Question

But some bacterium always lives in surroundings with the same concentration of dissolved substances as in their own cytoplasm. what structure do these bacteria not need? (fourth paragraph of subsection implies the answer)

Answer 1

Periplasmic space

Step-by-step explanation:

The periplasmic space is a colloidal layer that contains a large amount of hydrolytic and other enzymes that direct essential nutrients to the plasma membrane transport proteins, preventing them from spreading back to the outside. For this reason, bacteria living in environments with the same concentration of dissolved substances as in their own cytoplasm need the periplasmic space to prevent the loss of structures to the external environment.

The periplasmic space contains antibiotic inactivating enzymes, chemoreceptors (sensors that help the cell to detect changes in the environment) and oligosaccharides that appear to help the bacteria resist the molarity of the environment.

In the periplasmic space of many Gram-negative bacteria, between the cell wall and the phospholipid layer of the outer membrane there are lipoproteins that would assist in anchoring the outer membrane to the cell wall.

Answer 2

Cell wall

The rigid bacterial cell wall protects them from osmotic lysis or rupture when they are placed in hypotonic solutions (solutes concentration outside the cell is less than inside the cells). The cell wall is a rigid limit to the swelling cytoplasm. Therefore, if the concentration of the solutes in the surrounding of the bacteria the same as its cytoplasm, in this regard the cell wall wouldn’t be necessary.