For epidemic prevention and control, the identification of SARS-CoV-2 subpopulations sharing similar micro-epidemiological patterns and evolutionary histories is necessary for a more targeted investigation into the links among COVID-19 outbreaks caused by SARS-CoV-2 with similar genetic backgrounds. Genomic sequencing analysis has demonstrated the ability to uncover viral genetic diversity. However, an objective analysis is necessary for the identification of SARS-CoV-2 subpopulations. Herein, we detected all the mutations in 186 682 SARS-CoV-2 isolates. We found that the GC content of the SARS-CoV-2 genome had evolved to be lower, which may be conducive to viral spread, and the frameshift mutation was rare in the global population. Next, we encoded the genomic mutations in binary form and used an unsupervised learning classifier, namely PhenoGraph, to classify this information. Consequently, PhenoGraph successfully identified 303 SARS-CoV-2 subpopulations, and we found that the PhenoGraph classification was consistent with, but more detailed and precise than the known GISAID clades (S, L, V, G, GH, GR, GV and O). By the change trend analysis, we found that the growth rate of SARS-CoV-2 diversity has slowed down significantly. We also analyzed the temporal, spatial and phylogenetic relationships among the subpopulations and revealed the evolutionary trajectory of SARS-CoV-2 to a certain extent. Hence, our results provide a better understanding of the patterns and trends in the genomic evolution and epidemiology of SARS-CoV-2.

MOTIVATION: Bacteria can usually acquire certain advantageous genes that enable the bacteria to adapt to rapidly changing niches, thereby leading to a wide range of intraspecific genome content and genetic redundancy. The minimal genome of Escherichia coli, which is the most important bacterial species, and the association between E.coli and its human host are worthy of further exploration. RESULTS: We used gene prediction and phylogenetic analysis to reveal a rich phylogenetic diversity among 491 E.coli strains and to reveal substantial differences between these strains with respect to gene number and genome length. We used pan-genomic analysis to accurately identify 867 core genes, in which only 243 genes are shared by essential genes. This analysis revealed that core genes mainly provide essential functions to the basic lifestyle of E.coli, and accessory genes are likely to confer selective advantages such as niche adaptation or the ability to colonize specific hosts. By association analysis, we found that E.coli strains in non-human hosts may more easily utilize foreign genetic materials to adapt to their surroundings, but the population in human hosts has higher demands for the control of population density, indicating that highly accurate quorum-sensing behavior is very important for harmony between E.coli and its human host. By considering core genes and previous deletions together, we proposed a potential direction for further reduction of the E.coli genome. AVAILABILITY AND IMPLEMENTATION: The data, analysis process and detailed information on software tools used in this study are all available in the supplementary material. SUPPLEMENTARY INFORMATION: Supplementary data are available at Bioinformatics online.

Bioinformatics (2017) doi: 10.1093/bioinformatics/btx619 The publisher wishes to inform readers that the following grant number was inadvertently left off the published article: Grant No. 2015AA020101. This has now been corrected online.

Motivation: In the evolution of species, a kind of special sequences, termed ultraconserved sequences (UCSs), have been inherited without any change, which strongly suggests those sequences should be crucial for the species to survive or adapt to the environment. However, the UCSs are still regarded as mysterious genetic sequences so far. Here, we present a systematic study of ultraconserved genomic regions in the budding yeast based on the publicly available genome sequences, in order to reveal their relationship with the adaptability or fitness advantages of the budding yeast. Results: Our results indicate that, in addition to some fundamental biological functions, the UCSs play an important role in the adaptation of Saccharomyces cerevisiae to the acidic environment, which is backed up by the previous observation. Besides that, we also find the highly unchanged genes are enriched in some other pathways, such as the nutrient-sensitive signaling pathway. To facilitate the investigation of unique UCSs, the UCSC Genome Browser was utilized to visualize the chromosomal position and related annotations of UCSs in S.cerevisiae genome. Availability and implementation: For more details on UCSs, please refer to the Supplementary information online, and the custom code is available on request. Contact: [email protected]. Supplementary information: Supplementary data are available at Bioinformatics online.

Motivation: The budding yeast Saccharomyces cerevisiae is a model species powerful for studying the recombination of eukaryotes. Although many recombination studies have been performed for this species by experimental methods, the population genomic study based on bioinformatics analyses is urgently needed to greatly increase the range and accuracy of recombination detection. Here, we carry out the population genomic analysis of recombination in S.cerevisiae to reveal the potential rules between recombination and evolution in eukaryotes. Results: By population genomic analysis, we discover significantly more and longer recombination events in clinical strains, which indicates that adverse environmental conditions create an obviously wider range of genetic combination in response to the selective pressure. Based on the analysis of recombinational double strand breaks (DSBs)-intersected genes (RDIGs), we find that RDIGs significantly converge on specific disease- and adaptability-related pathways, indicating that recombination plays a biologically key role in the repair of DSBs related to diseases and environmental adaptability, especially the human neurological disorders. By evolutionary analysis of RDIGs, we find that the RDIGs highly prevailing in populations of yeast tend to be more evolutionarily conserved, indicating the accurate repair of DSBs in these RDIGs is critical to ensure the eukaryotic survival or fitness. Supplementary information: Supplementary data are available at Bioinformatics online.