Publications

3992

Abstract  The Gemmatimonadota phylum has been widely detected in diverse natural environments, yet their specific ecological roles in many habitats remain poorly investigated. Similarly, the Candidatus ARS69 phylum has been identified only in a few habitats, and literature on their metabolic functions is relatively scarce. In the present study, we investigated the ecological significance of phyla Ca. ARS69 and Gemmatimonadota in the Arctic glacier foreland (GF) ecosystems through genome-resolved metagenomics. We have reconstructed the first high-quality metagenome-assembled genome (MAG) belonging to Ca. ARS69 and 12 other MAGs belonging to phylum Gemmatimonadota from the three different Arctic GF samples. We further elucidated these two groups phylogenetic lineage and their metabolic function through phylogenomic and pangenomic analysis. The analysis showed that all the reconstructed MAGs potentially belonged to novel species. The MAGs belonged to Ca. ARS69 consist about 8296 gene clusters, of which only about 8% of single-copy core genes (n = 980) were shared among them. The study also revealed the potential ecological role of Ca. ARS69 is associated with carbon fixation, denitrification, sulfite oxidation, and reduction biochemical processes in the GF ecosystems. Similarly, the study demonstrates the widespread distribution of different classes of Gemmatimonadota across wide ranges of ecosystems and their metabolic functions, including in the polar region. Key points • Glacier foreland ecosystems act as a natural laboratory to study microbial community structure. • We have reconstructed 13 metagenome-assembled genomes from the soil samples. • All the reconstructed MAGs belonged to novel species with different metabolic processes. • Ca. ARS69 and Gemmatimonadota MAGs were found to participate in carbon fixation and denitrification processes.

Cottony ash psyllid (CAP, Psyllopsis discrepans) is an important, invasive insect pest of ash trees in North America, where it has established populations and is the host of a newly identified strain of ‘ Candidatus Liberibacter solanacearum’. However, not much is known about the diversity of its introduced population. In this study, a CAP mitochondrial genome (mitogenome) sequence was obtained from a collection in Saskatoon, Saskatchewan, Canada. The CAP mitogenome is a circular DNA of 18,824 bp, encoding 13 protein-coding genes, 21 transfer RNA genes, and two ribosomal RNA genes. BLAST search using the CAP mitogenome as a query against the GenBank sequence database showed the mitogenome of Euphyllura phillyreae (15,202 bp) was the most similar (query coverage = 77%; percentage identity = 78.90%). The CAP mitogenome is significantly different from other known psyllid mitogenomes with the presence of a 4,357-bp control region. The mitogenome sequence will further the genomic understanding of CAP. [Formula: see text] The author(s) have dedicated the work to the public domain under the Creative Commons CC0 “No Rights Reserved” license by waiving all of his or her rights to the work worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law, 2024.

‘Candidatus Phytoplasma ulmi’ (16SrV-A) is the causal agent of elm yellows (EY), a lethal and/or decline disease of several Ulmus (elm) species and hybrids in North America and Europe. In this study, field observations and PCR assays were used to detect phytoplasma infections in diseased U. minor, U. pumila and U. glabra trees in southern Italy. Also, a multigene sequence analysis employing various less conserved genes was carried out to explore the genetic variation in detected strains. All the symptomatic elm trees tested were infected with ‘Ca. Phytoplasma ulmi’. No other phytoplasmas or variants could be detected. Although ‘Ca. Phytoplasma ulmi’ was already known to occur in southern Italy on European field elm, the current work expands the information on the presence, disease incidence and severity, plant host range and molecular aspects of EY phytoplasma strains occurring in southern Italy. In addition, this is the first report from Italy on the molecular characterization of EY phytoplasma strains through map, imp and groEL gene sequence and phylogenetic analyses. Among the newly detected EY phytoplasma strains, some proved distantly related to each other and to other previously characterized EY phytoplasma strains within the genes examined. This implies the presence of distinct taxonomic entities within the material examined. The occurrence of different strains was not linked to the biological traits and geographical distribution. However, the data obtained may provide a basis for further studies aimed at elucidating several other unknown aspects of the EY agent, knowledge of which is essential for effective disease management and control strategies. The results of the current work also show that the EY phytoplasma is particularly widespread in southern Italy and is of considerable economic and ecological relevance.

Dehalobacter is a genus of organohalide-respiring bacteria that is recognized for its fastidious growth using reductive dehalogenases (RDases). In the SC05 culture, however, a Dehalobacter population also mineralizes dichloromethane (DCM) produced by chloroform dechlorination using the mec cassette, just downstream of its active RDase. A closed genome of this DCM-mineralizing lineage has previously evaded assembly. Here, we present the genomes of two novel Dehalobacter strains, each of which was assembled from the metagenome of a distinct subculture from SC05. A pangenomic analysis of the Dehalobacter genus, including RDase synteny and phylogenomics, reveals at least five species of Dehalobacter based on average nucleotide identity, RDase and core gene synteny, as well as differential functional genes. An integration hotspot is also pinpointed in the Dehalobacter genome, in which many recombinase islands have accumulated. This nested recombinase island encodes the active RDase and mec cassette in both SC05 Dehalobacter genomes, indicating the transfer of key functional genes between species of Dehalobacter. Horizontal gene transfer between these two novel Dehalobacter strains has implications for the evolutionary history within the SC05 subcultures and of the Dehalobacter genus as a whole, especially regarding adaptation to anthropogenic chemicals.

Abstract Candidatus Patescibacteria is a diverse bacterial phylum that is notable for members with ultrasmall cell size, reduced genomes, limited metabolic capabilities and dependence on other prokaryotic hosts. Despite the prevalence of the name Ca. Patescibacteria in the scientific literature, it is not officially recognized under the International Code of Nomenclature of Prokaryotes (ICNP) and lacks a nomenclatural type. Here, we rectify this situation by describing two closely related circular metagenome-assembled genomes (MAGs) and by proposing one of them (ABY1TS) to serve as the nomenclatural type for the species Patescibacterium danicumTS gen. Nov., sp. nov. according to the rules of the SeqCode. Rank-normalized phylogenomic inference confirmed the stable placement of P. danicumTS in the class ABY1 within Ca. Patescibacteria. Based on these results, we propose Patescibacterium gen. Nov. to serve as the type genus for associated higher taxa, including the phylum Patescibacteriota phyl. Nov. We complement our proposal with a genomic characterization, metabolic reconstruction, and biogeographical analysis of Patescibacterium. Our results confirm small genome sizes (< 1Mbp), low GC content (>36%), and the occurrence of long gene coding insertions in the 23S rRNA sequences, along with reduced metabolic potential, inferred symbiotic lifestyle, and a global distribution. In summary, this effort, focused on the fourth-largest phylum in the bacterial domain, aims to provide nomenclatural stability in the scientific literature.