in the natural environment.
Relationship between hydrogen consumption, dehalogenation, and the reduction of sulfur oxyanions by Desulfomonile tiedjei
Authors: DeWeerd K A , Concannon F , Suflita J M
Published: January 2020

Resting-cell suspensions of Desulfomonile tiedjei consumed H2 with 3-chloro-, 3-bromo-, and 3-iodobenzoate as electron acceptors with rates of 0.50, 0.44, and 0.04 mumol h-1 mg-1, respectively. However, benzoate and 3-fluorobenzoate were not metabolized by this bacterium. In addition, H2 uptake was at least fourfold faster when sulfate, sulfite, or thiosulfate was available as the electron acceptor instead of a haloaromatic substrate. When sulfite and 3-chlorobenzoate were both available for this purpose, the rate of H2 uptake by D. tiedjei was intermediate between that obtained with either electron acceptor alone. Hydrogen concentrations were reduced to comparably low levels when either 3-chlorobenzoate, sulfate, or sulfite was available as an electron acceptor, but significantly less H2 depletion was evident with benzoate or nitrate. Rates of 3-chlorobenzoate dechlorination increased from an endogenous rate of 14.5 to 17.1, 74.0, 81.1, and 82.3 nmol h-1 mg-1 with acetate, pyruvate, H2, and formate, respectively, as the electron donors. Sulfite and thiosulfate inhibited dehalogenation, but sulfate and NaCl had no effect. Dehalogenation and H2 metabolism were also inhibited by acetylene, molybdate, selenate, and metronidazole. Sulfite reduction and dehalogenation were inhibited by the same respiratory inhibitors. These results suggest that the reduction of sulfite and dehalogenation may share part of the same electron transport chain. The kinetics of H2 consumption and the direct inhibition of dehalogenation by sulfite and thiosulfate in D. tiedjei cells clearly indicate that the reduction of sulfur oxyanions is favored over aryl dehalogenation for the removal of reducing equivalents under anaerobic conditions.(ABSTRACT TRUNCATED AT 250 WORDS)
Laboratory-Based Model of Microbiologically Induced Corrosion of Copper
Authors: Bremer Philip J. , Geesey Gill G.
Published: January 2020

The interactions of bacteria isolated from corroded copper coupons on thin films of copper evaporated onto germanium internal reflection elements were evaluated nondestructively in real time by attentuated total reflectance Fourier transform infrared spectroscopy. The films were stable in the presence of flowing or static sterile culture medium. When exposed to and colonized by the bacterium CCI 8, the copper thin film corroded. Corrosion was enhanced under quiescent conditions. In conjunction with corrosion of the copper thin film was an increase in the concentration of polysaccharide material at the copper-biofilm interface. A different bacterium (CCI 11) did not corrode the copper thin film, and the establishment of this bacterium on the copper surface prevented corrosion of the thin film by CCI 8.
Experimental apparatus for selection of adherent microorganisms under stringent growth conditions
Authors: Murgel G A , Lion L W , Acheson C , Shuler M L , Emerson D , Ghiorse W C
Published: January 2020

A bioreactor apparatus is described for studying bacterial attachment. A cyclic, on-off, flow regime was imposed within the apparatus. Model calculations illustrate the utility of this flow pattern in the selection and maintenance of slow-growing, adherent organisms. The apparatus is believed to have general utility in testing bacterial attachment influenced by many types of experimental or environmental constraints, including variations in fluid dynamics, presence of toxic substances (metals or organics), nature of the substratum surface, concentrations of limiting nutrients, and competition between bacterial strains. As an example application, the apparatus was employed to test 14 bacterial strains for surface attachment in a nutrient-limited growth medium. The medium was developed, using the chemical equilibrium program MINEQL, for planned studies of biofilms in a solution with a chemically defined composition that permits calculation of trace metal speciation. The apparatus was used to select organisms with growth and attachment characteristics that could not be evaluated by conventional batch, or chemostat, culture conditions. When supplied with acetate, pyruvate, or succinate as a carbon and energy source, the gram-negative strains Pseudomonas cepacia 17616 and Zoogloea sp. WGO4 showed superior attachment characteristics to glass surfaces in the chemically defined medium but only moderate fluid-phase growth. The gram-positive Arthrobacter sp. strain 9G4D and gram-negative species P. pickettii and Zoogloea sp. WNJ8, when supplied with pyruvate as a carbon and energy source, were capable of superior growth in the fluid phase but formed only a low to moderate biofilm surface coverage.
In situ measurement of methane oxidation in groundwater by using natural-gradient tracer tests
Authors: Smith R L , Howes B L , Garabedian S P
Published: January 2020

