Formaldehyde tolerance in E. coli VU3695 and
Halomonas MAC involves the outer membrane
The outer membrane is the first barrier encountered by
formaldehyde to penetration of Gram-negative bacteria.
We therefore investigated whether differences in for-
maldehyde tolerance of the strains and their sensitive
revertants was correlated with differences in the structure
of their outer membranes. The outer membrane pre-
parations obtained were found to be free of formaldehyde
dehydrogenase activity, showing that contamination with
cytoplasmic proteins was insignificant. As in other Gram-
negative bacteria (Lidstrom, 1992), the formaldehyde-
oxidizing activity in Halomonas MAC and E. coli VU3695
was found to be located in the cytoplasmic fraction.
Comparison of the outer membrane protein profile of E.
coli VU3695 and its formaldehyde-sensitive revertants 31
and 21 showed that an additional high-molecular-mass
protein (apparent molecular mass > 143 kDa) was
present in the wild-type strain, but missing in both
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