Bakterije rezistentne na selen

undergraduate thesis

• Title (english): Bacteria resistant to selenium
• Author: Marina Mihaljević
• Mentor: Jasna Hrenović (mentor)
• Granter: University of Zagreb; Faculty of Science; (Department of Biology); Zagreb
• Defense date and country: 2018, Croatia
• Scientific / art field, discipline and subdiscipline: NATURAL SCIENCES; Biology

Abstract

Selen je esencijalni element u tragovima za sve tri domene ţivih bića (bakterije, arheje, eukarioti), ali je u visokim koncentracijama toksičan. Selenovi oksianioni (selenat i selenit) su dobro topivi u vodi i vrlo toksični, te u okoliš dospijevaju prirodnim procesima ili ljudskom djelatnošću (industrija, poljoprivreda). Neke bakterije su sposobne podnijeti veće koncentracije toksičnih selenovih spojeva, odnosno selenovih oksianiona u svojoj okolini, a to im je omogučeno različitim mehanizmima poput redukcije selenovih oksianiona u procesu anaerobne respiracije ili rjeĎe uočene redukcije u aerobnim uvijetima procesima detoksifikacije. Bakterije koje reduciraju selenove oksianione proizvode nanosfere elementarnog selena sa specifičnim fizikalnim svojstvima, ili ih rjeĎe metiliraju i reduciraju do selenida stvarajući tako plinovite metilirane selenove spojeve.
Cilj ovog rada je sakupiti sadašnja saznanja o bakterijama koje imaju neku vrstu rezistencije na selen, odnosno na njegove toksične spojeve, kao i o mehanizmima kojima to postiţu. Mehanizmi koji bakterijama omogućavaju rezistenciju na selen nisu još sasvim razjašnjeni, pogotovo oni koji se dogaĎaju u aerobnim uvijetima, te su otvorena mnoga pitanja poput načina izlučivanja samih nanosfera selena iz stanica bakterija.

Abstract (english)

Selenium is an essential trace element for living creatures from all three domains of life (Bacteria, Archaea, Eukaryota), but it is toxic in high concentrations. Selenium oxyanions (selenate and selenite) are water soluble and highly toxic, and get released in the environment through natural processes or through human activity (industry, agriculture). Some bacterias are capable of coping with higher concentrations of toxic selenic forms, i. e. selenium oxyanions in its environment, and that is possible due to different mechanisms possessed by those bacteria like reduction of selenium oxyanions in a process of anaerobic respiration or, not as often, aerobic reduction through processes of detoxification. Bacteria that reduce selenium oxyanions produce nanospheres of elemental selenium that have specific physical properties, or rarely methylate them and reduce them to selenide, producing gaseous methylated selenium compounds.
The main objective of this paper is to collect the current knowledge of bacteria that exhibit some kind of resistance to selenium – to its toxic forms, as well as the mechanisms whit which it is obtained. The mechanisms that provide resistance to selenium are not jet well explained, especially the ones that occure in aerobic conditions, and many questions remain unanswered like the ones regarding the expulsion of the selenium nanospheres out of the bacteria cells.

• Keywords: bakterije; rtezistencija
• Language: croatian
• URN:NBN: urn:nbn:hr:217:371670
• Study programme: Title: Ecology; Study programme type: university; Study level: undergraduate; Academic / professional title: sveučilišni/a prvostupnik/prvostupnica (baccalaureus/baccalaurea) biologije (sveučilišni/a prvostupnik/prvostupnica (baccalaureus/baccalaurea) biologije)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Open access
• Created on: 2018-10-10 09:25:30