Efficient removal of bacteria from aqueous media with kaolinite and diatomaceous earth products.

AIMS: To understand the relationships between physical and chemical parameters of kaolinite and diatomaceous earth, and their capacities to remove bacteria from aqueous media. To determine the optimal aqueous media parameters for use of these products in water disinfection processes. METHODS AND RESULTS: Seven kaolinite and three diatomaceous earth products were evaluated. Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus and Bacillus megaterium were used as proxy for bacterial pathogens. Fully calcined kaolin and amorphous diatomaceous earth demonstrated the highest extent and consistency in removing all the bacteria. The removal depended on ionic strength and pH of aqueous media with 100 mmol l-1 pH 5 potassium hydrogen phthalate buffer revealing the highest (2 log per gram) extent of the removal. Al3+ cations enhanced sorption up to 4 log per gram. CONCLUSIONS: Calcined kaolin and amorphous diatomaceous earth are excellent sorbents for bacteria. SIGNIFICANCE AND IMPACT OF THE STUDY: Fully calcined kaolin and amorphous diatomaceous earth are perspective tools for wastewater and water disinfection against waterborne bacterial pathogens.

Origins and environmental mobility of antibiotic resistance genes, virulence factors and bacteria in a tidal creek's watershed.

AIMS: To compare bacterial compositions of watershed run-offs released by a human settlement and a forested area, and to evaluate their role as carriers of antibiotic resistance and virulence genes. METHODS AND RESULTS: Run-offs from a forested area and a small settlement in a tidal creek' s watershed were compared for bacterial composition and profiles of 16 tetracycline resistance (TRG), eight virulence (VG) and integrase1 and 2 genes. Integrase 1 gene was detected only once. No integrase 2 gene was observed. VGs were detected only in settlement's run-offs, and TRG incidence frequency there was twice as high as in the forest's run-offs. Gene incidences revealed a positive correspondence to the rainfall, and weak correlations to water parameters. Metagenomic, Principle Coordinates and Shannon analyses together revealed distinctive bacterial compositions of the forest's and settlement's run-offs. Passage of the latter through a salt marsh resulted in the elimination of TRGs and three-fold decrease in VG incidence, and their bacterial composition was shifted towards that of the tidal creek. CONCLUSIONS: The settlement was a major source of TRGs and VGs in the watershed, but these contaminants were mitigated by a salt marsh system. SIGNIFICANCE AND IMPACT OF THE STUDY: Our data revealed the role of small settlements in biological contamination of the coastal waters. They also indicated that salt marshes are capable of reducing not only chemical but also biological contamination of run-offs.

Positive and negative selection towards tetracycline resistance genes in manure treatment lagoons.

AIMS: To evaluate the role of manure treatment lagoons of swine operations in the fate of faeces- and feed-borne tetracycline-resistant genes (TRG). METHODS AND RESULTS: Samples of feed, faeces, lagoon liquid and lagoon sediment in farm's vicinity were collected at three swine operations varied on their operational practices and analysed on the presence and frequencies of incidence of sixteen TRG in upstream sources (feed, faeces) and downstream receptacles (lagoon liquid and sediments). The highest frequency of TRG incidence was observed in a farm with extensive antibiotic usage and the lowest in the antibiotic-free farm. The study revealed a decrease in TRG richness and diversity in the downstream habitats of each farm. The observed TRG diverged into two groups, the persistent genes that were detected both upstream and downstream, and the transient genes that were detected in the upstream habitats but became nondetectable in the lagoons. Quantitative PCR analysis revealed that upstream concentrations and abundances (determined as TRG/16S rRNA gene ratios) of transient and persistent TRG were similar; however, the former were attenuated in the lagoons to the levels below the detection limit, whereas the latter were ∼ 100-1000 fold amplified in their (mostly) liquid phases and were also detected in farms' vicinities. CONCLUSION: Manure lagoons of swine operations imposed both positive and negative selection towards faeces- and feed-borne TRG that, respectively, caused either their proliferation or attenuation in those environments. SIGNIFICANCE AND IMPACT OF THE STUDY: The study reveals that discharge of antibiotic resistance genes from swine farms to the environment is linked to their positive selection (defined as an impact leading to proliferation of those genes) in manure lagoons.

