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Research into Piscirickettsia salmonis biofilms on materials commonly used in salmon farming is crucial for understanding its persistence and virulence. We used the CDC Biofilm Reactor to investigate P. salmonis (LF-89 and EM-90) biofilm formation on Nylon, Stainless steel (316L), Polycarbonate and High-Density Polyethylene (HDPE) surfaces. After 144 h of biofilm visualization by scanning confocal laser microscopy under batch growth conditions, Nylon coupons generated the greatest biofilm formation and coverage compared to Stainless steel (316L), Polycarbonate and HDPE. Additionally, P. salmonis biofilm formation on Nylon was significantly greater (p ≤ .01) than Stainless steel (316L), Polycarbonate and HDPE at 288 h. We used Nylon coupons to determine the kinetic parameters of the planktonic and biofilm phases of P. salmonis. The two strains had similar latencies in the planktonic phase; however, LF-89 maximum growth was 2.5 orders of magnitude higher (Log cell ml

Microplastics (MPs) correspond to plastics between 0.1 μm and 5 mm in diameter, and these can be intentionally manufactured to be microscopic or generated from the fragmentation of larger plastics. Currently, MP contamination is a complicated subject due to its accumulation in the environment. They are a novel surface and a source of nutrients in soils because MPs can serve as a substrate for the colonization of microorganisms. Its presence in soil triggers physical (stability of aggregates, soil bulk density, and water dynamics), chemical (nutrients availability, organic matter, and pH), and biological changes (microbial activity and soil fauna). All these changes alter organic matter degradation and biogeochemical cycles such as the nitrogen (N) cycle, which is a key predictor of ecological stability and management in the terrestrial ecosystem. This review aims to explore how MPs affect the N cycle in the soil, the techniques to detect it in soil, and their effects on the physicochemical and biological parameters, emphasizing the impact on the main bacterial groups, genes, and enzymes associated with the different stages of the N cycle.

The digestion efficiency of liquid industrial wastes increases when using bioreactors colonized by microbial biofilms. High concentrations of proteins derived from the fish processing industry lead to the production of ammonia, which inhibits methane production. Two bioreactors were constructed to compare methanogenic activity: one enriched with mMPA consortia (control bioreactor), and the second with NH3 tolerant consortia (treatment bioreactor). Ammonia tolerant activity was assessed by applying an ammonia shock (755 mg NH3/L). Methane production, consumption of total organic carbon (TOC) and the taxonomic composition of bacteria and archaea was evaluated using 16S rDNA in the acclimatization, ammonia shock, and recovery phases. The ammonia shock significantly affected both methane production and the consumption of TOC in the control reactor (pMethanomethylovorans sp., and probably two different species of Methanosarcina sp.) in bioreactors. These results demonstrate that using acclimated biofilms enriched with ammonia tolerant methanogens control the inhibitory effect of ammonia on methanogenesis.

Wastewater-Based Epidemiology is a tool to face and mitigate COVID-19 outbreaks by evaluating conditions in a specic community. This study aimed to analyze the microbiome proles using nanopore technology for full-length 16S rRNA sequencing in wastewater samples collected from a penitentiary (P), a residential care home (RCH), and a quarantine or health care facilities (HCF). The HCF microbiome was strongly associated with enteric bacteria previously reported in patients with chronic disease and psychological disorders. During the study, the wastewater samples from the RCH and the P were negative for SARS-CoV-2 based on qPCRs, except during the fourth week when was detected. Unexpectedly, the wastewater microbiome from RCH and P prior to week four was correlated with the samples collected from the HCF, suggesting a core bacterial community is expelled from the digest tract of individuals infected with SARS-CoV-2. We provide novel evidence that the wastewater microbiome associated with gastrointestinal manifestations appears to precede the SARS-CoV-2 detection in sewage. This nding suggests that the wastewaters microbiome can be applied as an indicator of community-wide SARS-CoV2 surveillance., This study was funded by “Fondo de Emergencia Sanitaria COVID-19, Intendencia Región de Ñuble, Chile” and FONDAP #15110027 granted by National Research and Development Agency (ANID), Chile. We also thank MINSAL and MinCiencia to support this research and provide the epidemiological data.

Currently, some quinoline-based anticancer drugs are successful repurposed for treatment of bacterial infections. This study assessed the antibacterial activity of the new anticancer compound 4,7-dichloro-2-quinolinemethylacrylate (AQM) against bacteria of both clinical and agricultural interest, and also determined the influence of some metal cations (Fe3+, Mn2+, Zn2+, Na+, Mg2+, Co2+ and Ni2+) on the AQM photophysics. The synthesis of AQM was carried out by the reported method. The antibacterial activity of AQM on Pectobacterium carotovorum subsp. carotovorum (Pcc), Ralstonia solanacearum, Klebsiella pneuminiae, Pseudomonas syringae, Staphylococcus aureus y Bacillus sp., was evaluated using the spectrophotometric method of broth microdilution. At 125 ppm, AQM produced growth inhibition of 51.7% in Pcc, and a bacteriostatic effect in S. aureus and Bacillus sp., but no effect was seen against the other bacteria. In addition, fluorescence quenching of AQM solution induced only by Fe3+ ion, and not by the other metal cations, was confirmed. These results postulate that AQM could be a molecule with potential application in antibacterial therapy or in the fluorometric detection of Fe3+ ions.

