Background Viral-encoded auxiliary metabolic genes (AMGs) are important toolkits for modulating their hosts’ metabolisms and the microbial-driven biogeochemical cycles. Although the functions of AMGs have been extensively reported in numerous environments, we still know little about the drivers that shape the viral community-wide AMG compositions in natural ecosystems. Exploring the drivers of viral community-wide AMG compositions is critical for a deeper understanding of the complex interplays among viruses, hosts, and the environments. Results Here, we investigated the impact of viral lifestyles (i.e., lytic and lysogenic), habitats (i.e., water, particle, and sediment), and prokaryotic hosts on viral AMG profiles by utilizing metagenomic and metatranscriptomic techniques. We found that viral lifestyles were the most important drivers, followed by habitats and host identities. Specifically, irrespective of what habitats viruses came from, lytic viruses exhibited greater AMG diversity and tended to encode AMGs for chaperone biosynthesis, signaling proteins, and lipid metabolism, which could boost progeny reproduction, whereas temperate viruses were apt to encode AMGs for host survivability. Moreover, the lytic and temperate viral communities tended to mediate the microbial-driven biogeochemical cycles, especially nitrogen metabolism, in different manners via AMGs. When focusing on each lifestyle, we further found clear dissimilarity in AMG compositions between water and sediment, as well the divergent AMGs encoded by viruses infecting different host orders. Conclusions Overall, our study provides a first systematic characterization of the drivers of viral community-wide AMG compositions and further expands our knowledge of the distinct interactions of lytic and temperate viruses with their prokaryotic hosts from an AMG perspective, which is critical for understanding virus-host-environment interactions in natural conditions.

1. Microbial biogeography has predominantly been studied through a taxonomic lens. However, functional properties of microbial communities are often decoupled from their taxonomic compositions, emphasizing the need to study the biogeography of microbial functional genes directly.2. Here, using the Pearl River Estuary (PRE) sediments as a study system, we characterized the biogeographical patterns of the diversities and abundances of key microbial nitrogen-cycling genes using metagenomic techniques.3. We found that functional genes involved in denitrification and dissimilatory nitrate reduction to ammonium pathways were more diverse and abundant than genes involved in other processes (i.e. nitrogen fixation, nitrification, assimilatory nitrite reduction). The diversities and abundances of certain nitrogen-cycling genes were, to some extent, spatially decoupled. Specifically, the diversities of narG, napA, nirK and nrfA were greater adjacent to the river outlet, whereas the abundances of narG, napA and norB were greater in the downstream of the PRE. These spatial variations were mainly driven by water depth, C/N and NH + 4 . 4. Moreover, nitrogen-cycling genes involved in the same pathways (e.g. denitrification) showed no consistent responses to environmental changes and the main taxa involved in different nitrogen-cycling steps were diverse, providing important clues for explaining why the abundance of single functional gene often seems not to be a reliable proxy for the specific process rate. Overall, our results demonstrate that studying the biogeography of microbial functional genes can help expand our knowledge of the nitrogen cycle from a biogeographical perspective.

A novel arsenic-resistant bacterium, designated 42-50T, was isolated from the high-arsenic sediment of Jianghan Plain, Hubei Province, China. Phylogenetic and biochemical analysis indicated that this bacterium represents the first species of a novel genus belonging to the family Hyphomicrobiaceae. The 16S rRNA gene of strain 42-50T shares 96.3-94.2, 96.3, 96.2 and 94.9-93.8 % sequence identities to those of species from the genera Devosia, Youhaiella, Paradevosia and Pelagibacterium, respectively. The major cellular fatty acids are C16 : 0, C18 : 0, C18 : 1ω7c 11-methyl and summed feature 8 (comprising C18 : 1ω7c and C18 : 1ω6c). The predominant polar lipids are diphosphatidylglycerol, phosphatidylglycerol and two unidentified glycolipids. The predominant respiratory quinone is ubiquinone-10 (Q-10). The DNA G+C content of strain 42-50T is 73.7 mol%. The distinct phylogenetic lineage and unique cellular fatty acids suggest that strain 42-50T represents a novel species of a new genus affiliated with the family Hyphomicrobiaceae, for which the name Arsenicitalea aurantiaca gen. nov., sp. nov. is proposed. The type strain is 42-50T (=CCTCC AB 2014325T=KCTC 42825T).

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A Gram-positive, aerobic, non-motile, non-spore forming strain, designated DSD51W(T), was isolated using a resuscitative technique from a soil sample collected from Kyoto park, Japan, and characterized by using a polyphasic approach. The morphological and chemotaxonomic properties of the isolate were typical of those of members of the genus Rhodococcus. Strain DSD51W(T) was found to form a coherent cluster with Rhodococcus hoagii ATCC 7005(T), Rhodococcus equi NBRC 101255(T), Rhodococcus defluvii Call(T) and Rhodococcus kunmingensis YIM 45607(T) as its closest phylogenetic neighbours in 16S rRNA gene sequence analysis. However, the DNA-DNA hybridization values with the above strains were 58.2 ± 2.2, 58.4 ± 1.9, 45.1 ± 1.4 and 40.3 ± 4.7 %, respectively. In combination with differences in physiological and biochemical properties, strain DSD51W(T) can be concluded to represent a novel species of the genus Rhodococcus, for which the name Rhodococcus soli sp. nov. is proposed, with the type strain DSD51W(T) (=KCTC 29259(T) = JCM 19627(T) = DSM 46662(T) = KACC 17838(T)).