A simple method for differential isolation of freely dispersed and particle-associated peat microorganisms.

Differential isolation of physiologically and ecologically diverse microbial groups facilitates evaluation of their activities in the environment. Here we describe a new method for differential isolation of freely dispersed and particle-associated peat microorganisms. The method is based on sequential elution of peat. Two types of natural peat, "young" sphagnum peat and "old" reed-based peat that have significantly different molecular composition as revealed by solid-state 13C NMR, were used for the method development. Various combinations of elution parameters (pH values, surfactant concentration, and sonication) were tested. Protein yield, CFU counts, 16S rDNA gene sequence, and T-RFLP analyses were used as criteria for evaluating the effectiveness of the elution protocols. The optimal method consisted of sequential elutions with (i) pH 6.2, 0.1 M potassium phosphate buffer, (ii) the same buffer amended with 0.01% of Tween 80, and (iii) treatment (ii) amended with sonication for 2 min. This method allowed differential isolation of freely dispersed and particle-associated microorganisms with (i) highest yield, (ii) highest diversity within the each microbial fraction, and (iii) best discrimination between the freely dispersed and particle-associated microbial communities. The method was applied for characterization of peat microbial communities and revealed different taxonomic composition and similar spatial organization of sphagnum and reed-sage peat microorganisms.

Dioxin cycling in aquatic sediments: the Passaic River Estuary.

The contribution of dechlorination reactions to the transformation of dioxins in river sediments was evaluated under a range of geochemical conditions mimicking freshwater, estuarine and marine environments, and interpreted in the light of recent evidence for their accumulation at the air-water interface. The yield of dechlorinated products increased with salinity, but never exceeded 20% of the initial dioxins present. Among the homologue groups in saline conditions, diCDDs were dominant at 32-47 mol% (8-16 nM). The production of 2,3,7,8-TCDD increased with decreasing salinity and in the presence of dissolved organic matter, exhibiting a maximum ratio (2,3,7,8-TCDD:non-2,3,7,8-TCDD) of 0.5. These differences in patterns may be related to the dominant microbial respiratory processes responsible for carbon turnover under the imposed conditions, and are strongly affected by the presence of organic matter. Based on these results, a conceptual dechlorination and carbon turnover model is proposed to help explain the likely reactivity of dioxins in the Passaic River Estuary.

Microbial dechlorination of historically present and freshly spiked chlorinated dioxins and diversity of dioxin-dechlorinating populations.

The ability of a microbial consortium eluted from dioxin-contaminated Passaic River sediments to dechlorinate polychlorinated dibenzo-p-dioxins (PCDDs) was investigated under methanogenic conditions. Aged 2,3,7,8-tetraCDD, which had partitioned into the microbial consortium from sediments, was stoichiometrically converted to tri- and monoCDD congeners. During dechlorination, dominant microbial activity within the consortium shifted from methanogenic to nonmethanogenic activity. Freshly spiked octaCDD was converted to hepta-, hexa-, penta-, tetra-, tri-, di-, and monochlorinated isomers, but the reaction stoichiometry was not determined. No methanogenic activity was observed, and the maximum yield of protein coincided with the production of less-chlorinated DD congeners. Two distinct pathways of dechlorination were observed: the peri-dechlorination pathway of 2,3,7,8-substituted hepta- to pentaCDDs, resulting in the production of 2,3,7,8-tetraCDD, and the peri-lateral dechlorination pathway of non-2,3,7,8-substituted congeners. Direct evidence of further lateral dechlorination of 2,3,7,8-tetraCDD was obtained from the historically contaminated incubations; no isomer-specific identification of triCDDs in spiked incubations was determined. Pasteurized cells exhibited no peri-dechlorination pathway, and triCDDs were the least-chlorinated congeners produced in these treatments. These results demonstrate that (i) both freshly spiked and aged PCDDs are available to microbial reductive dechlorination, (ii) the peri and triCDD dechlorinations are attributed to activities of nonmethanogenic, non-spore-forming microbial subpopulations, and (iii) the 2,3,7,8-residue patterns in historically contaminated sediments are likely affected by microbial activity.

