Environmentally relevant concentrations of pharmaceuticals influence the initial adhesion of bacteria

Pharmaceuticals are abundant at low concentrations (i.e. ng L(-1); microg L(-1)) in natural aquatic systems. However, very little is known about their effects on microorganisms. This study investigated the influence of the pharmaceuticals phenazone, amoxicillin and erythromycin, at low, non-toxic concentrations (i.e. 0.5-50 microg L(-1)), on the initial adhesion of bacteria to uncoated and iron-coated polystyrene. The influence of the pharmaceuticals on the initial adhesion of bacterial pure cultures (Escherichia coli, Aquabacterium commune, Bacillus subtilis) isolated from natural aquatic systems, was investigated with a plate assay. Initial adhesion of the pure cultures depended on the selected pharmaceutical, its concentration, the bacterial strain and the adhesion surface. Different combinations of these parameters resulted in inhibition, enhancement or had no effect on initial adhesion. In addition, a continuous flow system was used to investigate the influence of the pharmaceuticals on the initial adhesion of a drinking water microbial community. The drinking water community showed decreased adhesion in the presence of the pharmaceuticals regardless of adhesion surface. The results show that pharmaceuticals at environmentally relevant concentrations can influence the initial adhesion of bacteria. Thus, pharmaceutical compounds that are introduced to natural aquatic systems are able to exert subtle effects on bacteria.

Spongiibacter marinus gen. nov., sp. nov., a halophilic marine bacterium isolated from the boreal sponge Haliclona sp. 1

Strain HAL40b(T) was isolated from the marine sponge Haliclona sp. 1 collected at the Sula Ridge off the Norwegian coast and characterized by physiological, biochemical and phylogenetic analyses. The isolate was a small rod with a polar flagellum. It was aerobic, Gram-negative and oxidase- and catalase-positive. Optimal growth was observed at 20-30 degrees C, pH 7-9 and in 3 % NaCl. Substrate utilization tests were positive for arabinose, Tween 40 and Tween 80. Enzyme tests were positive for alkaline phosphatase, esterase lipase (C8), leucine arylamidase, acid phosphatase, naphthol-AS-BI-phosphohydrolase and N-acetyl-beta-glucosaminidase. The predominant cellular fatty acid was C(17 : 1) omega8, followed by C(17 : 0) and C(18 : 1) omega7. Analysis by matrix-assisted laser desorption/ionization time-of-flight MS was used to characterize the strain, producing a characteristic low-molecular-mass protein pattern that could be used as a fingerprint for identification of members of this species. The DNA G+C content was 69.1 mol%. Phylogenetic analysis supported by 16S rRNA gene sequence comparison classified the strain as a member of the class Gammaproteobacteria. Strain HAL40b(T) was only distantly related to other marine bacteria including Neptunomonas naphthovorans and Marinobacter daepoensis (type strain sequence similarity >90 %). Based on its phenotypic, physiological and phylogenetic characteristics, it is proposed that the strain should be placed into a new genus as a representative of a novel species, Spongiibacter marinus gen. nov., sp. nov.; the type strain of Spongiibacter marinus is HAL40b(T) (=DSM 17750(T) =CCUG 54896(T)).

Bacillus plakortidis sp. nov. and Bacillus murimartini sp. nov., novel alkalitolerant members of rRNA group 6

