Mini-revue : les bactéries lactiques, ces êtres vivants apparus il y a près de 3 milliards d'années

Abstract

Lactic acid bacteria (LAB) are known to be useful for humans. They contribute to the manufacture and the preservation of many foods. Despite their importance, only few phylogenetic studies adress the position and role of LAB in the evolution of life on Earth. This review examines molecular data and data of paleontology and metabolism that can be used to determine when LAB first appeared. Phylogenetic studies based on ribosomal DNA sequence comparisons and on signature-sequence analysis present in well-conserved proteins suggests an ancestral position in evolution of Gram positive bacteria with low GC%, including LAB. By these criteria, LAB may have appeared before the photosynthetic cyanobacteria. As the latter were found in sediments dated 2.75 billion years ago, LAB may have emerged 3 billion years ago. Their poor adaptation to aerobic environments also suggests that they may have emerged during the transition of Earth's atmosphere from anaerobic to aerobic.