Microbiome Analysis of the Bamboo Aphid Melanaphis bambusae Infected with the Aphid Obligate Pathogen Conidiobolus obscurus (Entomophthoromycotina)

SIMPLE SUMMARY: Bamboo are widespread fast-growing perennials with multiple economic and ecological values. Bamboo aphids are the main pests that threaten bamboo forests. The naturally occurring entomopathogenic fungi in these forests are locally effective in controlling aphid populations, especially during monsoon. This study investigated the community structures of bacteria and fungi in the bamboo aphid Melanaphis bambusae and their changes under the stress of fungal infection or starvation. Results showed a difference in community structure between the infected and starved aphids. Moreover, the relative abundance of several operational taxonomic units increased dramatically in response to infection by Conidobolus obscurus. This implied that the aphid-borne microbes possibly facilitated the infection process, highlighting its potential for improving the control efficacy of fungal biological agents on bamboo aphids. ABSTRACT: Insect-associated microbes exert diverse effects on host fitness. This study provides insights into the microbiota of the bamboo aphid, Melanaphis bambusae, and their response to Conidiobolus obscurus infection. 16S rRNA and ITS sequencing data were used to analyze the bacterial and fungal samples associated with healthy, infected, and starved aphids. At ≥97% nucleotide similarity, the total reads were clustered into 79 bacteria and 97 fungi operational Taxonomic Units (OTUs). The phyla Proteobacteria and Ascomycota dominated the bacterial and fungal communities, respectively. The significant divergence in OTU distribution presented differential profiles of the microbiota in response to host conditions. Lower α-diversity indices were found in bacterial and fungal diversity when the aphids were experiencing fungal infection and starvation stresses, respectively. The β-diversity analyses of the communities showed significant differences among the three host conditions, demonstrating that aphid-associated microbiota could significantly shift in response to varying host conditions. Moreover, some OTUs increased under fungal infection, which potentially increased aphid susceptibility. Presumably, C. obscurus infection contributed to this increase by causing the disintegration of host tissues other than host starvation. In conclusion, understanding the differentiation of aphid microbiota caused by fungal entomopathogens helped facilitate the development of novel pest management strategies.