Which one of the following is not true about bacterial chromosomes ?
(a) There is generally only one chromosome in each bacterial cell
(b) A bacterial chromosome is attached to the plasma membrane
(c) A bacterial chromosome is in a loop
(d) A bacterial chromosome contains both DNA and associated histones

Options

A. There is generally only one chromosome in each bacterial cell
B. A bacterial chromosome is attached to the plasma membrane
C. A bacterial chromosome is in a loop
D. A bacterial chromosome contains both DNA and associated histones

Explanation

To determine which statement is not true about bacterial chromosomes, let's analyze each option step by step:

1. **Option (a): There is generally only one chromosome in each bacterial cell.**
- Bacterial cells typically contain a single circular chromosome. This statement is true.

2. **Option (b): A bacterial chromosome is attached to the plasma membrane.**
- In bacterial cells, the chromosome is not attached to the plasma membrane. Instead, it is located in the cytoplasm, often in a region called the nucleoid. This statement is false.

3. **Option (c): A bacterial chromosome is in a loop.**
- The structure of the bacterial chromosome is circular, and it can be described as being in a loop. This statement is true.

4. **Option (d): A bacterial chromosome contains both DNA and associated histones.**
- Bacterial chromosomes do not have histones in the same way that eukaryotic chromosomes do. Instead, they have proteins that help in organizing the DNA, but they are not classified as histones. This statement is misleading because while there are proteins associated with bacterial DNA, they are not true histones. However, it is often considered true in a broader context since some bacteria do have histone-like proteins.

Based on the analysis, the statement that is not true about bacterial chromosomes is **(b)**: "A bacterial chromosome is attached to the plasma membrane."

### Final Answer:
**(b) A bacterial chromosome is attached to the plasma membrane.**