Sandwich freezing device for rapid freezing of viruses, bacteria, yeast, cultured cells and animal and human tissues in electron microscopy

Comparative genomic and morphological analyses of capsular and capsular-deficient pneumococcal strains simultaneously isolated from a patient with invasive pneumococcal disease

INTRODUCTION

To understand the in-vivo dynamics in pneumococci, investigation into the carriage in patients with invasive pneumococcal disease (IPD) is extremely important.

METHODS

To clarify genomic and morphological differences between pneumococcal strains simultaneously isolated from different sites in a patient with IPD, we conducted comparative analyses of two strains. A capsular strain isolated from the blood and a non-capsular strain isolated from the sputum of a patient with IPD were used.

RESULTS

The strain isolated from blood was serotype 24B with capsule. The strain isolated from sputum with capsular type 24 genes was non-encapsulated, and genomic analysis revealed an insertion region in the wcxK gene. Its biofilm-forming capacity was higher than that of the capsular strain, as was that of the pspK-positive true non-encapsulated strain. Furthermore, observing the microbe using transmission electron microscopy revealed that the strain isolated from sputum lacked a capsule, like the pspK-positive true non-encapsulated strain.

CONCLUSIONS

Our analysis of the two strains isolated from the blood and sputum of a patient with IPD showed one possible in-vivo morphological change in Streptococcus pneumoniae.

Sandwich freezing and freeze substitution of Arabidopsis plant tissues for electron microscopy

Sandwich freezing is a method of rapid freezing by sandwiching specimens between two copper disks, and it has been used for observing exquisite close-to-native ultrastructure of living yeast and bacteria. Recently, this method has been found to be useful for preserving cell images of glutaraldehyde-fixed cultured cells, as well as animal and human tissues. In the present study, this method was applied to observe the fine structure of living Arabidopsis plant tissues and was found to achieve excellent ultrastructural preservation of cells and tissues. This is the first report of applying the sandwich freezing method to observe plant tissues.

Activation of CWI pathway through high hydrostatic pressure, enhancing glycerol efflux via the aquaglyceroporin Fps1 in Saccharomyces cerevisiae

The fungal cell wall is the initial barrier for the fungi against diverse external stresses, such as osmolarity changes, harmful drugs, and mechanical injuries. This study explores the roles of osmoregulation and the cell-wall integrity (CWI) pathway in response to high hydrostatic pressure in the yeast Saccharomyces cerevisiae. We demonstrate the roles of the transmembrane mechanosensor Wsc1 and aquaglyceroporin Fps1 in a general mechanism to maintain cell growth under high-pressure regimes. The promotion of water influx into cells at 25 MPa, as evident by an increase in cell volume and a loss of the plasma membrane eisosome structure, activates the CWI pathway through the function of Wsc1. Phosphorylation of Slt2, the downstream mitogen-activated protein kinase, was increased at 25 MPa. Glycerol efflux increases via Fps1 phosphorylation, which is initiated by downstream components of the CWI pathway, and contributes to the reduction in intracellular osmolarity under high pressure. The elucidation of the mechanisms underlying adaptation to high pressure through the well-established CWI pathway could potentially translate to mammalian cells and provide novel insights into cellular mechanosensation.

Ultrastructural Examination of Mouse Glomerular Capillary Loop by Sandwich Freezing and Freeze-Substitution

Sandwich freezing is a method of rapid freezing by sandwiching specimens between two metal disks, and has been used for observing exquisite close-to-native ultrastructure of living yeast and bacteria. Recently, this method has been found to be useful for preserving cell images of glutaraldehyde-fixed animal and human tissues. In the present study, this method was applied to observe fine structure of mouse glomerular capillary loops. Morphometry was then performed, and the results were compared with the data obtained by in vivo cryotechnique, which may provide the closest ultrastructure to the native state of living tissue. The results show that the ultrastructure of glomerular capillary loops obtained by sandwich freezing-freeze substitution after glutaraldehyde fixation was close to that of the ultrastructure obtained by in vivo cryotechnique, not only in quality of cell image but also in quantitative morphometry. They indicate that the ultrastructure obtained by sandwich freezing-freeze-substitution after glutaraldehyde fixation may more closely reflect the living state of cells and tissues than conventional chemical fixation and dehydration at room temperature and conventional rapid freezing freeze-substitution of excised tissues without glutaraldehyde fixation. Sandwich freezing-freeze substitution technique should be used routinely as a standard method for observing close-to-native ultrastructure of biological specimens.