The Gram-positive, alkali- and salt-tolerant marine bacterium strain P203T is described together with its closest phylogenetic neighbour, terrestrial isolate LMG 21005T. Strain P203T was isolated from material from the sponge Plakortis simplex that was obtained from the Sula-Ridge, Norwegian Sea. Strain LMG 21005T was an undescribed strain that was isolated from a church wall mural in Germany. Strains P203T and LMG 21005T were identified as novel alkalitolerant members of the Bacillus rRNA group 6 with a 16S rRNA gene sequence similarity of 99.5 %. The closest described neighbour, Bacillus gibsonii DSM 8722T, showed 99.0 % gene sequence similarity with P203T and 98.8 % similarity with strain LMG 21005T. Despite the high 16S rRNA gene sequence similarity, DNA–DNA cross-hybridization revealed only 25.8–34.1 % similarity amongst the three strains. The DNA G+C contents were 41.1 mol% for strain P203T and 39.6 mol% for strain LMG 21005T. Both strains grew well between pH 7 and pH 11. Strain P203T showed growth at moderate temperatures (from 4 to 30 °C) and in the presence of up to 12 % (w/v) NaCl at pH 9.7, whereas strain LMG 21005T was not salt tolerant (up to 4 % NaCl) and no growth was observed at 4 °C. The major fatty acids of strains P203T, LMG 21005T and the type strain of B. gibsonii were the saturated terminally methyl-branched compounds iso-C15 : 0 (19.8, 15.6 and 28.0 %, respectively) and anteiso-C15 : 0 (57.1, 48.6 and 45.2 %, respectively). Physiological and biochemical tests allowed genotypic and phenotypic differentiation of strains P203T and LMG 21005T from the six related Bacillus species with validly published names and supported the proposal of two novel species, Bacillus plakortidis [type strain P203T (=DSM 19153T=NCIMB 14288T)] and Bacillus murimartini [type strain LMG 21005T (=NCIMB 14102T)].

Ultrastructural and electron energy-loss spectroscopic analysis of an extracellular filamentous matrix of an environmental bacterial isolate

Strain F8, a bacterial isolate from 'river snow', was found to produce extracellular fibres in the form of a filamentous network. These extracellular filaments, which were previously shown to be composed of DNA, have been studied for the first time by ultrastructural and electron energy-loss spectroscopy in the present work. 'Whole mount' preparations of strain F8 indicate these polymers are ultrastructurally homogeneous and form a network of elemental filaments, which have a width of 1.8-2.0 nm. When incubated at pH 3.5 with colloidal cationic ThO(2) tracers they become intensely stained (electron dense), affording direct evidence that the fibres are negatively charged and thus acidic chemically. Elemental analysis of the extracellular filaments by Energy-filtered Transmission Electron Microscopy revealed phosphorus to be the main element present and, because pretreatment of F8 cells with DNase prevented thorium labelling, the fibres must be composed of extracellular DNA (eDNA). Neither ultrathin sections nor 'whole mount negative stain' caused DNA release by general cell lysis. Additionally, cells infected with phages were never observed in ultrathin sections and phage particles were never detected in whole mount samples, which rules out the possibility of phages being directly involved in eDNA release.

A marine Mesorhizobium sp. produces structurally novel long-chain N-acyl-L-homoserine lactones

Our study focused on a Mesorhizobium sp. that is phylogenetically affiliated by 16S rRNA gene sequence to other marine and saline bacteria of this genus. Liquid chromatography-mass spectrometry investigations of the extract obtained from solid-phase extraction of cultures of this bacterium indicated the presence of several N-acyl homoserine lactones (AHLs), with chain lengths of C(10) to C(16). Chromatographic separation of the active bacterial extract yielded extraordinarily large amounts of two unprecedented acylated homoserine lactones, 5-cis-3-oxo-C(12)-homoserine lactone (5-cis-3-oxo-C(12)-HSL) (compound 1) and 5-cis-C(12)-HSL (compound 2). Quorum-sensing activity of compounds 1 and 2 was shown in two different biosensor systems [Escherichia coli MT102(pSB403) and Pseudomonas putida F117(pKR-C12)]. Furthermore, it was shown that both compounds can restore protease and pyoverdin production of an AHL-deficient Pseudomonas aeruginosa PAO1 lasI rhlI double mutant, suggesting that these signal molecules maybe used for intergenus signaling. In conclusion, these data indicate that the quorum-sensing activity of compounds 1 and 2 is modulated by the chain length and functional groups of the acyl moiety. Additionally, compound 1 showed antibacterial and cytotoxic activities.