Background: Trimethylamine (TMA) is the main responsible for the odor associated with rotting fish and other annoying odors generated in many industrial activities. Biofiltration has proved to be efficient for treating odorous gaseous emissions. The main objective of this work was to determine the removal capacity of TMA of a biotrickling filter inoculated with Aminobacter aminovorans and to evaluate the effect of H2S on its performance. Results: The maximum specific growth rate of A. aminovorans in a liquid culture was 0.15 h-1, with a TMA to biomass yield of 0.10 (g g-1) and a specific consumption rate of 0.062 g·g-1·h-1. The initial specific consumption rate of TMA was highly influenced by the presence of H2S in liquid culture at concentrations of 20 and 69 ppm in heading space of the flasks. A BTF inoculated with A. aminovorans showed removal efficiencies higher than 98% in a range of loading rate of 0.2 to 8 g·m-3·h-1 at empty bed residence time (EBRT) of 85 and 180 s. No effect on the elimination capacity and efficiency was detected when H2S was added at 20 and 50 ppm to the inlet gaseous emission, though the fraction of A. aminovorans measured by qPCR in the biofilm decreased. Conclusions: A biotrickling filter inoculated with A. aminovorans can remove efficiently the TMA in a gaseous stream. The elimination capacity of TMA can be negatively affected by H2S, but its effect is not notorious when it is forming part of a biofilm, due to its high specific consumption rate of TMA.How to cite: Aguirre A, Bernal P, Maureira D, et al. Biofiltration of trimethylamine in biotrickling filter inoculated with Aminobacter aminovorans. Electron J Biotechnol 2018;33. https://doi.org/10.1016/j.ejbt.2018.04.004. Keywords: Aminobacter aminovorans, Biofiltration, Biotrickling filter, Deodorization, Gaseous emissions, Hydrogen sulfide, Odor nuisance, Odorous emissions, Rotting fish, Trimethylamine, Volatile amines

Normal 0 21 false false false ES-TRAD X-NONE X-NONE Background: Sulphur-oxidizing microorganisms are widely used in the biofiltration of total reduced sulphur compounds (odorous and neurotoxic) produced by industries which include high temperature process steps, such as the cellulose and petrochemical industries. Some hyperthermophilic microorganisms have the capability to oxidize these compounds at high temperatures (>60oC), and archaea of this group, e.g. Sulfolobus metallicus , are commonly used in biofiltration technology. Results: In this study, a hyperthermophilic sulphur-oxidizing strain of archaea was isolated from a hot spring (Chillan, Chile) and it was called M1. It was identified archaea of the genus Sulfolobus (99% homology with Sulfolobus solfataricus 16S rDNA). Biofilms of this culture grown on polyethylene rings showed an elemental sulphur oxidation rate of 95.15 ± 15.39 mg S l -1 d -1 , higher than the rate exhibited by the biofilm of the sulphur-oxidizing archaea Sulfolobus metallicus (56.8 ± 10.91 mg l -1 d -1 ) Conclusions: The results suggest that the culture M1 is useful for biofiltration of total reduced sulphur gases at high temperatures, as well as other biotechnological applications. /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Tabla normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:"Times New Roman","serif"; mso-ansi-language:ES-TRAD; mso-fareast-language:ES-TRAD;}

Wastewater-Based Epidemiology is a tool to face and mitigate COVID-19 outbreaks by evaluating conditions in a specific community. This study aimed to analyze the microbiome profiles using nanopore technology for full-length 16S rRNA sequencing in wastewater samples collected from a penitentiary (P), a residential care home (RCH), and a quarantine or health care facilities (HCF). During the study, the wastewater samples from the RCH and the P were negative for SARS-CoV-2 based on qPCRs, except during the fourth week when was detected. Unexpectedly, the wastewater microbiome from RCH and P prior to week four was correlated with the samples collected from the HCF, suggesting a core bacterial community is expelled from the digest tract of individuals infected with SARS-CoV-2. The microbiota of wastewater sample positives for SARS-CoV-2 was strongly associated with enteric bacteria previously reported in patients with risk factors for COVID-19. We provide novel evidence that the wastewater microbiome associated with gastrointestinal manifestations appears to precede the SARS-CoV-2 detection in sewage. This finding suggests that the wastewaters microbiome can be applied as an indicator of community-wide SARS-CoV-2 surveillance., Graphical Abstract Unlabelled Image, Highlights • Nanopore 16S rRNA sequencing reveals species-specific profiling in wastewater. • Wastewater microbiome signals appears to precede SARS-CoV-2 detection in sewage. • Integrating microbiome analyses into WBE provided an early indicator for COVID-19.

Aquaculture settings present a number of surfaces that can potentially act as a reservoir for Flavobacterium psychrophilum, resulting in a serious threat to the health of farmed salmonids. The aim of this study was to employ the CDC Biofilm Reactor to evaluate the capacity of F. psychrophilum to form biofilms on stainless steel, polystyrene, polyurethane, and polycarbonate. Scanning electron microscopy and confocal laser scanning microscopy were used to assess biofilm formation, while epifluorescence and qPCR methods were effectively used to determine cell contents. After a 72 h incubation period, F. psychrophilum had formed mature biofilms composed by dense, multilayered clusters of short bacilli on stainless steel, polystyrene, and polycarbonate. Nevertheless, biofilms formed on stainless steel presented a significantly higher cell density than those formed on polyurethane. Biofilm growth was poor on polyurethane surfaces. These findings will facilitate the design of appropriate guidelines for more efficiently managing F. psychrophilum and controlling the persistence of this pathogen in fish-farming environments.

