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Anthony G Hay

Publications and source records attributed to Anthony G Hay.

14 recordsLinked to original sources
PubMed2007

Transcription in Escherichia coli PHL628 biofilms.

The biofilm-specific gene expression of Escherichia coli PHL628 was compared with that from exponentially growing planktonic cells using macroarray technology. In duplicate experiments, both biofilm and planktonic cells were grown in separate continually stirred tank reactors at 57% of the maximal planktonic growth rate. When transcriptional results from planktonic cultures were compared with that of biofilm grown cells, c. 4.5% of the genome showed a significant change in expression. The results presented here point to an extremely heterogeneous biofilm wherein specific gene induction was consistent with the response of biofilm cells to gradients in electron acceptors, nutrients, carbon source and a variety of stresses. A mutant in one of the genes, gspM (pshM), that was induced in biofilms was constructed and was shown to be compromised for its ability to form mature biofilms. This analysis provides additional insight into the genes induced during biofilm development, the gradients they respond to, the contribution of one gene to biofilm development, and a comparison of this with other transcriptional profiles from E. coli biofilms.

Biofilms↗
PubMed2006

Phenylacetylene reversibly inhibits the phenol hydroxylase of Pseudomonas sp. CF600 at high concentrations but is oxidized at lower concentrations.

Alkynes are mechanism-based inhibitors of several bacterial monooxygenases, including the soluble methane monooxygenase (sMMO) of Methylococcus capsulatus and the toluene o-monooxygenase (TOM) of Burkholderia cepacia G4. In this paper, we investigated the inhibition of the phenol hydroxylase of Pseudomonas sp. CF600 by the alkyne phenylacetylene. Growth of CF600 on phenol and phenol hydroxylase activity were inhibited by phenylacetylene concentrations greater than 1.0 mM. Unlike other alkynes, which irreversibly inhibit a number of monooxygenases, inhibition of phenol hydroxylase by phenylacetylene was reversible, as demonstrated by the ability of washed cells to regain phenol hydroxylase activity. Additionally, phenylacetylene was metabolized by phenol-grown cells, yielding a yellow meta-ring fission product which absorbed light maximally at 412 nm. Phenol-grown CF600 transformed phenylacetylene to hydroxyphenylacetylene and 2-hydroxy-6-oxo-octa-2,4-dien-7-ynoic acid as detected by gas chromatography--mass spectroscopy and high-performance liquid chromatography (HPLC), respectively, while neither a derivative of CF600 with a non-functional phenol hydroxylase nor wild-type CF600 grown on acetate transformed phenylacetylene. These results demonstrate that the phenol hydroxylase of CF600 has broader substrate specificity than previously reported. They also suggest that phenylacetylene acts as a competitive inhibitor rather than as a mechanism-based inhibitor of this phenol hydroxylase.

Acetylene↗
PubMed2006

Global analysis of candidate genes important for fitness in a competitive biofilm using DNA-array-based transposon mapping.

Escherichia coli strain PHL628 was subjected to saturating Tn5 transposon mutagenesis and then grown under competitive planktonic or biofilm conditions. The locations of transposon insertions from the remaining cells were then mapped on a gene array. The results from the array mapping indicated that 4.5 % of the E. coli genome was important under these conditions. Specifically, 114 genes were identified as important for the biofilm lifestyle, whereas 80 genes were important for the planktonic lifestyle. Four broad functional categories were identified as biofilm-important. These included genes encoding cell structures, small-molecule transport, energy metabolism and regulatory functions. For one of these genes, arcA, an insertion mutant was generated and its biofilm-related phenotype was examined. Results from both the transposon array and insertion mutagenesis indicated that arcA, which is known to be a negative response regulator of genes in aerobic pathways, was important for competitiveness in E. coli PHL628 biofilms. This work also demonstrated that ligation-mediated PCR, coupled with array-based transposon mapping, was an effective tool for identifying a large variety of candidate genes that are important for biofilm fitness.

Bacterial Outer Membrane Proteins↗
PubMed2005

1-Methylcyclopropene interactions with diphenylamine on diphenylamine degradation, alpha-farnesene and conjugated trienol concentrations, and polyphenol oxidase and peroxidase activities in apple fruit.

