MICROBIAL CANNIBALISM IN EXTREME STARVED ENVIRONMENT

Due to their geochemical characteristics, some soils can be considered as extreme. This is the case with some New Caledonia soils, such as ultramafic soils, that are characterized by deficiencies in essential elements and overabundance of heavy metals, particularly nickel. This phenomenon is amplified in mine spoils where carbon and nitrogen concentrations are extremely low, thus, classifying mine spoils as starved environments. Our objective was to determine which adaptive strategies enable bacterial populations to adapt to extreme environments. A comparative metagenomic analysis applied to partial metagenomic sequences of two ultramafic soils (pristine ultramafic soil, mine spoils) and two “classical“ soils (prairie soil and corn field soil) was developed to detect genes and bacterial populations specific to each soil. The new program and the graphical interface that we developed specifically for this study helped highlight the effect of the ultramafic origin, the “human” influence (mining, farming), and the starvation conditions on bacterial community function. Our results highlight the originality of the bacterial community structure and its metabolism in the mine spoils. To adapt to these extreme edaphic conditions, bacterial populations tend to minimize nutrient loss and to enhance biosynthetic pathways reaction by using dead bacterial cells as nutrients.