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Bioplin nastaje procesom anaerobne pretvorbe organskih materijala uz prisustvo anaerobnih organizama. Jedno od biotehnoloških rješenja za proizvodnju bioplina su reaktori s aktivnim muljem koji koriste poljoprivrednu energetsku kulturu Miscanthus x giganteus kao alternativnu sirovinu kukuruznoj silaži. Cilj rada je bioaugmentirati reaktore za proizvodnju bioplina s ciljem povećanja njihove učinkovitosti. Bakterije koje smo uspjeli izolirati iz aktivnog mulja koristile su M. giganteus kao jedini izvor ugljika. Nakon izolacije bakterije uspješno su se imobilizirale na perlit biofilmom te tako su tvorile biočestice. Postavljanjem 9 različitih bioreaktora i njihovim praćenjem proizvodnje bioplina ukazalo se da nema značajnih razlika u proizvodnji bioplina između reaktora s biočesticama, bakterijskom suspenzijom i aktivnog mulja s dodatkom M. giganteus. Predlaže se daljnje i opširnije istraživanje s više replika te s različitim koncentracijama biočestica, da bi se vidjelo može li se povećati prinos bioplina u nekoj drugoj konfiguraciji, ili možda da se poveća stabilnost različitih bioreaktora. Biogas is produced during the process of anaerobic conversion of organic materials in the presence of anaerobic organisms. A biotechnological solution for biogas production is active sludge reactor using the agricultural energy crop Miscanthus x giganteus as an alternative raw material to corn silage. The aim of this paper is to bioaugment production reactors biogas in order to increase their efficiency. Successfully isolating the bacteria from activated sludge required using M. giganteus as the only carbon source. After isolating the bacteria, they were successfully immobilized on perlite using biofilm and subsequently formed bioparticles. Setting 9 different bioreactors and monitoring biogas production indicated that there are no significant differences in biogas production between bioparticle reactors, bacterial suspension and activated sludge with added M. giganteus. The recommendation is to undertake further and more extensive research with more replications and different concentrations of bioparticles, in order to ascertain whether biogas can be increased in another configuration, or perhaps increase the stability of different types of bioreactors.

Biofilm se najčešće opisuje kao zajednica mikroorganizama pričvršćenih na podlogu i uklopljenih u matriks izvanstanične polimerne tvari (engl. extracellular polymeric su bstance, EPS ). Pokretljivost je ključna za razne oblike bakterijskog ponašanja kao što je virulencija, kolonizacija novih staništa pa tako i stvaranje biofilma. S obzirom da se infekcije uzrokovane biofilmom puno teže liječe zbog veće rezistenc ije na antim ikrobnu terapiju, istraživanja na području biofilma i bakterijske pokretljivosti mogu dati vrlo korisne informacije za formiranje strategija kontrole bakterijskih infekcija. Za istraživanje su korištene bakterije Acinetobacter baumannii i Bacil lus cereus . Cilj istraživanja bio je pobliže istražiti oblik bakterijske pokretljivosti, pri kojoj bakterijske stanice migriraju iz biofilma formiranog na sučelju zraka i tekućine vertikalno gore po čvrstoj, inertnoj staklenoj površini koja nije bila u dot icaju s hran jivim medijem. Za vizualizaciju bakterija, preparati su se bojili Alcian blue metodom. Zaključeno je da viša koncentracija bakterija pogoduje bržem i snažnijem formiranju biofilma te da biofilm prethodi i posreduje u napredovanju bakterija. Tak ođer, zaklju čeno je da napredovanje bakterija putem biofilma omogućuju kapilarne sile i aktivni oblici bakterijske pokretljivosti. Biofilm is most commonly described as a consortium of microorganisms attached to a solid surface and incorporated into an extracellular polymeric substance. Mobility is crucial for various forms of bacter ial behavior such as v irulence, colonization of new habitats and thus biofilm formation. Given that biofilm infections are much more difficult to treat because of their high er resistance to antimicrobial therapy, research on biofilm and bacterial motility can provide very usef ul information for developing bacterial infection control strategies. In this research, bacteria Acinetobacter baumannii and Bacillus cereus were used. The goal of the study was to investigate more closely the form of bacterial motili ty, in which bacterial cells migrate from the biofilm formed at the air liquid interface vertically upwards over a solid, inert glass surface that was not covered with nutrie nt medium. For the visualization of bacteria, the preparations were stained using alcian blue metho d. It was concluded that higher bacterial concentration favors faster and stronger biofilm formation and that biofilm precedes and mediates bacterial progres s. Also, it was concluded that bacterial mobility was facilitated by capillar y for ces and active fo rms of bacterial motility.

