Emergence and dissemination of three mild outbreaks of Neisseria gonorrhoeae with high-level resistance to azithromycin in Barcelona, 2016-18.

BACKGROUND: Neisseria gonorrhoeae (NG) isolates with high-level azithromycin resistance (HL-AziR) have emerged worldwide in recent decades, threatening the sustainability of current dual-antimicrobial therapy. OBJECTIVES: This study aimed to characterize the first 16 NG isolates with HL-AziR in Barcelona between 2016 and 2018. METHODS: WGS was used to identify the mechanisms of antimicrobial resistance, to establish the MLST ST, NG multiantigen sequence typing (NG-MAST) ST and NG sequence typing for antimicrobial resistance (NG-STAR) ST and to identify the clonal relatedness of the isolates with other closely related NG previously described in other countries based on a whole-genome SNP analysis approach. The sociodemographic characteristics of the patients included in the study were collected by comprehensive review of their medical records. RESULTS: Twelve out of 16 HL-AziR isolates belonged to the MLST ST7823/NG-MAST ST5309 genotype and 4 to MLST ST9363/NG-MAST ST3935. All presented the A2059G mutation in all four alleles of the 23S rRNA gene. MLST ST7823/NG-MAST ST5309 isolates were only identified in men who have sex with women and MLST ST9363/NG-MAST ST3935 were found in MSM. Phylogenomic analysis revealed the presence of three transmission clusters of three different NG strains independently associated with sexual behaviour. CONCLUSIONS: Our findings support the first appearance of three mild outbreaks of NG with HL-AziR in Spain. These results highlight the continuous capacity of NG to develop antimicrobial resistance and spread among sexual networks. The enhanced resolution of WGS provides valuable information for outbreak investigation, complementing the implementation of public health measures focused on the prevention and dissemination of MDR NG.

Assessing the abundance of fungal populations in a full-scale membrane bioreactor (MBR) treating urban wastewater by using quantitative PCR (qPCR).

The abundance of fungi in a full-scale membrane bioreactor (MBR) treating urban wastewater and experiencing seasonal foaming was assessed by quantitative PCR (qPCR), comparing three different sets of widely used universal fungal primers targeting the gene encoding the small ribosomal subunit RNA, 18S-rDNA, (primers NS1-Fung and FungiQuant) or the internal transcribed spacer ITS2 (primers ITS3-ITS4). Fungi were a numerically important fraction of the MBR microbiota (≥106 18S-rDNA copies/L activated sludge), and occurred both in the aerated and anoxic bioreactors. The numbers of copies of fungal markers/L activated sludge calculated using the NS1-Fung or ITS3-ITS4 primer sets were up to 2 orders of magnitude higher than the quantifications based on the FungiQuant primers. Fungal 18S-rDNA counts derived from the FungiQuant primers decreased significantly during cold seasons, concurring with foaming episodes in the MBR. Redundancy analysis corroborated that temperature was the main factor driving fungi abundance, which was also favored by longer solid retention time (SRT), lower chemical oxygen demand/biochemical oxygen demand at 5 days (COD/BOD5) of influent water, and lower biomass accumulation in the MBR.

Effect of salinity variation on the autotrophic kinetics of the start-up of a membrane bioreactor and hybrid moving bed biofilm reactor-membrane bioreactor at low hydraulic retention time.

A membrane bioreactor (MBR) and a hybrid moving bed biofilm reactor-membrane bioreactor (hybrid MBBR-MBR) for municipal wastewater treatment were studied to determine the effect of salinity on nitrogen removal and autotrophic kinetics. The biological systems were analyzed during the start-up phase with a hydraulic retention time (HRT) of 6 h, total biomass concentration of 2,500 mg L-1 in the steady state, and electric conductivities of 1.05 mS cm-1 for MBR and hybrid MBBR-MBR working under regular salinity and conductivity variations of 1.2-6.5 mS cm-1 for MBR and hybrid MBBR-MBR operating at variable salinity. The variable salinity affected the autotrophic biomass, which caused a reduction of the nitrogen degradation rate, an increase of time to remove ammonium from municipal wastewater and longer duration of the start-up phase for the MBR and hybrid MBBR-MBR.

