Now, earlier, I mentioned that there are two different types of bacterial cells. So how exactly do we categorize different types of bacterial cell? So, bacterial cells can be categorized based on their structure of the cell envelope. And we use a technique called Gram staining to basically differentiate between these two different types of bacterial cells. So we have Grampositive bacteria and Gram negative bacteria. So, Grampositive bacteria contain a very thick peptidogly cell wall, about four times as thick as the actual plasma membrane.