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CRISPR-Cas systems defend prokaryotic cells from invasive DNA of viruses, plasmids and other mobile genetic elements. Here, we show using metagenomics, metatranscriptomics and single-cell genomics that CRISPR systems of widespread, uncultivated archaea can also target chromosomal DNA of archaeal episymbionts of the DPANN superphylum. Using meta-omics datasets from Crystal Geyser and Horonobe Underground Research Laboratory, we find that CRISPR spacers of the hosts Candidatus Altiarchaeum crystalense and Ca. A. horonobense, respectively, match putative essential genes in their episymbionts' genomes of the genus Ca. Huberiarchaeum and that some of these spacers are expressed in situ. Metabolic interaction modelling also reveals complementation between host-episymbiont systems, on the basis of which we propose that episymbionts are either parasitic or mutualistic depending on the genotype of the host. By expanding our analysis to 7,012 archaeal genomes, we suggest that CRISPR-Cas targeting of genomes associated with symbiotic archaea evolved independently in various archaeal lineages.

Widespread marine microbiomes exhibit compositional and functional differentiation as a result of adaptation driven by environmental characteristics. We investigated the microbial communities in both seawater and sediments on the slope (7–9 km) and the bottom (9–11 km) of the Challenger Deep of the Mariana Trench to explore community differentiation. Both metagenome‐assembled genomes (MAGs) and 16S rRNA amplicon sequence variants (ASVs) showed that the microbial composition in the seawater was similar to that of sediment on the slope, while distinct from that of sediment in the bottom. This scenario suggested a potentially stronger community interaction between seawater and sediment on the slope, which was further confirmed by community assembly and population movement analyses. The metagenomic analysis also indicates a specific stronger potential of nitrate reduction and sulphate assimilation in the bottom seawater, while more versatile nitrogen and sulphur cycling pathways occur on the slope, reflecting functional differentiations among communities in conjunction with environmental features. This work implies that microbial community differentiation occurred in the different hadal niches, and was likely an outcome of microbial adaptation to the extreme hadal trench environment, especially the associated hydrological and geological conditions, which should be considered and measured in situ in future studies. [ABSTRACT FROM AUTHOR]

The paper examines the impact of specialization and diversity on economic growth of tourist cities. Industrial diversity is decomposed into two parts, related and unrelated diversity (UV). The paper constructs a panel threshold model with city size as the threshold variable, and empirically tests the nonlinear effects of specialization and diversity on economic growth of tourist cities from the perspective of city size. The results show that: First, tourism specialization has a positive impact on economic growth of tourist cities, and there is a double threshold effect based on city size. When the city size exceeds two thresholds, tourism specialization plays a significant role in promoting economic growth of tourist cities. Second, related diversity (RV) has a positive impact on economic growth of tourist cities, and there is no threshold effect based on city size. Third, the impact of unrelated diversity on economic growth of tourist cities has a single threshold effect based on city size. Specifically, when the city size is lower than the threshold value, unrelated diversity inhibits economic growth of tourist cities. Otherwise, unrelated diversity will promote economic growth of tourist cities. The conclusions are still valid after a series of robustness tests. The paper highlights that local governments of tourist cities should not pursue absolute tourism specialization or industrial diversity, but should design and adjust industrial structure reasonably according to the city size. [ABSTRACT FROM AUTHOR]

To date there has been little agreement on the effect of retirement on tourism consumption, and "retirement-tourism consumption puzzle" has not been empirically tested. Taking advantage of the mandatory retirement policy in China, this study adopts the fuzzy regression discontinuity design (RDD) approach to examine whether there is a "retirement-tourism consumption puzzle." The findings indicate that the retirement of household heads significantly boosts household tourism consumption. The results also illustrate the considerable moderating effects of self-assessed health level and pension level on household tourism consumption. The research framework can be generalized to other countries to identify the effect of retirement on tourism consumption. [ABSTRACT FROM AUTHOR]

