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Pederin, a group of antitumor compounds, is produced by an endosymbiotic bacterium of Paederus fuscipes. Pederin content differed between male and female P. fuscipes, but the reason why these differences are maintained remains unexplored. Here, the pederin‐producing bacteria (PPB) infection rate in P. fuscipes was investigated. Furthermore, we assessed the microbiota structure differences in male and female P. fuscipes harbouring PPB and sequenced the transcriptome of both sexes to shed light on genes of interest. Of the 625 analysed beetles (275 females, 350 males), 96.36% of females and 31.14% of males were positive for PPB infection. PPB accounted for 54.36%–82.70% of the bacterial population in females but showed a much lower abundance in males (0.92%–3.87%). Reproductive organs possessed the highest PPB abundance compared with other parts of females, but no such relationships existed in males. Moreover, we provide the first transcriptome analysis of male and female P. fuscipes harbouring PPB and identified 8893 differentially expressed unigenes. Our results indicated that the pederin content difference between males and females might be caused by the PPB density difference in hosts. The biosequence data would be helpful for illustrating the mechanism that regulates PPB density in P. fuscipes. [ABSTRACT FROM AUTHOR]

Aim: The latitudinal diversity gradient (LDG) is one of the most pervasive large‐scale trends in biodiversity. However, whether microbial taxa also conform to this pattern remains poorly known. This study uses the gill and shell‐surface microbiomes of the marine bivalve Mytilus californianus to test whether the diversity of host‐associated microbial communities declines with increasing latitude, as predicted by the LDG. Location: Northeastern Pacific coast, ranging from Sitka, AK to La Jolla, CA, USA (spanning 24.12 degrees of latitude). Taxon: Bacteria and Archaea associated with M. californianus gills and shell‐surfaces. Methods: We amplified and sequenced the 16S rRNA gene from M. californianus gill and shell‐surface samples. We used linear and quadratic regressions, accounting for spatial autocorrelation when needed, of average alpha and gamma diversities of the whole microbiome, as well as individual microbial clades, to determine whether these taxa conformed to the traditional LDG. We also used permutational multivariate analysis of variance to determine the level of compositional differentiation among sampling sites. Results: Gill and shell‐surface microbiota show differing latitudinal diversity patterns, with both micro‐environments exhibiting high levels of compositional differentiation along latitude. Individual microbial clades within each micro‐environment also show different latitudinal trends, most likely due to differing ecologies and life histories. Main conclusions: Mytilus californianus‐associated microbial taxa show a flat, hump‐shaped or contrarian LDG, suggesting that a steep decline in diversity with increasing latitude may not be a universal pattern across different domains of life. [ABSTRACT FROM AUTHOR]

Thanks to the emergence and recent advances in high‐throughput sequencing technologies, it is becoming more evident every day that changes in the microbiome composition are linked to a myriad of health conditions. Despite this, the mechanisms of host–microbiota signalling remain largely unknown. The microbiome has an extensive metabolic activity that leads to the generation of a large number of compounds that are likely to influence host health. Therefore, the microbiome–host cross‐talk is in part mediated by microbial‐derived metabolites. Unlike metagenomics, which only provides information about microbial genes and thus the microbiome functional potential, metabolic phenotyping is well suited to capture their actual metabolic activity. Here, we provide an overview of these approaches and propose an integration of metagenomics, as a microbiome compositional readout, with faecal and plasma/urine metabolomics, as a functional readout, to unravel novel mechanisms linking the microbiome to host health and disease. [ABSTRACT FROM AUTHOR]