Influence of Ripening Stage at Harvest on Chilling Injury Symptoms of Persimmon cv. Rojo Brillante Stored at Different Temperatures

Changes in the quality during storage of persimmon fruits cv. Rojo Brillante harvested at two different maturity stages were studied. Early and late harvested fruit were stored at 1°C or 15°C for different periods of time. Harvest time had a relevant influence on chilling injury (CI) sensitiveness, since CI symptoms were found in fruits stored at 1°C only when they were early harvested. The most important CI manifestation was a drastic decrease of firmness that occurred when fruit were transferred from cold storage to 20°C. Other observed CI symptoms were internal browning, darkness of the skin, flesh structural changes, and increase of ethylene and CO2 production. Harvest date had also a considerable effect on the storage at 15°C, in this way, late harvested fruits maintained good quality for more time than early harvested ones.

Effect of Cold Storage and Removal Astringency on Quality of Persimmon Fruit (Diospyros kaki, L.) cv. Rojo Brillante

Cold storage and removal of astringency effects on quality of persimmon fruit cv. Rojo brillante were determined. Persimmon fruit were stored at 1, 8, 11 and 15 ºC (85–90% RH) and after 6, 13, 20, 27 and 34 days of storage at these temperatures, astringency was removed. Fruit quality was assessed after the removal of the astringency and after a simulated retail storage period of 6 days at 20 ºC. Storage temperature affected fruit firmness, colour, appearance, acetaldehyde and ethanol production but not total soluble solids or flavour. Fruit stored at 15 ºC followed by 6 days at 20 ºC maintained the best commercial firmness and the lowest ethanol and acetaldehyde production. Chilling injury was observed after storage at 20 ºC on those fruits previously stored at 1 or 8 ºC.

Localization of adhesins on the surface of a pathogenic bacterial envelope through atomic force microscopy

Bacterial adhesion is the first and a significant step in establishing infection. This adhesion normally occurs in the presence of flow of fluids. Therefore, bacterial adhesins must be able to provide high strength interactions with their target surface in order to maintain the adhered bacteria under hydromechanical stressing conditions. In the case of B. pertussis, a Gram-negative bacterium responsible for pertussis, a highly contagious human respiratory tract infection, an important protein participating in the adhesion process is a 220 kDa adhesin named filamentous haemagglutinin (FHA), an outer membrane and also secreted protein that contains recognition domains to adhere to ciliated respiratory epithelial cells and macrophages. In this work, we obtained information on the cell-surface localization and distribution of the B. pertussis adhesin FHA using an antibody-functionalized AFM tip. Through the analysis of specific molecular recognition events we built a map of the spatial distribution of the adhesin which revealed a non-homogeneous pattern. Moreover, our experiments showed a force induced reorganization of the adhesin on the surface of the cells, which could explain a reinforced adhesive response under external forces. This single-molecule information contributes to the understanding of basic molecular mechanisms used by bacterial pathogens to cause infectious disease and to gain insights into the structural features by which adhesins can act as force sensors under mechanical shear conditions.

Adhesin contribution to nanomechanical properties of the virulent Bordetella pertussis envelope

Adherence to a biological surface allows bacteria to colonize and persist within the host and represents an essential first step in the pathogenesis of most bacterial diseases. Consequently, the physicochemical properties of the outer membrane in bacteria play a key role for attachment to surfaces and therefore for biofilm formation. Bordetella pertussis is a Gram-negative bacterium that colonizes the respiratory tract of humans, producing whooping cough or pertussis, a highly infectious disease. B. pertussis uses various adhesins exposed on its surface to promote cell-surface and cell-cell interactions. The most dominant adhesin function is displayed by filamentous hemagglutinin (FHA). B. pertussis Tohama I wild-type (Vir+) strain and two defective mutants, an avirulent (Vir-) and a FHA-deficient (FHA-) B. pertussis strains were studied by AFM under physiological conditions to evaluate how the presence or absence of adhesins affects the mechanical properties of the B. pertussis cell surface. Quantitative information on the nanomechanical properties of the bacterial envelope was obtained by AFM force-volume analysis. These studies suggested that the presence of virulence factors is correlated with an increase in the average membrane rigidity, which is largely influenced by the presence of FHA. Moreover, for this system we built a nanoscale stiffness map that reveals an inhomogeneous spatial distribution of Young modulus as well as the presence of rigid nanodomains on the cell surface.