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Research background. In recent decades, laccases (p-diphenol-dioxygen oxidoreductases; EC 1.10.3.2) have attracted the attention of researchers due to their wide range of biotechnological and industrial applications. Laccases can oxidize a variety of organic and inorganic compounds, making them suitable as biocatalysts in biotechnological processes. Even though the most traditionally used laccases in the industry are of fungal origin, bacterial laccases have shown an enormous potential given their ability to act on several substrates and in multiple conditions. The present study aims to characterize a plasmid-encoded laccase-like multicopper oxidase (LMCO) from Ochrobactrum sp. BF15, a bacterial strain previously isolated from polluted soil. Experimental approach. We used in silico profile hidden Markov models to identify novel laccase-like genes in Ochrobactrum sp. BF15. For laccase characterization, we performed heterologous expression in Escherichia coli, purification and activity measurement on typical laccase substrates. Results and conclusions. Profile hidden Markov models allowed us to identify a novel LMCO, named Lac80. In silico analysis of Lac80 revealed the presence of three conserved copper oxidase domains characteristic of three-domain laccases. We successfully expressed Lac80 heterologously in E. coli, allowing us to purify the protein for further activity evaluation. Of thirteen typical laccase substrates tested, Lac80 showed lower activity on 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS), pyrocatechol, pyrogallol and vanillic acid, and higher activity on 2,6-dimethoxyphenol. Novelty and scientific contribution. Our results show Lac80 as a promising laccase for use in industrial applications. The present work shows the relevance of bacterial laccases and highlights the importance of environmental plasmids as valuable sources of new genes encoding enzymes with potential use in biotechnological processes., Pozadina istraživanja. Posljednjih su desetljeća lakaze (p-difenol:dioksigen oksidoreduktaze; EC 1.10.3.2) privukle pažnju znanstvenika zbog raznolikosti moguće primjene u biotehnologiji i industriji. Lakaze mogu oksidirati različite organske i anorganske spojeve u biokatalizatore prikladne za biotehnološke procese. Iako se u industriji najčešće koriste lakaze iz plijesni, lakaze iz bakterija pokazale su veliki potencijal primjene jer djeluju na više raznih supstrata u različitim uvjetima. Svrha je ovoga rada bila opisati plazmidno kodiranu višebakrenu oksidazu sličnu lakazama iz bakterije Ochrobactrum sp. BF15, prethodno izolirane iz zagađenog tla. Eksperimentalni pristup. Za identifikaciju novih gena za oksidazu sličnu lakazi u bakteriji Ochrobactrum sp. BF15 koristili smo in silico profil skrivenih Markovljevih modela. Da bismo okarakterizirali lakazu, proveli smo heterolognu ekspresiju gena u bakteriji Escherichia coli, pročistili enzim i mjerili njegovu aktivnost u supstratima karakterističnim za lakazu. Rezultati i zaključci. Dobiveni profili skrivenih Markovljevih modela omogućili su identifikaciju nove oksidaze slične lakazi, koju smo nazvali Lac80. In silico analiza nove Lac80 pokazala je prisutnost triju konzerviranih domena bakrene oksidaze karakterističnih za lakaze s tri domene. Uspješno smo proveli heterolognu ekspresiju Lac80 u E. coli, čime nam je omogućeno pročišćavanje proteina za daljnju analizu aktivnosti. Od trinaest ispitanih supstrata tipičnih za lakazu, Lac80 je imao slabiju aktivnost u 2,2’-azino-bis(3-etilbenzotiazolin-6-sulfonskoj kiselini) (ABTS), pirokateholu, pirogalolu i vanilinskoj kiselini, te veću aktivnost u 2,6-dimetoksifenolu. Novina i znanstveni doprinos. Dobiveni rezultati pokazuju da Lac80 može imati obećavajuću primjenu u industriji. U ovom je radu prikazan značaj lakaza iz bakterija te je naglašena važnost plazmida izoliranih iz okoliša kao vrijednih izvora novih gena koji kodiraju enzime za primjenu u biotehnološkim procesi

Genetic competence for the uptake and integration of extracellular DNA is a key process in horizontal gene transfer (HGT), one of the most powerful forces driving the evolution of bacteria. In several species, development of genetic competence is coupled with cell lysis. Using Bacillus subtilis as a model bacterium, we studied the role of surfactin, a powerful biosurfactant and antimicrobial lipopeptide, in genetic transformation. We showed that surfactin itself promotes cell lysis and DNA release, thereby promoting HGT. These results, therefore, provide evidence for a fundamental mechanism involved in HGT and significantly increase our understanding of the spreading of antibiotic resistance genes and diversification of microbial communities in the environment.