Autogenic versus environmental control during development of river biofilm

In the natural environment, microbial community structure of river biofilm is controlled by biotic and abiotic factors. This study explored the capacity to manipulate the structure of microbial communities by modifying environmental conditions during the course of biofilm development. River epilithic biofilm was cultivated in situ on artificial substrates placed parallel to river water flow. Substrates were incubated for 3 and 5.5 weeks in river to allow natural biofilm development, at two sites with contrasting physico-chemical characteristics. The first site (Aurade´ , Gers, France) was located in an agricultural watershed basin and the second site (Larroque, Haute-Garonne, France) was located in a forested watershed basin. After 3 weeks of biofilm development, a subset of substrates was collected from one site and transplanted to the second site where they remained for 2.5 further weeks. Epilithic bacterial community structure (at 3 weeks from each site and at 5.5 weeks from biofilms with and without transplantation) was assessed using PCR-DGGE of 16S rDNA fragment. Biofilm biomass was estimated using ash free dry mass (AFDM). After 3 weeks of development, biofilms from the two sites exhibited comparable AFDM values (average of 1.4¡0.2 g.mx2). A difference between the two sites was observed after 5.5 weeks of development: AFDM decreased for biofilms from the agricultural watershed basin (from 1.4 to 0.18 g.mx2) as a consequence of grazing pressure (Bithynia), and increased for biofilms from the forested agricultural watershed (from 1.4 to 2.6 g.mx2). Microbial community analyses revealed a differentiated community structure between biofilms from the different sites and exhibited a change of microbial community structure after 5.5 weeks of biofilm development. These observations confirm a process of ecological succession in microbial communities. Changing the incubation site during biofilm development modified the trajectory of these ecological successions, suggesting that site characteristics mainly conditioned the structure of these microbial communities

Identification and quantification of microbial populations in activated sludge and anaerobic digestion processes

Eight different phenotypes were studied in an activated sludge process (AeR) and anaerobic digester AnD) in a full-scale wastewater treatment plant by means of fluorescent in situ hybridization (FISH) and automated FISH quantification software. The phenotypes were ammonia-oxidizing bacteria, nitrite-oxidizing bacteria, denitrifying bacteria, phosphate-accumulating organisms (PAO), glycogen-accumulating organisms (GAO), sulphate-reducing bacteria (SRB), methanotrophic bacteria and methanogenic archaea. Some findings were unexpected: (a) Presence of PAO, GAO and denitrifiers in the AeR possibly due to unexpected environmental conditions caused by oxygen deficiencies or its ability to survive aerobically; (b) presence of SRB in the AeR due to high sulphate content of wastewater intake and possibly also due to digested sludge being recycled back into the primary clarifier; (c) presence of methanogenic archaea in the AeR, which can be explained by the recirculation of digested sludge and its ability to survive periods of high oxygen levels; (d) presence of denitrifying bacteria in the AnD which cannot be fully explained because the nitrate level in the AnD was not measured. However, other authors reported the existence of denitrifiers in environments where nitrate or oxygen was not present suggesting that denitrifiers can survive in nitrate-free anaerobic environments by carrying out low-level fermentation; (e) the results of this paper are relevant because of the focus on the identification of nearly all the significant bacterial and archaeal groups of microorganisms with a known phenotype involved in the biological wastewater treatment.This study was realized with support from the Universitat Politecnica de Valencia, Universitat de Valencia and CONACYT (National Council of Science and Technology of Mexico).Reyes Sosa, MB.; Borrás Falomir, L.; Seco Torrecillas, A.; Ferrer, J. (2015). Identification and quantification of microbial populations in activated sludge and anaerobic digestion processes. Environmental Technology. 36(1):45-53. doi:10.1080/09593330.2014.934745S455336

Co-existence of physiologically similar sulfate-reducing bacteria in a full-scale sulfidogenic bioreactor fed with a single organic electron donor

