Multicellular behavior of Bacillus cereus growing as a biofilm in soil.

摘要

Members of Bacillus cereus are commonly isolated from soils, yet their ecology and physiology in soil are poorly understood. The aim of this work was to investigate the growth of B. cereus under soil nutrient conditions using soil extracted soluble organic matter (SESOM) and artificial soil microcosms (ASM). In SESOM, B. cereus spores germinated, grew as filaments, formed clumps, and sequentially sporulated. The clumps were encased in extracellular matrix containing DNA and proteins. Two genes, purA and galE were required for multicellular growth. B. cereus and some soil-isolated Bacillus were able to translocate through ASM as bundles of parallel filaments. Proteomics analysis of exponentially growing populations revealed the switching on of various anabolic pathways when growing in SESOM, including amino acid and nucleotide biosynthesis. The results indicate that B. cereus is able to grow and forms biofilms between soil particles, translocating through soil by employing a multicellular mode of growth.