Efficacy and safety of wet wrap therapy for patients with atopic dermatitis: a systematic review and meta-analysis.

Wet wrap therapy (WWT) consists of topical steroids administered under a layer of wet cotton bandages or garments. Several trials with WWT have reported promising results in atopic dermatitis (AD). However, no systematic review and meta-analysis on its efficacy and safety has been published. Our objective was to conduct a systematic review of the literature on WWT in AD to assess its efficacy and safety. We included randomized controlled trials among patients of all ages with a diagnosis of AD based on predefined criteria or made by a dermatologist. Electronic searches were performed from 1970 to 30 March 2016 in the Cochrane Central Register of Controlled Trials, MEDLINE, Embase and the World Health Organization International Clinical Trials Registry. Selection of studies and data extraction were performed independently by two researchers, and discrepancies were resolved by consensus. Six trials comparing WWT with topical steroids in children or adults with AD were included. Sample sizes ranged from 19 to 51 patients. Results on clinical severity and quality of life were reported incompletely and proved heterogeneous across studies. A nonsignificant tendency to increased risk of mild skin infections was observed in those treated with WWT (pooled relative risk 6·35, 95% confidence interval 0·83-48·55). The overall grade of quality of evidence for the efficacy and safety outcomes was low. In conclusion, the evidence that WWT is more effective than conventional treatment with topical steroids in AD is of low quality. Further clinical trials should establish the efficacy of WWT in AD.

Toxicity and biofilm-based selection for methyl tert-butyl ether bioremediation technology.

Extractive membrane biofilm reactor (EMBFR) technology offers productive solutions for volatile and semi-volatile compound removal from water bodies. In this study, the bacterial strains Paenibacillus etheri SH7T (CECT 8558), Agrobacterium sp. MS2 (CECT 8557) and Rhodococcus ruber strains A5 (CECT 8556), EE6 (CECT 8612) and EE1 (CECT 8555), previously isolated from fuel-contaminated sites, were tested for adherence on tubular semipermeable membranes in laboratory-scale systems designed for methyl tert-butyl ether (MTBE) bioremediation. Biofilm formation on the membrane surface was evaluated through observation by field-emission scanning electron microscope (FESEM) as well as the acute toxicity (as EC50) of the bacterial growth media. Moreover, extracellular polymeric substance (EPS) production for each strain under different MTBE concentrations was measured. Strains A5 and MS2 were biofilm producers and their adherence increased when the MTBE flowed through the inner tubular semipermeable membrane. No biofilm was formed by Paenibacillus etheri SH7T, nevertheless, the latter and strain MS2 exhibited the lowest toxicity after growth on the EMBFR. The results obtained from FESEM and toxicity analysis demonstrate that bacterial strains R. ruber EE6, A5, P. etheri SH7T and Agrobacterium sp. MS2 could be excellent candidates to be used as selective inocula in EMBFR technology for MTBE bioremediation.

Mobile genetic elements related to the diffusion of plasmid-mediated AmpC ß-lactamases or carbapenemases from Enterobacteriaceae: findings from a multicenter study in Spain.