A combination of culture-dependent and independent methods was used to study the co-existence of different sulfate-reducing bacteria (SRB) in an upflow anaerobic sludge bed reactor treating sulfate-rich wastewater. The wastewater was fed with ethanol as an external electron donor. Twenty six strains of SRB were randomly picked and isolated from the highest serial dilution that showed growth (i.e. 108). Repetitive enterobacterial palindromic polymerase chain reaction and whole cell protein profiling revealed a low genetic diversity, with only two genotypes among the 26 strains obtained in the pure culture. The low genetic diversity suggests the absence of micro-niches within the reactor, which might be due to a low spatial and temporal micro-heterogeneity. The total 16S rDNA sequencing of two representative strains L3 and L7 indicated a close relatedness to the genus Desulfovibrio. The two strains differed in as many as five physiological traits, which might allow them to occupy distinct niches and thus co-exist within the same habitat. Whole cell hybridisation with fluorescently labeled oligonucleotide probes was performed to characterise the SRB community in the reactor. The isolated strains Desulfovibrio L3 and Desulfovibrio L7 were the most dominant SRB, representing 30–35% and 25–35%, respectively, of the total SRB community. Desulfobulbus-like bacteria contributed for 20–25%, and the Desulfobacca acetoxidans-specific probe targeted approximately 15–20% of the total SRB. The whole cell hybridisation results thus revealed a consortium of four different species of SRB that can be enriched and maintained on a single energy source in a full-scale sulfidogenic reactor

Escalfament global i bacteris marins

1 page, 1 figureLes prediccions més optimistes per a aquest segle estimen increments de 2,5 ºC de temperatura en la superfície dels oceans, fet que implicarà canvis en el metabolisme i la diversitat de les comunitats planctòniques, que es traduirà en alteracions en els fluxos de carboni al mar. Així, petits increments de temperatura poden provocar canvis en l’estructura de les comunitats bacterianes marines i un augment de producció i respiració, fet que afavorirà l’efecte d’hivernaclePeer Reviewe

Goudzoekers, cowboys en vlottrekkers: Haagse wijkambtenaren in tussenfuncties

Dit artikel biedt een tussenstand van een lopend onderzoek naar het functioneren van de wijkteams die vorm gaven aan de eerste fase van het Haagse krachtwijkenbeleid. De focus ligt op het professionele handelen van ambtenaren met ‘één been in het stadhuis en één been in de wijk’. Als conceptueel kader maak ik gebruik van het concept tussenfuncties, gedefinieerd als functies binnen de organisatie van de bureaucratie die niet passen bij de logica van diezelfde bureaucratie. In de zoektocht naar wat dit bewegen tussen verschillende schurende logica’s vraagt van de vakbekwaamheid van deze ambtenaren, biedt het concept praktische wijsheid goede handvatten. Waar competenties al snel ‘ontaarden’ in mechanische, gestandaardiseerde lijstjes, verlegt praktische wijsheid de focus naar persoonlijke capaciteiten die succesvol handelen in een specifieke werkpraktijk mogelijk maken en die in die praktijk verder ontwikkeld kunnen worden. Abstract This article provides an intermediate report on an ongoing research into the functioning of teams of community civil servants who implemented the first phase of the krachtwijken (power neighbourhoods) policy in the city of The Hague in which the focus is on the professional skills of civil servants who work with ‘one foot in city hall and one foot in the community’. As a conceptual framework, I used the concept of a tussenfunctie, (in-between position) defined as position within the organisation of a bureaucracy that does not fit the logic of that bureaucracy. In the search for what this moving back and forth between different logics requires from these civil servants in terms of professional expertise, the concept of practical wisdom is useful. Whereas the use of competencies easily degenerates into mechanical one-size-fits-all lists, practical wisdom shifts the focus to personal capabilities that enable one to deal successfully with specific situations and that can be developed by acquiring hands-on experience