1-Methylcyclopropene (1-MCP) is a new technology that is applied commercially to inhibit ethylene action in apple fruit, but its interactions with existing technologies such as diphenylamine (DPA) for control of superficial scald development in fruit during and after storage is unknown. To investigate possible interactions between 1-MCP and DPA, Delicious apples were untreated or treated with 2 g L(-1) DPA, and then with or without 1 microL L(-1) 1-MCP. Ethylene production and respiration rates of fruit were measured immediately following treatment, and fruit was stored at 0.5 degrees C for 12 weeks. Internal ethylene concentrations (IEC), alpha-farnesene and conjugated trienol (CTol) concentrations, activities of peroxidase and polyphenol oxidase (PPO), and DPA levels in the skin of the fruit were measured at intervals during storage. 1-MCP reduced the rate of DPA loss from peel tissue so that by 12 weeks of storage concentrations of the chemical were 25% higher than in untreated fruit. 1-MCP, with and without DPA, markedly inhibited ethylene production and respiration rates, maintained low IEC and alpha-farnesene and CTol concentrations, while DPA had little effect on these factors except inhibition of CTol accumulation. Treatment effects on peroxidase and PPO activities were inconsistent.

Catechol Oxidase↗
PubMed2005

A simple solid phase assay for the detection of 2,4-D in soil.

Contaminated soils are usually characterized using chemical analyses. However, these do not assess the bioavailability of pollutants, a factor which may be important in estimating the risks associated with contamination. Thus there is a need to support chemical analyses with information on biological effects to determine the potential risks a pollutant may pose in the soil. Although bacterial bioreporters have been used to detect the presence of contaminants in soils, in general these studies have been carried out in slurries or soil extracts rather than soil itself. The following study presents the development of a simple solid-phase bioassay for the direct detection of the herbicide 2,4-dichlorophenoxy acetic acid (2,4-D) in soil using Ralstonia eutropha JMP 134-32, a luxCDABE-based 2,4-D whole cell bioreporter. The bioreporter was spotted onto glass microfibre filter discs that allowed its retrieval and analysis after exposure to 2,4-D amended soils. These disc-fixed cells responded in a concentration dependent manner to 2,4-D in solution (0-25 mg/L) and in spiked soil (0-50 mg/kg). The influence of environmental factors on bioavailability was demonstrated in soil with a low moisture content which prevented 2,4-D-induced bioluminescence but which did not affect bioluminescence from already induced cells. This rapid and low cost bioassay provides a proof of concept demonstrating that retrievable disk-fixed cells can be induced in soil, thus providing a measure of solid-phase bioavailability. This method overcomes some of the limitations associated with the inoculation and monitoring of bioreporters directly in soil. Additionally, this simple system should be amenable to use with other bioreporters.

2,4-Dichlorophenoxyacetic Acid↗
PubMed2005

Molecular characterization of fungal community dynamics in the initial stages of composting.

Composting relies on a complex network of bacteria and fungi to process crude organic material. Although it is known that these organisms drive dynamic changes in temperature and pH, little is known about the temporal dynamics of fungal populations during the rise to thermophilic conditions. This study employed F-ARISA (fungal-automated rRNA intergenic spacer analysis) and 18S rRNA gene cloning and sequencing to examine changes in community structure during this period. Sequencing of the 18S rRNA portion of cloned F-ARISA products revealed the presence of four distinct fungal genera including Backusella sp., Mucoraceae, Geotrichum sp. and the yeast Pichia sp. Based on the presence and absence of these ARISA operational taxonomic units (A-OTUs), we observed a shift in fungal community structure between 48 and 60 h. This change in community structure preceded a rise in pH and coincided with an increase in temperature. Clone libraries constructed using fungi-specific 18S rRNA primers contained sequences similar to several other fungal genera including Penicillium sp., Aspergillus sp., Hamigera sp., Neurospora sp. and the yeast Candida sp. While the fungal species richness was relatively low at any time point, the community structure was dynamic and paralleled changes in bacterial community structure.

Fungi↗
PubMed2005

Isolation and characterization of allelopathic volatiles from mugwort (Artemisia vulgaris).

Several volatile allelochemicals were identified and characterized from fresh leaf tissue of three distinct populations of the invasive perennial weed, mugwort (Artemisia vulgaris). A unique bioassay was used to demonstrate the release of volatile allelochemicals from leaf tissues. Leaf volatiles were trapped and analyzed via gas chromatography coupled with mass spectrometry. Some of the components identified were terpenes, including camphor, eucalyptol, alpha-pinene, and beta-pinene. Those commercially available were tested individually to determine their phytotoxicity. Concentrations of detectable volatiles differed in both absolute and relative proportions among the mugwort populations. The three mugwort populations consisted of a taller, highly branched population (ITH-1); a shorter, lesser-branched population (ITH-2) (both grown from rhizome fragments from managed landscapes); and a population grown from seed with lobed leaves (VT). Considerable interspecific variation existed in leaf morphology and leaf surface chemistry. Bioassays revealed that none of the individual monoterpenes could account for the observed phytotoxicity imparted by total leaf volatiles, suggesting a synergistic effect or activity of a component not tested. Despite inability to detect a single dominant phytotoxic compound, decreases in total terpene concentration with increase in leaf age correlated with decreases in phytotoxicity. The presence of bioactive terpenoids in leaf surface chemistry of younger mugwort tissue suggests a potential role for terpenoids in mugwort establishment and proliferation in introduced habitats.