Application of culture-independent methods to assess the bacteria removal efficiency of subsurface flow constructed wetlands

The bacteriologic treatment efficiency of vertical and horizontal subsurface flow constructed wetlands (SFCWs) was analysed in two multistage wastewater treatment systems by culture dependent and independent methods. When assessed with standard cultivation procedures, bacteria removal efficiency of the vertical and horizontal SFCWs was similar. However, microscopic enumerations of the wastewater bacteria after DNA staining revealed a completely different removal pattern: bacteria removal efficiency of the horizontal SFCWs was in general low and erratic, whereas the vertical SFCWs displayed high bacteria removal rates. The discrepancies in the results obtained by bacteria enumeration and cultivation was due to a strong decrease in bacterial culturability after treatment by the horizontal SFCWs, leading to overestimation of the real bacterial concentrations in these effluents. Additionally, a PCR based approach for the detection of the enteropathogenic bacteria Campylobacter jejuni and Yersinia enterocolitica was tested in the wastewater samples. The methods were specific and reproducible in the analysed samples and could be carried out within 12 h, proving very adequate as an alternative to cultivation. This work recommends a review of the current standard methodology for wastewater quality surveillance, as well as of the design of SFCW.

Bacterial extracellular DNA forming a defined network-like structure

It is generally assumed that nucleic acids are localized inside of living cells and that their primary function is the storage of information. In contrast, extracellular DNA is mainly considered as a remnant of lysed cells. Here, we report the formation of extracellular bacterial DNA as a spatial structure. An aquatic bacterium, strain F8, was isolated, which produced a stable filamentous network of extracellular DNA. Different staining and enzymatic techniques confirmed that it was DNA. We were able to amplify the 16S rRNA gene from the extracellular DNA. Restriction endonuclease cleavage and randomly amplified polymorphic DNA analysis of extracellular and genomic DNAs revealed major similarities, but also some differences in both sequences. Our data demonstrate a new function and relevance for extracellular DNA.

Bacterial dynamics in spring water of alpine karst aquifers indicates the presence of stable autochthonous microbial endokarst communities

Spring water of two alpine karst aquifers differing in hydrogeology but of nearby catchments were investigated for their bacterial population dynamics. Dolomite karst aquifer spring 1 (DKAS 1) represents a dolomitic-limestone karst aquifer spring showing high average water residence time and relative constant flow. Limestone karst aquifer spring 2 (LKAS 2) constitutes a typical limestone karst aquifer spring with a dynamic hydrological regime and discharge. Dolomite karst aquifer spring 1 yielded constantly lower cell counts and biomasses (median of 15 x 10(6) cells l(-1) and 0.22 microg C l(-1)) as the LKAS 2 (median of 63 x 10(6) cells l(-1) and 1.1 microg C l(-1)) and distribution of morphotypes and mean cell volumes was also different between the considered systems, indicating the influence of hydrogeology on microbial spring water quality. Molecular bacterial V3 16S-rDNA profiles revealed remarkable constancy within each spring water throughout the investigation period. Time course analysis of a flood event in LKAS 2 further supported the trend of the temporal constancy of the microbial community. Except for one case, retrieval of partial and full length 16S rDNA gene sequences from the relative constant DKAS 1 revealed similarities to presently known sequences between 80% to 96%, supporting the discreteness of the microbial populations. The gathered results provide first evidence for the presence of autochthonous microbial endokarst communities (AMEC). Recovery of AMEC may be considered of relevance for the understanding of alpine karst aquifer biogeochemistry and ecology, which is of interest as many alpine and mountainous karst springs are important water resources throughout the world.

