• lactic acid bacteria


  The group of Gram-positive bacteria generating lactic acid as the major end product of their fermentive metabolism
• LAB


  - heterogeneous group ofGram-positivecocci and rods- non-respiring (generally); non-spore-forming; non-motile (generally)- catalase negative- free living, found in milk (products), decaying plant, animal / human microbiome
• LAB in human microbiome


  positive influence on normal microflora, competitive exclusion of pathogens, and stimulation/modulation of mucosal immunity.
• LAB food industry


  contribute to taste and texture, inhibit food spoilage and pathogenic bacteria by producing lactic acid
• Probiotic


  deliver live, potentially beneficial, bacteria to the gut ecosystem of humans/animalshomoe
• LAB need


  energy only from sugars (need environments with sugars) and limited synthetic ability (need complex media)
• LAB core genera


  Streptococcus, Lactobacillus, Enterococcus, Lactococcus, Leuconostoc,Pediococcus, Carnobacterium, Oenococcus, Tetragenococcus, Vagococcus,Aerococcus, andWeisella
• lactic acid fermentation


  anaerobic fermentation reaction which can be categorized into two ways
• heterolactic fermentation


  glucose is fermented to a mixture of lactic acid, acetic acid, and carbon dioxideNegativefor Gas ProductionPositivefor Sugar Fermentation
• homolactic fermentation


  produces two molecules of lactic acid from one glucose moleculePositivefor Gas ProductionPositivefor Sugar Fermentation
• Yeast Dextrose Calcium carbonate agar (YDC)


  differential agar that determines whether organism plated produced lactic acid

  CaCO3 (gives white appearance) in YDC plates is broken in the presence of lactic acid to H2O + CO2 + Ca-Lactate, producing a clearing = indicator of a lactic acid + bacterium
• Glucose durham fermentation tubes


  determine whether an organism is homo or hetero with basal media w high glucose and pH indicator- Phenol Red turns from red to yellow with the acidification (acidic pH) of the medium due to acidic end products of fermentation- If bacteria cannot ferment, they may utilized peptone to grow in the broth. This leads to basic pH in the broth, which turns the broth pink (from original red).TheDurham tube captures gasbeing produced (bubble or gas pocket)