Filamentous fungi occurrence in free water and biofilms from drinking water storage tanks

In some regions of Brazil, especially where the water is scarce, drinking water is stored in water storage tanks. This practice gives the consumer the guarantee of available water. The water storage conditions such as the exposure to hot weather when the tanks are on rooftops allow the development of microorganisms and microbial biofilms which can deteriorate the water quality and increase the risk to human health [1,2]. This study describes the filamentous fungi (FF) detected in free water and biofilms in drinking water storage tanks in Recife - Pernambuco, Brazil. Five sampling times in triplicate were performed at two distinct points. Colony-forming units (CFU) of FF fungi were determined with 0.45 μm filtration membranes using peptone glucose rose Bengal agar (PGRBA). From the 30 samples analysed a total of 1136 CFU were obtained. The water biofilms were collected from samplers consisting of polyethylene coupons, previously installed in the reservoirs. These coupons were transferred to PGRBA plates and incubated using with the same conditions described for free FF. For the in situ detection of FF in biofilms the Calcofluor White staining technique was used. This procedure demonstrated FF forming biofilms on the surfaces of the coupons. Brazilian legislation does not define limits for FF in drinking water. However considering the potential risk of fungal contamination, the data obtained in this study will contribute to developing future quantitative and qualitative parameters for the presence of fungi in drinking water distribution systems in Brazil

In situ detection of fungal biofilms in a water distribution system, Alto do Céu, Recife, Brazil

Recent investigations on water microbiology have shown that most of the biomass present in the drinking water network is located at the pipe walls as biofilms. Biofilms are organized in highly efficient and stable ecosystems and can be viewed as a survival mechanism; this way of life can provide protection from chemical, biological or physical stresses. Moreover, biofilms play a major role in the accumulation, protection and dissemination of pathogens through water distribution systems. Although filamentous fungi are especially adapted for growth on surfaces, fungal water biofilms have received less attention when compared with bacterial biofilms, thus remaining a lack of information in this field. The use of microscopy techniques associated with image analyses has become a valuable tool for in situ studies. Fluorescent in situ hybridization (FISH) and fluorescent dyes are non-invasive and nondestructive techniques which provide information on cell morphology, metabolism and phylogeny. In this work, we aimed to detect filamentous fungal biofilm in a water distribution system using FISH (EUK516 and FUN1429 probes) and Calcofluor staining in replaced pipes. We also presented a sampler developed to study in situ fungal biofilms formation in water distribution system. Calcofluor staining was a rapid and easy method to detect filamentous biofilms on pipes surfaces. Additionally, FISH provided phylogenetic information by the detection of eukaryotic and fungal cells. Ours results contributed to demonstrate the presence of fungi in water biofilms and emphasised that fungi play an important role in water biofilms and microbial water quality

Biofilms from a Brazilian water distribution system include filamentous fungi

Filamentous fungi in drinking water can block water pipes, can cause organoleptic biodeterioration, and are a source of pathogens. There are increasing reports of the involvement of the organisms in biofilms. This present study describes a sampling device that can be inserted directly into pipes within water distribution systems, allowing biofilm formation in situ. Calcofluor White M2R staining and fluorescent in situ hybridization with morphological analyses using epifluorescent microscopy were used to analyse biofilms for filamentous fungi, permitting direct observation of the fungi. DAPI (4=,6-diamidino-2- phenylindole) was applied to detect bacteria. Filamentous fungi were detected in biofilms after 6 months on coupons exposed to raw water, decanted water and at the entrance of the water distribution system. Algae, yeast, and bacteria were also observed. The role of filamentous fungi requires further investigations.The authors acknowledge Companhia Pernambucana de Saneamento (COMPESA) for its support in making the work by H.M.B. Oliveira possible. V.M. de Siqueira is supported by the grant SFRH/BD/43719/2008 from Fundacao para a Ciencia e Tecnologia (FCT), Portugal

Filamentous fungi in drinking water tanks of a water supply system in Recife-PE, Brazil

Drinking water reservoirs are widely used in various building constructions in Brazil for as a source of potable water for users. However, they are susceptible to the growth of microorganisms such as fungi. From these, several negative factors may ensue, namely, unpleasant odors and flavours, pigments, biofilm formation and mycotoxins. This is caused fungal resistance to treatment and disinfection. Brazilian law and those of other countries offer no encouragement for the research of the species of fungi that cause these problems. There are no legal limits as to the presence in drinking water. This study assesses the occurrence of filamentous fungi in drinking water reservoirs connected to the Alto do Céu distribution system located in Recife, Pernambuco, Brazil. Four monthly collections were carried out, in triplicate, at two fixed points in the network, at the same treatment area, and another 2.0 km away from this site. For water physicochemical characterization at the time of collection, pH, temperature and free residual chlorine were analyzed. Filamentous fungi were quantified by filtration through cellulose nitrate membrane with a 0.45 μm porosity. All strains were grown in Petri dishes containing Peptone Glucose, Rose Bengal Agar (PGRBA) and were incubated at 30°C for 48h. Fungal occurrence was quantified as colony forming units (CFU) per litre. Twenty-four samples were analyzed, and these accounted for 807 CFU. Considering the potential for water spreading diseases, and the high toxicity of fungi into account it is intended that this work may prompt the creation of acceptable parameters as to the presence of fungi in drinking water networks