For the first time, this laboratory-scale study evaluates the feasibility of incorporating diffusive exchange in permeable reactive barriers. In order to do this, the performance of two permeable reactive barriers (PRB) with different internal substrate arrangements were compared during the administration of a sulfate solution without metals (for 163 days) and with metals (for 60 days), simulating groundwater contaminated with acid mine drainage (AMD). In order to simulate a traditional PRB, a homogeneous distribution was implemented in the first reactor and the other PRB reactor utilized diffusion-active technology (DAPRB). In the DAPRB, the distribution of the reactive material was interspersed with the conductive material. The measurements in the internal ports showed that transverse gradients of sulfide formed in the DAPRB, causing the diffusion of sulfide from the substrate toward the layer interface, which is where the sulfide reacts by forming complexes with the metal. The DAPRB prevents the microorganisms from direct contact with AMD. This protection caused greater activity (sulfide production).

Flavobacterium psyhrophilum affects farmed salmon and trout worldwide and is the etiological agent of bacterial cold water disease. The treatment of this disease is made with antibiotics. The emergence of resistant strains and its ability to form biofilms have increased the resistance to antibiotics. Considering the diverse bioactivity of Antarctic bacteria, we evaluated the inhibitory effect of compounds secreted by Antarctic bacterial strains on the biofilm formation of F. psychrophilum 19749. 26.9% of the Antarctic bacterial isolates inhibited strongly the biofilm, the greatest effect was shown by M19B. Proteins (48-56 kDa) secreted by M19B may be related to the inhibition of the biofilm formation of F. psychrophilum 19749.

The main goal of this study was to find bacterial isolates with the ability to inhibit the growth of the fish pathogens Aeromonas hydrophila, Vibrio anguillarum, and Flavobacterium psychrophilum and to inhibit the blockage of the quorum-sensing (QS) system. A total of 80 gram-negative strains isolated from various freshwater Chilean salmonid farms were studied. We determined that 10 strains belonging to the genus Pseudomonas inhibited at least one of the assayed fish pathogens. Of these, nine strains were able to produce siderophores and two strains were able to inhibit the growth of all assayed pathogenic species. When the 80 strains were examined for QS-blocking activity, only the strains Pseudomonas sp. FF16 and Raoultella planticola R5B1 were identified as QS blockers. When the QS-blocker strains were analyzed for their ability to produce homoserine lactone (HSL) molecules, thin-layer chromatography analysis showed that both strains were able to produce C6-HSL- and C8-HSL-type molecules. Strain R5B1 did not show growth inhibition properties, but strain FF16 also led to inhibition of growth in A. hydrophila and F. psychrophilum as well as to siderophore production. Pseudomonas sp. FF16 exhibited potentially useful antagonistic properties and could be a probiotic candidate for the salmon farming industry.

Odour emissions are a major environmental issue associated with fishmeal production. Laboratory-scale biotrickling filters (BTFs) were inoculated with microbial consortia derived from sewage sludge, with the goal to study the biotreatment of low-loads of methylamines and ammonia that are main components of odorous exhaust gases produced by fishmeal processing plants. A BTF packed with ceramic rings was subjected to a real fishmeal plant emission containing trimethylamine (TMA), dimethylamine (DMA) and monomethylamine (MMA). The highest elimination capacities (ECs) obtained were 372 mg TMA m−3 h−1, 5.518 mg DMA m−3 h−1 and 1.038 mg MMA m−3 h−1, with maximal removal efficiencies of 92% (TMA), 83% (DMA) and 95% (MMA) after 30 days operation. In a different experiment, a polyurethane foam packing was employed to treat ammonia (NH3) at low inlet loads, reaching an EC of 47.19 mg N m−3 h−1 with 99.8% efficiency (inlet load of 47.27 mg N m−3 h−1). Likewise, the microbial community of the polyurethane-associated biofilm was diverse and stable during operation. These results suggested that elimination of volatile amino-compounds using BTFs inoculated with a methylotrophic microbial consortium holds potential for odour removal. In addition, sequencing analysis of 16S rDNA gene fragments allowed the identification of heterotrophic ammonia-oxidizing bacteria that are promising candidates to effectively maintain ammonia elimination in a biotreatment operation of nitrogenous compounds present in exhaust gases from fishmeal facilities.

Paradigms based on competition have shown to be useful for solving difficult problems. In this paper we present a new approach for solving hard problems using a collaborative philosophy. A collaborative philosophy can produce paradigms as interesting as the ones found in algorithms based on a competitive philosophy. Furthermore, we show that the performance - in problems associated to explosive combinatorial - is comparable to the performance obtained using a classic evolutive approach.

Magnesium is an element essential for life and is found ubiquitously in all organisms. The different cations play important roles as enzymatic co-factors, as signaling molecules, and in stabilizing cellular components. It is not surprising that magnesium salts in microbiological experiments are typically associated with positive effects. In this study with Listeria monocytogenes as a model organism, we focus however on the usefulness of magnesium (in form of MgCl2) as a stress enhancer. Whereas MgCl2 does not affect bacterial viability at near-neutral pHs, it was found to strongly compromise culturability and redox activity when cell suspensions were exposed to the salt at acidic pH. The principle was confirmed with a number of gram-negative and gram-positive species. The magnesium salt dramatically increased the acidity to a level that was antimicrobial in the presence of anionic bases such as phosphate, lactate, or acetate, but not TRIS. The antimicrobial activity of MgCl2 was much stronger than that of NaCl, KCl, or CaCl2. No effect was observed with MgSO4 or when cells were exposed to MgCl2 in phosphate buffer with a pH ≥ 5. Acid stress was reinforced by an additional, salt-specific effect of MgCl2 on microbial viability that needs further examination. Apart from its implications for surface disinfection, this observation might support the commonly stated therapeutic properties of MgCl2 for the treatment of skin diseases (with healthy skin being an acidic environment), and could contribute to understanding why salt from the Dead Sea, where Mg(2+) and Cl(-) are the most abundant cation/anion, has healing properties in a microbiological context.

