Myxococcus xanthus, a soil bacterium, predates collectively using motility to invade prey colonies. Prey lysis is mostly thought to rely on secreted factors, cocktails of antibiotics and enzymes, and direct contac with Myxococcus cells. In this study, we show that on surfaces the coupling of A-motility and contact-dependent killing is the central predatory mechanism driving effective prey colony invasion and consumption. At the molecular level, contact-dependent killing involves a newly discovered type IV filament-like machinery (Kil) that both promotes motility arrest and prey cell plasmolysis. In this process, Kil proteins assemble at the predator-prey contact site, suggesting that they allow tight contact with prey cells for their intoxication. Kil-like systems form a new class of Tad-like machineries in predatory bacteria, suggesting a conserved function in predator-prey interactions. This study further reveals a novel cell-cell interaction function for bacterial pili-like assemblages.

We developed a computational pipeline for homology based identification of the complete repertoire of olfactory receptor (OR) genes in the Asian honey bee species, Apis florea. Apis florea is phylogenetically the most basal honey bee species and also the most distant sister species to the Western honey bee Apis mellifera, for which all OR genes had been identified before. Using our pipeline, we identified 180 OR genes in A. florea, which is very similar to the number of ORs identified in A. mellifera (177 ORs). Many characteristics of the ORs including gene structure, synteny of tandemly repeated ORs and basic phylogenetic clustering are highly conserved. The composite phylogenetic tree of A. florea and A. mellifera ORs could be divided into 21 clades which are in harmony with the existing Hymenopteran tree. However, we found a few nonorthologous OR relationships between both species as well as independent pseudogenization of ORs suggesting separate evolutionary changes. Particularly, a subgroup of the OR gene clade XI, which had been hypothesized to code cuticular hydrocarbon receptors showed a high number of species-specific ORs. RNAseq analysis detected a total number of 145 OR transcripts in male and 162 in female antennae. Most of the OR genes were highly expressed on the female antennae. However, we detected five distinct male-biased OR genes, out of which three genes (AfOr11, AfOr18, AfOr170P) were shown to be male-biased in A. mellifera, too, thus corroborating a behavioral function in sex-pheromone communication.