Project description:Full title: Environmental transcriptome analysis of LfeRT32a in its natural microbial community comparing the biofilm and planktonic modes of life. Extreme acidic environments are characterized among other features by the high metal content and the lack of nutrients (oligotrophy). Macroscopic biofilms and filaments usually grow on the water-air interface or under the stream attached to solid substrates (streamers). In the Tinto River (Spain), brown filaments develop under the water stream where the Gram-negative iron-oxidizing bacteria Leptospirillum ferrooxidans and Acidithiobacillus ferrooxidans are abundant. Both microorganisms play a critical role in bioleaching processes for industrial (biominery) and environmental applications (acid mine drainage, bioremediation). The aim of this study was to investigate the physiological differences between the free living (planktonic) and the sessile (biofilm associated) lifestyles of L. ferrooxidans as part of a natural extremely acidophilic community.
Project description:Bacteria of the genus Thiomonas are found ubiquitously in arsenic contaminated waters such as Acid Mine Drainage (AMD), where they contribute to the precipitation and the natural bioremediation of arsenic. In these environments, these bacteria have developed a large range of resistance strategies, such as biofilm formation, which is one of the most ubiquitous adaptive response observed in prokaryotes to various stresses, such as those induced in the presence of toxic compounds. This study focused on the process of biofilm formation in several Thiomonas strains isolated from the same AMD. The results obtained here show that these bacteria are all capable of forming biofilms, but the architecture and the kinetics of formation of these biofilms differ depending on whether arsenic is present in the environment and from one strain to another. Indeed, two strains favored biofilm formation, whereas three others favored motility in the presence of arsenic. In order to identify the underlying mechanisms, the patterns of expression of some genes possibly involved in the process of biofilm formation were investigated in Thiomonas sp. CB2 in the presence and absence of arsenite, using a transciptomic approach (RNAseq). The findings obtained here shed interesting light on how the formation of biofilms and the motility processes contribute to the adaptation of Thiomonas strains to extreme environments.