This study investigated chlorate reduction kinetics in multiple samples of sediments from a longitudinal profile of a wetland located downstream of the effluent discharge of a cellulose plant, including characterisation of the bacterial communities involved. The sediments were exposed to different initial chlorate concentrations in microcosm tests, with and without the addition of acetate as an external electron donor, and in a matrix of natural water or a defined medium. At a high initial chlorate concentration of 100 mg/L, in the absence of an external electron source, the degradation curves presented first-order kinetics, influenced by electron donor availability. The first-order kinetic constant varied between 0.05 and 0.17 day(-1). Subsequently, when the initial chlorate concentration was reduced to 7 mg/L, a zero-order kinetic was obtained, with the kinetic constant presenting values between 1.1 and 1.3 mg/L-day. No correlation was observed between chlorate degradation kinetics and the location of the sampling points or the previous history of exposure to chlorate. Other factors evaluated, such as the availability of organic matter or the chlorate reducing bacteria count, also proved not to have any incidence on the results. The richness of chlorate reducing bacteria species in the different samples analysed were also similar, with the greatest similarity being found between cld genes in the samples from the upstream or downstream sampling points. Additionally, cld genes most similar to those present in PCRB like Dechlorospirillum sp., Alicycliphilus denitrificans, Dechloromonas agitata, Dechloromonas sp. LT1 and Ideonella dechloratans were detected. This study showed that the anaerobic sediments of the Cruces river wetland present a high potential for chlorate natural attenuation, regardless of the previous history of exposure to chlorate. This capacity is associated with the presence of a diverse community of chlorate reducing bacteria.

Industrial fishing effluents are characterized by high loads of protein and sulfate that stimulate the activity of proteolytic and sulfate reducing bacteria during anaerobic digestion. Their metabolic products (NH3 and H2S respectively) have a well-known detrimental effect on the activity of methanogens. Since methylamine is a carbon source used by methylaminotrophic methane producing archaea (mMPA) but not by sulfate reducing bacteria (SRB), enriched mMPA anaerobic biofilms have been developed on ceramics. We propose that methylated amines could be produced in the biofilm by using betaine, a known precursor of methylamine, as a carbon and energy source. We isolated an anaerobic betainotrophic methylaminogenic bacterial strain (bMB) from an anaerobic bioreactor, using betaine as the only carbon and energy source. This strain was identified by a standard biochemical test (API 20NE), cloning, and 16S rDNA sequencing. bMB biofilm structure and biofilm growth kinetic parameters were determined by means of scanning electron microscopy (SEM), and the Gompertz growth model, respectively. Monomethylamine production was determined by infrared spectroscopy and by high pressure liquid chromatography. The isolated bMB strain was determined as Stappia stellulata (Proteobacteria phylum). It was able to form biofilm on ceramics and its kinetic growth parameters resulted in: maximum biofilm bacterial count (A) of 6.25 x 10(8) UFC/cm(2) and maximum specific growth rate (mu(m)) of 0.0221/h. Production of monomethylamine was about 4.027 atogram/cell/day (at/cell/day) after 15 days of incubation in biofilms. This study confirms the adhesion capacity of this bMB strain on ceramic supports, assuring that monomethylamine production in biofilms could be enriched with mMPA that use monomethylamine.

The latest advances in the field of microbial ecology have shown that planktonic Archaea are one of the most abundant unicellular microorganisms of the oceans. However, no information is available on the contribution this group makes to the prokaryote assemblages that inhabit the eastern South Pacific Ocean. Here, we describe the relative abundance and vertical distribution of planktonic Archaea off northern and central-southern Chile. Data come from several cruises and a 45-month time series at a station located on the shelf off central-southern Chile. Both the taxonomic composition of the prokaryote community and its relative abundance were determined using quantitative dot blot 16S-rRNA hybridizations. Total Archaea in central-southern Chile made up 6–87% of the prokaryote rRNA in the water column and did not present evidence of any seasonal pattern. Crenarchaea were the most abundant archaeal group at this site and were significantly associated with the ammonium concentration ( r 2 =0.16, p =0.0003, n =80). Archaeal abundance in the time series was usually greater in the deeper layer (>50 m), with contributions reaching up to ∼90% of the prokaryote rRNA on certain occasions, and decreasing towards the surface. Important increments in the relative abundance of total Archaea were observed on given dates at the surface of the time-series station off central-southern Chile. Off northern Chile, total Archaea normally contributed from ∼10% to 50% of the prokaryote rRNA found between 10 and 1000 m, and were generally important in the mesopelagic realm. Our results indicate that Archaea constitute an important fraction of the prokaryote assemblage in the water column of the Humboldt Current System, especially in the oxygen minimum zone.

