Department of Biological Sciences, Mississippi State University, Mississippi State, MS, 39762, USA.
Department of Biology, University of Victoria, Victoria, BC, V8W 2Y2, Canada.
Curr Opin Insect Sci. 2019 Apr;32:36-41. doi: 10.1016/j.cois.2018.10.004. Epub 2018 Oct 23.
Defensive microbes are of great interest for their roles in arthropod health, disease transmission, and biocontrol efforts. Obligate bacterial passengers of arthropods, such as Spiroplasma, confer protection against the natural enemies of their hosts to improve their own fitness. Although known for less than a decade, Spiroplasma's defensive reach extends to diverse parasites, both microbial and multicellular. We provide an overview of known defensive phenotypes against nematodes, parasitoid wasps, and fungi, and highlight recent studies supporting the role of Spiroplasma-encoded ribosome-inactivating proteins in protection. With cellular features well-suited for life in the hemolymph, broad distribution among invertebrate hosts, and the capacity to repeatedly evolve vertical transmission, Spiroplasma may be uniquely equipped to form intimate, defensive associations to combat extracellular parasites. Along with insights into defensive mechanisms, recent significant advances have been made in male-killing - a phenotype with interesting evolutionary ties to defense. Finally, we look forward to an exciting decade using the genetic tools of Drosophila, and the rapidly-advancing tractability of Spiroplasma itself, to better understand mechanisms and evolution in defensive symbiosis.
防御性微生物因其在节肢动物健康、疾病传播和生物防治方面的作用而备受关注。节肢动物的专性细菌乘客，如螺旋体，为其宿主的天敌提供保护，以提高自身适应性。尽管人们对螺旋体的了解还不到十年，但它的防御范围已经扩展到了各种微生物和多细胞寄生虫。我们概述了已知的针对线虫、寄生蜂和真菌的防御表型，并强调了最近的研究支持螺旋体编码核糖体失活蛋白在保护中的作用。由于具有适合血淋巴生活的细胞特征、在无脊椎动物宿主中的广泛分布以及能够反复进化垂直传播的能力，螺旋体可能具有独特的能力来形成亲密的防御性共生关系，以对抗细胞外寄生虫。除了对防御机制的深入了解外，近年来在雄性杀伤方面也取得了重大进展——这一表型与防御有有趣的进化联系。最后，我们期待着未来十年利用果蝇的遗传工具，以及螺旋体自身快速发展的可操作性，来更好地理解防御共生中的机制和进化。
