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621.
Adhesion of Acinetobacter venetianus to Diesel Fuel Droplets Studied with In Situ Electrochemical and Molecular Probes
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Franco Baldi Nadica Ivoevi Andrea Minacci Milva Pepi Renato Fani Vesna Svetlii Vera
uti 《Applied microbiology》1999,65(5):2041-2048
The adhesion of a recently described species, Acinetobacter venetianus VE-C3 (F. Di Cello, M. Pepi, F. Baldi, and R. Fani, Res. Microbiol. 148:237–249, 1997), to diesel fuel (a mixture of C12 to C28 n-alkanes) and n-hexadecane was studied and compared to that of Acinetobacter sp. strain RAG-1, which is known to excrete the emulsifying lipopolysaccharide, emulsan. Oxygen consumption rates, biomass, cell hydrophobicity, electrophoretic mobility, and zeta potential were measured for the two strains. The dropping-mercury electrode (DME) was used as an in situ adhesion sensor. In seawater, RAG-1 was hydrophobic, with an electrophoretic mobility (μ) of −0.38 × 10−8 m2 V−1 s−1 and zeta potential (ζ) of −4.9 mV, while VE-C3 was hydrophilic, with μ of −0.81 × 10−8 m2 V−1 s−1 and ζ of −10.5 mV. The microbial adhesion to hydrocarbon (MATH) test showed that RAG-1 was always hydrophobic whereas the hydrophilic VE-C3 strain became hydrophobic only after exposure to n-alkanes. Adhesion of VE-C3 cells to diesel fuel was partly due to the production of capsular polysaccharides (CPS), which were stained with the lectin concanavalin A (ConA) conjugated to fluorescein isothiocyanate and observed in situ by confocal microscopy. The emulsan from RAG-1, which was negative to ConA, was stained with Nile Red fluorochrome instead. Confocal microscope observations at different times showed that VE-C3 underwent two types of adhesion: (i) cell-to-cell interactions, preceding the cell adhesion to the n-alkane, and (ii) incorporation of nanodroplets of n-alkane into the hydrophilic CPS to form a more hydrophobic polysaccharide–n-alkane matrix surrounding the cell wall. The incorporation of n-alkanes as nanodroplets into the CPS of VE-C3 cells might ensure the partitioning of the bulk apolar phase between the aqueous medium and the outer cell membrane and thus sustain a continuous growth rate over a prolonged period. 相似文献
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623.
Despite iodine being one of the most abundant of the minor elements in oxic seawater, the principal processes controlling
its interconversion from iodate to iodide and vice versa, are still either elusive or largely unknown. The two major hypotheses
for iodate reduction involve either phytoplankton growth in primary production, or bacteria during regeneration. An earlier
study intended to exploit the unusual nature of anchialine environments revealed that iodide is oxidised to iodate in the
bottom of such caves, whereas reduction of iodate occurs in the shallower parts of the water column. This investigation was
made on the hypothesis that study of the nitrogen and phosphorus nutrient systems within the caves might offer a bridge between
the iodine chemistry and the marine bacteria which are assumed to be the agent of change of the iodine in the caves. Accordingly,
the hydrography, the nutrient chemistry, and some further iodine studies were made of two anchialine caves on the east coast
of the Adriatic Sea in Croatia. Iodate and iodide were determined by differential pulse voltammetry and cathodic stripping
square-wave voltammetry, respectively. Total iodine was determined indirectly, as iodate, after oxidation of reduced iodine
species with UV irradiation and strong chemical oxidants. Nutrient concentrations were measured by spectrophotometry. Nutrient
profiles within the well stratified water columns indicate a relatively short-lived surface source of nitrate and phosphate
to the caves, with a more conventional, mid-water, nutrient regeneration system. The latter involves nitrite and ammonium
at the bottom of the halocline, suggestive of both autotrophic and heterotrophic microbial activity. High iodate/low iodide
deep water, and conservative behaviour of total inorganic iodine were confirmed in both systems. Iodate is reduced to iodide
in the hypoxic region where nutrient regeneration occurs. The concentrations of organic iodine were surprisingly high in both
systems, generally increasing toward the surface, where it comprised almost 80% of total iodine. As with alkalinity and silica,
the results suggest that this refractive iodine component is liberated during dissolution of the surrounding karst rock. A
major, natural flushing of one of the caves with fresh water was confirmed, showing that the cave systems offer the opportunity
to re-start investigations periodically. 相似文献
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Mato Drenjančević Toni Kujundžić Vladimir Jukić Maja Karnaš Ulrike Braun Florian Schwander Tihana Teklić Vesna Rastija 《The Annals of applied biology》2023,183(1):43-52