Because the marine picoplanktonic communities are made up of phylogenetically different microbial groups, the re-evaluation of key processes such as bacterial secondary production (BSP) has become an important contemporary issue. The difficulty of differentiating the metabolic processes of Bacteria from the rest of the microorganisms in the water column (i.e., Archaea and Eukarya) has made it difficult to estimate in situ BSP. This work presents the seasonal variability of the prokaryote secondary production (PSP) measured by the incorporation of 14C-leucine in the oxygen minimum zone (OMZ) off central-southern Chile. The BSP and potential archaeal secondary production (PASP) were determined through the combined use of 14C-leucine and N1-guanyl-1, 7-diaminoheptane (GC7), an efficient inhibitor of archaeal and eukaryote cell growth. BSP accounted for the majority of the PSP (total average, 59 ± 7.5%); maximum values were ∼600 μg C m−3 h−1 and, on several dates, BSP represented 100% of the PSP. Similarly, PASP was also an important fraction of the PSP (total average, 42.4 ± 8.5%), although with levels that ranged from not detectable (on given dates) to levels that represented up to ∼97% of PSP (winter 2003). Our results showed that both Bacteria and Archaea accounted for almost equal portions of the prokaryote heterotrophic metabolism in the OMZ, and that PASP is notoriously enhanced through temporal pulses of heterotrophy. This indicates that, at least in marine systems with high abundance of Archaea (e.g., mesopelagic realm), the secondary production obtained through methods measuring the uptake of radiolabeled substrates should be considered as PSP and not as BSP. If the latter is the target measurement, then the use of an inhibitor of both archaeal and eukaryote cell growth such as GC7 is recommended.

The composition of ammonia-oxidizing bacteria from the β- Proteobacteria subclass (βAOB) was studied in the surface and upper-oxycline oxic waters (2- to 50-m depth, ∼200 to 44 μM O 2 ) and within the oxygen minimum zone (OMZ) suboxic waters (50- to 400-m depth, ≤10 μM O 2 ) of the eastern South Pacific off northern Chile. This study was carried out through cloning and sequencing of genes coding for 16S rRNA and the ammonia monooxygenase enzyme active subunit ( amoA ). Sequences affiliated with Nitrosospira -like cluster 1 dominated the 16S rRNA gene clone libraries constructed from both oxic and suboxic waters. Cluster 1 consists exclusively of yet-uncultivated βAOB from marine environments. However, a single clone, out of 224 obtained from the OMZ, was found to belong to Nitrosospira lineage cluster 0. To our knowledge, cluster 0 sequences have been derived from βAOB isolated only from sand, soil, and freshwater environments. Sequences in clone libraries of the amoA gene from the surface and upper oxycline could be grouped in a marine subcluster, also containing no cultured representatives. In contrast, all 74 amoA sequences originating from the OMZ were either closely affiliated with cultured Nitrosospira spp. from clusters 0 and 2 or with other yet-uncultured βAOB from soil and an aerated-anoxic Orbal process waste treatment plant. Our results reveal the presence of Nitrosospira -like βAOB in both oxic and suboxic waters associated with the OMZ but with a clear community shift at the functional level ( amoA ) along the strong oxygen gradient.

The growing biogeochemical and economic importance of biogenic methane contained in gas hydrates necessitates a better understanding of the microorganisms involved in the last phase of organic matter degradation. Here, the distribution and relative abundance of methylotrophic methane-producing Archaea (mMPA) were studied in an upwelling area off central Chile by rRNA dot blot hybridization. The mMPA were detected mostly during active upwelling periods, and were more abundant in the deeper layer of the water column (>50 m), where they represented ~10% of the prokaryote rRNA extractable from seawater samples in the oxygen minimum zone (OMZ). Significant correlations were found between the concentration of rRNA from mMPA and (i) nitrate concentration (r=-0.54, p=0.0392) and (ii) temperature (r=-0.51, p=0.0267). Enrichment experiments with water samples from the OMZ were carried out to evaluate the cellular viability of mMPA. These experiments showed that some of these Archaea remain viable in the planktonic environment although not essentially associated with fecal pellets or any type of compact macroaggregate. The results suggest that mMPA in the water column come mostly from sediment and that a fraction correspond to psychrophilic varieties of facultative methylotrophs.

Several studies have been done in order to detect antibiotics from natural sources, seaweeds among them. With the aim of identifying antibacterial compounds, 6 species of seaweeds have been evaluated. The raw extracts were analyzed against bacteria, Gram-positive and negative, with diffusion discs and bioautography, then, they were characterized by GC-MS. The seaweeds Gracilaria chilensis, Ulva Complex and Macrocystis pyrifera present inhibition in the bacterial growth of tested strains. Three molecules, Phytol, 6-methyl-2-phenylquinoline and Neophytadiene were identified from M. pyrifera and in Ulva Complex extracts. The results represent a potential use to incorporate these properties into biomaterials.

The hydrolysis of soluble proteins in an anaerobic, saline (24 g dm−3 NaCl) and mesophilic (37 °C) environment was studied. The inhibitory effect of a volatile fatty acid, acetic acid (HAc), on the hydrolysis rate and hydrolytic biomass activity for a model saline wastewater with a high protein load (total organic carbon, 1153 mg dm−3 and 1572 mg dm−3 proteins) was studied. Initial inhibitor concentrations were tested in the range of 0–2000 mg dm−3 HAc. The microbiological characterization was performed using a total microorganism count by epifluorescence, and hydrolytic bacterial activity was determined by plate count. The protein hydrolysis was modeled according to first order kinetics. The effect of biomass on hydrolysis was analyzed by varying its concentration in the range of 42–210 mg dm−3 volatile suspended solids. The following apparent hydrolysis kinetic constants (Kh) for proteins at 37 °C were obtained: 1.3, 0.8, 0.6, 0.2 and 0.1 d−1 for initial concentrations of 250, 500, 750, 880, and 1000 mg dm−3 HAc, respectively. At concentrations of HAc greater than 1000 mg dm−3, total inhibition of hydrolysis was observed. The intrinsic hydrolysis constant () at 37 °C, without inhibition, was 2.3 d−1. The hydrolysis kinetic constant was not affected by the biomass concentration. The hydrolysis kinetics constant was filted to three models: Luong, Levenspiel and non-competitive inhibition. The model that best represented the experimental data was Luong, obtaining an inhibition constant (KI) of 1087 mg dm−3 of HAc and the exponent γ = 0.54. The hydrolysis was inhibited by the presence of HAc, which corresponds to an intermediate compound of the anaerobic process. Copyright © 2004 Society of Chemical Industry

