Bacteria have an undefined nuclear region which lacks a nuclear membrane and contains only DNA without proteins. Such a region is called:

In bacteria and other prokaryotes, the genetic material is not enclosed within a nuclear envelope. Instead, these organisms possess an undefined nuclear region in the cytoplasm known as the nucleoid [1]. Unlike the well-defined nucleus of eukaryotes, which contains chromosomes associated with histone proteins, the bacterial nucleoid typically consists of a single circular DNA molecule that lacks these basic histone proteins [2]. This region is in direct contact with the cytoplasm and contains the genetic information necessary for reproduction and cellular activity. While the nucleoid may contain some RNA and non-histone proteins for structural organization and supercoiling, it is fundamentally characterized by the absence of a surrounding membrane, distinguishing it from the eukaryotic nucleus [2]. Therefore, the region containing DNA without a nuclear membrane in bacteria is the nucleoid.

Sources

1. [1] Science ,Class VIII . NCERT(Revised ed 2025) > Chapter 2: The Invisible Living World: Beyond Our Naked Eye > 2.5 Why Is Cell Considered to Be a Basic Unit of Life? > p. 24
2. [2] https://pmc.ncbi.nlm.nih.gov/articles/PMC6907758/