Utjecaj diklofenaka na bakterijsku populaciju aktivnog mulja u reaktoru s pritokom supstrata

Research background. The occurrence and environmental toxicity of pharmaceuticals have recently attracted increasing attention. Diclofenac is a highly consumed non-steroidal anti-inflammatory drug, which is often detected in wastewaters, but investigations of its influence on bacteria are scarce. Experimental approach. We investigated the influence of this pharmaceutical on bacterial community in activated sludge exposed to increasing concentrations of diclofenac in fed-batch reactors over 41 days. Nitrification activity of the activated sludge was measured and changes in bacterial community structure were followed using culture-independent molecular method (terminal restriction fragment length polymorphism, T-RFLP) and by the cultivation approach. Results and conclusions. Nitrification activity was not detectably influenced by addition of diclofenac, while the main change of the bacterial community structure was detected only at the end of incubation (after 41 days) when diclofenac was added to artificial wastewater as the only carbon source. Changes in community composition due to enrichment were also observed using cultivation approach. However, taxonomic affiliation of isolates did not match taxons identified by T-RFLP community profiling. Isolates obtained from inoculum activated sludge belonged to five genera: Comamonas, Arthrobacter, Acinetobacter, Citrobacter and Aeromonas, known for their potential to degrade aromatic compounds. However, only Pseudomonas species were isolated after the last enrichment step on minimal agar plates with diclofenac added as the sole carbon source. Novelty and scientific contribution. Our results suggested that the selected recalcitrant and commonly detected pharmaceutical does not strongly influence the sensitive and important nitrification process of wastewater treatment neither. Moreover, the isolated strains obtained after enrichment procedure that were able to grow on minimal agar plates with diclofenac added as the only carbon source could serve as potential model bacteria to study bacterial diclofenac degradation.Pozadina istraživanja. U zadnje vrijeme prisutnost i toksičnost farmaceutskih proizvoda u okolišu pobuđuju veliki interes javnosti. Diklofenak je nesteroidni protuupalni lijek koji se uvelike koristi, pa često dospijeva u otpadne vode, no usprkos tome postoji vrlo malo istraživanja o njegovom utjecaju na bakterije aktivnog mulja. Eksperimentalni pristup. Ispitali smo utjecaj ovog lijeka na bakterijsku populaciju aktivnog mulja u reaktoru s pritokom supstrata kojem smo dodavali diklofenak tijekom 41 dana. Izmjerena je nitrifikacijska aktivnost bakterija aktivnog mulja, a promjena sastava bakterijske populacije praćena je molekularnom metodom za izravnu identifikaciju (T-RFLP) te uzgojem bakterija. Rezultati i zaključci. Dodatak diklofenaka nije vidljivo utjecao na nitrifikacijsku aktivnost bakterija, a veća je promjena sastava bakterijske populacije opažena tek na kraju inkubacije (nakon 41 dana), kad je diklofenak bio dodan kao jedini izvor ugljika u otopinu koja simulira sastav otpadnih voda. Promjene sastava bakterijske populacije nakon obogaćivanja podloge diklofenakom primijećene su nakon izolacije i praćenja rasta bakterija na minimalnoj podlozi. Međutim, taksonomska pripadnost izolata nije odgovarala taksonima identificiranim metodom T-RFLP. Izolati dobiveni iz aktivnog mulja te korišteni kao inokulum spadali su u pet rodova bakterija: Comamonas, Arthrobacter, Acinetobacter, Citrobacter i Aeromonas, koje su poznate po sposobnosti razgradnje aromatskih spojeva. Međutim, nakon posljednjeg dodatka diklofenaka kao jedinog izvora ugljika minimalnoj podlozi izolirane su jedino bakterije vrste Pseudomonas. Novina i znanstveni doprinos. Rezultati pokazuju da ispitani lijek, koji ima ograničenu biorazgradivost a često ga nalazimo u otpadnim vodama, ne utječe u velikoj mjeri na osjetljiv i bitan postupak nitrifikacije otpadnih voda. Osim toga, zaključeno je da izolirani sojevi bakterija koji su rasli na minimalnoj podlozi s diklofenakom kao jedinim izvorom ugljika mogu poslužiti kao model za proučavanje bakterijske razgradnje diklofenaka

Učinak statičkog magnetskog polja male gustoće na oksidaciju amonijaka s pomoću bakterije Nitrosomonas europaea i aktivnog mulja u komunalnim otpadnim vodama