Selection, acclimation, and kinetic characterization of a nitrifying microflora chosen from natural sources and capable of degrading total ammonia nitrogen (TAN) at high concentration was performed. The inocula of animal manure and of marine sediments were selected due to their nitrate production (55.8 mg N/L⋅day) and tolerance to salinity (16 g Cl-/L). An acclimation continuous culture was made using TAN up to 1,000 mg N/L and nitrogen load rate of 250 to 1,000 mg N/L⋅day. The TAN degradation rate after acclimation reached 0.16 mg N/mg VSS⋅h (VSS=volatile suspended solids) at a feed concentration of 1,000 mg N/L; the ammonia-oxidizing population increased from 60 to 77% whereas nitrite-oxidizing bacteria decreased from 40 to 23%. The following substrate-inhibition Haldane parameters were determined: rTAN,max=0.21 and 0.19 mg N/mg VSS⋅h; Ks=3.0 and 4.8 mg NH3-N/L; Ki=22.4 and 35.6 mg NH3-N/L for sludge before and after acclimation, respectively. Differences between rTAN,max values were not statistically s...

Fifteen native Chilean plants were evaluated against the quorum sensing (QS) biosensor AI-1, Chromobacterium violaceum ATCC 12472. Three extracts showed inhibitory activity of QS: Drymis winteri J.R, Psoralea glandulosa L and Peumus boldus. Purification of secondary metabolites from barks of Drimys winteri showed that drimane sesquiterpenes were the main compounds in the tree. Polygodial, drimenol, isodrimeninol, drimenin, isodrimenin, cinnamolide and valdiviolide were isolated and evaluated in QS inhibition assays. Two α,β unsaturated lactones, cinnamolide and valdiviolide, with the carbonyl on position 12 of the drimane skeleton were found to be inhibitors of QS; other drimane lactones were not active.

Nitrification with pure O of fisheries wastewaters high in N-NH4+ (0.2-1g/l) and in organic matter (1-2gCOD/l) gave specific growth rates for the bacteria degrading organic matter of 0.24h and for nitrifying bacteria of 0.15h. Average organic matter abatement was 75% whereas N-NH (0.7g/l as initial concentration) oxidation to nitrite and nitrate was 20%.

Treatment of microbiological samples with viability dyes prior to extraction of DNA and PCR amplification for downstream analysis has evolved into a commonly applied method. The addition of this easy-to-perform step to the sample analysis procedure inhibits the amplification of DNA from dead cells with compromised cell membranes. The method is currently used both in combination with quantitative PCR (qPCR), end-point PCR, and isothermal amplification. We present here a detailed study of the effect of amplicon size on amplification signals from unstressed and heat-exposed cells after treatment with propidium monoazide (PMA). PMA treatment was shown to be more efficient in excluding dead cells from the analysis both in combination with qPCR (PMA-qPCR) and denaturing gradient gel electrophoresis (PMA-DGGE), when longer amplicons were used. When applied to pure cultures of the fish pathogens Vibrio anguillarum and Flavobacterium psychrophilum exposed to a heat gradient ranging from mild to lethal, qPCR product lengths did not influence PMA-qPCR results at low temperatures, whereas an increasingly strong impact was seen at higher temperatures. Membrane permeability as a result of heat exposure might however have to be considered a conservative parameter for cell death for these pathogens as culturability and redox activity were lost at lower stress intensities than membrane integrity. When applying PMA-DGGE to an environmental water sample which was either left untreated or was exposed to heat, differences to non-PMA treated samples tended to slightly increase when amplified fragments in the first round of the nested PCR were longer, whereas the impact of 1st-round cycle numbers remains unclear.

Reduced volatile sulphur compounds generate an impact on the environment, because of the bad smell and its low odour threshold. Compared with the existing physicochemical technologies for their elimination, biotrickling filters are an economically and environmentally sustainable alternative. Usually mixed cultures of microorganisms are used for inoculating biotrickling filters, in this case a pure culture of Thiobacillus thioparus is used for generating a biofilm, allowing to measure its capacity for the oxidation of four volatile reduced sulphur compounds: hydrogen sulphide, dimethyl sulphide, methyl mercaptan and dimethyl disulphide, using a residence time of 0.033 hrs. The viable cells of the biofilm were quantified by epifluorescence microscopy, staining the cells with ethidium bromide and acridine orange, polymerase chain reaction analysis in real time was used for testing the predominance of T. thiopharus in the biofilm. The microorganism was able to adhere and grow on the surface of rings made of polyethylene, with a viable population of 7·10 7 cell·ring -1 , a 74% of total cells. The real time PCR showed a persistence of the population of T. thioparus for more than 300 days of operation, without being displaced by other microbial species. The maximum elimination capacities for each compound were 34.4; 21.8; 30.8 and 25.6 gS·m -3 ·h -1 for H2S, dimethylsulphide, dimethyldisulphide and methyl mercaptan, respectively. We conclude that it is possible to implement a biotrickling filter with the bacteria T. thioparus, which can oxidize volatile reduced sulphur compounds efficiently.