Artemisia↗
PubMed2005

Formation of catechols via removal of acid side chains from ibuprofen and related aromatic acids.

Although ibuprofen [2-(4-isobutylphenyl)-propionic acid] is one of the most widely consumed drugs in the world, little is known regarding its degradation by environmental bacteria. Sphingomonas sp. strain Ibu-2 was isolated from a wastewater treatment plant based on its ability to use ibuprofen as a sole carbon and energy source. A slight preference toward the R enantiomer was observed, though both ibuprofen enantiomers were metabolized. A yellow color, indicative of meta-cleavage, accumulated transiently in the culture supernatant when Ibu-2 was grown on ibuprofen. When and only when 3-flurocatechol was used to poison the meta-cleavage system, isobutylcatechol was identified in the culture supernatant via gas chromatography-mass spectrometry analysis. Ibuprofen-induced washed-cell suspensions also metabolized phenylacetic acid and 2-phenylpropionic acid to catechol, while 3- and 4-tolylacetic acids and 2-(4-tolyl)-propionic acid were metabolized to the corresponding methyl catechols before ring cleavage. These data suggest that, in contrast to the widely distributed coenzyme A ligase, homogentisate, or homoprotocatechuate pathway for metabolism of phenylacetic acid and similar compounds, Ibu-2 removes the acidic side chain of ibuprofen and related compounds prior to ring cleavage.

Catechols↗
PubMed2005

Determination of spatial distributions of zinc and active biomass in microbial biofilms by two-photon laser scanning microscopy.

The spatial distributions of zinc, a representative transition metal, and active biomass in bacterial biofilms were determined using two-photon laser scanning microscopy (2P-LSM). Application of 2P-LSM permits analysis of thicker biofilms than are amenable to observation with confocal laser scanning microscopy and also provides selective excitation of a smaller focal volume with greater depth localization. Thin Escherichia coli PHL628 biofilms were grown in a minimal mineral salts medium using pyruvate as the carbon and energy source under batch conditions, and thick biofilms were grown in Luria-Bertani medium using a continuous-flow drip system. The biofilms were visualized by 2P-LSM and shown to have heterogeneous structures with dispersed dense cell clusters, rough surfaces, and void spaces. Contrary to homogeneous biofilm model predictions that active biomass would be located predominantly in the outer regions of the biofilm and inactive or dead biomass (biomass debris) in the inner regions, significant active biomass fractions were observed at all depths in biofilms (up to 350 microm) using live/dead fluorescent stains. The active fractions were dependent on biofilm thickness and are attributed to the heterogeneous characteristics of biofilm structures. A zinc-binding fluorochrome (8-hydroxy-5-dimethylsulfoamidoquinoline) was synthesized and used to visualize the spatial location of added Zn within biofilms. Zn was distributed evenly in a thin (12 microm) biofilm but was located only at the surface of thick biofilms, penetrating less than 20 microm after 1 h of exposure. The relatively slow movement of Zn into deeper biofilm layers provides direct evidence in support of the concept that thick biofilms may confer resistance to toxic metal species by binding metals at the biofilm-bulk liquid interface, thereby retarding metal diffusion into the biofilm (G. M. Teitzel and M. R. Park, Appl. Environ. Microbiol. 69:2313-2320, 2003).

Biofilms↗
PubMed2004

Quantifying bacterial population dynamics in compost using 16S rRNA gene probes.

