Asociacije bakterij z meduzami v obalnih morjih

Kos Kramar, Maja (author), Turk, Valentina (mentor)

Površine morskih nevretenčarjev naseljujejo številni mikroorganizmi, kar se kaže v veliki pestrosti sestave pritrjenih mikrobnih združb. Dosedanje raziskave mikrobioma meduz so pokazale prisotnost raznolikih in specifičnih bakterijskih združb, ki so različne v različnih okoljih, se razlikujejo med populacijami meduz in so le malo podobne združbam v okolni vodi. Z metodami molekularne biologije (denaturacijska gradientna elektroforeza (DGGE) in bakterijske genske klonske knjižnice), mikrobiološkimi tehnikami gojenja in različnimi tehnikami mikroskopiranja (epifluorescentna in vrstična elektronska mikroskopija (SEM)) smo preverili prisotnost bakterij pri meduzah, ki se redno pojavljajo v Tržaškem zalivu, tj. Aurelia sp., Chrysaora hysoscella in Cotylorhiza tuberculata. Rezultati so potrdili, da so bakterijske združbe, ki so asociirane z meduzami, različne od združb, prisotnih v okolni morski vodi. Sestava združbe se razlikuje med različnimi vrstami meduz kot tudi med posameznimi telesnimi deli meduze. Posnetki elektronske vrstične mikroskopije so pokazali, da epidermis sestavljajo številne knidocite in da je prekrit s številnimi cilijami. Mukus, ki prekriva površino, se lušči v obliki mukusnih krp. Z mikroskopijo smo prisotnost bakterij potrdili izključno v sloju mukusa. Na podlagi taksonomske analize gena za 16S rRNA so bile v združbah prisotne bakterije razredov Alphaproteobacteria in Gammaproteobacteria, med njimi Ruegeria, Phaeobacter, Pseudoalteromonas, Vibrio in Alteromonas, ter rodov Burkholderia, Cupriavidus, in Achromobacter razreda Betaproteobacteria. Hkrati smo pokazali, da v polzaprtem ekosistemu, Velikem jezeru na otoku Mljet (južni Jadran), celoletna prisotnost meduz Aurelia sp. 5 lahko vpliva na sestavo naravne populacije bakterij. S postavitvijo obogatitvenega eksperimenta smo pokazali, da razgradnja nehomogenizirane odmrle meduzne biomase poteka počasneje kot razgradnja homogenizirane meduze. Ob razgradnji je prišlo do sprememb v strukturi bakterijske združbe in do akumulacije amonija in ortofosfata v okolju.

• Language: Slovenian
• Keywords: bakterije, meduze, asociacije, razgradnja meduzne biomase, Tržaški zaliv, Veliko jezero (otok Mljet), DGGE, klonske knjižnice, bakterijski izolati, mikroskopija
• Work type: Doctoral dissertation
• Typology: 2.08 - Doctoral Dissertation
• Organization: BF - Biotechnical Faculty
• Publisher: [M. Kos Kramar]
• Year: 2019
• PID: 20.500.12556/RUL-113390
• UDC: 577:593.7:341.221.2(043.3)
• COBISS.SI-ID: 303516160
• Publication date in RUL: 28.12.2019

Secondary language

• Language: English
• Title: Associations between bacteria and jellyfish in the coastal seas

Abstract

Surfaces of marine invertebrates are colonized by different microorganisms, resulting in formation of diverse microbial communities. Recent studies on jellyfish microbiomes, revealed presence of diverse and specific bacterial communities, which differ between environments, jellyfish populations and are distinct from seawater assemblages. Using molecular biology (denaturing gradient gel electrophoresis (DGGE) and bacterial gene clone libraries) and culture based methods, and different microscopic techniques (epifluorescence and scanning electron microscopy (SEM)), we examined the presence of bacteria on jellyfish, regularly present in the Gulf of Trieste, Aurelia sp., Chrysaora hysoscella and Cotylorhiza tuberculata. Results confirmed that bacterial communities associated with jellyfish are distinct from sea water assemblages. Bacterial community composition differs between different jellyfish species and between individual body parts of medusa. SEM microscopic technique revealed that the jellyfish epidermis contains numerous cnidocytes and is densely covered by cilia. Surface is covered with thin mucus layer, that dissolute off the surface in form of mucus sheets. Using microscopy, presence of bacteria was detected exclusively in mucus. Based on the 16 rRNA gene taxonomic analysis, bacteria of classes Alphaproteobacteria and Gammaproteobacteria, among them Ruegeria, Phaeobacter, Pseudoalteromonas, Vibrio and Alteromonas, and genera Burkholderia, Cupriavidus and Achromobacter of the class Betaproteobacteria, were present in the association. Additionally, results showed that in semi- closed ecosystem, the Big Lake of Mljet Island (South Adriatic), the year-round presence of jellyfish Aurelia sp. 5, may affect the community composition of natural bacterial assemblage. With enrichment experiment we showed, that bacterial degradation of whole dead jellyfish is slower, in comparison with homogenized jellyfish. Degradation resulted in change of bacterial community structure and accumulation of ammonium and orthophosphate.

• Keywords: bacteria, jellyfish, associations, jellyfish biomass degradation, the Gulf of Trieste, the Big Lake (Mljet Island), DGGE, clone libraries, bacterial isolates, microscopy