Rapid screening and dereplication of bacterial isolates from marine sponges of the sula ridge by intact-cell-MALDI-TOF mass spectrometry (ICM-MS)

Rapid grouping of bacterial isolates is critical in comprehensive microbial studies of environmental samples or screening programmes e.g. in unknown marine environments where large numbers of strains have to be isolated on different growth media. Sets of bacteria have been cultured from the marine sponges Isops phlegraei, Haliclona sp. 1, Phakellia ventilabrum and Plakortis sp. growing at a depth of about 300 m on the Sula Ridge close to the Norwegian coast. We employed Intact-Cell MALDI-TOF (ICM) mass spectrometry to achieve a rapid proteometric clustering of a subset of the strain collection including 456 isolates. Cluster analysis of mass spectra resolved the strains into 11 groups corresponding to species of Alteromonas (15), Bacillus (3), Colwellia (31), Erythrobacter (19), Marinobacter (14), Marinococcus (6), Pseudoalteromonas (297), Pseudomonas (56), Roseobacter (3), Sphingomonas (2) and Vibrio (10) as verified by 16 S rDNA analysis. A further discrimination into subgroups was demonstrated for different isolates from the genus Pseudoalteromonas. The approach described here permits the rapid identification of isolates for dereplication, and the selection of strains representing rare species for subsequent characterization.

Optimization of PCR-based methods for rapid detection of Campylobacter jejuni, Campylobacter coli and Yersinia enterocolitica serovar 0:3 in wastewater samples

PCR-based methods were evaluated for their adequacy to assess the removal of pathogens from wastewater samples. For the development and optimization of the methods, samples were taken at two different sites from two different constructed wetlands. Campylobacter jejuni/coli and Yersinia enterocolitica serogroup 0:3 were selected as model pathogens and Enterococcus faecalis as a standard microbiological indicator. The chosen PCR protocols were optimized for wastewater DNA extracts in order to obtain high sensitivity and reproducibility independently of the background flora. All PCR protocols were successfully performed and reproducible with a background of up to 10(10) nontarget cells per reaction. Five cells of Y. enterocolitica, 50 cells of C. jejuni/coli, and 500 cells of E. faecalis per 100ml treated water could be detected. The method detection limit in the settled wastewater was higher: 200 cells per 100ml for Y. enterocolitica, 2000 cells per 100ml for C. jejuni/coli, and 20,000 cells per 100ml for E. faecalis. C. jejuni/coli and Y. enterocolitica PCRs were adapted to municipal wastewater, with higher loads of potential PCR inhibitors. Sensitivity was lower for this type of wastewater: 200 cells of Y. enterocolitica and 2000 cells of C. jejuni/coli were detected per 100ml treated wastewater, 2500 cells of Y. enterocolitica and 25,000 cells of C. jejuni/coli per 100ml settled wastewater. The developed PCR methods enable the detection of C. jejuni/coli, Y. enterocolitica serogroup 0:3 and E. faecalis within 12h. They show specificity, reproducibility and low detection limits for the investigated pathogens.

A new enzymatic method for the detachment of particle associated soil bacteria

A new enzymatic technique for the detachment of bacteria from soil particles was developed and applied to different soil samples taken at various sampling sites and depths. Many soil microorganisms are closely associated with the organic matrix of soil particles. They produce extracellular polymeric substances (EPS), which promote the irreversible adhesion of cells to soil particulates. To characterize the EPS, a prestaining of the soil samples with different lectins was performed. Samples from a sewage field, an urban park, a farmland, a mixed forest and garden mold were stained with a set of FITC-labelled lectins from Triticum vulgaris, Ulex europaeus, Concanavalin A and Pseudomonas aeruginosa. Based on the results, a combination of alpha-glucosidase, beta-galactosidase and a lipase was chosen for degradation of the EPS structures, followed by gentle mechanical and chemical dispersion in a modified sodium pyrophosphate buffer. The samples were fixed with formaldehyde and total cell counts were determined by DAPI staining. With the exception of the wheat field sample, this technique revealed up to 22-fold higher total cell counts for all investigated soil samples compared to the conventional detachment method, a simple dispersion with sodium pyrophosphate buffer. Efficiency of the technique was assessed by scanning electron microscopy. These images showed convincingly that the enzymatic treatment followed by sonication efficiently detached the bacteria and left the soil particles almost blank.

