Grey Layer
Less bacteria are found in the grey layer than in the black bands. Here are some spirochaetes along with two empty shells of diatoms. The bright spot in the center was not identified.
Phase contrast micrograph. 150X150 µm
Shells of diatoms consist of silicate. Therefore, they are long lasting. Their fine structure is often used to classify the diatoms. Here are a few examples.
Phase contrast micrograph.
Sometimes bacteria in the grey layer (and elsewhere) live together in associations.
Phase contrast micrograph