The dynamics of the microbial community in fall armyworm Spodoptera frugiperda during a life cycle

The fall armyworm, Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae), is a destructive pest that causes serious damage worldwide, particularly to maize cultivars. The microbiota of S. frugiperda might play a role in its development and adaptability to different environments. However, the dynamics of microbial communities in S. frugiperda during its life cycle remain poorly understood. In this study, we used the amplification of the 16S rRNA gene to characterize the microbiome of all developmental stages of S. frugiperda fed with maize and adults fed with an artificial diet. The microbial composition of maize leaves, soil, and artificial diet was analyzed. Alpha diversity indices indicated that the neonate and early-phase larvae had higher bacterial diversity than late-phase larvae, pupae, and adults, and the bacterial diversity of adults fed with natural leaves was higher than that of adults fed an artificial diet. Proteobacteria and Firmicutes were the major phyla found in most life stages of S. frugiperda, especially in adults, sixth instars, and pupae. Neonate and early-phase larvae harbored a higher abundance of OD1 and microbes of unassigned taxonomy. A co-occurrence network of the highly abundant genera within S. frugiperda was then constructed, which revealed a potential interaction between the microbiota in insects, such as Enterococcus and Pseudomonas, and the dietary microbiota. Dynamic changes in bacterial communities led to changes in the metabolic functions of the microbiota across developmental stages. The genera OD1, Enterococcus, Comamonas, and Elizabethkingia were estimated to contribute to most of the functional changes in the microbiota of S. frugiperda. Our findings provide a comprehensive understanding of the composition of S. frugiperda and its dynamic interaction with dietary microbiota.