Intergeneric transfer of the Enterococcus faecalis plasmid pIP501 to Escherichia coli and Streptomyces lividans and sequence analysis of its tra region

The nucleotide sequence of the transfer (tra) region of the multiresistance broad-host-range Inc18 plasmid pIP501 was completed. The 8629-bp DNA sequence encodes 10 open reading frames (orf), 9 of them are possibly involved in pIP501 conjugative transfer. The putative pIP501 tra gene products show highest similarity to the respective ORFs of the conjugative Enterococcus faecalis plasmids pRE25 and pAMbeta1, and the Streptococcus pyogenes plasmid pSM19035, respectively. ORF7 and ORF10 encode putative homologues of type IV secretion systems involved in transport of effector molecules from pathogens to host cells and in conjugative plasmid transfer in Gram-negative (G-) bacteria. pIP501 mobilized non-selftransmissible plasmids such as pMV158 between different E. faecalis strains and from E. faecalis to Bacillus subtilis. Evidence for the very broad-host-range of pIP501 was obtained by intergeneric conjugative transfer of pIP501 to a multicellular Gram-positive (G+) bacterium, Streptomyces lividans, and to G- Escherichia coli. We proved for the first time pIP501 replication, expression of its antibiotic resistance genes as well as functionality of the pIP501 tra genes in S. lividans and E. coli.

Toxicity and microcystin content of extracts from a Planktothrix bloom and two laboratory strains

Toxic effects and microcystin content from various extracts of a Planktothrix agardhii bloom and two different strains of Planktothrix agardhii, HUB 076, and NIVA 34 were investigated. Extracts were obtained with solvents of different polarity such as hexane, dichloromethane, methanol, and water. Additionally, different pre-treatments were used to break the cells before extraction. Acute toxicity was determined with the fairy shrimp Thamnocephalus platyurus, subchronic effects were detected in embryos and larvae of the zebrafish Danio rerio. The extracts affected the test species to a different extent. Effects were severe in polar extracts (water and methanol) of all strains tested. Although the strain NIVA 34 did not contain any microcystins, aqueous extracts of this strain showed the highest acute toxicity to the crustacean species tested (LC50= 0.08 mg ml(-1)). In contrast aqueous extracts of the Planktothrix bloom containing high amounts of microcystins were less acutely toxic (LC50 = 0.46 mg ml(-1)). Our results indicate the existence of further toxic metabolites in different Plankorothrix agardhii strains.

The tra region of the conjugative plasmid pIP501 is organized in an operon with the first gene encoding the relaxase

The tra genes orf1 to orf11 of pIP501 were shown to be transcribed as a single operon of 11.3 kb in Enterococcus faecalis by reverse transcription-PCR. The transcriptional start site of the tra mRNA was mapped at 110 bp upstream from the predicted TTG start codon of the first gene of the operon, the traA relaxase. The TraA protein (660 amino acids) and a C-terminally truncated version of the TraA protein (293 amino acids) were purified as fusions with glutathione S-transferase. oriT cleavage activity of both TraA proteins was demonstrated in vitro on supercoiled plasmid pVA2241 DNA containing oriT(pIP501). The activity of the DNA relaxase TraA is strictly dependent on the presence of Mg(2+) or Mn(2+) and is highest at temperatures of between 42 and 45C.

Investigation of lotic microbial aggregates by a combined technique of fluorescent in situ hybridization and lectin-binding-analysis

A technique combining fluorescent in situ hybridization and lectin-binding-analysis (FISH-LBA) was developed and applied for the simultaneous detection of cellular components and glycoconjugates in lotic microbial aggregates (river snow). River snow aggregates were directly collected from the bulk water phase into coverslip chambers, in which the complete procedure including fixation, fluorescent in situ hybridization, lectin-binding and optical analysis by confocal laser scanning microscopy was performed. Neither autofluorescence originating from phyotosynthetic organisms nor inorganic particles did negatively interfere with the FISH-LBA technique. In river snow samples obtained from the river Elbe, Germany, distinct compartments of the river snow structure could be visualized with FITC-labelled lectins from Triticum vulgaris, Limulus polyphemus, Arachis hypogaea, Phaseolus vulgaris and Pseudomonas aeruginosa, binding to frequently occurring saccharide residues in the river snow matrix. The analysis could be performed on different levels of complexity. The combined technique visualized bacteria of different phylogenetic groups in the entire river snow structure as well as glycoconjugate components linked with various microcolonies. Different lectins stained slime layers and cell-envelopes of individual eukaryotic and prokaryotic cells. Consequently, application of the FISH-LBA technique allows the linkage between cellular and glycoconjugate identity in complex microbial communities.

