Exopolymeric substances (EPS) are important for biofilm formation and their chemical composition may influence the biofilm properties. To explore these relationships chemical composition of EPS from Bacillus subtilis biofilms grown in different media was studied. We observed marked differences in composition of EPS polymers isolated from biofilms grown in different media. The polysaccharide levan dominated the EPS in biofilms grown in sucrose rich media in addition to proteins and DNA. Biofilms also differed in thickness and the biofilm defective phenotypes of tasA and eps mutants were partially compensated in the sucrose rich medium. Since sucrose is essential for synthesis of levan and the presence of levan was confirmed in all biofilms grown in media containing sucrose, this study for the first time shows that levan, although not essential for biofilm formation, can be a structural and possibly stabilizing component of B. subtilis floating biofilms. In addition, we propose that this polysaccharide, when incorporated into the biofilm EPS, may also serve as a nutritional reserve.
COBISS.SI-ID: 4242040
Carboxymethyl cellulose is one of the most used thickeners in industry. Structural changes of CMC during biodeterioration with Bacillus subtilis subsp. subtilis NCIB 3610 were studied with small-angle X-ray scattering (SAXS), size exclusion chromatography, and viscosity measurements. Cleavage of CMC polymers changed flow characteristics from those of non-Newtonian pseudoplastic fluid to those of Newtonian fluid. The viscosity decreased from 10 to 1.4 mPas and the concentration of reducing sugar increased by 18-fold. Upon biodeterioration the average radius of gyration decreased from 147 to 123 Å; cleaved polymer chains remained in close contact in unstirred medium as reflected by a relatively large apparent radius of gyration. However, such degraded CMC aggregates were easily dispersed with shear stress. The results suggest that biodeterioration mainly affects CMC structural features that are larger than 5 nm. Furthermore, the results also suggest that CMC metabolism and biodeterioration may be decoupled; B. subtilis subsp. subtilis NCIB 3610 produces cellulases that effectively cleave CMC but cannot efficiently utilize hydrolyzed products. There were no structural or rheological changes observed in the absence of B. subtilis subsp. subtilis NCIB 3610 growth.
COBISS.SI-ID: 36573957
In this aticle we describe the identification of a novel putative regulatory protein SACE_5599 in the erytromycin producing organism Saccharopolyspora erythraea. The regulation of erythromycin biosynthesis has for a long time remained poorly characterized mainly because no regulatory genes are encoded in the erythromycin biosynthetic cluster. We used a comparative proteomics approach to identify regulatory proteins which are significantly overexpressed in the industrial, erythromycin high-producing S. erythraea strain, compared to the natural NRRL23338 strain. Among those SACE_5599 showed biggest difference in expression levels. Further on, we inactivated this gene in the high-producing strain, which caused a significant drop in erythromycin yield as well as significantly decreased sporulation intensity. In contrast, constitutive overexpression of SACE_5599 in the NRRL 23338 strain lead to increased erythromycin production. Therefore, we have identified a novel putative regulatory gene, which is involved in morphological differentiation and erythromycin biosynthesis and possesses significant potential for improvement of fermentation processes for production of this extremely important antibiotic.
COBISS.SI-ID: 3005775
We confirmed in vitro stress responses and the consequent in vivo modulation of Campylobacter jejuni pathogenicity in BALB/c mice, as a result of the exposure of the C. jejuni to environmental stress (starvation, oxidative stress, heat shock). Additionally, changes in bacteria numbers and the levels of several cytokines (interleukins 6 and 10, tumor necrosis factor-a, interferon-c) were followed in vivo, in liver homogenates from the mice intravenously infected with either control (untreated) or stressed C. jejuni. These in vivo studies of environmental impact on bacterial virulence reveal that microbial adaptation during stress challenge is crucial not just for pathogen survival out of the host, but also during host–pathogen interactions, and thus for the bacterial pathogenicity.
COBISS.SI-ID: 4242296
At high cell density or under low nutrient conditions, yeasts collectively adapt their metabolism by secreting aromatic alcohols in what is known as quorum sensing. However, the mechanisms and role of quorum sensing in yeast are poorly understood, and the methodology behind this process is not well established. This paper describes an effective approach to study quorum sensing in yeast fermentations. The separation, detection, and quantification of the putative quorum-sensing molecules 2-phenylethanol, tryptophol, and tyrosol have been optimized on a simple HPLC-based system. With the use of a phenyl HPLC column and a fluorescence detector, the sensitivity of the system was significantly increased. This allowed extraction and concentration procedures to be eliminated and the process to be scaled down to 2 mL mini-fermentations. Additionally, an innovative method for rapid viable-cell counting is presented. This study forms the basis for detailed studies in kinetics and regulation of quorum sensing in yeast fermentation.
COBISS.SI-ID: 4215160