Circadian input kinases and their homologs in cyanobacteria: Evolutionary constraints versus architectural diversification

The circadian input kinase A (cikA) gene encodes a protein relaying environmental signal to the central circadian oscillator in cyanobacteria. The CikA protein has a variable architecture and usually consists of four tandemly arrayed domains: GAF, histidine kinase (HisKA), histidine kinase-like ATPase (HATPase-c), and a pseudo-receiver (REC). Among them, HisKA and HATPase-c are the least polymorphic, and REC is not present in heterocystic filamentous cyanobacteria. CikA contains several conserved motifs that are likely important for circadian function. There are at least three types of circadian systems, each of which possesses a different set of circadian genes. The originally described circadian system (kaiABC system) possesses both cikA and kaiA, while the others lack either only cikA (kaiABC Δ) or both (kaiBC). The results we obtained allowed us to approximate the time of the cikA origin to be about 2600-2200 MYA and the time of its loss in the species with the kaiABC Δ or kaiBC system between 1100 and 600 MYA. Circadian specialization of CikA, as opposed to its non-circadian homologs, is a result of several factors, including the unique conserved domain architecture and high evolutionary constraints of some domains and regions, which were previously identified as critical for the circadian function of the gene. © 2010 Springer Science+Business Media, LLC.postprin

Home-site advantage for host species–specific gut microbiota

Mammalian species harbor compositionally distinct gut microbial communities, but the mechanisms that maintain specificity of symbionts to host species remain unclear. Here, we show that natural selection within house mice (Mus musculus domesticus) drives deterministic assembly of the house-mouse gut microbiota from mixtures of native and non-native microbiotas. Competing microbiotas from wild-derived lines of house mice and other mouse species (Mus and Peromyscus spp.) within germ-free wild-type (WT) and Rag1-knockout (Rag1−/−) house mice revealed widespread fitness advantages for native gut bacteria. Native bacterial lineages significantly outcompeted non-native lineages in both WT and Rag1−/− mice, indicating home-site advantage for native microbiota independent of host adaptive immunity. However, a minority of native Bacteriodetes and Firmicutes favored by selection in WT hosts were not favored or disfavored in Rag1−/− hosts, indicating that Rag1 mediates fitness advantages of these strains. This study demonstrates home-site advantage for native gut bacteria, consistent with local adaptation of gut microbiota to their mammalian species

Microbiota assembly, structure, and dynamics among Tsimane horticulturalists of the Bolivian Amazon

Selective and neutral forces shape human microbiota assembly in early life. Here, Sprockett et al. study microbial community assembly in 47 infant-mother pairs from the Tsimane, an indigenous Bolivian population, highlighting the importance of neutral forces during microbiota assembly