Methane oxidation was measured in an unconfined sand and gravel aquifer (Cape Cod, Mass.) by using in situ natural-gradient tracer tests at both a pristine, oxygenated site and an anoxic, sewage-contaminated site. The tracer sites were equipped with multilevel sampling devices to create target grids of sampling points; the injectate was prepared with groundwater from the tracer site to maintain the same geochemical conditions. Methane oxidation was calculated from breakthrough curves of methane relative to halide and inert gas (hexafluroethane) tracers and was confirmed by the appearance of 13C-enriched carbon dioxide in experiments in which 13C-enriched methane was used as the tracer. A Vmax for methane oxidation could be calculated when the methane concentration was sufficiently high to result in zero-order kinetics throughout the entire transport interval. Methane breakthrough curves could be simulated by modifying a one-dimensional adevection-dispersion transport model to include a Michaelis-Menten-based consumption term for methane oxidation. The Km values for methane oxidation that gave the best match for the breakthrough curve peaks were 6.0 and 9.0 microM for the uncontaminated and contaminated sites, respectively. Natural-gradient tracer tests are a promising approach for assessing microbial processes and for testing in situ bioremediation potential in groundwater systems.
Some chemical and physical properties of extracellular polysaccharides produced by Butyrivibrio fibrisolvens strains
Authors: Ha Y W , Stack R J , Hespell R B , Gordon S H , Bothast R J
Published: January 2020

Most strains of Butyrivibrio fibrisolvens are known to produce extracellular polysaccharides (EPs). However, the rheological and functional properties of these EPs have not been determined. Initially, 26 strains of Butyrivibrio were screened for EP yield and apparent viscosities of cell-free supernatants. Yields ranged from less than 1.0 to 16.3 mg per 100 mg of glucose added to the culture. Viscosities ranged from 0.71 to 5.44 mPa.s. Five strains (CF2d, CF3, CF3a, CE51, and H10b) were chosen for further screening. The apparent viscosity of the EP from each of these strains decreased by only 50 to 60% when the shear rate was increased from 20 to 1,000 s-1. Strain CE51 produced the EP having the highest solution viscosity. A detailed comparison of shear dependency of the EP from strain CF3 with xanthan gum showed that this EP was less shear sensitive than xanthan gum and, at a shear rate of 1,000 s-1, more viscous. EPs from strains CF3 and H10b were soluble over a wide range of pH (1 to 13) in 80% (vol/vol) ethanol-water or in 1% (wt/vol) salt solutions. The pH of 1% EP solutions was between 4.5 and 5.5. Addition of acid increased solution viscosities, whereas addition of base decreased viscosity. EPs from strains CF3, CE51, and H10b displayed qualitatively similar infrared spectra. Calcium and sodium were the most abundant minerals in the three EPs. The amounts of magnesium, calcium, and iron varied considerably among the EPs, but the potassium contents remained relatively constant.
D-value determinations are an inappropriate measure of disinfecting activity of common contact lens disinfecting solutions
Authors: Sutton S V , Franco R J , Porter D A , Mowrey-McKee M F , Busschaert S C , Hamberger J F , Proud D W
Published: January 2020

Determination of a D value for specific test organisms is a component of the efficacy evaluation of new contact lens disinfecting solutions. This parameter is commonly defined as the time required for the number of surviving microorganisms to decrease 1 logarithmic unit. The assumption made in establishing a D value is that the rate of kill exhibits first-order kinetics under the specified conditions. Such exponential kill rates are seen with thermal contact lens disinfection system. A comparison of the death rate kinetics for a variety of chemical contact lens disinfecting solutions was undertaken to ascertain the suitability of D-value determination for these chemical disinfectants. The active agents of these different solutions included hydrogen peroxide, thimerosal, chlorhexidine, tris(2-hydroxyethyl)tallow ammonium chloride, thimerosal, polyaminopropyl biguanide, and polyquaternium-1. The solutions were challenged with 10(6) CFU of either Pseudomonas aeruginosa, Serratia marcescens, or Staphylococcus hominis per ml, and survival rate was determined. This study clearly demonstrates the nonlinear nature of the inactivation curves for most contact lens chemical disinfecting solutions for the challenge organisms. D-value determination is, therefore, an inappropriate method of reporting the biocidal activity of these solutions.
Effect of pH on Anaerobic Mild Steel Corrosion by Methanogenic Bacteria
Authors: Boopathy R. , Daniels L.
Published: January 2020

