Details

Autor(en) / Beteiligte

• Wilhelm, Michael J
• Sheffield, Joel B
• Sharifian Gh, Mohammad
• Wu, Yajing
• Spahr, Christian
• Gonella, Grazia
• Xu, Bolei
• Dai, Hai-Lung

Titel

Gram’s Stain Does Not Cross the Bacterial Cytoplasmic Membrane

Ist Teil von

• ACS chemical biology, 2015-07, Vol.10 (7), p.1711-1717

Ort / Verlag

United States: American Chemical Society

Erscheinungsjahr

2015

Quelle

MEDLINE

Beschreibungen/Notizen

• For well over a century, Hans Christian Gram’s famous staining protocol has been the standard go-to diagnostic for characterizing unknown bacteria. Despite continuous and ubiquitous use, we now demonstrate that the current understanding of the molecular mechanism for this differential stain is largely incorrect. Using the fully complementary time-resolved methods: second-harmonic light-scattering and bright-field transmission microscopy, we present a real-time and membrane specific quantitative characterization of the bacterial uptake of crystal-violet (CV), the dye used in Gram’s protocol. Our observations contradict the currently accepted mechanism which depicts that, for both Gram-negative and Gram-positive bacteria, CV readily traverses the peptidoglycan mesh (PM) and cytoplasmic membrane (CM) before equilibrating within the cytosol. We find that not only is CV unable to traverse the CM but, on the time-scale of the Gram-stain procedure, CV is kinetically trapped within the PM. Our results indicate that CV, rather than dyes which rapidly traverse the PM, is uniquely suited as the Gram stain.