Melissa is studying a gram-stained slide of curd bacteria. she sees many rod-shaped, violet-colored bacteria. what type of bacteria are they?

By the observation, the rod shape violet-colored bacteria could be a Gram-positive bacillus which is Lactobacillus spp.  in curd.

Explanation:

Gram-stain is a staining method to isolate and study the Gram-positive or Gram-negative bacteria with the help of the crystal violet dye. Crystal violet dye stains both Gram-positive and Gram-negative bacteria in purple stain. After decolorization, Gram-negative bacteria appears to be pink in color, however,Gram-positive bacteria remain purple.

According to bacteria structure, they term as bacillus (rod), strepto (clusters or threads) or Diplo (in pairs).

Thus, according to the observation, the rod shape violet colored bacteria are Gram-positive bacillus which is Lactobacillus spp. in curd.