Performance of a bioreactor with submerged membranes for aerobic treatment of municipal waste water

Aerobic treatment of municipal waste water in a membrane bioreactor was studied for 535 d. Apart from sampling, sludge was retained completely by a submerged hollow fibre membrane with a pore-size of 0.2 microm. The pilot plant comprised an anoxic zone to enable denitrification. The maximum liquid hold-up of the plant was 3.9 m3. In this study the reactor performance and the stability of the process and the membrane capacity were investigated. A stable flux of 181 m(-2)h(-1) could be realised with a mean transmembrane pressure difference of 0.3bar with air-bubbling and backflushing the membrane and cleaning it in place every two months for one or two hours. For about 140d, a flux of 271 m(-2)h(-1) was achieved, but cleaning became necessary more often. The hydraulic retention time (HRT) varied between 10.4 and 15.6h. Accordingly the volumetric loading rate was between 1.1 and 1.7kg CODm(-3)d(-1). No inoculum was used. The mixed liquor suspended solids (MLSS) concentration gradually increased to 18-20g MLSSl(-1). The feed to microorganism (F/M) ratio varied according to the operation conditions but decreased against a value of 0.07 kg COD kg(-1) MLSSd(-1). Treatment performance was very stable and on a high level. The COD was reduced by 95%. Nitrification was complete and up to 82% of the total nitrogen could be denitrified.

Microbiological aspects of a bioreactor with submerged membranes for aerobic treatment of municipal wastewater

An aerobic membrane bioreactor treating municipal wastewater at complete biomass retention was studied in respect of microbiological parameters over a period of 380 days. The results were compared to those obtained from a conventional activated sludge wastewater treatment plant (WWTP) treating the same wastewater. Microscopically, significant changes in the structure of the flocs and of the ratio between free suspended and aggregated cells could be observed. The presence of filamentous bacteria varied from almost not present to very high numbers. With the exception of short periods after changes in operating conditions, protozoa and metazoa were rarely present in the sludge community. The rate of oxygen consumption and the cell detectability by fluorescence in situ hybridizatio (FISH) with rRNA-targeted oligonucleotide probes were used to assess the physiological state of the bacterial cells Oxygen consumption rates of sludge samples obtained from both the conventional and membrane filtration plant wer determined without and after addition of different energy and carbon sources. In contrast to the conventional activate sludge, a pronounced increase in respiration activity upon the addition of organic substrates could be observed in th membrane filtration sludge. In situ probing with the Bacteria-specific probe EUB338 visualized 40-50% of all DAPI stainable bacteria in the membrane bioreactor, compared to 80% cells detectable by FISH in the conventional activate sludge. These results suggest that bacteria present in the highly concentrated biomass of the membrane reactor use the energy supplied for their maintenance metabolism and were not in a physiological state characteristic for growth This assumption could explain the zero net biomass production observed in the reactor.

Sulfophthalimide as major metabolite formed from sulfonated phthalocyanine dyes by the white-rot fungus Bjerkandera adusta

The reaction products formed during the decolorization of the sulfophthalocyanine textile dyes Reactive blue 15 (RB15) and Reactive blue 38 (RB38) by the white-rot fungus Bjerkandera adusta were analyzed by high-performance liquid chromatography with diode array detection and with liquid chromatography-electrospray ionization-tandem mass spectrometry. Sulfophthalimides (SPI; 3 and 4) were identified as major metabolites by comparison with synthesized reference compounds. SPI was formed from both dyes in fungal cultures and by incubation with its purified manganese peroxidase and lignin peroxidase. Quantitative assessment of the SPI formed from RB15 accounted for approximately 60% of the theoretical amount.

