Reologija je veda o pretočnih lastnostih snovi in snovnih sistemov. Bacillus subtilis je ubikvitarna bakterija, ki toku tekočine najpogosteje klubuje v pritrjeni obliki, s tvorbo biofilma. Da pa lahko ustvari biofilm, mora bakterija proizvesti in izločiti različne zunajcelične polimerne snovi (EPS). V delu smo opazovali reološke spremembe v gojišču pri gojenju mutante bakterije B. subtilis PS 216 srf-cfp ter ga primerjali z reološkim obnašanjem divjega tipa. Z rotacijskimi in oscilacijskimi testi na reometru smo ugotovili, da je izrabljeno gojišče mnogo bolj viskozno ter elastično od primerljivo izrabljenega gojišča z divjim tipom bakterije B. subtilis PS 216. Dodani viri ogljika so različno vplivali na reologijo bakterijske suspenzije. Z dodatkom aminokisline glutamata v gojišče smo ugotovili, da tudi divji tip B. subtilis tvori viskozno gojišče, kar je kazalo v smer sinteze polimera poliglutamata (PGA), kar smo potrdili z visokoločljivostno tekočinsko kromatografijo (HPLC) in nuklearno magnetno resonanco (NMR). Uspešno smo izolirali EPS iz izrabljenega gojišča z mutanto B. subtilis, vendar s klasičnimi kemijskimi testi nismo uspeli določiti večinske sestave EPS.
| Language: | English |
|---|
| Title: | Rheological characterisation of mutant bacterium Bacillus subtilis PS 216 spent medium |
|---|
| Abstract: |
|---|
Rheology is the study of the flow properties of materials and material systems. Bacillus subtilis is an ubiquituos bacterium, which resist liquid flow in a biofilm by synthesis and secretion of different extracellular polymeric substances (EPS). In this work we observed rheological changes of medium during the incubation of mutant bacterium B. subtilis PS 216 srf-cfp. By perfroming rotational and oscilation rheological tests we showed that the spent medium is much more viscous and elastic compared to the wild type bacterium B. subtilis PS 216. The addition of varius carbon sources changed significantly the rheological behavior of bacterial suspensions. The results of aminoacid glutamate addition to the medium suggested that B. subtilis made polymer polyglutamate (PGA) which was confirmed by high-performance liquid chromatography (HPLC) and nuclear magnetic resonance (NMR). The chemical nature of the isolated EPS was not further determined.
|
| Keywords: | Bacillus subtilis, mutant bacterium Bacillus subtilis, growth of microorganisms, medium, spent medium, rheological properties, medium viscosity, viscosity measurement, extracellular polymeric substances, EPS, PGA |
|---|
