Advanced biofilm analysis in streams receiving organic deicer runoff.

Prolific heterotrophic biofilm growth is a common occurrence in airport receiving streams containing deicers and anti-icers, which are composed of low-molecular weight organic compounds. This study investigated biofilm spatiotemporal patterns and responses to concurrent and antecedent (i.e., preceding biofilm sampling) environmental conditions at stream sites upstream and downstream from Milwaukee Mitchell International Airport in Milwaukee, Wisconsin, during two deicing seasons (2009-2010; 2010-2011). Biofilm abundance and community composition were investigated along spatial and temporal gradients using field surveys and microarray analyses, respectively. Given the recognized role of Sphaerotilus in organically enriched environments, additional analyses were pursued to specifically characterize its abundance: a consensus sthA sequence was determined via comparison of whole metagenome sequences with a previously identified sthA sequence, the primers developed for this gene were used to characterize relative Sphaerotilus abundance using quantitative real-time PCR, and a Sphaerotilus strain was isolated to validate the determined sthA sequence. Results indicated that biofilm abundance was stimulated by elevated antecedent chemical oxygen demand concentrations, a surrogate for deicer concentrations, with minimal biofilm volumes observed when antecedent chemical oxygen demand concentrations remained below 48 mg/L. Biofilms were composed of diverse communities (including sheathed bacterium Thiothrix) whose composition appeared to shift in relation to antecedent temperature and chemical oxygen demand. The relative abundance of sthA correlated most strongly with heterotrophic biofilm volume (positive) and dissolved oxygen (negative), indicating that Sphaerotilus was likely a consistent biofilm member and thrived under low oxygen conditions. Additional investigations identified the isolate as a new strain of Sphaerotilus montanus (strain KMKE) able to use deicer components as carbon sources and found that stream dissolved oxygen concentrations related inversely to biofilm volume as well as to antecedent temperature and chemical oxygen demand. The airport setting provides insight into potential consequences of widescale adoption of organic deicers for roadway deicing.

Use of an aerobic selector to overcome filamentous bulking in an activated sludge wastewater treatment plant.

An urban wastewater treatment plant (WWTP) with two different parallel lines of treatment and located in the north of Portugal was studied during four months, following recurrent episodes of filamentous bulking caused by Sphaerotilus natans and eventual occurrences of Nocardioforms and Type 1863. An aerobic selector was introduced in both lines in the beginning of the studied period, suppressed in one of the lines during six weeks, and then put into operation again until the end of the study. A total of 14 filamentous bacteria morphotypes were identified. The results showed that the presence of an aerobic biological selector in continuous operation prevented the overgrowth of the filamentous Type 1863, of Nocardioforms and, in particular, of S. natans. Simultaneously, it allowed lowering the oxygen levels in the aeration tanks without negative consequences in the overall performance of the WWTP, namely bulking occurrence. Dissolved oxygen (DO) in the aeration tank varied initially between 2 and 3 mg/L, but the introduction of the selector enabled to lower it to 1-1.5 mg/L in the aeration tank and around 0.5 mg/L in the selector. A significant energy save was allowed, even considering the aeration of the selector. The results are more relevant if one considers the fact that the main cause of the bulking problems in this WWTP was the overgrowth of S. natans, a filamentous bacterium known to be stimulated by low DO levels.

[Ecophysiology of lithotrophic sulfur-oxidizing Sphaerotilus species from sulfide springs in the Northern Caucasus].

Six strains of sulfur-oxidizing bacteria of the known organotrophic species Sphaerotilus natans were isolated from two North Caucasian sulfide springs. Similar to known colorless sulfur bacteria, all the strains accumulated elemental sulfur when grown in media with sulfide. Unlike previously isolated S. natans strains, new isolates had higher temperature growth optima (33-37 degrees C) and variable metabolism. All the strains were capable of organotrophic, lithoheterotrophic, and mixotrophic growth with sulfur compounds as electron donors for energy metabolism. Variable metabolism of new Sphaerotilus isolates is a highly important adaptation mechanism which facilitates extension of their geographic range and supports their mass development in new habitats, e.g. sulfide springs. Within the cluster of new isolates, the physiological heterogeneity was shown to result from the inducible nature of the enzymes of oxidative sulfur metabolism and from their resistance to aerobic cultivation.

