UNIDENTIFIED GROWTH FACTOR FOR A LACTIC ACID BACTERIUM

Area of Science:

• Microbiology
• Bacteriology
• Nutritional Science

Background:

• Lactobacillus bulgaricus, a key lactic acid bacterium, requires specific nutrients for optimal growth.
• A semisynthetic basal medium was used to study the nutritional requirements of the Lactobacillus bulgaricus Georgia strain.
• Previous studies had not identified all essential growth factors for this specific strain.

Purpose of the Study:

• To identify an unknown growth factor required by Lactobacillus bulgaricus Georgia strain.
• To characterize the properties and sources of this unidentified growth factor.
• To investigate the effects of various compounds on the growth of Lactobacillus bulgaricus.

Main Methods:

• Cultivation of Lactobacillus bulgaricus on a semisynthetic basal medium.
• Extraction and testing of various biological materials (yeast, liver) as potential sources of the growth factor.
• Chromatographic analysis (paper chromatography) and solubility tests to characterize the factor.
• Assay of known growth factors and compounds for activity.

Main Results:

• An unidentified growth factor, termed Georgia bulgaricus factor (GBF), was essential for Lactobacillus bulgaricus growth.
• Aqueous extracts of torula yeast and beef liver were identified as the richest sources of GBF.
• Adenine, RNA, and Mg(++) showed some growth stimulation, while DNA, dAMP, and dGMP inhibited growth.
• GBF demonstrated stability to heat (pH 2.5-11) and light, but was destroyed at pH 1.0.
• Paper chromatography indicated GBF moved as a single component, with firm charcoal adsorption and poor organic solvent solubility.
• A 28-fold concentrate of GBF was prepared.

Conclusions:

• A novel growth factor, GBF, is necessary for Lactobacillus bulgaricus Georgia strain.
• The unique properties of GBF suggest it is distinct from previously known growth factors.
• Further research is required to definitively identify the chemical nature of GBF.