Isolation and identification of lactic acid bacteria from sediments of a coastal marsh using a differential selective medium

Aims: To identify lactic acid bacteria (LAB) colonies isolated from sediments of a coastal marsh by the reduction of 2,3,5-triphenyltetrazolium chloride (TTC) in MRS medium. Methods and Results: Single colonies isolated from sediments of a coastal marsh by enrichment in MRS broth were selected from MRS-TTC plates and classified according to colony phenotype based on TTC reduction. A total of 37 colonies grouped in seven different phenotypes were identified by analysis of its 16S ribosomal gene sequence. Most isolates belonged to the Firmicutes phylum, mainly to orders Bacillales and Lactobacillales. LAB were represented by 20 isolates, 15 of which belong to the genus Weissella. Conclusions: Enrichment in MRS was highly selective for the isolation of bacteria belonging to phylum Firmicutes. Several different phenotypes were developed by LAB and must be considered during LAB isolation based on TTC reduction. Significance and Impact of the Study: To our knowledge, this is the first study aimed at determining a relationship between colony phenotype from TTC reduction and a partial identification of isolates based on 16S ribosomal gene sequence similarities. Besides, this is the first report of isolation of W. cibaria from environmental samples.