We examined the genetic context of 74 acquired ampC genes and 17 carbapenemase genes from 85 of 640 Enterobacteriaceae isolates collected in 2009. Using S1 pulsed-field gel electrophoresis and Southern hybridization, 37 of 74 bla AmpC genes were located on large plasmids of different sizes belonging to six incompatibility groups. We used sequencing and PCR mapping to investigate the regions flanking the acquired ampC genes. The bla CMY-2-like genes were associated with ISEcp1; the surrounding bla DHA genes were similar to Klebsiella pneumoniae plasmid pTN60013 associated with IS26 and the psp and sap operons; and the bla ACC-1 genes were associated with IS26 elements inserted into ISEcp1. All of the carbapenemase genes (bla VIM-1, bla IMP-22, and bla IMP-28) were located in class 1 integrons. Therefore, although plasmids are the main cause of the rapid dissemination of ampC genes among Enterobacteriaceae, we need to be aware that other mobile genetic elements, such as insertion sequences, transposons, or integrons, can be involved in the mobilization of these genes of chromosomal origin. Additionally, three new integrons (In846 to In848) are described in this study.

Impact of influenza season and environmental factors on the clinical presentation and outcome of invasive pneumococcal disease.

Influenza and meteorological factors have been associated with increases in the incidence of invasive pneumococcal disease (IPD). However, scant data regarding the impact of influenza and the environment on the clinical presentation of IPD are available. An observational study of all adults hospitalized with IPD was performed between 1996 and 2012 in our hospital. The incidence of IPD correlated with the incidence rates of influenza and with environmental data. A negative binominal regression was used to assess the relationship between these factors. Clinical presentation of IPD during the influenza and non-influenza periods was compared. During the study, 1,150 episodes of IPD were diagnosed. After adjusting for confounding variables, factors correlating with the rates of IPD were the incidence of influenza infection (IRR 1.229, 95% CI 1.025-1.472) and the average ambient temperature (IRR 0.921, 95% CI 0.88-0.964). Patients with IPD during the influenza period had a worse respiratory status. A greater proportion of patients had respiratory failure (45.6% vs 52%, p = 0.032) and higher requirements for ICU admission (19.3% vs 24.7%, p = 0.018) and mechanical ventilation (11% vs 15.1%, p = 0.038). When we stratified by invasiveness of pneumococcal serotypes and the presence of comorbid conditions, the increase in the severity of clinical presentation was focused on healthy adults with IPD caused by nonhighly invasive serotypes. Beyond the increase in the burden of IPD associated with influenza, a more severe clinical pattern of pneumococcal disease was observed in the influenza period. This effect varied according to pneumococcal serotype, host comorbidities, and age.

Influence of sludge retention time and temperature on the sludge removal in a submerged membrane bioreactor: comparative study between pure oxygen and air to supply aerobic conditions.

Performance of a bench-scale wastewater treatment plant, which consisted of a membrane bioreactor, was monitored daily using pure oxygen and air to supply aerobic conditions with the aim of studying the increases of the aeration and sludge removal efficiencies and the effect of the temperature. The results showed the capacity of membrane bioreactor systems for removing organic matter. The alpha-factors of the aeration were determined for six different MLSS concentrations in order to understand the system working when pure oxygen and air were used to supply aerobic conditions in the system. Aeration efficiency was increased between 30.7 and 45.9% when pure oxygen was used in the operation conditions (a hydraulic retention time of 12 h and MLSS concentrations between 4,018 and 11,192 mg/L). Sludge removal efficiency increased incrementally, from 0.2 to 1.5% when pure oxygen was used at low sludge retention time and from 1.5% to 15.4% at medium sludge retention time when temperature conditions were lower than 20°C. Moreover, the difference between calculated and experimental sludge retention time was lesser when pure oxygen was used to provide aerobic conditions, so the influence of the temperature decreased when the pure oxygen was used. These results showed the convenience of using pure oxygen due to the improvement in the performance of the system.

Bilateral macular edema in sistemic sclerosis.

Systemic sclerosis is a chronic, autoimmune, multisystem disease characterized by vascular dysfunction, chronic inflammation and widespread fibrosis. Although vascular involvement commonly manifests in the skin, it can also affect other organs, including the eyes. The characteristic vascular alteration is an obliterative fibroproliferative vasculopathy leading to hypoxia and tissue ischemia. We present a case of bilateral macular edema in a patient diagnosed with systemic sclerosis, as a consequence of retinal and choroidal vascular changes.

