%0 Journal Article
%T Defining lower limits of biodegradation: atrazine degradation regulated by mass transfer and maintenance demand in Arthrobacter aurescens TC1
%J -
%D 2019
%R https://doi.org/10.1038/s41396-019-0430-z
%X Exploring adaptive strategies by which microorganisms function and survive in low-energy natural environments remains a grand goal of microbiology, and may help address a prime challenge of the 21st century: degradation of man-made chemicals at low concentrations (¡°micropollutants¡±). Here we explore physiological adaptation and maintenance energy requirements of a herbicide (atrazine)-degrading microorganism (Arthrobacter aurescens TC1) while concomitantly observing mass transfer limitations directly by compound-specific isotope fractionation analysis. Chemostat-based growth triggered the onset of mass transfer limitation at residual concentrations of 30£¿¦Ìg£¿L£¿1 of atrazine with a bacterial population doubling time (td) of 14 days, whereas exacerbated energy limitation was induced by retentostat-based near-zero growth (td£¿=£¿265 days) at 12£¿¡À£¿3£¿¦Ìg£¿L£¿1 residual concentration. Retentostat cultivation resulted in (i) complete mass transfer limitation evidenced by the disappearance of isotope fractionation (¦Å13C£¿=£¿£¿0.45¡ë£¿¡À£¿0.36¡ë) and (ii) a twofold decrease in maintenance energy requirement compared with chemostat cultivation. Proteomics revealed that retentostat and chemostat cultivation under mass transfer limitation share low protein turnover and expression of stress-related proteins. Mass transfer limitation effectuated slow-down of metabolism in retentostats and a transition from growth phase to maintenance phase indicating a limit of ¡Ö10£¿¦Ìg£¿L£¿1 for long-term atrazine degradation. Further studies on other ecosystem-relevant microorganisms will substantiate the general applicability of our finding that mass transfer limitation serves as a trigger for physiological adaptation, which subsequently defines a lower limit of biodegradation
%U https://www.nature.com/articles/s41396-019-0430-z