Zhang Juanmei, Meng Li, Zhang Yubing, Sang Lidan, Liu Qing, Zhao Linlin, Liu Fengying, Wang Gang
Engineering Research Center for Applied Microbiology of Henan Province, Kaifeng, China.
School of Pharmaceutical, Henan University, Kaifeng, China.
Front Microbiol. 2020 Dec 7;11:591926. doi: 10.3389/fmicb.2020.591926. eCollection 2020.
0-9, a Gram-positive endospore-forming bacterium isolated from healthy wheat roots, has biological control capacity against several soil-borne plant diseases of wheat such as sharp eyespot and take-all. The bacterium can produce various biofilms that differ in their architecture and formation mechanisms, possibly for adapting to different environments. The gene, encoding a glyceraldehyde-3-phosphate dehydrogenase (GAPDH), plays a key role in 0-9 biofilm formation. We studied the function of GapB and the mechanism of its involvement in regulating 0-9 biofilm formation. GapB has GAPDH activities for both NAD- and NADP-dependent dehydrogenases and is a key enzyme in gluconeogenesis. Biofilm yield of the Δ strain decreased by 78.5% compared with that of wild-type 0-9 in lysogeny broth supplemented with some mineral salts (LBS), and the Δ:: mutants were recovered with gene supplementation. Interestingly, supplementing the LBS medium with 0.1-0.5% glycerol restored the biofilm formation capacity of the Δ mutants. Therefore, GapB regulates biofilm formation relative to its function in gluconeogenesis. To illustrate how GapB is involved in regulating biofilm formation through gluconeogenesis, we carried out further research. The results indicate that the GapB regulated the 0-9 biofilm formation independently of the exopolysaccharides and regulatory proteins in the typical SinI/R system, likely owing to the release of extracellular DNA in the matrix. Transcriptome analysis showed that the deletion caused changes in the expression levels of only 18 genes, among which, was the most significantly increased by 6.17-fold. We confirmed this hypothesis by counting the dead and living cells in the biofilms and found the number of living cells in the biofilm formed by the Δ strain was nearly 7.5 times than that of wild-type 0-9. Therefore, we concluded that the GapB is involved in the extracellular DNA release and biofilm formation by regulating the expression or activities of LrgAB. These results provide a new insight into the regulatory mechanism of bacterial biofilm formation and a new foundation for further studying the stress resistance of .
0-9是一种从健康小麦根部分离出的革兰氏阳性产芽孢细菌，对小麦的几种土传植物病害如纹枯病和全蚀病具有生物防治能力。该细菌能产生多种生物膜，其结构和形成机制各不相同，这可能是为了适应不同环境。编码甘油醛-3-磷酸脱氢酶（GAPDH）的基因在0-9生物膜形成中起关键作用。我们研究了GapB的功能及其参与调控0-9生物膜形成的机制。GapB对依赖NAD和NADP的脱氢酶均具有GAPDH活性，并且是糖异生中的关键酶。在补充了一些矿物盐的溶源肉汤（LBS）中，Δ菌株的生物膜产量与野生型0-9相比降低了78.5%，并且通过基因补充使Δ::突变体得以恢复。有趣的是，在LBS培养基中添加0.1-0.5%的甘油可恢复Δ突变体的生物膜形成能力。因此，GapB相对于其在糖异生中的功能来调控生物膜形成。为了阐明GapB如何通过糖异生参与调控生物膜形成，我们进行了进一步研究。结果表明，GapB独立于典型的SinI/R系统中的胞外多糖和调节蛋白来调控0-9生物膜形成，这可能是由于基质中细胞外DNA的释放。转录组分析表明，缺失仅导致18个基因的表达水平发生变化，其中，增加最为显著，增加了6.17倍。我们通过对生物膜中的死细胞和活细胞进行计数来证实这一假设，发现由Δ菌株形成的生物膜中的活细胞数量几乎是野生型0-9的7.5倍。因此，我们得出结论，GapB通过调节LrgAB的表达或活性参与细胞外DNA释放和生物膜形成。这些结果为细菌生物膜形成的调控机制提供了新的见解，并为进一步研究0-9的抗逆性奠定了新的基础。
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