Lactobacillus spp. - Classification, Characteristics, Habitat, Culture, Pathogenicity
Classification of Lactobacillus spp.
Domain: Bacteria
Phylum: Bacillota
Class: Bacilli
Order: Lactobacillales
Family: Lactobacillaceae
Genus: Lactobacillus
Characteristics of Lactobacillus spp.
Lactobacillus spp. is gram-positive, non-sporing, sometimes filamentous bacteria. They are arranged singly or in pairs. Metachromatic granules are present in some species such as Lactobacillus lacti, Lactobacillus bulgaricus, Lactobacillus leichamannii
Fig: Lactobacillus spp. (Source: atsu.edu)
Habitat of Lactobacillus spp.
They are found where the carbohydrate-containing substrate is available. Lactobacillus spp. live on the mucosal surface (oral cavity, intestine, vagina) and are also found in foods such as milk, fermented milk products, cheese, beverages, etc.
Cultural characteristics of Lactobacillus spp.
Cultural characteristics of Lactobacillus spp. are
selective media: Acetate medium
colonies are usually small (1-3mm) with entire margins
Three groups on the positive basis of the nature of the product form:
Obligate homofermenters
includes Lactobacillus delbruckii, Lactobacillus audophilus
Facultative heterofermenter
comprises more than 30 species. Eg: Lactobacillus sake, Lactobacillus intestinalis, Lactobacillus rhamnosus
Obligate heterofermenter
closely related to Leuconostoc spp.
Pathogenicity of Lactobacillus spp.
Lactobacillus spp. is associated with dental caries and is occasionally isolated from bacteremic patients.
Role of Lactobacillus spp. as normal human flora
Lactobacillus spp. is commensals of the mucosal membrane of the oral cavity, intestine, and vagina. They usually comprise a minor part of the flora. They produce bacteriocins that reduce pH in the local environment. Thus, colonization by potential pathogens on the mucosal surface is prevented. It has a probiotic effect on the human body.