Methanogens can use H
2
produced by cathodic depolarization-mediated oxidation of elemental iron to produce methane. Thermodynamic consideration of the cathodic depolarization mechanism predicts more oxidation of Fe
0
at lower pH. Methanogenic responses to pH by
Methanococcus deltae, Methanococcus thermolithotrophicus
, and
Methanosarcina barkeri
were examined. When grown on H
2
-CO
2
, these bacteria had pH optima from 6.2 to 7.0, but when all H
2
was supplied from Fe
0
, methanogenic pH optima were lower, 5.4 to 6.5. Corrosion was monitored with and without cultures and at various pHs; more corrosion occurred when cultures were present, biologically induced corrosion was greatest at the pH optima for methanogenesis from Fe
0
, and corrosion without cultures increased with a drop in pH.
Ecology of bacteriophages infecting activated sludge bacteria
Authors: Hantula J , Kurki A , Vuoriranta P , Bamford D H
Published: January 2020

Little is known about the endemic bacteriophages of activated sludge. In this investigation 49 virus-host systems were studied by isolating co-occurring bacteria and bacteriophages from the aeration basin of a sewage treatment plant during 5 successive weeks. The phage titers were high and fluctuated during the time period. The occurrence of phage-sensitive and -resistant hosts did not depend on the presence or absence of phages. Several phage-host systems expressed variable plating efficiencies. In addition, phages with broad host ranges were observed. These results show that phages are an active part of this ecosystem and that they may exert selection pressure for phage resistance on their bacterial host populations.
Ultrasound Treatment for Harvesting an Aminopeptidase from Lactic Acid Bacteria and Quantitation of the Enzyme by Enzyme-Linked Immunosorbent Assays
Authors: Boquien C. Y. , Nakache F. , Paraf A.
Published: January 2020

Ultrasound treatment of
Lactococcus lactis
subsp.
cremoris
AM2 was optimized to release a maximum amount of intracellular aminopeptidase without modifying the antigenicity of the enzyme. The cells were sonicated three times for 30 s at 23 W. Antibodies produced against the aminopeptidase purified from
L. lactis
subsp.
cremoris
AM2 enabled us to use immunoblotting to detect the enzyme in the lysates of all of the lactococci tested but not in the lysates of
Leuconostoc
strains, lactobacilli, and
Streptococcus salivarus
subsp.
thermophilus
. A sandwich enzyme-linked immunosorbent assay (ELISA) was developed to quantify the purified aminopeptidase; the detection limit was 4 ng/ml. The aminopeptidase in the supernatant obtained after the ultrasound treatment of strain AM2 cells was detected with the ELISA starting with a total protein concentration of 200 ng/ml. The proportion of equivalent purified aminopeptidase in the supernatant of
L. lactis
subsp.
cremoris
AM2 was about 2% of the total protein. Similarly, the aminopeptidase was quantified in different lactococci; the percentages varied between 0.16 and 2%, depending on the strain. The aminopeptidase content in a mixture of several lactic bacteria was also determined with the sandwich ELISA.
Rapid method for processing soil samples for polymerase chain reaction amplification of specific gene sequences
Authors: Pillai S D , Josephson K L , Bailey R L , Gerba C P , Pepper I L
Published: January 2020

Bacterial cells can be differentially separated from soil colloids on the basis of their buoyant densities. By using this principle, a modified sucrose gradient centrifugation protocol has been developed for separating bacterial cells from most of the soil colloids. Since the bacterial cell suspension still contained some colloidal soil particles, which inhibited polymerase chain reaction amplification, a new "double" polymerase chain reaction method of analysis was adopted for amplification of Tn5-specific gene sequences. This new protocol allowed rapid detection of small numbers (1 to 10 CFU/g) of bacterial cells present in soil samples.
Photoadaptation Alters the Ingestion Rate of
Paramecium bursaria,
a Mixotrophic Ciliate
Authors: Berk Sharon G. , Parks Lissa H. , Ting Rebecca S.
Published: January 2020

