Three peptides comprising mono-, di-, and tri-fluoroethylglycine
(MfeGly, DfeGly, and TfeGly) residues alternating with lysine were
digested by readily available proteases (elastase, bromelain, trypsin,
and proteinase K). The degree of degradation depended on the enzyme
employed and the extent of fluorination. Incubation of the peptides
with a microbial consortium from garden soil resulted in degradation,
yielding fluoride ions. Further biodegradation studies conducted with
the individual fluorinated amino acids demonstrated that the degree
of defluorination followed the sequence MfeGly > DfeGly > TfeGly.
Enrichment of the soil bacteria employing MfeGly as a sole carbon
and energy source resulted in the isolation of a bacterium, which
was identified asSerratia liquefaciens. Cell-free extracts of this bacterium enzymatically defluorinated
MfeGly, yielding fluoride ion and homoserine.In silicoanalysis of the genome revealed the presence of a gene that putatively
codes for a dehalogenase. However, the low overall homology to known
enzymes suggests a potentially new hydrolase that can degrade monofluorinated
compounds.19F NMR analysis of aqueous soil extracts revealed
the unexpected presence of trifluoroacetate, fluoride ion, and fluoroacetate.
Growth of the soil consortium in tryptone soya broth supplemented
with fluoride ions resulted in fluoroacetate production; thus, bacteria
in the soil produce and degrade organofluorine compounds.