Mnoge bakterije mogu postojati kao zajednice vezane na površinu poznate kao biofilmovi. Bakterijski biofilm je sesilna zajednica čije su stanice ireverzibilno povezane sa supstratom i međusobno, te uronjene u matriks izvanstanične polimerne tvari (eng. extracellular polymeric substance, EPS) koji su same stvorile. Istraživanje je bilo usmjereno na statičke sustave biofilma koji su posebno korisni za ispitivanje ranijih stadija formiranja biofilma. Za istraživanje su korištene bakterije Bacillus cereus i Acinetobacter junii. Cilj istraživanja bio je odrediti model rasta biofilma kojeg tvore te vrste bakterija u stacionarnim uvjetima, kao i vizualizirati biofilm, usporediti količine nastalog EPS-a, te usporediti rast planktonskih i imobiliziranih bakterija kroz vrijeme u stacionarnim uvjetima (batch culture) te uvjetima kontinuiranog rasta (continuous culture). Budući da se pratila biomasa bakterija kroz vrijeme i količina nastalog EPS-a, bakterije su se bojale bojilom Alcian blue i Karbol-fuksinom. Zaključeno je da u stacionarnim uvjetima model rasta bakterijskog biofilma koji se odvija u pet faza nije primjenjiv za bakteriju B. cereus, dok je primjenjiv za bakteriju A. junii. Također je zaključeno da stacionarni uvjeti pogoduju vrsti B. cereus, dok kod bakterije A. junii nema značajne razlike u uvjetima kontinuiranog rasta i u stacionarnim uvjetima. Many bacteria may exist as surfaces-related communities known as biofilms. Bacterial biofilm is a sessile community whose cells are irreversibly linked to the substrate and mutually, and immersed in the matrix of extracellular polymeric substances (EPS) that they have created. The research was focused on static biofilm systems that are particularly useful for the early stages of biofilm formation. Bacteria Bacillus cereus and Acinetobacter junii were used for the study. The goal was to determine a model of biofilm created by these bacteria species in stationary conditions. Also, visualize the biofilm, compare the amount of produced EPS and compare the growth of planktonic and immobilized bacteria over time in batch culture and continuous culture. Given that we monitored bacterial biomass through the time and the amount of produced EPS, bacteria were stained with Alcian-blue which dye the EPS and Carbol-fuchsin which dye the cells. It was concluded that in stationary conditions the five stage model of biofilm development is not applicable to B. cereus, but is applicable to A. junii. It was also concluded that stationary conditions were beneficial for the growth of B. cereus, whereas in comparison with A. junii there was no significant difference in the stationary assay relative to the continuous growth assay.

Bakterijski biofilm je kompleks građen od jedne ili češće više vrsta bakterija koje su ugrađene u matriks izvanstanične polimerne tvari (eng. extracellular polymeric substance EPS) kojeg same proizvode. Takvi bakterijski sustavi rade velike štete kako na medicinskoj opremi, tako i u ljudskim organizmima. Razumijevanje mehanizma formacije viševrsnog biofilma može znatno olakšati razvoj metoda za borbu protiv bakterijskih biofilmova u bolnicama, okolišu ili industrijama. Za istraživanje su korištene bakterije Staphylococcus aureus i Pseudomonas aeruginosa. Cilj istraživanja bio je napraviti model biofilma kojeg tvore te vrste bakterija, vizualizirati ga, usporediti rast bakterija na granici voda – zrak kod uzoraka u kojima se bakterijama mijenja medij s uzorcima u kojima se medij ne mijenja, te usporediti količine proizvedenog EPS-a. Obzirom da se pratila biomasa bakterija na pojedinim područjima na predmetnom stakalcu (vodeni medij, interfaza i zrak), te da se pratila količina nastalog EPS-a, bakterije su se bojile metodama po Gramu i Alcian blue radi bolje vidljivosti EPS-a i usporedbe uzoraka u navedena dva slučaja. Zaključeno je da se većina biofilma nalazi na interfazi, te da mijenjanje medija više pogoduje bakteriji P. aeruginosa, a ne mijenjanje medija više pogoduje bakteriji S. aureus. Bakterija S. aureus u oba slučaja nakon nekog vremena nadvlada bakteriju P. aeruginosa. Bacterial biofilm is a complex of one or more species of bacteria that are embedded within an extracellular matrix composed of extracellular polymeric substances (EPS) produced by the cells. Such bacterial systems are doing significant damage both on medical equipment and in human organisms. Understanding the mechanism of multiple-species biofilm formation can ease the development of methods for bacterial biofilm prevention in hospitals, environment or industry. In this research, bacteria Staphylococcus aureus and Pseudomonas aeruginosa were used. The goal was to determine a model of biofilm created by these bacteria, visualize it, compare the growth of bacteria on air–liquid interface in systems in which the medium was continuously being replenished and when it is not, and compare the amount of produced EPS. Given that we monitored bacterial biomass in different areas (liquid medium, interface and air), and the amount of produced EPS, bacteria were Gram-stained, but also stained with Alcian blue to achieve better visibility of EPS and to compare samples in two aforementioned cases. It was concluded that biofilm is mostly located on the interface and that changing the medium was more beneficial to the growth of P. aeruginosa, while not changing the medium was more beneficial to the growth of S. aureus. Eventually, S. aureus outgrew P. aeruginosa in both cases.