Gyrate atrophy of the choroid and retina: Update on diagnosis and treatment.

Gyrate atrophy of the choroid and retina (GACR) is a rare autosomal recessive disease characterised by elevated plasma ornithine levels due to deficiency of the enzyme ornithine aminotransferase (OAT). The accumulation of this amino acid in plasma leads to the development of patches of chorioretinal atrophy in the peripheral retina extending into the macular area. Patients usually present with night blindness followed by constriction of the visual field and, finally, decreased central vision and blindness. The disease is diagnosed by the presence of the characteristic clinical picture, the presence of hyperornithinaemia in plasma and the detection of mutations in the OAT enzyme gene. There is currently no effective gene therapy and the most common therapeutic intervention mainly involves dietary modifications with arginine restriction. This article aims to summarise the pathogenesis, clinical and diagnostic findings and treatment options in patients with GACR.

Arthrobacter siccitolerans sp. nov., a highly desiccation-tolerant, xeroprotectant-producing strain isolated from dry soil.

A novel desiccation-tolerant, xeroprotectant-producing bacterium, designated strain 4J27(T), was isolated from a Nerium oleander rhizosphere subjected to seasonal drought in Granada, Spain. Phylogenetic analysis based on 16S rRNA gene sequencing placed the isolate within the genus Arthrobacter, its closest relative being Arthrobacter phenanthrenivorans Shep3 DSM 18606(T), with which it showed 99.23 % 16S rRNA gene sequence similarity. DNA-DNA hybridization measurements showed less than 25 % relatedness between strain 4J27(T) and Arthrobacter phenanthrenivorans DSM 18606(T). The DNA base composition of strain 4J27(T) was 65.3 mol%. The main fatty acids were anteiso C15 : 0, anteiso C17 : 0, C16 : 0 and iso C16 : 0 and the major menaquinone was MK-9 (H2). The peptidoglycan type was A3α with an l-Lys-l-Ser-l-Thr-l-Ala interpeptide bridge. The bacterium tested positive for catalase activity and negative for oxidase activity. Phylogenetic, chemotaxonomic and phenotypic analyses indicated that the desiccation-tolerant strain 4J27(T) represents a novel species within the genus Arthrobacter, for which the name Arthrobacter siccitolerans is proposed. The type strain is 4J27(T) ( = CECT 8257(T) = LMG 27359(T)).

Prevalence and molecular epidemiology of acquired AmpC ß-lactamases and carbapenemases in Enterobacteriaceae isolates from 35 hospitals in Spain.

The purpose of this investigation was to determine the prevalence of plasmid-mediated AmpC (pAmpC) and carbapenemases in Enterobacteriaceae collected from 35 hospitals in Spain and to establish their epidemiological relationships. We conducted a prospective multi-centre study on pAmpC- or carbapenemase-producing Enterobacteriaceae isolates from clinical samples collected from February to July 2009. The strains suspected to carry pAmpC were resistant or showed intermediate susceptibility to co-amoxiclav and second- or third-generation cephalosporins. Strains suspected to carry a carbapenemase were selected because they showed a minimum inhibitory concentration (MIC) to imipenem >1 mg/L. Polymerase chain reaction (PCR) and a sequencing strategy were used to characterise the enzymes. The clonal relationships between isolates was analysed by pulsed field gel electrophoresis (PFGE). Among 100,132 Enterobacteriaceae isolates collected, 1,654 were compatible with the production of pAmpC or carbapenemases. We found a prevalence of 0.64 % of pAmpC (n = 635) and 0.04 % of carbapenemases (n = 43). The most prevalent pAmpC enzymes were CMY-type (78.3 %), DHA-type (19.5 %), ACC-type (1.6 %) and FOX-type (0.6 %). The CMY-type was the most frequent in Escherichia coli and Proteus mirabilis species, whereas the DHA-type was mainly found in Klebsiella spp. The enzymes involved in carbapenem resistance were VIM-1, IMP-22 and the new IMP-28. Nine new bla genes were described: bla (CMY-54), bla (CMY-55), bla (CMY-56), bla (CMY-57), bla (CMY-96), bla (DHA-6), bla (DHA-7), bla (FOX-8) and bla (IMP-28). The prevalence of pAmpC or carbapenemases found is not negligible. The CMY-types were the predominant pAmpC, whereas the VIM or IMP enzymes were the predominant carbapenemases. Furthermore, we observed a great genetic diversity among pAmpC-producing strains and a close clonal relationship between carbapenemase-producing strains.