Adequacy of in situ glass slides and direct sand extractions to assess the microbiota within sand columns used for drinking water treatment

Historically, Cholodny-Rossi buried glass slide techniques have been used to study the microbiota of subsurface environments, yet the bias of such a technique has not been compared against direct sand extraction using modern in situ probing. Over a period of 34 wk, four separate 4-m-deep sand columns receiving raw lake water were examined to compare direct extraction of sand filter biofilm material against in situ glass slide biofilms. Significantly different DAPI direct counts and fluorescent in situ hybridization signals for major phylogenetic groups were observed. Not only were lower proportions (P < 0.001) of EUB338-probed DAPI cells observed on in situ glass slides, but also fewer γ-Proteobacteria (12%–21%) and more α-Proteobacteria (16%–33%) when compared to direct sand extracts. Hence, investigators of the microbial ecology of even simple sand biofilms must consider the inherent biases from "accepted" methods and seek further independent methods to identify those which may be most accurate.Key words: sand filter, biofilms, in situ hybridization, groundwater recharge.

Adequacy of in situ glass slides and direct sand extractions to assess the microbiota within sand columns used for drinking water treatment

Historically, Cholodny-Rossi buried glass slide techniques have been used to study the microbiota of subsurface environments, yet the bias of such a technique has not been compared against direct sand extraction using modern in situ probing. Over a period of 34 wk, four separate 4-m-deep sand columns receiving raw lake water were examined to compare direct extraction of sand filter biofilm material against in situ glass slide biofilms. Significantly different DAPI direct counts and fluorescent in situ hybridization signals for major phylogenetic groups were observed. Not only were lower proportions (P < 0.001) of EUB338-probed DAPI cells observed on in situ glass slides, but also fewer gamma-Proteobacteria (12%-21%) and more alpha-Proteobacteria (16%-33%) when compared to direct sand extracts. Hence, investigators of the microbial ecology of even simple sand biofilms must consider the inherent biases from "accepted" methods and seek further independent methods to identify those which may be most accurate.

Bacterial growth based on reductive dechlorination of trichlorobenzenes

An anaerobic mixed bacterial culture was enriched for bacteria dechlorinating 1,2,3- and 1,2,4-trichlorobenzene (TCB) to dichlorobenzenes by exclusive use of non-fermentable substrates and the application of vancomycin. Growth and dechlorination occurred in a purely synthetic medium with formate or hydrogen, acetate, and TCB. Neither acetogenesis nor methanogenesis was detected in the culture. Repeated subculturing maintaining high dechlorinating activities was also achieved when only hydrogen and TCB were supplied. This indicated that reductive dechlorination of TCB was the primary energy conservating process. The number of dechlorinating bacteria was strictly limited by the amount of TCB supplied in the medium. In addition, the dechlorinating activity could be maintained only in the presence of TCB. A most probable number analysis showed that the dechlorinating species amounted to at least 6 x 10(5) cells per ml at a total cell number of about 2 x 10(6) cells per ml. Vitamin B12 significantly stimulated the dechlorinating activity.

Microbiological safety of drinking water

Emerging pathogens in drinking water have become increasingly important during the decade. These include newly-recognized pathogens from fecal sources such as Cryptosporidium parvum, Campylobacter spp., and rotavirus, as well as pathogens that are able to grow in water distribution systems, like Legionella spp., mycobacteria, and aeromonads. To perform a risk analysis for the pathogens in drinking water, it is necessary to understand the ecology of these organisms. The ecology of the drinking-water distribution system has to be evaluated in detail, especially the diversity and physiological properties of water bacteria. The interactions between water bacteria and (potential) pathogens in such diverse habitats as free water and biofilms are essential for the survival or growth of hygienically relevant organisms in drinking water. Results of epidemiological studies together with ecological data are the basis for effective resource protection, water treatment, and risk assessment.