The role of intercellular signalling in the regulation of genes and phenotypes in a broad range of bacterial species is now firmly established. In contrast, the impact of intercellular signalling on microbial community parameters, such as species diversity and function, is less well understood. In this study the role of N-acyl-l-homoserine lactones (AHLs) in microbial community dynamics in an industrial wastewater treatment system is addressed. Seven proteobacterial strains producing compounds with AHL-like activity were isolated from the treatment plant. Three of these belong to genera with no previously identified AHL producing species. Addition of AHLs at 2 micro M to sludge samples generated changes in both community function (phenol degradation) and composition as determined by length heterogeneity PCR and denaturing gradient gel electrophoresis. Phenol degradation was more stable as a result of the AHL augmentation. A dominant functional member of the Thauera genus was transiently supplanted by a member of the Comomonas genus in response to AHL addition. This suggests that AHLs can play a role in mediating microbial community parameters and has implications for ecosystem function and industrial wastewater treatment.

Aims:  This research focused on the effects of low electric current (LEC) on the cell viability and metabolic activity of Escherichia coli and Bacillus cereus. Methods and Results:  Different LEC intensities at fixed amperage were applied, employing either graphite or copper electrode pairs, and the effects were determined by conventional cultural methods and bioindicators. On E. coli, the LEC with graphite electrodes at 5 and 10 mA led to no significant variation, but at 20 and 40 mA there was increasing inhibition of both the enzymatic activities and growth, and a reduction in ATP content. On B. cereus, similar experiments at the lower amperages did not have any inhibitor effects, however, the 40 mA current stimulated growth, ATP content and some enzymatic activities. The LEC treatment using copper electrodes caused, already at 5 mA, inhibition of bacterial growth and metabolic and enzymatic activities in both E. coli and B. cereus. Conclusions:  On the basis of the obtained results using different amperages and electrodes, we can conclude that E. coli seem to be more sensitive compared with B. cereus. Significance and Impact of the Study:  The study increases the knowledge on LEC treatment effects on the pure bacterial cultures.

Two sulfonylurea herbicides, chlorsulfuron and metsulfuron-methyl, were studied under laboratory conditions, in order to elucidate the biodegradation pathway operated by Aspergillus niger, a common soil fungus, which is often involved in the degradation of xenobiotics. HPLC-UV was used to study the kinetic of degradation, whereas LC-MS was used to identify the metabolites structure. In order to avoid the chemical degradation induced by a decrease in pH, due to the production of citric acid by the fungus, the experiments were performed in a buffered neutral medium. No significant degradation for both compounds was observed in mineral medium with 0.2% sodium acetate. On the contrary, in a rich medium, after 28 days the degradations, chemical degradation excluded, were about 30% for chlorsulfuron and 33% for metsulfuron-methyl. The main microbial metabolites were obtained via cleavage of the sulfonylurea bridge. In addition the fungus seems to be able to hydroxylate the aromatic ring of chlorsulfuron. In the case of metsulfuron-methyl the only detected metabolite was the triazine derivative, while the aromatic portion was completely degraded. Finally, the demethylation of the methoxy group on the triazine ring, previously observed with a Pseudomonas fluorescens strain, was not observed with A. niger.

Aims:  Azimsulfuron is a recently introduced sulfonylurea herbicide useful in controlling weeds in paddy fields. To date very little information is available on the biodegradation of this pesticide and on its effect on the soil microbial community. The aim of this work was to study its biodegradation both in slurry soil microcosms and in batch tests with mixed and pure cultures. Methods and Results:  Azimsulfuron was applied to forest bulk soil in order to study its effect on the structure of the bacterial soil community, as detectable by denaturant gradient gel electrophoresis (DGGE) analyses. Biodegradation and abiotic processes were investigated by HPLC analyses. In addition, a microbial consortium was selected, that was able to use azimsulfuron as the sole energy and carbon source. One of the metabolites produced by the consortium was isolated and identified through LC‐MS analyses. Cultivable bacteria of the consortium were isolated and identified by 16S rDNA sequencing (1400 bp). Conclusions:  Azimsulfuron treatment seems to have the ability to cause changes in the bacterial community structure that are detectable by DGGE analyses. It is easily biodegraded both in microcosms and in batch tests, with the formation of an intermediate that was identified as 2‐methyl‐4‐(2‐methyl‐2H‐tetrazol‐5‐yl)‐2H‐pyrazole‐3‐sulfonamide. Significance and Impact of the Study:  The study increases the knowledge on the biodegradation of azimsulfuron and its effects on the soil microbiota.

Animal, civil and industrial waste matter is a source of potential chemical, microbiological and air pollutants. In populated areas the presence of faecal bacteria and the production of malodorous compounds during waste storage and in the tanks of wastewater treatment plants, can cause concern. The general aim of the work was to study electrolytic waste treatment (recently applied on animal slurry) using low electric current across graphite and copper electrodes, determining its effect on the microflora of sludge, collected from the equalisation basin of an industrial aerobic wastewater treatment plant, and on odour emission abatement. Biochemical and enzymatic indicators like ATP content and a pool of 19 enzymatic activities were tested, comparing them with viable cell counts by traditional microbiological methods, to verify the validity of such indicators in monitoring the electrolytic treatment and to assess their correlation with odour reduction. The preliminary results of our laboratory-scale trials showed that in the presence of inert electrodes, such as graphite, metabolic activity is stimulated, whereas with copper electrodes the ATP content and some enzymatic activities are inhibited quite considerably after only four days, this being accompanied by a marked reduction in odour. Consideration was also given to the total copper released from the electrodes and its recovery using iron electrodes.