Weltzer Michael L, Govaerts Jack, Wall Daniel
Department of Molecular Biology, University of Wyoming, 1000 E University Avenue, Laramie, WY, USA.
bioRxiv. 2024 Dec 4:2024.12.04.626738. doi: 10.1101/2024.12.04.626738.
Aggregative multicellularity is a cooperative strategy employed by some microorganisms. Unlike clonal expansion within protected environments during multicellular eukaryotic development, an aggregation strategy introduces the potential for genetic conflicts and exploitation by cheaters, threatening the stability of the social system. , a soil-dwelling bacterium, employs aggregative multicellularity to form multicellular fruiting bodies that produce spores in response to starvation. Studies of natural fruiting bodies show that this process is restricted to close kin or clonemates. Here, we investigate the mechanisms underlying kin recognition during development in . By co-culturing two distantly related strains under vegetative and starvation conditions, we observed that the strains segregate in both contexts. During vegetative growth, one strain antagonized the other using the type VI secretion system (T6SS). T6SS-mediated antagonism was also observed during development, resulting in monoclonal fruiting bodies when WT strains were mixed. In contrast, mixtures of T6SS knockout strains formed chimeric fruiting bodies, that produced viable spores from both strains. These findings suggest that T6SS is the primary mechanism of kin discrimination in distantly related strains, and its use ensures the development of monoclonal fruiting bodies and social integrity.
聚集性多细胞性是一些微生物采用的一种合作策略。与多细胞真核生物发育过程中在受保护环境内的克隆扩张不同，聚集策略引入了基因冲突以及作弊者进行剥削的可能性，威胁到社会系统的稳定性。粘质沙雷氏菌是一种土壤细菌，它采用聚集性多细胞性来形成多细胞子实体，这些子实体在饥饿时产生孢子。对天然子实体的研究表明，这个过程仅限于近亲或克隆体。在这里，我们研究了粘质沙雷氏菌发育过程中亲缘识别的潜在机制。通过在营养和饥饿条件下共培养两个远缘相关的粘质沙雷氏菌菌株，我们观察到这两个菌株在两种情况下都会分离。在营养生长期间，一个菌株使用VI型分泌系统（T6SS）对抗另一个菌株。在发育过程中也观察到T6SS介导的对抗，当野生型菌株混合时会产生单克隆子实体。相比之下，T6SS基因敲除菌株的混合物形成了嵌合子实体，这些嵌合子实体从两个菌株中产生了有活力的孢子。这些发现表明，T6SS是远缘相关粘质沙雷氏菌菌株中亲缘识别的主要机制，其使用确保了单克隆子实体的发育和社会完整性。
