Table 1.
Bacterial strains and plasmids used in this study.
Table 2.
Program of gradient elution.
Fig 1.
Changes in biofilm formation due to the B. subtilis Bs916 and ΔgltB mutants in MSgg culture medium with 20 μg/mL Congo Red and 10 μg/mL Coomassie brilliant blue.
(1) B. subtilis Bs916 biofilm was dense and solid with clear lines. In contrast, the ΔgltB mutant formed an uneven biofilm with an irregular shape. (2) The net weight of the ΔgltB mutant biofilm was more than three times less than the net weight of the WT B. subtilis Bs916 biofilm.
Fig 2.
Differences in antibacterial activity against R. solani between WT B. subtilis Bs916 and the ΔgltB mutant.
The ΔgltB mutant completely lost its antibacterial activity compared to the WT B. subtilis Bs916.
Table 3.
Analysis of differentially expressed genes in wild type B. subtilis Bs916 and the ΔgltB mutant.
Table 4.
Biocontrol of rice sheath blight in pot cultures of WT B. subtilis 916 and the ΔgltB mutant strain.*
Fig 3.
Colonisation of the rice plant against rice sheath blight.
Over time, the number of both WT B. subtilis Bs916 and ΔgltB mutant cells initially increased and then began to decrease. However, although WT B. subtilis Bs916 could produce normal clusters of cells, the ΔgltB mutant also demonstrated this same trend. By the last time point (i.e., 15 d), there were very few cells in either the WT B. subtilis Bs916 or the ΔgltB mutant, and the clustering of WT B. subtilis Bs916’s had disappeared.
Fig 4.
Antibiotic secretion of bacillomycin L (a), fengycin (c), and surfactin (b). The ΔgltB mutant no longer secreted bacillomycin L or fengycin. In contrast, the ΔgltB mutant produced significantly higher (approximately five times higher) levels of surfactin compared to the WT B. subtilis Bs916.
Fig 5.
γ-PGA and glutamate content of WT B. subtilis Bs916 and the ΔgltB mutant in the process of biofilm formation.
For glutamate detection, in addition to standard L-glutamate and double dilution to B. subtilis Bs916, all treatments were diluted tenfold for detection. For γ-PGA detection, all treatments were also diluted tenfold for detection.
Table 5.
Glutamate consumption and γ-PGA production of ΔgltB mutant and WT B. subtilis Bs916.
Fig 6.
Biofilm restoration in the ΔgltB mutant.
A final concentration of 10 g/L, 20 g/L, and 30 g/Lγ-PGA solution were added into the ΔgltB mutant in 4mL EM medium. The final concentration of 10 g/L and 20 g/Lγ-PGA were able to recover biofilm formation in the ΔgltB mutant, however, high final concentration of 30 g/Lγ-PGA inhibited biofilm formation in WT B. subtilis Bs916 and the ΔgltB mutant.
Fig 7.
Biofilm restoration by B. subtilis Bs916’sγ-PGA in the ΔgltB mutant.
The ΔgltB mutant grew next to B. subtilis Bs916 on solid EM plate with 1.5% agar to observe their biofilm formation. Biofilm formation of ΔgltB mutant was no significant restoration before 36 h. But in 72h, its biofilm formation had been restored to most parts.
Table 6.
Biofilm dry weight analysis of Bs916 and ΔgltB mutant by adding γ-PGA and polyaspartic acid.