What type of bacteria can be directly examined using darkfield microscopy?

Darkfield microscopy is particularly valuable for visualizing certain types of bacteria that are difficult to see using standard light microscopy due to their size or lack of pigmentation. Treponemes, which are spiral-shaped bacteria, are best examined using darkfield microscopy because this technique enhances the contrast of these thin organisms against a dark background. This allows for clearer visualization of their motility and morphology.

In contrast, mycobacteria are often examined using special staining techniques, as they are notoriously difficult to visualize with regular light microscopy due to their waxy cell wall. Staphylococcus species, which are typically circular and can be easily stained, do not require darkfield microscopy for effective visualization. Bacillus cereus, a rod-shaped bacterium, is also easily viewed with conventional staining methods, making darkfield microscopy unnecessary. Thus, the unique structure and characteristics of treponemes make them ideally suited for observation through darkfield microscopy.