The bacterium Rhodococcus rhodochrous NCIMB 13064, isolated from an in
dustrial site, could use a wide range of 1-haloalkanes as sole carbon
source but apparently utilized several different mechanisms simultaneo
usly for assimilation of substrate. Catabolism of 1-chlorobutane occur
red mainly by attack at the C-1 atom by a hydrolytic dehalogenase with
the formation of butanol which was metabolized via butyric acid. The
detection of small amounts of gamma-butyrolactone in the medium sugges
ted that some oxygenase attack at C-4 also occurred, leading to the fo
rmation of 4-chlorobutyric acid which subsequently lactonized chemical
ly to gamma-butyrolactone. Although 1-chlorobutane-grown cells exhibit
ed little dehalogenase activity on 1-chloroalkanes with chain lengths
above C-10, the organism utilized such compounds as growth substrates
with the release of chloride. Concomitantly, gamma-butyrolactone accum
ulated to 1 mM in the culture medium with 1-chlorohexadecane as substr
ate. Traces of 4-hydroxybutyric acid were also detected. It is suggest
ed that attack on the long-chain chloroalkane is initiated by an oxyge
nase at the non-halogenated end of the molecule leading to the formati
on of an omega-chlorofatty acid. This is degraded by beta-oxidation to
4-chlorobutyric acid which is chemically lactonized to gamma-butyrola
ctone which is only slowly further catabolized via 4-hydroxybutyric ac
id and succinic acid. However, release of chloride into the medium dur
ing growth on long-chain chloroalkanes was insufficient to account for
all the halogen present in the substrate. Analysis of the fatty acid
composition of 1-chlorohexadecane-grown cells indicated that chlorofat
ty acids comprised 75% of the total fatty acid content with C-14:0, C-
16:0, C-16:1, and C-18:1 acids predominating. Thus the incorporation o
f 16-chlorohexadecanoic acid, the product of oxygenase attack directly
into cellular lipid represents a third route of chloroalkane assimila
tion. This pathway accounts at least in part for the incomplete minera
lization of long-chain chloroalkane substrates. This is the first repo
rt of the coexistence of a dehalogenase and the ability to incorporate
long-chain haloalkanes into the lipid fraction within a single organi
sm and raises important questions regarding the biological treatment o
f haloalkane containing effluents.