Prevalence of Nitrosomonas cluster 7 populations in the ammonia-oxidizing community of a submerged membrane bioreactor treating urban wastewater under different operation conditions.

A pilot-scale ultrafiltration membrane bioreactor (MBR) was used for the aerobic treatment of urban wastewater in four experimental stages influenced by seasonal temperature and different sets of operation conditions. The structure of the ammonia-oxidizing bacteria (AOB) community was profiled by temperature gradient gel electrophoresis (TGGE), based on the amplification and separation of partial ammonia-monoxygenase subunit A (amoA) genes. Canonical correspondence analysis revealed that temperature, hydraulic retention time and percentage of ammonia removal had a significant effect on the fingerprints of AOB communities. Phylogenetic analysis conducted on amoA/AmoA sequences of reamplified TGGE bands showed, however, that closely related ammonia-oxidizing populations inhabited the sludge of the MBR in all experimental stages. Nitrosomonas cluster 7 populations (N. europaea-N. eutropha cluster) prevailed under all conditions tested, even when the MBR was operated under complete biomass retention or at low temperatures, suggesting that the high ammonia concentrations in the system were determinant to select r-strategist AOB.

Biological and technical study of a partial-SHARON reactor at laboratory scale: effect of hydraulic retention time.

This study was on the technical and biological characteristics of a partial-SHARON submerged-filter bioreactor of 3 L. The main focus was the influence of the hydraulic retention time (HRT) on biofilms. For this purpose, we used molecular tools based on the partial 16S rRNA genes. The results showed that the HRT may affect the nitrification processes of a bioreactor using synthetic wastewater containing 600 mg/L of ammonia. It was found that an HRT of 0.5 day transformed 100 % of the ammonium into nitrite. However, when the HRT was decreased to 0.4 day, there was a significant reduction (35 %) in the quantity of ammonia transformed, which confirmed the complexity of the system operation. Moreover, a PCR-TGGE approach highlighted the differences observed. The results obtained showed that an HRT of 0.5 day reduced bacterial biodiversity in the biofilms, which were mainly formed by Nitrosomonas and Diaphorobacter. In contrast, an HRT of 0.4 day facilitated the formation of heterogeneous biofilms formed by nitrifying bacteria, such as Nitrosomonas sp., Nitrosospira sp., and Nitrosovibrio sp.).

Removal and degradation characteristics of quinolone antibiotics in laboratory-scale activated sludge reactors under aerobic, nitrifying and anoxic conditions.

