This is the first study about communication at the microscale in B. subtilis and showed that remarkable diversity of the comQXPA QS system is present also at the microscale. The comQXPA is highly polymorphic in closely related strains and comprises four communication groups such that strains belonging to the same group exchange information efficiently, but strains from different groups not. In this work, using Bacillus isolates from the bank of the river Sava, we showed that the same number of communication types exists at the microscale (1 cm3) as was found among strains from macroscales.
COBISS.SI-ID: 3565432
In this contribution, the influence of various physicochemical factors on Saccharomyces cerevisiae invasive growth is examined quantitatively. Agar-invasion assays are generally applied for in vitro studies on S. cerevisiae invasiveness, the phenomenon observed as a putative virulence trait in this clinically more and more concerning yeast. However, qualitative agar-invasion assays, used until now, strongly limit the feasibility and interpretation of analyses and therefore needed to be improved. Besides, knowledge in this field concerning the physiology of invasive growth, influ enced by stress conditions related to the human alimentary tract and food, is poor and should be expanded. For this purpose, a quantitative agar-invasion assay, presented in our previous work, was applied in this contribution to clarify the significance of the stress factors controlling the adhesion and invasion of the yeast in greater detail. Ten virulent and non-virulent S. cerevisiae strains were assayed at various temperatures, pH values, nutrient starvation, modified atmosphere, and different concentrations of NaCl, CaCl2 and preservatives. With the use of specific parameters, like a relative invasion, eight invasive growth models were hypothesized, which enabled intelligible interpretation of the results. A strong preference for invasive growth (meaning high relative invasion) was observed when the strains were grown on nitrogen- and glucose-depleted media. A significant increase in the invasion of the strains was also determined at temperatures typical for human fever (37–39 °C). On the other hand, a strong repressive effect on invasion was found in the presence of salts, anoxia and some preservatives.
COBISS.SI-ID: 3750520
We described new approach for the isolation and quantitative analysis of the cell wall proteins from invasively growing S. cerevisiae. This method is compatible with agar-invasion assays and is a screening tool for rapid analysis of proteins related to yeast adhesion and invasion. The extraction was optimized for fast, direct analysis of multiple protein samples by SDS-PAGE, avoiding preconcentration or purification. We compare protein profile of invasive and non-invasive strains, invasive and non-invasive part of the colony and cells cultivated at optimal and increased growth temperature.
COBISS.SI-ID: 3709816
In this study, the pigment production of Vibrio sp. was studied under different physicochemical conditions. There was no pigment production at high or low temperatures, high or low salt concentrations in peptone yeast extract (PYE) medium, low glucose concentration in mineral growth medium or high glucose concentration in PYE medium. This indicates that the red pigment production is a luxurious good that Vibrio sp. makes only under favorable conditions. The red pigment is also a redundant antibacterial agent of Vibrio sp.
COBISS.SI-ID: 3772024
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 yeasts are poorly understood, and the methodology behind this process is not well established. In this study, we described an effective approach to study quorum sensing in yeast fermentations. We have optimized the separation, detection and quantification of the putative quorum sensing molecules 2-phenylethanol, tryptophol and tyrosol 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 us to eliminate extraction and concentration procedures, and to scale-down the process to 2-ml mini-fermentations. Additionally, we present an innovative method for rapid viable-cell counting. This study forms the basis for detailed studies in kinetics and regulation of quorum sensing in yeast fermentation.
COBISS.SI-ID: 4215160