Ammonium removal is a key step in biological wastewater treatment and novel approaches that improve this process are in great demand. The aim of this study is to test the hypothesis that ammonium removal from wastewater can be stimulated by static magnetic fields. This was achieved by analysis of the eff ects of static magnetic field (SMF) on the growth and activity of Nitrosomonas europaea, a key ammonia-oxidising bacterium, where increased growth and increased ammonia oxidation rate were detected when bacteria were exposed to SMF at 17 mT. Additionally, the eff ect of SMF on mixed cultures of ammonia oxidisers in activated sludge, incubated in sequencing batch bioreactors simulating wastewater treatment process, was assessed. SMFs of 30 and 50 mT, but not of 10 mT, increased ammonium oxidation rate in municipal wastewater by up to 77 % and stimulated ammonia oxidiser growth. The results demonstrate the potential for use of static magnetic fields in increasing ammonium removal rates in biological wastewater treatment plants.Uklanjanje amonijaka je ključni korak u biološkom pročišćavanju otpadnih voda. Potražnja za novim pristupom koji bi poboljšao ovaj proces sve je veća. Svrha je našeg istraživanja bila provjeriti pretpostavku da se uklanjanje amonijaka iz otpadnih voda može stimulirati pomoću statičkog magnetskog polja. Ispitan je učinak statičkog magnetskog polja na rast i aktivnost nitrificirajuće bakterije Nitrosomonas europaea, koja oksidira amonijak u biološkom procesu pročišćavanja otpadnih voda. Otkriveno je da se izlaganjem te bakterije statičkom magnetskom polju jačine 17 mT ubrzao rast bakterija i pospješila oksidacija amonijaka. Osim toga, izmjeren je učinak statičkog magnetskog polja na amonijak-oksidirajuće bakterije koje se nalaze u aktivnom mulju izdvojenom iz postrojenja za pročišćavanje otpadnih voda. Aktivni mulj je inkubiran u sekvencijalnim šaržnim reaktorima, koji simuliraju proces pročišćavanja otpadnih voda. Primjena statičkog magnetskog polja jačine 30 i 50 mT, no ne i 10 mT, pojačala je oksidaciju amonijaka u komunalnim otpadnim vodama do 77 %, te stimulirala rast amonijak-oksidirajućih bakterija. Rezultati istraživanja pokazuju da se pomoću statičkog magnetskog polja može povećati stupanj uklanjanja amonijaka u postrojenjima za biološko pročišćavanje otpadnih voda

Microbial Community Structure and Function in Peat Soil

Mnoga su tresetišta u Europi izlagana melioraciji i odvodnji, što je dovelo do promjena u procesima kruženja hranjivih tvari u tlu. Ovaj je rad sažetak objavljenih studija o mikrobnim procesima vezanim uz transformaciju ugljika i dušika u tlu Ljubljanskog barja. To je drenirano tresetište, smješteno nedaleko od Ljubljane, glavnoga grada Slovenije, poznato po bogatstvu biljnog i životinjskog svijeta. U radu je po prvi put dan širi pregled raznolikosti zajednice bakterija i arheja u tom organskoj tvari bogatom tlu, koje je izvor stakleničkih plinova, dušikovog oksida i ugljikovog dioksida, te ponor metana. U Ljubljanskom je barju metanogeneza ograničena velikim udjelom željeza, koje konkurira ostalim akceptorima elektrona. Osim toga, tlo je bogato vrlo aktivnim metanotrofima, naročito u slojevima tla s promjenjivom razinom podzemne vode. Denitrifikacija je ograničena akceptorima elektrona, a u dubljim slojevima tla i manjkom ugljičnih supstrata dostupnih za mikrobiološku razgradnju. Nitrifikacija je tla posljedica aktivnosti bakterija i arheja koje oksidiraju amonijak, pa je stupanj oksidacije amonijaka u Ljubljanskom barju među najvišim u svijetu. Zanimljivo, arheje iz odjeljka Thaumarchaeota u kiselim tresetištima uspijevaju samo na amonijaku što potječe iz organskog izvora i ne mogu oksidirati amonijak iz mineralnog izvora. U tlima je Ljubljanskoga barja pronađeno veliko bogatstvo gena što kodiraju bakterijske oksidoreduktaze slične lakazama. Uloga je tih enzima uglavnom nepoznata, a prema spoznajama o lakazama iz gljiva može se zaključiti da bakterijski enzimi sudjeluju u degradaciji lignina, oksidaciji različitih aromatskih i fenolnih spojeva, te oksidaciji metala. Budući su izazovi u ovom području istražiti specifične fiziološke uloge fenolnih oksidaza i ostalih enzima što sudjeluju u transformaciji tresetišta. Naše je poznavanje različitosti mikroorganizama u tresetištima, njihove funkcije i utjecaja na ekosustav još uvijek ograničeno, iako neophodno za učinkovito održavanje tresetišta, tih izvanrednih, ekološki značajnih, no osjetljivih staništa.Many peatlands in Europe have been subjected to land reclamation and systematic drainage, which have substantially affected nutrient cycles in the soil. This work reviews published studies on microbial processes linked to carbon and nitrogen transformations in the soils of the Ljubljana marsh, a drained peatland positioned close to Ljubljana, the capital of Slovenia. This region is known for its dramatic diversity of animal and plant life, but below ground it hides diverse bacterial and archaeal communities that are highly responsive to environmental changes and make the Ljubljana marsh soils a good source of N2O and CO2, and a sink for CH4. Methanogenesis is highly restricted in these soils due to competition for electron donors with iron reducers. In addition, methane is efficiently removed by methanotrophs, which are highly active, especially in the soil layers exposed to the changing water table. Denitrification is limited by electron acceptors and in deeper soil layers also by carbon, which becomes more recalcitrant with depth. Nitrification involves bacterial and archaeal ammonia oxidisers with ammonia oxidation rates being among the highest in the world. Interestingly, ammonia-oxidising Thaumarchaeota in acidic bog soils thrive only on ammonia released through mineralisation of organic matter and are incapable of oxidising added mineral ammonia. The soils of the Ljubljana marsh are rich in bacterial laccase-like genes, which may encode enzymes involved in lignin degradation and are therefore interesting for bioexploitations. Future challenges involve designing studies that will reveal specific physiological functions of phenol oxidases and other enzymes involved in peat transformations and address relations between microbial diversity, function and ecosystem responses to anthropogenic disturbances