Bacteriovorous protozoa harboring symbiotic algae are abundant in aquatic ecosystems, yet despite a recent interest in protozoan bacterivory, the influence of light on their ingestion rates has not been investigated. In this study,
Paramecium bursaria
containing endosymbiotic
Chlorella
was tested for the effect of light on its ingestion rate.
P. bursaria
was grown for 4 to 6 days under five different light fluxes ranging from 1 to 90 microeinsteins s
-1
m
-2
. Ingestion rates were determined by using 0.77-μm-diameter fluorescent microspheres. 4′,6-Diamidino-2-phenylindole dihydrochloride-labeled
Enterobacter cloacae
was used in one experiment to confirm differences in uptake rates of bacteria by
P. bursaria.
Unlike phagotrophic phytoflagellates, the ciliates demonstrated different ingestion rates in response to different light intensities. Although symbionts contribute carbon to their host via photosynthesis, the paramecia of the present study fed faster after exposure to higher light intensities, whereas their aposymbiotic counterparts (lacking endosymbionts) were unaffected. Light-induced changes in ingestion rates were not immediate, but corresponded to the period of time required for endosymbiont populations to change significantly. This strongly suggests that the symbionts, stimulated by higher light levels, may dictate the feeding rates of their hosts. Thus, light, apart from temperature, may influence the impact of certain protists on natural bacteria and may affect laboratory-based determinations of protistan feeding rates.
Risk factors for contamination of domestic hot water systems by legionellae
Authors: Alary M , Joly J R
Published: January 2020

To assess risk factors associated with the contamination of the domestic environment by legionellae, 211 houses in the Quebec City area were randomly selected and water samples were collected from the hot water tank, the shower heads, and the most frequently used faucet. After centrifugation, concentrated samples were seeded in triplicate on BCYE and GPV media. Data on the characteristics of the hot water system and plumbing in the house and on the personal habits of the occupants were collected for each house. Among these 211 houses, hot water was provided by either an oil or gas heater in 33 and by an electric heater in 178. Legionellae were isolated from none of the samples from houses with oil or gas heaters and from 39% (69 of 178) of those with electric water heaters (P less than 0.0001). This association remained highly significant after control for water temperature and other variables in a stratified analysis. In the 178 houses with an electric heater, 12% of the faucets, 15% of the shower heads, and 37% of the water heaters were contaminated. Legionella pneumophila serogroups 2 and 4 were the most frequently isolated strains. Logistic regression showed that factors associated with electric water heater contamination were (i) location of the house in older districts of the city (P less than 0.0001), (ii) old age of the water heater (P = 0.003), and (iii) low water temperature (P = 0.05). Contamination of the water heater was the only factor significantly associated with the contamination of peripheral outlets (P less than 0.0001).(ABSTRACT TRUNCATED AT 250 WORDS)
Characteristics of an inulinase produced by Bacillus subtilis 430A, a strain isolated from the rhizosphere of Vernonia herbacea (Vell Rusby)
Authors: Vullo D L , Coto C E , Siñeriz F
Published: January 2020

Bacillus subtilis 430A, isolated from the Vernonia herbacea (Vell Rusby) rhizosphere, produced an exocellular inulinase that fits the requirements for the production of syrups on an industrial scale. The partially purified enzyme, obtained by acetone precipitation, displayed a higher specificity for inulin (Km, 8 mM) than for sucrose (56 mM) and a total invertase/total inulase ratio of 0.62. In addition, it is stable at an optimal temperature of 45 to 50 degrees C for at least 7 h and is inhibited by the end product, fructose, at 14 mM.
Biodegradation of monoaromatic hydrocarbons by aquifer microorganisms using oxygen, nitrate, or nitrous oxide as the terminal electron acceptor
Authors: Hutchins S R
Published: January 2020

Microcosms were prepared from aquifer material, spiked with monoaromatic hydrocarbons, and amended with oxygen, nitrate, and nitrous oxide. Benzene and alkylbenzenes were degraded to concentrations below 5 micrograms/liter within 7 days under aerobic conditions, whereas only the alkylbenzenes were degraded when either nitrate or nitrous oxide was used. With limited oxygen, monoaromatic hydrocarbons were degraded but removal ceased once oxygen was consumed. However, when nitrate was also present, biodegradation of the alkylbenzenes continued with no apparent lag. Although benzene was still recalcitrant, levels were reduced compared with levels after treatment with nitrate or limited oxygen alone.
Production of fumonisins by Fusarium moniliforme strains from various substrates and geographic areas
Authors: Nelson P E , Plattner R D , Shackelford D D , Desjardins A E
Published: January 2020

Strains of Fusarium moniliforme from different geographic areas and from corn and other substrates were tested for the ability to produce fumonisins in culture. The test results indicate that the potential exists for production of fumonisins by such strains in agricultural commodities and other substrates in widespread geographic areas.
Cloning and expression of a chitinase gene from Aeromonas hydrophila in Escherichia coli
Authors: Chen J P , Nagayama F , Chang M C
Published: January 2020

