Trypan Blue Dye Enters Viable Cells Incubated with the Pore-Forming Toxin HlyII of Bacillus cereus

Trypan blue is a dye that has been widely used for selective staining of dead tissues or cells. Here, we show that the pore-forming toxin HlyII of Bacillus cereus allows trypan blue staining of macrophage cells, despite the cells remaining viable and metabolically active. These findings suggest that the dye enters viable cells through the pores. To our knowledge, this is the first demonstration that trypan blue may enter viable cells. Consequently, the use of trypan blue staining as a marker of vital status should be interpreted with caution. The blue coloration does not necessarily indicate cell lysis, but may rather indicate pore formation in the cell membranes and more generally increased membrane permeability

WACHSTUMSVERHALTEN VON METHYLOMONAS CLARA

A bacterium was chosen for single cell protein production from methanol because of its high protein content of over 80% anda potential yield of 0.6 g cell mass per g methanol. The selected organism Methylomonas clara is an obligate methylotroph; methanol is incorporated as formaldehyde via the ribulose monophosphate cycle. The maximum possible cell mass production in continuous culture in two different reactor systems was studied, to describe the kinetics of growth. The reactors compared were a normal stirred vessel with a Flarblade turbine and a newly designed completely filled bioreactor with a draft tube and propeller. The maximum achieved cell mass productivity in continuous culture in both reactor systems was 11.7 g . Ata methanol concentration in the inflow medium of 100 g I wash out of the cells occured at half maximum growth rate. By-products inhibition limited further enhancment of growth. The proof was given experimentally

A Vertebrate-type Ferredoxin Domain in the Na⁺-translocating NADH Dehydrogenase from Vibrio cholerae

The Na+-translocating NADH:quinone oxidoreductase from Vibrio cholerae contains a single Fe-S cluster localized in subunit NqrF. Here we study the electronic properties of the Fe-S center in a truncated version of the NqrF subunit comprising only its ferredoxin-like Fe-S domain. Mössbauer spectroscopy of the Fe-S domain in the oxidized state is consistent with a binuclear Fe-S cluster with tetrahedral sulfur coordination by the cysteine residues Cys70, Cys76, Cys79, and Cys111. Important sequence motifs surrounding these cysteines are conserved in the Fe-S domain and in vertebrate-type ferredoxins. The magnetic circular dichroism spectra of the photochemically reduced Fe-S domain exhibit a striking similarity to the magnetic circular dichroism spectra of vertebrate-type ferredoxins required for the in vivo assembly of iron-sulfur clusters. This study reveals a novel function for vertebrate-type [2Fe-2S] clusters as redox cofactors in respiratory dehydrogenases