The noodle defense

Phagocytosis: what's on the menu? 1

Phagocytosis is an evolutionarily conserved process. In Protozoa, phagocytosis fulfills a feeding mechanism, while in Metazoa, phagocytosis diversified to play multiple organismal roles, including immune defence, tissue homeostasis, and remodeling. Accordingly, phagocytes display a high level of plasticity in their capacity to recognize, engulf, and process targets that differ in composition and morphology. Here, we review how phagocytosis adapts to its multiple roles and discuss in particular the effect of target morphology in phagocytic uptake and phagosome maturation.

Suppression of ERK activation in urethral epithelial cells infected with Neisseria gonorrhoeae and its isogenic minD mutant contributes to anti-apoptosis

In gonococci-infected transduced human urethral epithelial cells (THUEC), the role of ERK, a mitogen-activated protein kinase (MAPK), in apoptosis is unknown. We observed lowering of ERK activation in THUEC following infection with anti-apoptosis-inducing Neisseria gonorrhoeae strain CH811. An isogenic cell division mutant of this strain, Ng CJSD1 (minD deficient), which is large and abnormally shaped, reduced ERK phosphorylation levels even more than its parental strain in THUEC. This led to higher anti-apoptosis in mutant-infected cells as compared to the parental strain-infected cells. Our results suggest that N. gonorrhoeae infection reduces ERK activation in THUEC contributing to anti-apoptosis.

Epifluorescence, SEM, TEM and nanoSIMS image analysis of the cold phenotype of Clostridium psychrophilum at subzero temperatures

We have applied an image-based approach combining epifluorescence microscopy, electron microscopy and nanoscale secondary ion mass spectrometry (nanoSIMS) with stable isotope probing to examine directly the characteristic cellular features involved in the expression of the cold phenotype in the Antarctic bacterium Clostridium psychrophilum exposed to a temperature range from +5 to -15 °C under anoxic conditions. We observed dramatic morphological changes depending on temperature. At temperatures below -10 °C, cell division was inhibited and consequently filamentous growth predominated. Bacterial cells appeared surrounded by a remarkably thick cell wall and a capsule formed of long exopolysaccharide fibres. Moreover, bacteria were entirely embedded within a dense extracellular matrix, suggesting a role both in cryo-protection and in the cycling of nutrients and genetic material. Strings of extracellular DNA, transient cell membrane permeability and release of membrane vesicles were observed that suggest that evolution via transfer of genetic material may be especially active under frozen conditions. While at -5 °C, the bacterial population was metabolically healthy, at temperatures below -10 °C, most cells showed no sign of active metabolism or the metabolic flux was extremely slowed down; instead of being consumed, carbon was accumulated and stored in intracellular granules as in preparation for a long-term survival.