A microbial biofilm is structured mainly by a protective sticky matrix of extracellular polymeric substances. Quantifying such structures is useful for microbiologists and a correct image segmentation process helps substantially reduce errors in quantification. This paper proposes an approach to segmentation of biofilm images using optimal multilevel thresholding and indices of clustering validity. A direct comparison through Rand Index and a quantification process is performed in a laboratory, obtaining results similar to the quantification and segmentation done by an expert.

A microbial biofilm is structured mainly by a protective sticky matrix of extracellular polymeric substances. The appreciation of such structures is useful for the microbiologist and can be subjective to the observer. Thus, quantifying the underlying images in useful parameters by means of an objective image segmentation process helps substantially to reduce errors in quantification. This paper proposes an approach to segmentation of biofilm images using optimal multilevel thresholding and indices of clustering validity. A comparison of automatically segmented images with manual segmentation is done through different thresholding criteria, and clustering validity indices are used to find the correct number of thresholds, obtaining results similar to the segmentation done by an expert.

The effect of pH and organic matter (total organic carbon, TOC) of effluents originating from fishing industries located in Talcahuano, Chile, on the ability to colonize different trophic group methanogenic bacteria (MB) over clay and polyethylene supports was evaluated. Both support materials enhanced all types of methanogenic bacterial growth compared to systems without support. The highest adherence was obtained at pH 8. At 8000 mg/l TOC, this had a significant effect on the growth rate of hydrogenotropic and methylaminotrophic methanogens on polyethylene and clay, respectively.

Toxicity effects produced by kraft mill effluents are due to the productive process. New bleaching processes have been proposed (e.g. total chlorine free, TCF) to reduce the production of toxic chlorine compounds. In the TCF processes large amounts of chelating compounds like the ethylenediaminetetraacetic acid (EDTA) and diethylenetriaminepentaacetic acid (DPTA) are used. The aim of this work is to research the feasibility of the degradation of low-strength synthetic TCF effluents in a anaerobic filter reactor (AF) and the biomass adhesion. The effects on the operation of the AF at different EDTA loading rates were tested in the range from 0.07 to 0.51 g EDTA l(-1) days(-1). The maximum EDTA removal percentage achieved was of 27%. Acute toxicity (measured as 24 h-LC(50)) with Daphnia magna was reduced from 14.23 to 54.53% before and after anaerobic treatment, respectively. Observations of biomass samples from the AF under the scanning microscope verified the attached biomass.

Emissions of hydrogen sulfide (H2S) by industrial activities is frequent cause of corrosion and unpleasant odours. Treatment of gaseous emissions contaminated with H2S by biotrickling filters inoculated with single cultures of sulfur oxidizer bacteria exhibit several advantages over physicochemical methods, such as shorter adaptation times and higher removal ability. Biofilms of Thiobacillus thioparus and Acidithiobacillus thiooxidans have proved to exhibit high removal capacities, yet no comparative studies between them have been reported. This article reports the efficiency of biotrickling filters inoculated with T. thioparus and A. thiooxidans under similar conditions excepting the pH, that was the optimal for the bacterial growth, for the removal of H2S. The support was selected by determining the respirometric coefficients of the biomass. The maximum removal capacity of the biofilter inoculated with T. thioparus, operating within the range of pH (5.5-7.0) was 14 gS m-3 h-1, lower the value obtained for the biotrickling filter inoculated with A. thiooxidans; 370 gS m-3 h-1. Therefore, it is concluded that acid biotrickling filter inoculated with A. thiooxidans constitute the best strategy to remove H2S, with the advantage that the system not require an exhaustive pH control of the liquid media.

We herein report the diversity and relative abundance of chemolithotrophic nitrifying bacteria in a continuous‐flow bioreactor using 16S‐ribosomal RNA quantitative dot‐blot hybridizations. About 14.9% of the total bacterial population, determined by epifluorescence microscopy in the bioreactor suspended phase, was represented by nitrifying bacteria. Of this fraction, ammonia‐ and nitrite‐oxidizing bacteria accounted for 10% and 90%, respectively, the latter group being mostly N/frospira‐like. On the other hand, the nitrifiers adhesion/colonization capacity on polyethylene surfaces as evaluated by scanning electron microscopy and hybridizations analyses was 12.6% of the total bacterial community adhered. Finally, in spite of the relatively small contribution of nitrifiers to the total bacterial abundance in the bioreactor, we determined a mean ammonia removal rate of 170.48 ± 8.29 mg N 11 d1; thus, the low percentage of ammonia‐oxidizing bacteria, was not limiting the bioreactor performance.