Leaf removal (LR) treatments improve the photosynthetic capacity of the remaining leaves and induce flavonoid synthesis as a stress response in the common grapevine (Vitis vinifera L.). However, excessive exposure of grape berries to UV-B radiation as a result of cultural practices in the Mediterranean climate may have negative effects on berry composition. This 2-year study determined the effects of defoliation on the autochthonous red grape variety ‘Babica’ in a Mediterranean climate (wine-growing region Dalmatia, Croatia). Six leaves were removed before flowering (FLR) and at the end of véraison (the onset of grape ripening; VerLR) and were compared to the untreated control. Yield parameters, sugar content, grape must pH, total polyphenols (TP), total anthocyanin (TA) content, and individual anthocyanin compounds were measured in grape skin extracts and wines. However, the greater mean daily temperature during the vegetation period and lesser rainfall before harvest in 2018 increased yield per vine, average cluster weights, density, and total acidity, compared to 2017. Both defoliation treatments significantly reduced TP in grape extracts, but these differences were not observed in wine. Compared to the control (NLR), VerLR treatment significantly reduced TA in grape skin extracts and wine. Significantly lesser TP concentrations, in grape skin extracts and wine, as well as TA were noticed during the 2017 season. VerLR treatment reduced the concentration of nine individual anthocyanins compared to the control in grape skin extracts, while this effect was not observed in wine. Season year was a statistically significant source of variability of the individual anthocyanin contents in wine. Under specific environmental conditions LR can decrease polyphenols, especially anthocyanins, and negatively impact grape and wine quality. 相似文献
627.
Vesna Musani Maja Sabol Diana Car Petar Ozretić Držislav Kalafatić Ivana Maurac Slavko Orešković Sonja Levanat 《Gene》2013
In this study we investigated the types and role of different genetic changes of PTCH1 gene in three different types of ovarian tumors: carcinomas, fibromas and dermoids. LOH of the PTCH1 region was detected in 27.3% ovarian carcinoma samples, 18.18% ovarian fibroma samples and 55.56% ovarian dermoid samples. No point mutations were detected in any of the three types of ovarian tumors. SNP c.3944C>T showed significant differences between ovarian carcinoma and control samples with the minor T allele being significantly higher in controls compared to ovarian carcinomas. Interestingly, a new polymorphism c.−1184G>A was found only in tumor samples and further analyses should be performed in order to elucidate its potential role in ovarian tumors. 相似文献
628.
Vesna Klokočovnik Dušan Devetak Marina Orlačnik 《Ethology : formerly Zeitschrift fur Tierpsychologie》2012,118(11):1102-1110
Behavioral plasticity allows animals to maximize their fitness in a variety of environmental conditions. Trap‐building predators represent case studies in such plasticity as the characteristics of their traps are dependent upon the substrate available. We investigated the effect of sand particle size on pit construction in antlions (Euroleon nostras), sand‐dwelling insect larvae that build pitfall traps to capture prey. The pit construction behavior of the species comprises six stages. When antlions were exposed to different sand particle sizes, their behavior differed in terms of the occurrence and duration of particular stages and in the frequency of jerks produced during sand tossing. Jerk frequency was negatively correlated with sand particle size and also changed during pit construction. Furthermore, at larger particle sizes, individuals occasionally constructed irregular traps with a figure of eight shape, and they crossed the center of the truncated cone during deepening. In the largest substrate, particle size of antlions did not construct pits. Our results demonstrate that variation in traps under differing environmental conditions stems directly from behavioral plasticity in this species. 相似文献
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Brain imaging methods allow a non-invasive assessment of both structural and functional connectivity. However, the mechanism of how functional connectivity arises in a structured network of interacting neural populations is as yet poorly understood. Here we use a modeling approach to explore the way in which functional correlations arise from underlying structural connections taking into account inhomogeneities in the interactions between the brain regions of interest. The local dynamics of a neural population is assumed to be of phase-oscillator type. The considered structural connectivity patterns describe long-range anatomical connections between interacting neural elements. We find a dependence of the simulated functional connectivity patterns on the parameters governing the dynamics. We calculate graph-theoretic measures of the functional network topology obtained from numerical simulations. The effect of structural inhomogeneities in the coupling term on the observed network state is quantified by examining the relation between simulated and empirical functional connectivity. Importantly, we show that simulated and empirical functional connectivity agree for a narrow range of coupling strengths. We conclude that identification of functional connectivity during rest requires an analysis of the network dynamics. 相似文献