Cell culture and induction of recombinant protein
expression
Cells were grown in f/2 medium under standard conditions
as described elsewhere (Apt et al. 1999) with either
0.9 mM NO3
- or 1.5 mM NH4
+ as the nitrogen source.
For in vivo localization studies on GFP fusion proteins
transfectants were grown in media containing NO3
- to
induce recombinant protein expression. After 3 days,
clones were analyzed by confocal laser scanning microscopy.
PhaA/phaB/phaC co-transfectants were first
determined to have genomic integration by colony PCR
for all three sequences. Subsequently, positive colonies
were grown in liquid culture containing NH4
+ and
allowed to reach exponential phase, whereupon they
were transferred to NO3
- containing medium for varying
time periods. For visualization of PHB granules, cells
were induced for 5 days and analyzed by electron and
confocal microscopic analyses, respectively. For confocal
microscopy, cells were pre-incubated with the lipophilic
dye Nile Red (0.5 μg/ml) for 24 h.