It's not accurate to talk about "rudimentary forms of bacteria". Bacteria are incredibly diverse and complex organisms, and even the "simplest" forms are highly sophisticated in their own right.

Instead of "rudimentary forms," we might talk about:

* Ancient lineages: Some bacterial groups are considered to be among the oldest forms of life on Earth, meaning they have evolved over billions of years and might retain some features of early life.

* Minimalist genomes: Certain bacteria have very small genomes compared to others. This doesn't mean they are less complex, but rather that they have adapted to survive in specific, nutrient-rich environments and rely on the host for essential functions.

* Cellular structure: Some bacteria have simpler structures than others, like lacking internal membrane-bound organelles.

It's important to remember:

* All bacteria are complex organisms: Even the simplest bacteria have a sophisticated cellular structure and intricate mechanisms for survival.

* Simplicity is relative: What might seem simple to us might be highly complex from a biological perspective.

* Evolution is ongoing: Bacteria are constantly evolving and adapting to new environments, which means there is no fixed hierarchy of "simplicity" or "complexity" within the group.

Instead of focusing on "rudimentary forms," we should appreciate the diversity and ingenuity of bacteria as a whole.