Inhibitory effect of a surfactant on pure cultures of a filamentous and a floc forming micro-organism.

Activated sludge is the most widely used biological process for wastewater treatment. Inorganic and organic compounds are removed by a biotic community in the aeration basin. Problems of these systems are loss of settleability and poor sludge compaction due to excessive growth of filamentous micro-organisms. The filamentous bulking can be controlled by the addition of chemical agents. Strong oxidants, such as chlorine, are utilized to eliminate filamentous bacteria; however, these substances also tend to attack floc-forming bacteria and to cause process breakdown. Besides, chlorine may become hazardous owing to the formation of chemical products as chloramines. Surfactant addition constitutes an interesting alternative for the control of filamentous bulking. In this work the effect of a surfactant Triton X-100 (octylphenol ethoxylate), on the respiratory activity (RA) of pure cultures of a filamentous (Sphaerotilus natans) and a floc-former microorganism (Acinetobacter anitratus) was evaluated. In the concentration range tested (60-220 mg l(-1)), the surfactant was observed to exhibit high RA specific inhibition of the filamentous micro-organism with no significant effect on the floc-forming bacteria. Light microscopy observations showed that the surfactant induced cell lysis, leaving only empty sheaths in the case of filamentous micro-organisms. A kinetic equation to predict the microbial RA fraction of a S. natans pure culture as a function of surfactant concentration and contact time was proposed. The effect of Triton X-100 on the inactivation of pure cultures of both micro-organisms was compared to that of chlorine. Triton X-100 results were adequate to eliminate filamentous bacteria emerging as an alternative for filamentous bulking treatment.

Effects of fatty acids on growth and poly-3-hydroxybutyrate production in bacteria.

The effects of saturated and unsaturated fatty acids (lauric acid, palmitic acid, steric acid, oleic acid, linoleic acid, soybean oil) on Sphaerotilus natans, 0B17 (Pseudomonas sp.), and recombinant Escherichia coli DH5(/pUC19/CAB were studied. Oleic acid enhances Poly-3-hydroxybutyrate (PHB) production in these three bacterial strains, suggesting that the single double bond of the acid activates the polyhydroxylkanoate accumulation enzymatic reaction. Under the effect of lauric acid and linoleic acid, the growth of S. natans and 0B17 were totally inhibited. However, the enhanced PHB accumulation in recombinant E. coli was observed.

Modelling of the acid-base properties of natural and synthetic adsorbent materials used for heavy metal removal from aqueous solutions.

In this paper a comparison about kinetic behaviour, acid-base properties and copper removal capacities was carried out between two different adsorbent materials used for heavy metal removal from aqueous solutions: an aminodiacetic chelating resin as commercial product (Lewatit TP207) and a lyophilised bacterial biomass of Sphaerotilus natans. The acid-base properties of a S. natans cell suspension were well described by simplified mechanistic models without electrostatic corrections considering two kinds of weakly acidic active sites. In particular the introduction of two-peak distribution function for the proton affinity constants allows a better representation of the experimental data reproducing the site heterogeneity. A priori knowledge about resin functional groups (aminodiacetic groups) is the base for preliminary simulations of titration curve assuming a Donnan gel structure for the resin phase considered as a concentrated aqueous solution of aminodiacetic acid (ADA). Departures from experimental and simulated data can be interpreted by considering the heterogeneity of the functional groups and the effect of ionic concentration in the resin phase. Two-site continuous model describes adequately the experimental data. Moreover the values of apparent protonation constants (as adjustable parameters found by non-linear regression) are very near to the apparent constants evaluated by a Donnan model assuming the intrinsic constants in resin phase equal to the equilibrium constants in aqueous solution of ADA and considering the amphoteric nature of active sites for the evaluation of counter-ion concentration in the resin phase. Copper removal outlined the strong affinity of the active groups of the resin for this ion in solution compared to the S. natans biomass according to the complexation constants between aminodiacetic and mono-carboxylic groups and copper ions.