In terms of grams, there are two types of cell; Gram-positive, and Gram-negative. The main difference between the two types of bacterial cell for the most part lies within the cell wall. More specifically, the amount of PEPTIDOGLYCAN in the cell wall. PEPTIDOGLYCAN consists of various amino acids and sugars that form a polymer, which creates a layer on the plasma membrane of different eubacterias (such as Lactobacillus Bulgaricus.) In a gram-POSITIVE bacteria cell, there is said to be roughly five times more PEPTIDOGLYCAN than there is in a gram-NEGATIVE bacteria cell.

In addition to this, Gram-positive bacteria have a few other characteristics that gram-negatives do not.

- A thicker cytoplasmic membrane (a phospholipid bilayer which can be found in all cells)

- A polysaccharide capsule (a layer outside of bacteria cell, mostly used to protect it from viruses)

Also, Gram negatives have an additional layer, (chemically different from the plasma membrane and outside the cell wall), and occasionally a gelatinous sheath outside that.

Below is a diagram depicting the differences between a Gram-positive cell, and a Gram-negative cell.

Now that you have an idea of what GRAM is, we can tell you, with confidence that...

LACTOBACILLUS BULGARICUSIS GRAM POSITIVE.

But how do you find out whether a bacteria cell is gram positive or Gram negative?

This is done through a process called GRAM STAINING. This is a complicated process, and it can mainly be characterized by application and staining of different materials. It begins by collecting bacteria, and, obviously, putting them on the stage of a microscope. Then, a violet stain is applied to the bacteria, and a short period of waiting must occur for the violet to seep through the cell membrane, a process we know as DIFFUSION. Then, an iodine solution is applied to the bacteria. Next, after those are applied, a solution primarily made up of ethanol and other forms of alchohol is applied. This acts as a "decolorization" agent. This is where you find out if your cell is gram-positive or negative. Due to the differences in cell wall and other layers about the ouside of the cell in the gram-negative cells, they are unable to retain color when decolorization agent is applied. However, gram-positive bacteria cells ARE able to retain this purple color. Therefore, when the Gram staining process is complete, a Gram-positive cell will be purple in color, while gram-negatives will remain invisible (unless safranin is applied, a counter stain used to identify gram-negative bacteria once the GRAM STAINING process is complete.