Azospirillum strains use phenolic compounds as intermediates for electron transfer under oxygen-limiting conditions.

The effects of catechol, vanillic, caffeic (CAF), 2-hydroxyphenylacetic, 4-hydroxy- and 3,4-dihydroxybenzoic (3,4-DHBA) acids on the growth of a common rice rhizosphere inhabitant, Azospirillum lipoferum were studied. Two strains of this nonfermenting nitrogen-fixing bacterium were used: a motile strain (4B), and a nonmotile strain (4T). Under atmospheric conditions (pO2 = 21 kPa), the growth of strain 4T was inhibited by catechol (0.1 mM) only. None of these compounds affected the growth of strain 413. Under 5 kPa O2, no effect was observed on strain 413, whereas three of the six tested phenolics stimulated the growth of strain 4T; maximum effects were observed for 3,4-DHBA and CAF. As revealed by TLC and HPLC, under low oxygen, more new lipophilic compounds were formed from CAF by strain 4T, differing from CAF autooxydation products and from the products obtained under 21 kPa O2. It was hypothesized that strain 4T had the ability to use an oxidized derivative of CAF as a terminal electron acceptor. This hypothesis was tested in experiments under nitrogen-fixing conditions, in the absence of oxygen, and in the presence of N2O as a reoxidizing agent for CAF. Acetylene was used both as a substrate to measure nitrogenase activity (ARA) and to inhibit the biological transfer of electrons to N2O. The addition of CAF in the presence of N2O had the same effect on ARA rates as an addition of oxygen. It is concluded that the strain 4T of Azospirillum lipoferum is able to sustain some of its activities (e.g., N2 fixation) using phenolics as alternative electron acceptors under low oxygen conditions.

[Bacterial polysaccharides of polymyxan 88A. Basic characteristics and extent of possible uses]. / Bakterial'noi polisakharid polimiksan 88A. Osnovnye kharakteristiki isfery vozmozhnogo primeneniia.

A new high-viscous polysaccharide polymyxan from Bacillus polymyxa 88A is described. Polymyxan consists of an acid high-viscous polysaccharide (Mw 1-10 MD) and a neutral low-viscous polysaccharide (Mw 100-300 kD), which is a glucomannan containing equal amounts of monosaccharides and traces of uronic acids. The acid high-viscous polysaccharide consists of 36% glucose, 36% mannose, 7% galactose and 21% glucuronic acid. Data are presented on the application of polymyxan in baking industry and for preparation of drilling muds.

[Acinetobacter calcoaceticus strain with a wide spectrum of utilizing aromatic compounds and carrying a plasmid for resorcin degradation]. / Shatmm Acinetobacter calcoaceticus s shirokim spektrom utilizatsii aromaticheskikh soedinenii, nesushchii plazmidu degradatsii rezortsina.

A bacterial strain was isolated from soil and identified as Acinetobacter calcoaceticus var. lwoffii. The strain can utilize a wide spectrum of aromatic compounds. It carries a transmissive plasmid pBSW13 which determines resorcin utilization via the ortho pathway including the following steps: resorcin-hydroxyhydroquinone-maleylacetate-beta-ketoadipi c acid. The plasmid has been transferred by conjugation into the recipient strains of A. calcoaceticus 5734 CCM rifr, Escherichia coli J-53 met-pro-rifr and Klebsiella sp. Plasmid DNA with a molecular mass close to that of phage gamma was detected by electrophoresis in the donor and recombinant strains. The degradation of other substrates is not a phenotypic expression of the genes of this plasmid.