A chemically-defined growth medium to support Lactobacillus-Acetobacter community analysis

Lactobacilli and acetobacters are commercially important bacteria that often form communities in natural fermentations, including food preparations, spoilage, and in the digestive tract of Drosophila melanogaster fruit flies. Communities of these bacteria are widespread and prolific, despite numerous strain-specific auxotrophies, suggesting they have evolved nutrient interdependencies that regulate their growths. The use of a chemically-defined medium (CDM) supporting the growth of both groups of bacteria would greatly facilitate identification of the precise metabolic interactions between these two groups of bacteria. While numerous such media have been developed that support specific strains of lactobacilli and acetobacters, there has not been a medium formulated to support both genera. We developed such a medium, based on a previous Lactobacillus CDM, by modifying the nutrient abundances to improve growth of both groups of bacteria. We further simplified the medium by substituting casamino acids for individual amino acids and the standard Wolfes vitamins and mineral stocks for individual vitamins and minerals, resulting in a reduction from 40 to 8 stock solutions. The new CDM and variations of it support robust growth of lactobacilli and acetobacters. We provide the composition and an example of its use to measure nutritional interactions.