Figure 9. Transmission electron microscopic view of the bacterial mass (BA, upper inset) illustrated in (8a). Morphologically, the bacterial population appears to be composed of only Gram-positive, filamentous organisms (arrowhead in lower inset). Note the distinctive Gram-positive cell wall. The upper inset is a magnification of the bacterial cluster (BA) in (8a). Magnification: 3400x. Insets: upper, 132x; lower, 21,300x. (From Nair et al., 1990a.)