3.9 Influence of rex and sigB on surfactin production and biofilm
formation
We further deleted the genes for globally regulating anti-oxidation
reactions such as rex and sigB in WH1 (Fig. S3 in
supplementary materials). The colony morphology and biofilm in
Δrex and ΔsigB were both similar to WH1 (Fig. 7A). The
growth of ΔsigB was also similar to WH1, but the growth of
Δrex was obviously weaker than WH1 (Fig. 7B).
Deletion of rex resulted in a significant decrease of surfactin
production when compared to WH1 at all time points. At 12 h, the biomass
of Δrex was similar to WH1, but the surfactin production was
significantly lower than WH1 (Fig. 7C). Knockout of sigB also led
to a significant decrease of surfactin production at 36 and 48 h when
compared to WH1 (Fig. 7C). The transcription of perR was
significantly increased in Δrex , while the transcription ofsrfAB and perR were both significantly increased and the
transcription of spx was significantly decreased in ΔsigBcompared to WH1 (Fig. 7D). Western blot analysis also showed that the
protein PerR was slightly increased in Δrex and ΔsigB when
compared to WH1 (Fig. 7D).
We constructed the rex complementary strain C-Δrex (Fig.
S3 in supplementary materials), and found it could form a robuster
biofilm than Δrex and WH1 (Fig. 7A), but unfortunately the
surfactin production was not well restored in C-Δrex when
compared to WH1 (Fig. 7C). This result also confirmed that the signal to
trigger biofilm formation is not always dependent on surfactin inB. amyloliquefaciens .