YmdB, which can regulate biofilm formation independently, has been reported to exist in Bacillus subtilis. The B. cereus 0-9 genome also encodes a YmdB-like protein, which has measureable phosphodiesterase activity, and 72.35% sequence identity to YmdB protein of B. subtilis 168. In this work, we studied the function of YmdB protein and its encoding gene, ymdB, in B. cereus 0-9. Our results indicated that YmdB protein is critical for the biofilm formation of B. cereus 0-9. In ΔymdB mutant, the transcriptional levels of sinR and hag were up-regulated, and those of genes closely related to biofilm formation, such as sipW, tasA and calY, were down-regulated. Deletion of ymdB gene stimulates the swarming motility of B. cereus 0-9, and enhances it to travel outward, but reduces its ability to form complex spatial structures on the solid surface of MSgg plates. Hence, it is considered that YmdB plays a key role in biofilm formation, and this effect is likely achieved through the function of repressor SinR in B. cereus 0-9. Furthermore, by comparing the amino acid sequences of YmdB by Basic Local Alignment Search Tool (BLAST) in Genebank, we found that YmdB homologues are present in a variety of bacteria (Including Gram-negative bacteria) except B. subtilis and B. cereus. All these bacteria come at different evolutionary distances and belong to different genera. Therefore, we believe that YmdB exists in many types of bacteria and plays an important role in the stress-resistance of bacteria to adapt to the environment. These results can help us to further understand the biocontrol characteristics of B. cereus 0-9.

中文翻译：

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YmdB 蛋白依赖于蜡状芽孢杆菌 0-9 中的抑制因子 SinR 调节生物膜形成

YmdB 可以独立调节生物膜形成，据报道存在于枯草芽孢杆菌中。B. cereus 0-9 基因组还编码了一种类似 YmdB 的蛋白，该蛋白具有可测量的磷酸二酯酶活性，并且与枯草芽孢杆菌 168 的 YmdB 蛋白具有 72.35% 的序列同一性。在这项工作中，我们研究了 YmdB 蛋白的功能及其编码基因，ymdB，在蜡状芽孢杆菌 0-9 中。我们的结果表明，YmdB 蛋白对于蜡状芽孢杆菌 0-9 的生物膜形成至关重要。在ΔymdB突变体中，sinR和hag的转录水平上调，与生物膜形成密切相关的基因，如sipW、tasA和calY的转录水平下调。ymdB 基因的缺失刺激了蜡状芽孢杆菌 0-9 的集群运动，并增强了其向外传播，但降低了它在 MSgg 板的固体表面上形成复杂空间结构的能力。因此，认为 YmdB 在生物膜形成中起关键作用，这种作用很可能是通过蜡状芽孢杆菌 0-9 中抑制因子 SinR 的功能实现的。此外，通过基因库中的基本局部比对搜索工具（BLAST）比较YmdB的氨基酸序列，我们发现YmdB同源物存在于除枯草芽孢杆菌和蜡状芽孢杆菌外的多种细菌（包括革兰氏阴性菌）中。所有这些细菌都处于不同的进化距离，属于不同的属。因此，我们认为YmdB存在于多种类型的细菌中，在细菌的抗逆性适应环境中发挥着重要作用。这些结果可以帮助我们进一步了解 B.