Bakterija Bacillus cereus je Gram-pozitivna, pokretljiva, štapićasta bakterija koja može biti obligatno aerobna ili fakultativno anaerobna te spada u rod Bacillus. Sveprisutna je u prirodi te je tipični saprofit tla i lako se širi na različite tipove hrane. Endospore su jako hidrofobne i izuzetno otporne na velik broj stresora. Uz to uzrokuje probleme i zbog svoje sposobnosti stvaranja biofilma na različitim supstratima. Bakterijski biofilm je višestanični kompleks formiran od sesilnih zajednica mikroorganizama pričvršćenih na podlogu i uronjenih u matriks koji se sastoji od izvanstaničnih polimernih tvari. Matriks im pruža mehaničku stabilnost, štiti ih od isušenja, djeluje kao prepreka protiv nepovoljnih kemijskih i bioloških utjecaja te pridonosi apsorpciji i skladištenju hranjivih tvari. Glavni cilj ovog istraživanja bio je razviti model stvaranja biofilma bakterije B. cereus na granici voda-zrak te je dokazano da interfaza služi kao mjesto širenja velike količine vegetativnih stanica i endospora. Uz to je potvrđeno da je granica voda-zrak povoljno područje za razvoj i razmnožavanje aerobne ili fakultativno anaerobne bakterije poput B. cereus jer joj pruža pristup kisiku u plinovitoj fazi i hranjivim tvarima u vodenoj fazi. Bacillus cereus is a Gram-positive, motile, rod-shaped bacterium that may be obligatory aerobic or facultatively anaerobic and belongs to the genus Bacillus. It is ubiquitously present in nature and is a typical soil saprofit that easily spreads to different types of food. Endospores are highly hydrophobic and extremely resistant to a large number of stressors. It also cause problems because of its ability to create biofilms on different substrates. Bacterial biofilm is a multicellular complex formed by sessile microorganisms attached to the substrate and immersed in a matrix consisting of extracellular polymeric substances. The matrix provides them with mechanical stability, protects them from desiccation, acts as an obstacle to adverse chemical and biological influences and contributes to the absorption and storage of nutrients. The main purpose of this study was to develop a model for biofilm formation of B. cereus at air-liquid interface and it was proven that the interface serves as a nidus for spreading large amounts of vegetative cells and endospores. It is confirmed that the air-liquid interface is a favorable area for the development and propagation of aerobic or facultatively anaerobic bacteria such as B. cereus because it provides access to oxygen (gaseous) and nutrients (liquid phase).

Biofilm je sve aktualnija tema i sve više se istražuje, a veće razumijevanje biofilma trebalo bi dovesti do novih, učinkovitijih strategija kontrole i poboljšanja liječenja pacijenata. Trend porasta rezistentnosti biofilma na antibiotike postaje sve ozbiljniji problem, a rješenje se pokušava pronaći kombinacijom različitih mjera poput izbjegavanja infekcija, blokiranja bakterijskih čimbenika virulencije ili pojačavanja imunološke obrane domaćina, potiskujući bakterije u biofilmu na prethodnu ulogu kao fakultativne ili rijetko patogene bakterije. Cilj rada je bio opisati najznačajnija svojstva biofilma: od procesa njegovog nastajanja, preko rasprostiranja u okoliš, kao uzročnika virulencije kod bakterija te rezistentnosti na antibiotike. Težište rada bilo je na biofilmovima koji su nastali djelovanjem bakterije Acinetobacter baumannii. Biofilm is an important topic and there is more and more research in this area. A better understanding of biofilm should lead to new, more effective strategies for controlling and improving treatment of patients. The increasing trend of a biofilm resistance to antibiotic treatment become more and more serious problem, and the solution is to find a combination of different measures such as avoiding infections, blocking the factors of a bacterial virulence, or the host immunity increasing by suppressing bacterial cells in biofilm to reduce their pathogenicity. The aim of the paper was to describe the most important biofilm properties: from the process of its formation, through migration to the environment, as a bacterial virulence agent and and biofilm antibiotic resistance. The focus of the theses was on biofilms produced by the Acinetobacter baumannii.