Ammonia is a metabolic product in the decomposition of protein wastes, and has a recognized inhibitory effect on methanogenesis; this effect has been slightly quantified on methanogenic biofilms and particularly those populated by methanogenic Archaea which produce ammonia as a catabolic product from methylated amines. This paper presents studies on the effect of ammonia on maximum methanogenic activity of anaerobic biofilms enriched by methylaminotrophic methane producing Archaea (mMPA). The effect of unionized free ammonia on the specific maximum methanogenic activity of a mMPA enriched biofilm was studied, using 250 mL flasks containing ceramic rings colonized by 30 day-old experimental biofilm and adding 48.8 (control system), 73.8, 98.8, 148.8, 248.8, 448.8 and 848.8 mg NH 3 -N/L. The systems were maintained for ten days at a pH of 7.5 and temperature of 37°C. The results showed that at 848.8 mg NH 3 -N/L, biofilm methane production required 36 h adaptation period, prior to entering into maximum production phase. The highest maximum methanogenic activity reached a value of 2.337±0.213 g COD methane/g VSS∗day when 48.8 mg NH 3 -N/L was added, and inhibition was clearly observed in those systems above 148.8 mg NH 3 -N/L, producing under 1.658±0.185 g COD methane/g VSS∗day. The lowest methanogenic activity reached was 0.639±0.162 g COD methane/g VSS∗day at the system added with 848.8 mg NH 3 -N/L. When applying the Luong and non-competitive inhibition models, the best fit was obtained with the non-competitive model, which predicted 50% inhibition of methanogenic activity at 365.288 mg NH 3 -N/L.

Sulphur Oxidizing Bacteria (SOB) is a group of microorganisms widely used for the biofiltration of Total Reduced Sulphur compounds (TRS). TRS are bad smelling compounds with neurotoxic activity which are produced by different industries (cellulose, petrochemical). Thiobacillus thioparus has the capability to oxidize organic TRS, and strains of this bacterium are commonly used for TRS biofiltration technology. In this study, two thiosulphate oxidizing strains were isolated from a petrochemical plant (ENAP BioBio, Chile). They were subjected to molecular analysis by real time PCR using specific primers for T. thioparus . rDNA16S were sequenced using universal primers and their corresponding thiosulphate activities were compared with the reference strain T. thioparus ATCC 10801 in batch standard conditions. Real time PCR and 16S rDNA sequencing showed that one of the isolated strains belonged to the Thiobacillus branch. This strain degrades thiosulphate with a similar activity profile to that shown by the ATCC 10801 strain, but with less growth, making it useful in biofiltration.

A cyanobacterial bloom occurring in 1998 in lake Tres Pascualas (Concepcion/Chile) was found to be dominated by Microcystis sp. The bloom contained both non-toxic (cyanopeptolin-type) and hepatotoxic (microcystin-type) peptides. Cyanopeptolin structure of the non-toxic peptides (called cyanopeptolin VW-1 and VW-2, respectively) was revealed by matrix assisted laser desorption ionization mass spectrometry (MALDI-TOF-MS) of whole cells, showing dominant molecular ions at m/z = 975 and m/z 995, respectively. On post source decay (PSD), both cyanopeptolins showed fragments deriving from Ahp-Phe-MTyr (3-amino-6-hydroxy-2-piperidone), the characteristic partial structure of cyanopeptolins. The amounts of each of the two cyanopeptolins could only roughly be estimated to be >0.1% of bloom material dry weight. In addition the blooms contained microcystins (20 microg/g bloom dry weight as determined by RP-HPLC, 13 microg/g according to ELISA determination). MALDI-TOF-MS revealed several structural variants of microcystin: MCYST-RR (microcystin with Arg and Arg, indicated by m/z 1,038 and confirmed by PSD revealing a m/z = 135 fragment deriving from the Adda side chain, MCYST-FR (microcystin with Phe and Arg, indicated by m/z = 1,015). The presence of [Asp(3)]-MCYST-LR (microcystin with Leu and Arg, Asp non-methylated, indicated by m/z 981), and [Asp(3)]-MCYST-YR (microcystin with Tyr and Arg, Asp non-methylated, indicated by m/z 1,031) were likely. The relative amounts of the peptides varied between February, April, and May. Whole cell extracts from the bloom material revealed specific enzyme inhibitory activities. The serin-proteases trypsin, plasmin, elastase were inhibited, assumable due to the cyanopeptolins found. Elastase and the cysteine-protease papain were not inhibited, inhibitions of protein kinase and glutathione S-transferase (GST) were low. Strong inhibition was observed with protein-phosphatase-1, likely due to the microcystins present in the samples.

Cyanobacterial blooms dominated by Microcystis sp. occurred in lake Rocuant ("marisma", near Concepcion/Chile) in February 1995 and 1996. In the bloom samples collected in both years the hepatotoxin microcystin was detected by RP-HPLC in both samples and in the sample of 1995 also by a toxicity assay using primary rat hepatocytes. In the bloom of 1995, the microcystin content of the dry bloom biomass was determined to be 130 micrograms/g on the basis of the RP-HPLC peak area and 800 micrograms/g on the basis of the rat hepatotoxicity assay, respectively. In the bloom of 1996, RP-HPLC analysis revealed a microcystin content of 8.13 micrograms/g bloom material dry weight. In this year no hepatotoxicity was measured using a concentration range up to 0.8 mg (d. w.) of bloom material per ml in the rat hepatotoxicity assay. This is the first report on the detection of microcystins in Chilean water bodies.

Quorum sensing (QS) is a regulatory mechanism that enables bacteria to make collective decisions such as an increase in virulence factors and biofilm production. Inhibitors of QS are important research tools in the discovery of new potential anti-bacterial agents. Polygodial, drimenol and drimendiol are drimane sesquiterpenoids isolated from Drimys winteri, a Chilean native tree. Their QS activity, when tested on Chromobacterium violaceum ATCC 12472, showed that drimendiol is an inhibitor of QS, decreasing violaceine production in C. violaceum and decreasing biofilm formation of Pseudomonas syringae strains. Consequently it increased the biocide effects of CuSO4 on biofilms of P. syringae.