Compound-specific hydrogen isotopes have increasingly been used as a powerful proxy for investigating biogeochemical cycles and climate change over the past 2 decades. Understanding the hydrogen isotope in extant organisms is fundamental for us to interpret such isotope signals preserved in natural environmental samples. Here, we studied the controls on hydrogen isotope fractionation between fatty acids and growth water by an Fe-reducing heterotrophic marine bacterium Shewanella piezotolerans WP3 growing on different organic substrates, including N-acetyl-D-glucosamine (GlcNac), glucose, acetate, pyruvate, L-alanine, and L-glutamate. Meanwhile, we also evaluated the impact of growth temperature on the hydrogen isotope composition of fatty acids using GlcNac as the sole organic substrate. Our results show that the abundance-weighted mean fatty-acid / water fractionations (εFA/water) display considerable variations for cultures grown on different substrates. Specifically, WP3 yielded the most 2H -enriched fatty acids growing on L-glutamate and pyruvate with an εFA/water of 52 ± 14 ‰ and 44 ± 4 ‰, respectively, and exhibited 2H depletion using GlcNac (- 76 ± 1 ‰) and glucose (- 67 ± 35 ‰) as sole carbon sources and relatively small fractionations on acetate (23 ± 3 ‰) and L-alanine (- 4 ± 9 ‰). Combined with metabolic model analysis, our results indicate that the central metabolic pathways exert a fundamental effect on the hydrogen isotope composition of fatty acids in heterotrophs. Temperature also has an obvious influence on the δ2H values of fatty acids, with strong 2H depletion at an optimal growth temperature (- 23 ± 2 ‰ and - 23 ‰ growing at 15 and 20 ∘C , respectively) and relatively small fractionations at non-optimal temperatures (4 ± 5 ‰, - 4 ± 12 ‰, and 15 ± 41 ‰ at 4, 10, and 25 ∘C , respectively). We hypothesized that this may be associated with temperature-induced enzyme activity for nicotinamide adenine dinucleotide phosphate (NADPH) production. This study helps understand the controlling factors of hydrogen isotope fractionation by marine bacteria, laying the foundation for further interpreting the hydrogen isotope signatures of lipids as an important proxy to decode the biogeochemical cycles and ecological changes in marine sediments. [ABSTRACT FROM AUTHOR]

As the main stakeholders and promoters, local governments are playing an increasingly significant role in local tourism development. However, up to now, little attention has been given to the effect of characteristics of local government leaders on tourism development. Based on a unique city leader–linked data set of 30 typical tourism-dependent cities for the period 2005–2018, this study explores the effect of the tenure and the personal characteristics of local leaders on tourism development. It is found that there is an inverted-U-shaped relationship between the tenure of the local leaders and tourism development. Moreover, compared with the local leaders without work experience in tourism sectors, the local leaders with work experience in tourism sectors have more advantages in boosting tourism development. [ABSTRACT FROM AUTHOR]

Summary: Bacteroidetes VC2.1 Bac22 (referred to as VC2.1) is an uncultured clade that is widely distributed in marine ecosystems, including hydrothermal vents, oxygen‐minimum zones and other anoxic, sulfide‐rich environments. However, the lack of cultured representatives and sequenced genomes of VC2.1 limit our understanding of its physiology, metabolism and ecological functions. Here, we obtained a stable co‐culture of VC2.1 with autotrophic microbes by establishing an autotrophy‐based enrichment from a hydrothermal vent chimney sample. We recovered a high‐quality metagenome‐assembled genome (MAG) that belonged to VC2.1. Phylogenetic analyses of both 16S rRNA genes and conserved protein markers suggested that VC2.1 belongs to a novel order in the Bacteroidetes phylum, which we named Candidatus Sulfidibacteriales. The metabolic reconstruction of this MAG indicated that VC2.1 could utilize polysaccharides, protein polymers and fatty acids as well as flexibly obtain energy via NO/N2O reduction and polysulfide reduction. Our results reveal the ecological potential of this novel Bacteroidetes for complex organic carbons mineralization and N2O sinks in deep‐sea hydrothermal vents. Furthermore, guided by the genome information, we designed a new culture medium in which starch, ammonium and polysulfide were used as the carbon source, nitrogen source and electron acceptor respectively, to isolate VC2.1 successfully. [ABSTRACT FROM AUTHOR]