Psyllids, It's What's on the Inside That Counts: Community Cross Talk Facilitates Prophage Interactions.

Despite the availability of massive microbial community data sets (e.g., metagenomes), there is still a lack of knowledge on what molecular mechanisms facilitate cross talk between microbes and prophage within a community context. A study published in mSphere by Jain and colleagues (M. Jain, L. A. Fleites, and D. W. Gabriel, mSphere 2:e00171-17, 2017, https://doi.org/10.1128/mSphereDirect.00171-17) reports on an intriguing new twist of how a prophage of the bacterium "Candidatus Liberibacter asiaticus" may have its lytic cycle suppressed partly because of a protein that is expressed by a cooccurring bacterium, Wolbachia. Both of these microbes coexist along with other microbial tenants inside their sap-feeding insect host, a psyllid. Although these results are still preliminary and alternative hypotheses need to be tested, these results suggest an interesting new dimension on how regulation of microbial genomes occurs in a community context.

The evolutionary development of plant-feeding insects and their nutritional endosymbionts.

Herbivorous insects have evolved diverse mechanisms enabling them to feed on plants with suboptimal nutrient availability. Low nutrient availability negatively impacts insect herbivore development and fitness. To overcome this obstacle numerous insect lineages have evolved intimate associations with nutritional endosymbionts. This is especially true for insects that specialize on nitrogen-poor substrates, as these insects are highly dependent on intracellular symbionts to provide nitrogen lacking in their insect host's diet. Emerging evidence in these systems suggest that the symbiont's and/or the insect's biosynthetic pathways are dynamically regulated throughout the insect's development to potentially cope with the insect's changing nutritional demands. In this review, we evaluate the evolutionary development of symbiotic insect cells (bacteriocytes) by comparing and contrasting genes and mechanisms involved in maintaining and regulating the nutritional symbiosis throughout insect development in a diversity of insect herbivore-endosymbiont associations. With new advances in genome sequencing and functional genomics, we evaluate to what extent nutritional symbioses are shaped by (i) the regulation of symbiont titer, (ii) the regulation of insect symbiosis genes, and (iii) the regulation of symbiont genes. We discuss how important these mechanisms are for the biosynthesis of essential amino acids and vitamins across insect life stages in divergent insect-symbiont systems. We conclude by suggesting future directions of research to further elucidate the evolutionary development of bacteriocytes and the impact of these nutritional symbioses on insect-plant interactions.