This work describes the removal of 6 quinolone antibiotics from wastewaters under different redox conditions (aerobic, nitrifying and anoxic) through batch experiments in laboratory scale activated sludge reactors using mixed liquor from a membrane bioreactor pilot plant (MBR). The main removal pathways for antibiotics from wastewaters involved in each treatment are described. Mass balances indicated that sorption on sludge played a dominating role in the elimination of antibiotics. Sorption potential depended on the redox conditions, being lower in nitrifying (Kd, 414-876 L kg(-1)) and anoxic (Kd, 471-930 L kg(-1)) sludge in comparison with aerobic sludge (Kd, 534-1137 L kg(-1)). Kd was higher for piperazinylic quinolones. Redox conditions also influenced biodegradation, a secondary pathway, which followed first-order kinetics with degradation rates constants ranging from 1.8·10(-3) to 8.2·10(-3) h(-1). Biodegradation rates under anoxic conditions were negligible. The experimental results have also demonstrated much higher removal efficiency by biodegradation (36.2-60.0%) under nitrifying conditions in comparison with aerobic conditions (14.9-43.8%). The addition of allylthiourea, an ammonia monooxygenase inhibitor, inhibited nitrification completely and reduced significantly the biodegradation of target antibiotics (16.5-29.3%). The residual biodegradation in the presence of allylthiourea may be due to the activity of heterotrophs in the enriched nitrifier culture. The removal of the selected antibiotics under the studied redox conditions depended significantly on the bacteria composition of the sludge. These results suggest that despite the known persistence of this group of antibiotics it is possible to enhance their degradation using nitrifying conditions, which at adequate working conditions as high SRT, typical in MBR, become a promising alternative for improving quinolones removal from environment.

Obscure digestive bleeding.

A 50-year-old woman presented to the emergency department with several episodes of melena in the last week. The patient was not hemodynamically compromised and was conservatively managed. Urgent upper gastrointestinal endoscopy and colonoscopy showed no source of bleeding. Abdominal CT demonstrated three mural nodular lesions up to 2cm in the mid jejunum with hypervascular characteristics in arterial phase without active bleeding in venous phase. Angiography (Figure 1A) revealed three tumours with neo-angiogenesis and no active bleeding. Each lesion was stained with methylene blue and followed by embolization with coils. Exploratory laparotomy (Figure 1B) showed the three nodules marked by angiography. Intestinal resection of the affected segment was performed. Histopathological study proved the diagnosis of suspicion (Figure 2).

Influence of filling ratio and carrier type on organic matter removal in a moving bed biofilm reactor with pretreatment of electrocoagulation in wastewater treatment.

At present, there is great concern about limited water resources and water quality, which require a more advanced technology. The Moving Bed Biofilm Reactor (MBBR) has been shown to be an efficient technology for removal of organic matter and nutrients in industrial and urban wastewater treatment. However, there are some pollutants which are more difficult to remove by biological processes, so this process can be improved with additional physical and chemical treatments such as electrocoagulation, which appears to be a promising technology in electrochemical treatments. In this research, urban wastewater was treated in an MBBR plant with an electrocoagulation pre-treatment. K1 from AnoxKaldnes and AQWISE ABC5 from Aqwise were the carriers studied under three different filling ratios (20, 35, and 50%). The experimental pilot plant had four bioreactors with 20 L of operation volume and a common feed tank with 100 L of operation volume. The movement of the carriers was generated by aeration and stirrer systems. Organic matter removal was studied by analysis of soluble chemical oxygen demand (sCOD). The maximum organic matter removal in this MBBR system was 65.8% ± 1.4% and 78.4% ± 0.1% for K1 and Aqwise ABC5 carriers, respectively. Moreover, the bacterial diversity of the biofilm was studied by temperature-gradient gel electrophoresis (TGGE) of PCR-amplified partial 16S rRNA genes. 20 prominent TGGE bands were successfully reamplified and sequenced, being the predominant population: ß-Proteobacteria, α-Proteobacteria, and Actinobacteria.

Hepatoerythropoietic porphyria due to a novel mutation in the uroporphyrinogen decarboxylase gene.