Composting provides a dynamic setting for studying ecological topics such as succession, competition, and community stability in a relatively short period of time. This study used hierarchical small sub-unit-based rRNA gene probes to quantify the change in the relative abundance of phylogenetic groups common to compost in laboratory scale reactors. Bacterial 16S rRNA gene targets accounted for only 37% of all small subunit (SSU) rRNA genes initially, but increased to a maximum of 83% of the total at 84 h. The sum of rRNA genes detected using probes specific to Pseudomonas and low-G+C Gram-positive rRNA genes represented between 16% and 87% of the total. The lack of hybridization to the taxon-specific probes was most pronounced between 36 h and 60 h, when the pH was between 4.6 and 4.8. During this period the relative abundance of taxon-specific gene targets accounted for only 17-33% of the total bacterial rRNA gene targets. Pseudomonas-type 16S rRNA genes were the most abundant of the groups measured until 72 h. Those genes had their highest relative abundance at 12 h (78% of bacterial rRNA genes; 30% of all rRNA genes), after which time their relative abundance began to decline as the temperature increased. Prior to 72 h, 16S rRNA genes from low-G+C Gram-positive bacteria (LGC-GPB) represented less than 7% of the bacterial rRNA genes. However, by 84 h the relative abundance of LGC-GPB and Bacillus rRNA genes had increased to 60% and 18% of the bacterial rRNA gene targets, respectively (50% and 15% of all rRNA genes, respectively).

Base Composition↗
PubMed2004

Effects of triclosan incorporation into ABS plastic on biofilm communities.

OBJECTIVE: This study compared the attached biofilm populations on acrylonitrile-butadiene-styrene (ABS) plastic with and without the incorporation of the antimicrobial triclosan [5-chloro-2-(2,4-dichlorophenoxy) phenol] after 1-3 weeks of exposure to drinking water. METHODS: Biofilms were cultivated on triclosan-incorporated (TP) and control plastics (CP) in continuous flow culture reactors with drinking water as the growth medium and inoculum. After 1-3 weeks of exposure, the plastics were removed and the biofilms aseptically harvested. The attached communities were examined with respect to direct cell counts, culturability, triclosan resistance and community composition. RESULTS: Based on these analyses, no significant differences were observed between the populations attached to TP and CP surfaces. Results from both a bioavailability assay and gas chromatography mass spectrometry analyses, revealed that only trace amounts of triclosan desorbed from the plastic. The lack of biofilm community difference, coupled with this limited desorption of triclosan from the TP indicates that the ABS plastic studied was no more effective at controlling bacterial populations than the control plastic because the antimicrobial was not bioavailable. CONCLUSIONS: These results call into question the long-term utility of triclosan incorporation into ABS plastic and highlight the need for proof of efficacy regarding the antimicrobial properties of such materials.

Acrylonitrile↗
PubMed2003

Effect of microbial activity on trace element release from sewage sludge.

The microbial role in mobilization of trace elements from land-applied wastewater sludge is not well-defined. Our study examined the leachability of trace elements (Cd, Cr, Cu, Mo, Ni, P, Pb, S, and Zn) from dewatered sludge as affected by treatments designed to alter microbial activity. Different levels of microbial activity were achieved by incubating sludge columns at 4, 16, 28, and 37 degrees C and by the addition of AgNO3 biocide at each temperature. Columns (with inert glass bead support beds) were subjected to six consecutive incubation-leaching cycles, each consisting of 7.3-d incubation followed by 16-h leaching with synthetic acid rain. Glucose mineralization tests were used to assess overall microbial activity. Significant acidification and trace element leaching occurred when conditions favored microbial activity (16 and 28 degrees C). Extent of mobilization was element-specific with Zn, Ni, and Cu showing the greatest mobilization (99, 67, and 57%, respectively). Mobilization was reduced but still substantial at 4 degrees C. Conditions that best inhibited microbial activity (37 degrees C or biocide at any temperature) resulted in the least mobilization. Characterization of enrichments performed using thiosulfate as the sole energy source revealed the presence of both known and putative S-oxidizing bacteria in the sludge. The results suggest that microbial acidification via S oxidation can mobilize trace elements from sludge. Elemental mobility in field situations would also be governed by other factors, including the capacity of soil to buffer acidification and to adsorb mobilized elements.

Adsorption↗
PubMed2002

Nonylphenol in anaerobically digested sewage sludge from New York State.

Nonylphenols (NPs) have been identified as xenoestrogens and have been found at high concentrations in Canadian and European biosolids. While nonylphenol polyethoxylates (NPEOs) are being phased out and regulated in several European countries, there is currently no regulation of these compounds in the United States, and little information is available concerning the presence of NPs in U.S. biosolids. Anaerobically digested sewage sludge from five wastewater treatment plants in central New York State was analyzed for the presence of NPs. Samples were taken from treatment plants in both small municipalities and larger metropolitan areas with a range of industrial inputs. Samples were extracted via Soxhlet apparatus and analyzed by GC/MS. The various isomers of NP were summed yielding total NP concentrations as high as 1840 mg/kg with a mean of 1500 mg/kg on a dry weight basis. These values are two to five times as high as previously reported concentrations for U.S. and Canadian biosolids from plants using similar treatment schemes.

Anaerobiosis↗