Effect of Low-Density Static Magnetic Field on the Oxidation of Ammonium by Nitrosomonas europaea and by Activated Sludge in Municipal Wastewater

Ammonium removal is a key step in biological wastewater treatment and novel approaches that improve this process are in great demand. The aim of this study is to test the hypothesis that ammonium removal from wastewater can be stimulated by static magnetic fields. This was achieved by analysis of the eff ects of static magnetic field (SMF) on the growth and activity of Nitrosomonas europaea, a key ammonia-oxidising bacterium, where increased growth and increased ammonia oxidation rate were detected when bacteria were exposed to SMF at 17 mT. Additionally, the eff ect of SMF on mixed cultures of ammonia oxidisers in activated sludge, incubated in sequencing batch bioreactors simulating wastewater treatment process, was assessed. SMFs of 30 and 50 mT, but not of 10 mT, increased ammonium oxidation rate in municipal wastewater by up to 77 % and stimulated ammonia oxidiser growth. The results demonstrate the potential for use of static magnetic fields in increasing ammonium removal rates in biological wastewater treatment plants

Kin discrimination modifies strain distribution, spatial segregation and incorporation of extracellular matrix polysaccharide mutants of Bacillus subtilis strains into mixed floating biofilms

Microorganisms in nature form multicellular groups called biofilms. In biofilms, bacteria embedded in the extracellular matrix (ECM) interact intensely due to their proximity. Most studies have investigated genetically homogeneous biofilms, leaving a gap in knowledge on genetically heterogeneous biofilms. Recent insights show that a Gram-positive model bacterium, Bacillus subtilis, discriminates between strains of high (kin) and low (nonkin) genetic similarity, reflected in merging (kin) and boundaries (nonkin) between swarms. However, it is unclear how kinship between interacting strains affects their fitness, the genotype assortment, and incorporation of the mutant lacking the main structural ECM polysaccharide (EpsA-O) into floating biofilms (pellicles). We cultivate Bacillus subtilis strains as mixtures of isogenic, kin and nonkin strain combinations in the biofilm-promoting medium (MSgg) in static conditions, allowing them to form pellicles. We show that in nonkin pellicles, the dominant strain strongly reduced the frequency of the other strain. Segregation of nonkin mixtures in pellicles increased and invasion of nonkin EpsA-O-deficient mutants into pellicles decreased compared to kin and isogenic floating biofilms. Kin and isogenic strains had comparable relative frequencies in pellicles and showed more homogenous cell mixing. Overall, our results emphasize kin discrimination as a social behavior that shapes strain distribution, spatial segregation and ECM mutant ability to incorporate into genetically heterogenous biofilms of B. subtili