Primary biofilm succession on artificial substrate in the sea

Svaka čvrsta podloga uronjena u more podložna je procesu stvaranja biofilma. Razvoj takvog biofilma također poznat kao naseljavanje živih organizama je složen i još uvijek nedovoljno istražen proces. Naseljavanje dijatomeja i bakterija istraživano je u periodu jednog mjeseca na umjetnim pleksiglas pločicama (polimer metil metakrilata) postavljenima u konstrukciju iznad morskog dna na dubinu od pet metara. Za bakteriološku analizu biofilm se odvojio pomoću ultrazvučne sonde, a uzorci su se nacijepili na selektivne agar ploče. Biofilm za algološku analizu sastrugao se sa četkicom i resuspendirao u poduzorke za epifluorescencijsku i elektronsku mikroskopiju kao i za analizu pigmenta HPLC metodom. Sve komponente biofilma su pokazale maksimalnu abundanciju nakon mjesec dana ekspozicije. U bakterijskoj zajednici dominirale su heterotrofne morske bakterije koje su dostigle 1,96±0,79x104 CFU cm-2. Iako su fekalni koliformi i intestinalni enterokoki opaženi u stupcu vode, fekalni koliformi nisu detektirani u biofilmu, a intestinalni eneterokoki su narasli nakon mjesec dana kontakta u zanemarivom broju kolonija 60±10 CFU cm-2. Fotoautotrofna komponenta biofilma dominirala je dijatomejama i dostigla 5,80x105 stanica cm-2, što potvrđuje i analiza pigmenata s fukoksantinom kao dominantnim u koncentraciji do 110 ng cm-2. Dominantna diatomeja bila je Cylindrotheca closterium. Detaljnija taksonomska analiza elektronskim mikroskopom otkrila je 30 različitih svojti dijatomeja. Istraživanje je potvrdilo da su pleksiglas ploče u morskom okolišu dobar supstrat za razvoj obraštaja u roku od 30 dana ekspozicije. Nadalje, redoslijed naseljavanja je potvrdio bakterije i cijanobakterije kao prve, a dijatomeje kao druge kolonizatore, sve skupa čineći primarni biofilm u moru.Every surface that is immersed in seawater is rapidly covered by unavoidable biofilm. Such biofilm formation, also known as fouling, is a complex multistage process and not yet thoroughly investigated. In this study, succession of diatoms and bacteria was investigated during a one month exposition on artificial plexiglass (polymer of methyl methacrylate) substrate mounted above the seafloor at 5 m depth. For the biofilm analyzes the fouling was investigated using selective agar plates, epifluorescence, light and electronic microscopy, as well as for HPLC pigment analysis. During biofilm development, the abundance of all biofilm components increased and reached maximum values after one month exposition. In the bacterial community heterotrophic marine bacteria were dominant and reached 1,96±0,79x104 CFU cm-2. Despite the fact that faecal coliforms and intestinal enterococci were detected in the water column, faecal coliforms were not detected in the biofilm and intestinal enterococci appeared after one month of exposition but in a negligible number of 60±10 CFU cm-2. The phototrophic component of the biofilm was dominated by diatoms and reached 5,80x105 cells cm-2, which was supported by pigment analysis with fucoxantin as dominant pigment in concentration up to 110 ng cm-2. Diatom community was dominated by Cylindrotheca closterium and other penate benthic diatoms. A detailed taxonomic analysis by electronic microscopy revealed 30 different taxa of diatoms. The study confirmed that the plexiglass surface in a marine environment is susceptible to biofouling within 30 days of contact. Furthermore, sequence of the colonization process firstly involved bacteria and cyanobacteria, and secondly diatoms, they all together formed a primary biofilm in the sea