Isolation and characterization of a Rhodococcus strain able to degrade 2-fluorophenol

Abstract

A pure bacterial culture able to utilize 2-fluorophenol (2-FP) as sole carbon and energy source was isolated by selective enrichment from sediments collected from a contaminated site in Northern Portugal. 16S rRNA gene analysis showed that the organism (strain FP1) belongs to the genus Rhodococcus. When grown aerobically on 2-FP, growth kinetics of strain FP1 followed the Luong model. An inhibitory effect of increasing 2-FP concentrations was observed with no growth occurring at 2-FP levels higher than ca. 4 mM. Rhodococcus strain FP1 was able to degrade a range of other organofluorine compounds, including 2-fluorobenzoate, 3-fluorobenzoate, 4-fluorobenzoate, 3-fluorophenol, 4-fluorophenol, 3-fluorocatechol, and 4-fluorocatechol, as well as chlorinated compounds such as 2-chlorophenol and 4-chlorophenol. Experiments with cell-free extracts and partially purified enzymes indicated that the first step of 2-fluorophenol metabolism was conversion to 3-fluorocatechol, suggesting an unusual pathway for fluoroaromatic metabolism. To our knowledge, this is the first time that utilization of 2-FP as a growth substrate by a pure bacterial culture is reported.

The biodegradation vs. biotransformation of fluorosubstituted aromatics

“…The compound is utilized as sole source of energy and carbon by various bacterial strains (Goldman et al 1967;Engesser et al 1980Engesser et al , 1990aHickey and Focht 1990;Higson and Focht 1990;Kozlovsky et al 1993;Emanuelsson et al 2009;Duque et al 2012). In other cases, a cosubstrate is needed to achieve substantial degradation (Fewson et al 1968;Clarke et al 1975;Schreiber et al 1980).…”

“…Growth with 4-fluorobenzoate has been reported for numerous bacterial strains (Vora et al 1988;Zaitsev et al 1995;Carvalho et al 2005;Emanuelsson et al 2009;Misiak et al 2011;Hoskeri et al 2011;Duque et al 2012;Hatta et al 2012). Others were shown to cometabolize it employing aromatic or non-aromatic cosubstrates for growth (Ali et al 1962;Fewson et al 1968;Clarke et al 1975;Mc Cullar et al 2002).…”

“…3-Fluorobenzoate may serve as a single growth substrate as well (Engesser et al 1990a;Zaitsev et al 1995;Boersma et al 2004;Emanuelsson et al 2009;Duque et al 2012) or be cooxidized with structurally related or nonrelated sources of carbon and energy (Fewson et al 1968;Clarke et al 1975). It is initially dioxygenated in 1,2-or 1,6-position under aerobic conditions (Fig.…”

“…strain FP1, however, was able to grow-albeit very slowly (1 mM within ca. 5 days)-with this substrate (Duque et al 2012). The authors even claimed growth with 3-fluorocatechol, indicating a degradation pathway previously thought to be unproductive, and their findings were seemingly supported by the growth of B. fungorum FLU100 on 3-fluorocatechol (Strunk and Engesser 2013).…”

“…An absolute (0:100) preference of the unfavorable 3-fluorocatechol generating pathway was seen in Penicillium frequentans Bi 7/2 (Hofrichter et al 1994), Bacillus thermoleovorans (Reinscheid et al 1996), Rhodococcus sp. strain FP1 (Duque et al 2012) as well as in Burkholderia fungorum strain FLU100 (Strunk and Engesser 2013). Moreover, further hydroxylated by-products like fluorohydroquinone or fluoropyrogallols may be formed (Finkelstein et al 2000;Kim et al 2010).…”