Stress response of some lactic acid bacteria with bionanotehnological applications
The first task of the project for 2016 is: Study of morphological, metabolic and structural changes induced under thermal and saline stress conditions
Six lactic acid bacterium (LAB) strains from our laboratory collection, isolated from Romanian artisan dairy products, fermented vegetables and other products of plant origin, such as borș or fresh vegetables, were selected for this study. These strains have been previously shown to have functional properties, such as production of bactericins (two strains, Grosu-Tudor et al., 2014), exopolysaccharides (two strains, Grosu-Tudor et al., accepted for publication), and S-layer proteins (two strains, Stefan et al., accepted for publication).
LAB strains were subjected to different stress conditions: lowest/highest incubation temperatures at which LAB were able to grow (ranging from 15 to 42°C), and addition to the growth medium of NaCl up to 7% (w/v). Growth was followed by measuring the pH and the optical density of the culture at 600 nm. The biochemical changes induced by stress were evaluated using different approaches.Total cell protein extracts were obtained by sonication. The differences in cytosolic protein patterns were analysed by one dimensional Sodium Dodecyl Sulfate Polyacrylamide Gel Electrophoresis (SDS-PAGE). The activity of some intracellular enzymes involved in different metabolic pathways (lactate dehydrogenase, alcohol dehydrogenase, superoxide dismutase, malate dehydrogenase, etc.) in the protein extracts were measured by spectrophotometrical methods (Vallee and Hoch, 1993; Winterbourn et al., 1975). The changes in their respective isoenzymes patterns were also detected by one dimensional native polyacrylamide gel electrophoresis.
The second task of the project for 2016 is: Influence of thermal and salin stress conditions on the production of compounds with bionanotechnological application
The biosynthesis of the bionanotechnologically important compounds (bacteriocins, exopolysaccharides, S-layer proteins) under thermal and saline stress conditions were monitored in terms of yield. Bacteriocins were looked for and quantified by an agar spot diffusion method (Mayr-Harting et al., 1972), using a serial dilution of the sample. Exopolysaccharides were isolated by acetone precipitation and gravimetrically cuantified (Degeest and De Vuyst, 1999), while and S-layer proteins were detected by SDS-PAGE (Dohm, 2011).
Articles published:
Articles in ISI journals
1. Grosu-Tudor S.S., Brown L., Fadda S., Brezeanu A., Brinzan A., Hebert E.M, Mozzi F., Zamfir M. S-layer production by Lactobacillus acidophillus IBB 801 under environmental stress conditions, Applied Microbiology and Biotechnology, 2016, DOI: 10.1007/s00253-016-7355-5.
Articles in BDI journals
1. Grosu-Tudor S.S., Ștefan I.R., Zamfir M., Growth/survival of some selected lactic acid bacteria under different stress conditions, Scientific Bulletin, Series F, Biotechnologies, 2016, vol. XX, accepted for publication
2. Ștefan I.R., Cornea P.C., Grosu-Tudor S.S., Zamfir M., Screening for S-layer production by some lactolactobacilli from home-made fermented foods, Scientific Bulletin, Series F, Biotechnologies, 2016, vol. XX, accepted for publication
The research team will atend the following International Conferences:
1. Grosu-Tudor S.S., Ștefan I.R., Zamfir M., Growth/survival of some selected lactic acid bacteria under different stress conditions, The International Conference of the University of Agronomic Sciences and Veterinary Medicine of Bucharest, Agriculture for Life, Life for Agriculture, June 9-11 2016, Bucharest (poster).
2. Ștefan I.R., Cornea P.C., Grosu-Tudor S.S., Zamfir M., Screening for S-layer production by some lactolactobacilli from home-made fermented foods, The International Conference of the University of Agronomic Sciences and Veterinary Medicine of Bucharest, Agriculture for Life, Life for Agriculture, June 9-11 2016, Bucharest (poster).
3. Grosu-Tudor S.S., Stancu M.M., Ștefan I.R., Cornea P.C., Zamfir M., Physicochemical and rheological properties of some exopolysaccharides produced by lactic acid bacteria isolated from plant origin materials, International Conference on Food Microbiology, August 8-10 2016, Birmingham, England (poster).
4. Zamfir M., Stancu M.M., Ștefan I.R., Grosu-Tudor S.S., Characterization of a nisin-like bacteriocin produced by Lactococcus lactis 19.3, isolated from raw milk, International Conference on Food Microbiology, August 8-10 2016, Birmingham, England (poster).