Lactobacillus is a gram-positive bacteria belonging to the Firmicutes phylum and the Lactobacillaceae family.
Lactobacillus bacteria are usually rod-shaped, with a length of 0.5 to 1.2 microns and a width of 1.0 to 10.0 microns.
They are mostly long rods, sometimes nearly spherical, and usually arranged in short chains.
They are facultative anaerobic or microaerobic bacteria that grow well in acidic environments, with an optimal pH of 5.5 to 6.2.