Filamentous fungi in biofilms of water tanks in a supply system in Recife-PE, Brazil

Fungi cause detrimental organoleptic effects in water, and their presence may facilitate the occurrence of infections, allergic reactions and harmful effects from mycotoxins. Despite the lack of knowledge on the biological structure of filamentous fungi in biofilms, it is known that they can contribute with bacteria, yeasts, protozoa and viruses. Hence, this study analyzed, in situ, filamentous fungi in biofilms found in drinking water reservoirs of the distribution network in Alto do Céu, Recife, Pernambuco, Brazil. Biofilms were collected, in triplicate from samplers consisting of a polyethylene plate (4.0cm x 1.5cm) established in drinking water reservoirs. Four monthly collections were carried out between August and November 2011 at two fixed points. Polyethylene samplers were taken to the laboratory and washed with sterile water and transferred to Petri dishes containing medium Peptone, Glucose, Rose Bengal Agar (PGRBA). The plates were incubated at 30°C for 48h. The occurrence of fungi was reported as CFU/L. Fifty three colony forming units of fungi were quantified. For water physicochemical characterization at the time of collection, pH, temperature and free residual chlorine were analyzed. For detection of biofilms, a combination of two fluorescent techniques was used: (A) Fluorescent “in situ” hybridization (FISH) using a rDNA universal probe EUK516 (ACCAGACTTGCCCTCC 5’-3’, MWG Biotech, Ebersberg, Germany) labeled with cyanine Cy3 at the 5’ end and (B) Calcofluor White M2R (CW). After FISH and CW, the samples were observed under an epifluorescent microscope. Fungal filaments which formed biofilms in the distribution network were observed establishing biofilm formation. These results confirm the presence and relevance of filamentous fungi in structuring biofilms

Orbital quantization in the high magnetic field state of a charge-density-wave system

A superposition of the Pauli and orbital coupling of a high magnetic field to charge carriers in a charge-density-wave (CDW) system is proposed to give rise to transitions between subphases with quantized values of the CDW wavevector. By contrast to the purely orbital field-induced density-wave effects which require a strongly imperfect nesting of the Fermi surface, the new transitions can occur even if the Fermi surface is well nested at zero field. We suggest that such transitions are observed in the organic metal $\alpha$-(BEDT-TTF)$_2$KHg(SCN)$_4$ under a strongly tilted magnetic field.Comment: 14 pages including 4 figure

Effect of band filling in the Kondo lattice: A mean-field approach

The usual Kondo-lattice, including an antiferromagnetic exchange interaction between nearest-neighboring localized spins, is treated here in a mean-field scheme that introduces two mean-field parameters: one associated with the local Kondo effect, and the other related to the magnetic correlations between localized spins. Phases with short-range magnetic correlations or coexistence between those and the Kondo effect are obtained. By varying the number of electrons in the conduction band, we notice that the Kondo effect tends to be suppressed away from half filling, while magnetic correlations can survive if the Heisenberg coupling is strong enough. An enhanced linear coefficient of the specific heat is obtained at low temperatures in the metallic state.Comment: 7 pages, ReVTeX two-column, 7 figure

Reconstructing Roma History from Genome-Wide Data

The Roma people, living throughout Europe and West Asia, are a diverse population linked by the Romani language and culture. Previous linguistic and genetic studies have suggested that the Roma migrated into Europe from South Asia about 1,000–1,500 years ago. Genetic inferences about Roma history have mostly focused on the Y chromosome and mitochondrial DNA. To explore what additional information can be learned from genome-wide data, we analyzed data from six Roma groups that we genotyped at hundreds of thousands of single nucleotide polymorphisms (SNPs). We estimate that the Roma harbor about 80% West Eurasian ancestry–derived from a combination of European and South Asian sources–and that the date of admixture of South Asian and European ancestry was about 850 years before present. We provide evidence for Eastern Europe being a major source of European ancestry, and North-west India being a major source of the South Asian ancestry in the Roma. By computing allele sharing as a measure of linkage disequilibrium, we estimate that the migration of Roma out of the Indian subcontinent was accompanied by a severe founder event, which appears to have been followed by a major demographic expansion after the arrival in Europe.Országos Tudományos Kutatási Alapprogramok (OTKA K 103983)Országos Tudományos Kutatási Alapprogramok (OTKA 73430)National Science Foundation (U.S.) (HOMINID grant 1032255)National Institutes of Health (U.S.) (grant GM100233