BACKGROUND: Hepatoerythropoietic porphyria (HEP) is a rare form of porphyria that results from a deficiency of uroporphyrinogen decarboxylase (UROD). The disease is caused by homoallelism or heteroallelism for mutations in the UROD gene. OBJECTIVE: To study a 19-year-old woman from Equatorial Guinea, one of the few cases of HEP of African descent and to characterize a new mutation causing HEP. METHODS: Excretion of porphyrins and residual UROD activity in erythrocytes were measured and compared with those of other patients with HEP. The UROD gene of the proband was sequenced and a new mutation identified. The recombinant UROD protein was purified and assayed for enzymatic activity. The change of amino acid mapped to the UROD protein and the functional consequences were predicted. RESULTS: The patient presented a novel homozygous G170D missense mutation. Porphyrin excretion showed an atypical pattern in stool with a high pentaporphyrin III to isocoproporphyrin ratio. Erythrocyte UROD activity was 42% of normal and higher than the activity found in patients with HEP with a G281E mutation. The recombinant UROD protein showed a relative activity of 17% and 60% of wild-type to uroporphyrinogen I and III respectively. Molecular modelling showed that glycine 170 is located on the dimer interface of UROD, in a loop containing residues 167-172 that are critical for optimal enzymatic activity and that the carboxyl side chain from aspartic acid is predicted to cause negative interactions between the protein and the substrate. CONCLUSIONS: The results emphasize the complex relationship between the genetic defects and the biochemical phenotype in homozygous porphyria.

Characterization of bacterial communities exposed to Cr(III) and Pb(II) in submerged fixed-bed biofilms for groundwater treatment.

Two pilot-scale submerged-bed microbial biofilms were set up for the removal of Cr(III) and Pb(II) from groundwater, and the biological activities and structure of the bacterial communities developed in the presence of the heavy metals were analyzed. Artesian groundwater was polluted with Cr(III) or Pb(II) (15 mg/l) and amended with sucrose (250 mg/l) as carbon source. While Pb(II) was over 99% removed from groundwater during long-term operation (130 days), the efficiency of the removal of Cr(III) significantly decreased in time (95-73% after 60 days). Cr(III)-amended biofilms displayed significant lower sucrose consumption, ATP cell contents and alkaline phosphatase activity, compared to biofilms formed in the presence of Pb(II), while analysis of exopolymers demonstrated significant differences in their composition (content of carbohydrates and acetyl groups) in response to each heavy metal. According to transmission electron microscopy (TEM) and electron-dispersive X-ray analysis (EDX), Cr(III) bioaccumulated in the exopolymeric matrix without entering bacterial cells, while Pb(II) was detected both extra and intracellularly, associated to P and Si. Temperature-gradient gel electrophoresis (TGGE) profiling based on partial amplification of 16S rRNA genes was used to analyze the differences in the structure of the biofilm bacterial communities developed under exposure to each heavy metal. Prevalent populations in the biofilms were further identified by reamplification and sequencing of isolated TGGE bands. 75% of the sequences in the Pb(II) biofilter were evolutively close to the Rhodobacterales, while in the Cr(III) biofilter 43% of the sequences were found affiliated to the Rhizobiales and Sphingomonadales, and 57% to Betaproteobacteria.

Submerged filter biofilm formation by nitrate-contaminated groundwater microbiota.

Denitrifying biofilms developed in a lab-scale submerged filter by autochthonous bacteria from nitrate-contaminated groundwater were studied. The system was supplied with groundwater (16 mg N-NO(3)(-)/L), from which the oxygen had been eliminated and to which an excess of carbon source had been added. The reactor was incubated in a thermostated chamber at 5°C, 10°C, 20°C and 30°C. Colonization of the support was studied using surface scanning microscopy, and biofilm bacterial composition was studied by PCR/TGGE. Support material was colonized at all the temperatures assayed, although this parameter affected the growth of the biofilm, which developed most at temperatures over 20°C. The composition of bacterial communities varied according to the temperature. Community profiles of the biofilm formed at 5°C and 10°C clustered away from those of the biofilm formed at 20°C and 30°C. 16S rDNA sequences reveled that the biofilm was mainly composed of psychrotolerant species typically inhabiting freshwaters, and we obtained sequencing bands that were affiliated to denitrifying and non-denitrifying heterotrophic species. The extent of colonization was low when compared to previously inoculated systems, and the capacity for nitrate elimination was also low.