An extracellular secreted chitinase gene from Aeromonas hydrophila was cloned in Escherichia coli, and the gene product was detected in the culture medium. Like the natural chitinase protein, the excreted chitinase had a molecular weight of approximately 85,000 and was subject to catabolite repression by glucose.
DNA probes for detection of copper resistance genes in Xanthomonas campestris pv. vesicatoria
Authors: Garde S , Bender C L
Published: January 2020

The copper resistance (Cur) genes encoded on pXV10A, a 190-kb plasmid in Xanthomonas campestris pv. vesicatoria XV10, were isolated on a 44-kb cosmid clone designated pCuR1. Tn5 mutagenesis of pCuR1 indicated that a 4.0-kb region was required for copper resistance. Three restriction fragments located within the 4.0-kb region demonstrated high specificity for the Cur genes present in X. campestris pv. vesicatoria and will be useful in monitoring the presence of these genes in the environment.
Characterization of an Unusual New
Agrobacterium tumefaciens
Strain from
Chrysanthemum morifolium
Ram
Authors: Bush Arla L. , Pueppke Steven G.
Published: January 2020

We characterized five isolates of
Agrobacterium tumefaciens
from naturally occurring galls on
Chrysanthemum morifolium.
The isolates are similar, possibly identical, members of a single strain of
A. tumefaciens
that we designate Chry5. The strain is a biotype I, as indicated by its response to both newly described and traditional biotype tests. Chry5 produces tumors on at least 10 plant species. It is unusual in its ability to form efficiently large tumors on soybean (
Glycine max
), a species normally refractory to transformation. Chry5 is unable to utilize octopine or mannopine as a carbon source. Although Chry5 can catabolize a single isomer each of nopaline and succinamopine, it differs from other known nopaline and succinamopine strains in its insensitivity to agrocin 84. This pattern of opine catabolism is unique among
Agrobacterium
strains examined to date. All five isolates of Chry5 contain at least two plasmids, one of which shares homology with pTiB6.

Images
Role of the competitive microbial flora in the radiation-induced enhancement of ochratoxin production by Aspergillus alutaceus var. alutaceus NRRL 3174
Authors: Chelack W S , Borsa J , Marquardt R R , Frohlich A A
Published: January 2020

The radiation sensitivity and the toxigenic potential of conidiospores of the fungus Aspergillus alutaceus var. alutaceus were determined after irradiation with 60Co gamma rays and high-energy electrons. Over the pH range of 3.6 to 8.8, the doses required for a 1 log10 reduction in viability based on the exponential portion of the survival curve ranged from 0.21 to 0.22 kGy, with extrapolation numbers (extrapolation of the exponential portion of the survival curve to zero dose) of 1.01 to 1.33, for electron irradiation, and from 0.24 to 0.27 kGy, with extrapolation numbers of 2.26 to 5.13, for gamma irradiation. Nonsterile barley that was inoculated with conidia of the fungus and then irradiated with either electrons or gamma rays and incubated for prolonged periods at 28 degrees C and at a moisture content of 25% produced less ochratoxin A with increasing doses of radiation. Inoculation of barley following irradiation resulted in enhanced ochratoxin levels compared with unirradiated controls. In these experiments, inoculation with 10(2) spores per g produced greater radiation-induced enhancement than inoculation with 10(5) spores per g. There was no radiation-induced enhancement when the barley was surface sterilized by chemical means prior to irradiation. These results are consistent with the hypothesis that a reduction in the competing microbial flora by irradiation is responsible for the enhanced mycotoxin production observed when nonsterile barley is inoculated with the toxigenic fungus A. alutaceus var. alutaceus after irradiation.
Use of modified diatomaceous earth for removal and recovery of viruses in water
Authors: Farrah S R , Preston D R , Toranzos G A , Girard M , Erdos G A , Vasuhdivan V
Published: January 2020

Diatomaceous earth was modified by in situ precipitation of metallic hydroxides. Modification decreased the negative charge on the diatomaceous earth and increased its ability to adsorb viruses in water. Electrostatic interactions were more important than hydrophobic interactions in virus adsorption to modified diatomaceous earth. Filters containing diatomaceous earth modified by in situ precipitation of a combination of ferric chloride and aluminum chloride adsorbed greater than 80% of enteroviruses (poliovirus 1, echovirus 5, and coxsackievirus B5) and coliphage MS2 present in tap water at ambient pH (7.8 to 8.3), even after filtration of 100 liters of tap water. Viruses adsorbed to the filters could be recovered by mixing the modified diatomaceous earth with 3% beef extract plus 1 M NaCl (pH 9).